[Federal Register Volume 61, Number 218 (Friday, November 8, 1996)]
[Rules and Regulations]
[Pages 57946-57958]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-28650]
[[Page 57945]]
_______________________________________________________________________
Part II
Department of Transportation
_______________________________________________________________________
Federal Aviation Administration
_______________________________________________________________________
14 CFR Part 25
Type and Number of Passenger Emergency Exits Required in Transport
Category Airplanes; Interim Rule
Federal Register / Vol. 61, No. 218 / Friday, November 8, 1996 /
Rules and Regulations
[[Page 57946]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. 26140; Amendment No. 25-88]
RIN 2120-AC43
Type and Number of Passenger Emergency Exits Required in
Transport Category Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
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SUMMARY: This amendment defines two new types of passenger emergency
exits in transport category airplanes, provides more consistent
standards with respect to the passenger seating allowed for each exit
type and combination of exit types, and requires escape slides to be
erected in less time. These changes allow more flexibility in the
design of emergency exits and reflect recent improvements in escape
slide technology. They will enable more cost-effective emergency exit
arrangements and, in the case of escape slides, enable more rapid
egress of passengers under emergency conditions.
EFFECTIVE DATE: December 9, 1996.
FOR FURTHER INFORMATION CONTACT: Gary L. Killion, Manager, Regulations
Branch (ANM-114), Transport Standards Staff, Transport Airplane
Directorate, Aircraft Certification Service, FAA, 1601 Lind Ave. SW.,
Renton, WA 98055-4056; telephone (206) 227-2194.
SUPPLEMENTARY INFORMATION:
Background
This amendment is based on Notice of Proposed Rulemaking (NPRM) No.
90-4 which was published in the Federal Register on February 22, 1990
(55 FR 6344). In that notice, the FAA proposed amendments to 14 CFR
part 25 that would revise the current requirements for the passenger
emergency exits of transport category airplanes and define two new exit
types. In addition, the FAA also proposed to require escape slides to
be erected in less time, a reflection of improvements in escape slide
state-of-the-art.
Since the time Notice No. 90-4 was published, a number of
amendments were adopted. The changes adopted with Amendment 25-72 (55
FR 29781, July 20, 1990) are largely nonsubstantive in nature; however,
the editorial structure of the sections involved in the proposals of
Notice No. 90-4 was changed considerably. The changes adopted with
Amendment 25-76 (57 FR 19220, May 4, 1992) do not have any substantive
bearing on those proposed in Notice 90-4; however, they also affect the
editorial structure of those sections. Where pertinent, the effect of
those amendments on the changes proposed in Notice 90-4 is discussed
below. None of the other amendments adopted during this period have any
bearing on the proposals of Notice No. 90-4.
Current Requirements of Part 25
Part 25 currently defines seven types of passenger emergency exits
for transport category airplanes--Type A, Types I through IV, tail cone
and ventral. As defined in Sec. 25.807, exits in fuselage sides range
in size from large Type A exits, which must be a minimum of 42 inches
wide by 72 inches high, to Type IV exits, which must be a minimum of 19
inches wide by 26 inches high. Although an exit may exceed the minimum
dimensions specified for a particular type, it is considered to be of
that type unless it qualifies in all respects as one of the larger exit
types. Typically, the larger exits are hinged or translating doors
while the smaller exits are typically removable hatches.
Section 25.809(b)(2) requires that each emergency exit must be
capable of being opened, when there is no fuselage deformation, within
10 seconds measured from the time when the opening means is actuated to
the time when the exit if fully opened.
It must be emphasized that, except for tail-cone or ventral exits,
all references to the types and numbers of required passenger emergency
exits in part 25 and this final rule refer to the exits required in
each side of the fuselage, not the total for the airplane. Although
they are not required to be symmetrical, corresponding exits on
opposite sides of the fuselage are usually referred to as ``exit
pairs'' to preclude confusion between the total number of exits and the
number of exits on each side. The number of additional passenger seats
that may be installed for each additional exit pair of a specific type
is sometimes referred to as the ``exit rating'' for that type. When an
``exit pair'' consists of two different types of exits, the exits are
both considered to be of the type with the smaller exit rating.
Generally, no credit is given for an exit on one side with no
corresponding exit on the other side. (Even though no credit is given
to such exits, they are required to meet all applicable exit design
requirements because they may be used by occupants under emergency
conditions.)
Note that the standards of part 25, including those for emergency
evacuation demonstrations as well as those concerning types and numbers
of exits, are based on the assumption that only half of the exits will
be usable during an actual emergency due to fire, structural damage or
other adverse circumstance.
Section 25.807(d) currently specifies the type and number of
emergency exits required for three ranges of passenger seating
capacities. The first range, passenger seating configurations of one to
179, is addressed in Sec. 25.807(d)(1) in a table that outlines the
specific type and number of exits that must be provided. Those
standards have been in effect for several decades and were based more
on industry practice during the reciprocating-engine transport airplane
era than on any particular testing.
For the second range, passenger seating configurations of 180 to
299, Sec. 25.807(d)(1) uses a different approach. Instead of specifying
the type and number of exits required for those airplanes, a second
table supplements the first by specifying the number of passenger
seats, in addition to 179, that may be installed for various types of
additional exits. For example, the first table specifies that an
airplane with 179 passenger seats must have two pairs of Type I exits
and two pairs of Type III exits. The second table specifies that the
seating may be increased by 45 passengers for each additional pair of
Type I exits installed. An airplane with three pairs of Type I exits
and two pairs of Type III exits would, therefore, be permitted, insofar
as the type and number of exits is concerned, to have a passenger
seating configuration of 224.
For the third range, passenger seating configurations greater than
299, Sec. 25.807(d)(2) simply states that each exit installed in the
side of the fuselage must be either a Type I or Type A exit and that
seating configurations of 45 and 110 are allowed for each pair of Type
I exits and each pair of Type A exits, respectively.
Section 25.807(d)(3) specifies the number of additional passenger
seats that may be provided when creditable ventral or tail-cone exits
are installed. In order to receive any credit as a passenger emergency
exit, a ventral or tail-cone exit must provide the same rate of egress
as a Type III exit with the airplane in the most adverse exit opening
condition that would result from the collapse of one or more landing
gear legs.
As amended recently by Amendment 25-72, Sec. 25.807(d)(5) provides
flexibility in the type and number of exits required by stating that an
alternate emergency exit configuration may be approved in lieu of that
specified in either Sec. 25.807(d) (1) or (2) provided the
[[Page 57947]]
overall evacuation capability is shown to be equal to or greater than
that of the specified emergency exit configuration. This means, for
example, that one pair of larger exits could be substituted in some
cases for two pairs of smaller exits.
Providing the type and number of exits specified for a given number
of passenger seats does not, in itself, ensure that an airplane can be
approved with that many seats. Other requirements, such as uniform
distribution of passenger seats and exits and the demonstrated
emergency evacuation capability, may actually limit seating to fewer
passengers.
Part 25 specifies that a means must be provided to assist
passengers in descending to the ground for each exit, other than an
overwing exit, that is more than six feet from the ground when the
airplane is on the ground with the landing gear extended. Section
25.810(a)(1)(i) specifies that the assist means must be deployed
automatically and that deployment must begin during the interval
between the time the exit opening means is actuated from inside the
airplane and the time the exit is fully opened. As noted above, that
time interval must be no more than 10 seconds. Section 25.810(a)(1)(ii)
further specifies that the assist means must be automatically erected
within 10 seconds after deployment is begun. Taking the maximum time
intervals permitted, the assist means must be erected and usable no
more than 20 seconds after the exit opening means is actuated.
Generally, inflatable slides are used for this purpose.
For an overwing exit, Sec. 25.810(d) specifies that a means must be
provided to assist passengers in descending to the ground whenever the
place on the airplane structure at which the escape route terminates
(typically the trailing edge of a wing flap) is more than six feet from
the ground. Inflatable slides are generally used for this purpose also.
Part 25 currently contains no specific maximum erection time for off-
wing slides; however, Technical Standard Order (TSO) C69b, which
contains design standards for inflatable escape slides, specifies that
off-wing escape slides must be fully erect within 10 seconds after
actuation of the inflation controls. (TSO-C69a, which was superseded by
TSO-C69b on August 17, 1988, had previously a maximum erection time of
15 seconds.)
Because the large Type A emergency exits are expected to
accommodate parallel lines of evacuees simultaneously,
Sec. 25.810(a)(1) specifies that the means provided for those exits to
assist the occupants in descending to the ground must also be capable
of carrying two parallel lines of evacuees simultaneously.
Section 25.813(b) requires adequate space next to one side of each
emergency exit, other than a Type A exit, that is required by
Sec. 25.810(a) to have an assist means to allow crewmembers to assist
in the evacuation. Because there are two parallel lines of evacuees to
assist, each Type A emergency exit is required to have an assist space
on each side of the exit. Unlike other exit types, Type A exits must
have such assist space regardless of whether the exit is required to
have an assist means. At the time Notice 90-4 was issued, the latter
requirement was contained in Sec. 25.807(a)(7)(vii); however, it has
since been consolidated with the former in Sec. 25.813(b) (Amendment
25-72).
Amendments Proposed in Notice 90-4
The FAA held a public technical conference in Seattle, Washington,
in September 1985, to review the existing safety regulations and
practices regarding the emergency evacuation of transport airplanes. As
a result of the conference, it was recommended, in part, that the
regulations relative to passenger emergency exits be revised to provide
design flexibility, and those concerning escape slide inflation time be
revised to reflect the current state-of-the-art. Subsequent to this
public conference, the following changes were proposed in Notice 90-4:
Type and Number of Emergency Exits
Unlike the standards for airplanes with more than 299 seats, the
number of additional passenger seats allowed for smaller passenger
capacities is not uniform. For example, the first table of
Sec. 25.807(d)(1) (Sec. 25.807(c) prior to Amendment 25-72) requires a
pair of Type I exits and a pair of Type III exits for a maximum
passenger seating capacity of 79. Adding another pair of Type I exits,
resulting in a total of two pairs of Type I exits and one pair of Type
III exits, would allow up to 139 passenger seats--an increase of 60
attributable to the additional pair of Type I exits. In contrast, one
pair of Type I exits and two pairs of Type III exits are required for a
maximum seating configuration of 109. Adding another pair of Type I
exits in that case, resulting in a total of two pairs of Type I exits
and two pairs of Type III exits, would allow up to 179 passengers--an
increase of 70 attributable to the additional pair of Type I exits. For
configurations beyond 179 passengers, the second table of
Sec. 25.807(d)(1) allows an increase of only 45 for each additional
pair of Type I exits. Thus the increase in the number of passenger
seats allowed, if one additional pair of Type I exits were installed,
varies from 45 to 70, depending on the initial airplane exit
configuration and the total passenger seating capacity.
The additional passenger seating capacity gained by adding a pair
of Type III exits varies in a similar manner. The first table of
Sec. 25.807(d)(1) currently allows 79 passenger seats if one pair of
Type I and one pair of Type III exits are installed. If one more pair
of Type III exits were installed, the allowable number of passenger
seats would be increased by 30 to a total of 109 passenger seats. In
contrast, two pair of Type I exits and one pair of Type III exits are
currently required for a maximum seating capacity of 139. Adding a pair
of Type III exits would allow a maximum seating capacity of 179, an
increase of 40 passenger seats. For configurations beyond 179
passengers, the second table of Sec. 25.807(d) allows an increase of 35
passenger seats for each additional pair of Type III exits.
When the exit configurations and maximum passenger capacities
specified in the first table of Sec. 25.807(d)(1) are compared with the
combined ratings specified in the second table of Sec. 25.807(d)(2) for
the same combination of exit types, it can be seen that the maximum
capacities for the first two configurations (19 and 39 passengers) are
conservative when compared to the assigned ratings. They are in close
agreement for the next two configurations (79 and 109) and generous for
the two largest configurations (139 and 170). A similar comparison can
not be made for Type IV exits since no ratings are established for
those exits in the second table.
As proposed in Notice 90-4, Sec. 25.807 would be revised to provide
one simple, consistent set of standards while still retaining an
equivalent level of safety. The exit ratings for Type I, Type II, Type
III and Type A exits would be the same as those currently shown in the
second table of Sec. 25.807(d)(1) for those types. Type IV exits would
be assigned a passenger rating of nine to be consistent with the
maximum passenger capacity currently shown in the first table of
Sec. 25.807(d)(1). Replacing the exiting tables with specific ratings
for each type of exit would enable the airplane manufacturer to design
an airplane with any combination of exits the manufacturer chooses,
subject to specific constraints. The following constraints, which would
be contained in Sec. 25.807(g), were proposed to ensure that the margin
of safety currently
[[Page 57948]]
associated with passenger capacities of approximately 40 and fewer
passenger seats would be retained and that there would be no
significant increases in passenger seating permissible with the various
combinations of exit types. In addition, unacceptable alternative
combinations of exits, such as one pair of Type A exits and three pairs
of Type III exits for a maximum passenger seating of 215 are precluded.
The first table of Sec. 25.807(d)(1) currently places several
limitations on the passenger emergency exit configuration. For example,
the table does not permit the use of Type IV exits in airplanes with
more than 9 seats. There must be at least two pairs of exits for any
passenger seating configuration above 19, and there must also be at
least one pair of Type I or larger exits for passenger seating
capacities of 40 or more. As proposed in Notice 90-4, these and other
limitations concerning the type and number of exits required for
specific passenger seating configurations would be retained. The
existing requirement that there must be at least one pair of Type I or
larger exits in each side of the fuselage for passenger seating
configurations of 40 or more would be retained except that it would
apply to passenger seating configurations of 41 or more rather than 40
or more. The existing requirement that there must be at least two Type
I or larger exits in each side of the fuselage for passenger seating
configurations of 110 or more would also be retained except that it
would apply to passenger seating configurations of 111 or more.
The FAA reviewed the results of previous evacuation demonstrations
involving airplanes with two adjacent Type III exits on each side of
the fuselage. From this review, it was noted that two adjacent Type III
exits consistently fail to provide a rate of egress that is double that
of a single Type III exit. Typically, some evacuees fail to bypass one
exit in order for there to be a steady flow through the adjacent exit.
The rate of egress through the exit that some evacuees must bypass is
generally equal to that through a single similar exit, but the rate of
egress through the second exit is consistently less. The FAA,
therefore, proposed in Notice 90-4 that the combined passenger rating
of two adjacent pairs of Type III exits would be limited to 65. For
purpose of compliance with this requirement, two Type III exits
separated by fewer than three passenger seat-rows would be considered
to be adjacent (i.e. fewer than three seat-rows plus two passageways
located between adjacent vertical edges of the two exits). The
pertinent parameter is the number of seat rows; however, with typical
row spacing this would be about 80 to 90 inches between adjacent
vertical edges of the two exits. (Notice 90-4 quoted 90 to 100 inches;
however, 80 to 90 inches is more likely.) It was also proposed that the
combined passenger rating for all Type III exits would not exceed 70.
Depending on whether the first two pairs were eligible for the full 70
passenger rating, no or very little additional credit would be given
for any additional pairs of Type III exits. An additional conservatism
in Type III exits because the widths of the accesses to the Type III
exits in the studied evacuation demonstrations were far less than that
required today because of recent safety regulatory changes.
Taking both the exit ratings and the specific constraints proposed
in Sec. 25.807(g), the practical effect of the proposed changes on
airplanes with 179 or fewer passenger seats would be as follows:
(a) With 1 through 9 passenger seats, the table of
Sec. 25.807(d)(1) specifies at least one Type IV exit in each side.
That requirement would remain unchanged. The table of Sec. 25.807(d)(1)
notwithstanding, Sec. 25.807(d)(4) currently specifies that an exit
meeting at least the dimensions of a Type III exit must be installed in
each side if the vertical location of the wing does not allow the
installation of overwing exits. That requirements would be retained in
proposed Sec. 25.807(g)(1).
(b) With 10 through 19 passenger seats, the table of
Sec. 25.807(d)(1) specifies at least one Type III exit in each side.
That requirement would remain unchanged.
(c) With 20 through 39 passenger seats, the first table of
Sec. 25.807(d)(1) specifies at least one Type II and one Type III exit
in each side even though the combined ratings shown in the second table
of that section would total 75 passenger seats. The combined ratings of
proposed Sec. 25.807(g) would also total 75 passenger seats for this
combination of passenger seats; however, the number of passenger seats
permissible with this combination of exit types would be limited to 40
by proposed Sec. 25.807(g)(5). That would be one more passenger seat
than currently permitted by this combination of exit types. The margin
of safety provided by the current rule would be maintained since 40
passenger seats is only 53% of the combined ratings of that combination
of exit types.
(d) With 40 through 79 passenger seats, the table of
Sec. 25.807(d)(1) specifies at least one Type I and one Type III exit
in each side. As proposed, the exit combination currently specified for
airplanes with 20 to 39 seats could also be used for one with 40
passenger seats. As in the case described above, a number of different
combinations of smaller exit types might provide sufficient combined
passenger ratings for airplanes with 41 through 79 passengers; however,
those combinations would be precluded by the constraints contained in
proposed Sec. 25.807(g). Proposed Sec. 25.807(g)(5) would specify that,
for more than 40 seats, there must be at least two exits in each side
and that one of those must be at least a Type I exit. That would
preclude for example, an alternative configuration of one smaller Type
II exit and two Type III exits in each side even though the combined
passenger ratings show in proposed Sec. 25.807(g) for that combination
of exits would total 105 or 110 passenger seats. It would also preclude
an arrangement with only one large Type A or Type B exit in each side
in lieu of the Type I and Type III exits. As proposed, the combination
of exit types currently specified for airplanes with 41 through 79
passenger seats could also be used for an airplane with 80 passenger
seats.
(e) With 80 through 109 passenger seats, the table of
Sec. 25.807(d)(1) specifies at least one Type I and two Type III exits
in each side. As proposed, the combination of exit types for airplanes
with 40 through 79 passenger seats could also be used for those with 80
passenger seats. Although the specific constraints of proposed
Sec. 25.807(g) would preclude certain undesirable combinations of exit
types, the proposed changes would allow a degree of flexibility in the
81 through 109 passenger seat range. For example, two of the newly
proposed Type C exits could be used in lieu of one Type I and two III
exits. Also, two Type I exits could be used in lieu of one Type I and
two Type III exits provided the number of passenger seats did not
exceed 90. As proposed, the combination of exit types currently
specified for 80 through 109 seats could also be used for airplanes
with up to 110 passenger seats; or 115 passenger seats if the Type III
exits were separated sufficiently to enhance their effectiveness.
(f) With 110 through 139 seats, the table of Sec. 25.807(d)(1)
specifies at least two Type I exits and one Type III exit in each side.
As proposed, the combination of exits currently specified for airplanes
with 80 through 109 passenger seats, could be used for those with 110
passenger seats. The combined passenger ratings of proposed
Sec. 25.807(g) would limit the exit combination currently specified for
110 through 139 passenger seats to 125
[[Page 57949]]
seats. Proposed Sec. 25.807(g)(6) would specify that, for more than 110
seats, there must be at least two Type I or larger exits in each side.
For airplanes with 111 through 125 there would be considerable
additional flexibility in the combination of exit types used; however,
the specific constraints of Sec. 25.807(g) would preclude certain
undesirable combinations of exit types. For example, proposed
Sec. 25.807(g)(6) would require the emergency exits of airplanes with
more than 110 passengers to include at least two Type I exits in each
side. For airplanes with more than 125 passenger seats, there would
have to be more or larger exit types than those currently required for
airplanes with 110 through 139 passenger seats. The choice of
additional or larger exit types would, of course, be subject to the
combined passenger ratings and specific constraints of proposed
Sec. 25.807(g).
(g) With 140 through 179 passenger seats, the table of
Sec. 25.807(d)(1) specifies at least two Type I exits and two Type III
exits in each side. The combined passenger rating of proposed
Sec. 25.807(g) would limit this exit combination to 160 seats. Proposed
Sec. 25.807(g)(7) would further limit this exit combination to 155
seats if the Type III exits were not separated sufficiently to enhance
their effectiveness. Proposed Sec. 25.807(g)(6) would specify that
there must be at least two Type I exits or larger in each side. That
would preclude an alternative configuration in which no exits are
larger than Type II. It would also preclude a combination of exits
involving only one exit larger than Type I and several smaller Type III
exits in each side. For airplanes with more than 160 passenger seats,
larger or additional exits would have to be provided. The choice of
additional or larger exit types would be subject to the combined
passenger ratings and specific constraints of proposed Sec. 25.807(g);
however, this range of passenger seats would be afforded the greatest
flexibility in the choice of exit type combinations.
In summary, the number of passenger seats permissible with one pair
of Type II and one pair to Type III exits would be increased from 39 to
40. Similarly, the number permissible with one pair of Type I and one
pair of Type III exits would be increased from 79 to 80. The increase
would be negligible in either case insofar as the egress capability of
the exits is concerned; however, it would be more than compensated for
by the proposed improvement in escape slide deployment time in any
event. The number permissible with one pair of Type I exits and two
pairs of Type III exits would be increased from 109 to either 110 or
115, depending on the proximity of the Type III exits. Those increases
would also be negligible insofar as the egress capability of the exits
is concerned, but they too would be more than compensated by the
proposed improvement in escape slide deployment time. With two pairs of
Type I exits and one pair of Type III exits, the permissible number
would be significantly decreased from 139 to 125; with two pairs of
Type I exits and two pairs of Type III exits, it would be significantly
decreased from 179 to either 155 or 160, again depending on the
proximity of the Type III exits. The permissible number of passenger
seats would remain unchanged for other exit combinations. As stated
above in the preamble, these new maximum passenger capacities are
calculated by summing the number of passengers rated for the specific
types of exit pairs; these ratings are identical to those in the former
Sec. 25.807(d)(1) for increases in seating configurations beyond 179.
As noted above, Sec. 25.807(d)(2) currently specifies that each
exit must be a Type A or Type I exit for passenger seating capacities
over 299. That limitation was introduced, along with the definition of
Type A exits, with Amendment 25-15 (32 FR 13255, September 20, 1967),
when the first wide-body airplanes were being proposed. Because those
airplanes were to have twin aisles, the large Type A exits were adopted
to permit simultaneous side-by-side egress of passengers from both
aisles. Although there was no operational experience at that time with
such airplanes, it was considered that they should not have a large
number of small exits. The requirement that all exits be Type A or Type
I was intended to discourage interior arrangements with numerous Type
III exits and fewer large exits. Subsequently, the Boeing Model 767 and
certain configurations of the Airbus Model A310 were both approved with
one or two pairs of Type III exits under the equivalent level of safety
provisions of Sec. 21.21(b)(1). Evacuation demonstrations and actual
evacuations under emergency conditions with those airplanes have shown
that a limited number of Type III overwing exits can be effective in
twin-aisle airplanes. The FAA, therefore, proposed in Notice 90-4 to
permit limited use of Type III exits in airplanes with passenger
seating capacities greater than 299. Subsequent to Notice 90-4,
Sec. 25.807(d)(5) was adopted with Amendment 25-72 to permit an
alternate emergency exit configuration provided the overall evacuation
capability is shown to be equal or greater than that specified. As a
result, the proposed change is no longer substantive.
To ensure that adequate evacuation capability is maintained if a
primary exit becomes unusable, the FAA proposed in Notice 90-4 that at
least two pairs of the larger exits (Type A or, as described below,
Type B or Type C) would have to be installed to receive full passenger
seating credit for those exits. If only one pair of Type A, B, or C
exits were installed, the exits would be considered to be Type I exits
and credited accordingly.
In order to provide greater flexibility in passenger emergency exit
design, two new exit types, Type B and Type C, were proposed in Notice
90-4. Both types would be larger than Type I exits but smaller than
Type A exits. They would be similar to exits that have been previously
approved by exemption or under the equivalent level of safety
provisions of Sec. 21.21(b)(1).
The proposed Type B exits would be required to meet the same
criteria as those for Type A exits except that their minimum width
would be 32 inches in lieu of 42 inches, and the maximum allowable
corner radii would be six inches in lieu of seven inches. Like Type A
exits, Type B exits would have to have passageways at least 36 inches
wide leading from each main aisle and be equipped with dual-lane escape
slides. Based on the egress rate demonstrated by the petitioner,
Exemption No. 1573 was granted to permit a passenger rating of 80 for a
pair of these exits in the McDonnell Douglas Model DC-10. Similar exit
pairs installed later in one configuration of the Boeing Model 757 were
given a passenger rating of 75 based on the egress rate demonstrated at
that time. That installation was approved under the equivalent safety
provisions of Sec. 21.21(b)(1).
The passenger flow to, through and from the proposed Type B exits
is similar to that through the wider Type A exits except that the two
parallel lines of evacuees typically twist their shoulders a few
degrees for the moment in which they are passing through the exit side-
by-side. The proposed passenger rating of Type B exits would be 68%
that of the larger Type A exits. In essence, the difference between the
proposed passenger rating of Type B exits and that of Type A exits
reflects this momentary partial merging of the two parallel lines of
evacuees as they pass through Type B exits.
In a report entitled Study of FAR 25.807(c) Emergency Exits dated
May 1975, the FAA Civil Aeromedical Institute (CAMI) recommended adding
[[Page 57950]]
several exit sizes to the regulations, including two that correspond to
the proposed Type B and C exits.
Based on a series of passenger evacuation rate tests conducted with
exit widths of 26 to 42 inches, CAMI recommended a passenger rating of
80 for an exit that is 32 inches wide and equipped with a dual-lane
escape slide. Because of the differences in motor skills and reaction
to situations typically exhibited in testing involving people, there is
some variation in the data presented in the CAMI report concerning
evacuation rate versus exit size.
Considering the variation in the CAMI test data and the data in
which approvals of the DC-10 and Boeing Model 757 doors were based, a
passenger rating of 75 was proposed in Notice 90-4 for Type B exits.
This would ensure that the passenger rating is appropriate for all such
exits regardless of the size of the airplane in which they are
installed or minor differences among the exits of different airplane
models.
The CAMI testing showed that other exits, similar to Type I exits
but with additional width, provide greater passenger egress rates than
those with the minimum width of 24 inches. CAMI, therefore, recommended
that exit pairs at least 30 inches wide should have a passenger rating
of 50--five greater than that for Type I exit pairs with the minimum
width of 24 inches. Their recommendation was based on the time of 20
seconds currently allowed for door opening and erection of the assist
means. The exits defined as Type C in Notice 90-4 evolved from these
CAMI recommendations.
The FAA previously proposed to increase the minimum height of Type
I exits to 60 inches; however, as discussed in the preamble to
Amendment 25-15 (32 FR 13255, September 20, 1967), the proposal was
withdrawn in light of test data showing that the greater height would
provide no material improvement in passenger egress rate. This finding
was corroborated by later CAMI testing.
As proposed in Notice 90-4, Type C exits would be similar to the
existing Type I exits, except that their minimum width, would be 30
inches in lieu of 24 inches. In light of the earlier test results, no
increase in minimum height was proposed for Type C exits. In addition,
Type C exits would be required to have assist means regardless of how
high they are above the ground. (Exits of this size without assist
means would be considered Type I exits even though they meet the
dimensional requirements for Type C exits.) The maximum time allowed
for door opening and erection of the assist means (exit preparation
time) would be reduced from 20 seconds to 10 seconds. In addition, the
10-second exit preparation time would have to be demonstrated for non-
overwing exits in each of the attitudes corresponding to collapse of
one or more legs of the landing gear. Such exits would not be required
to have power-assisted means for opening in an emergency, nor
automatically deployed slides; however, they would have to be so-
equipped, as a matter or practicality, in order to comply with the
proposed 10-second preparation time. Nevertheless, such features would
not be required, nor needed, if the door could be opened and the assist
means erected within 10 seconds without them.
In order to arrive at the passenger rating proposed in Notice 90-4,
experience with similar exits was considered. Exemption No. 3639, which
was granted for the British Aerospace Model BAe.146, allows a maximum
passenger seating capacity of 109 with two exit pairs, or a passenger
rating of 54.5 per exit pair. These exits are all 30.5 inches wide, and
those on the left side are 58 inches high. Due to considerations other
than emergency egress, those on the left side are 72 inches high. They
are equipped with assist means in the form of automatically deployed,
inflatable, self-supporting escape slides.
In another configuration, the Boeing Model 757 was approved for as
many as 219 passenger seats, with four exits on each side of the
airplane, or approximately 55 passenger seats per exit. Three of the
four exits on each side are similar to the proposed Type C exits. Exits
Nos. 1, 2, and 4 are over 30 inches in width and have power assist
means for opening in an emergency. It was demonstrated during full-
scale demonstrations that these exits could be opened and ready to
accept evacuees in approximately 8.2 seconds. The No. 3 exit is less
than 30 inches in width; however it does exceed the minimum width for a
Type I exit. That exit was demonstrated to be usable within 12 seconds.
In view of the testing conducted by CAMI and the consistency of
those test results with the approvals of British Aerospace BAe.146 and
Boeing 757 airplanes, a passenger rating of 55 was proposed in Notice
90-4 for Type C exits.
A number of conforming changes to other sections were also proposed
to include references to Types B and C exits as well as the existing
types.
The FAA also proposed in Notice 90-4 to make extensive non-
substantive changes to enhance the clarity of those sections involved
with emergency exits. In light of the changes already adopted by
Amendment 25-72, some are no longer relevant; those remaining would not
impose any additional burden on any persons.
Escape Slide Deployment
The FAA proposed in Notice 90-4 to revise Sec. 25.809 to require
that the assist means at all Type C exits must be erected within 10
seconds from the time the exit opening means is actuated. The FAA also
proposed to reduce the maximum permissible erection times for the
assist means serving other exit types. For non over-wing exits, the
assist means would have to be fully erected within 6 seconds. This
would reduce the time available to prepare the escape system to accept
evacuees in any emergency by 4 seconds. For off-wing assist means, the
FAA proposed that they must be fully erected within 10 seconds. This
would be consistent with the interval currently specified in TSO C69b.
As noted above, these erection times are in addition to the interval
permitted by Sec. 25.809(b)(2) for exit opening.
Discussion of Comments Received in Response to Notice 90-4
Fourteen commenters responded to the invitation in Notice 90-4--
five foreign airworthiness authorities; five airplane or equipment
manufacturers, or organizations representing such manufacturers; two
airline employee unions; an international airline organization; and an
individual.
Two foreign airworthiness authorities support the proposed
rulemaking without further comment.
The individual commenter recommends that no passenger seat be
installed adjacent to an overwing exit. (By ``overwing exit,'' the
commenter is undoubtedly referring to a Type III exit since
unobstructed passageways were already required for Type II and larger
exits at the time the comment was made.) The recommendation is
unrelated to the rulemaking proposed in Notice 90-4; however, the
subject was fully addressed by recently adopted Amendments 25-76, 121-
228 and 135-43 (57 FR 19220, May 4, 1992) which specify unobstructed
passageways leading to Type III exits.
Some commenters suggest that any rulemaking resulting from Notice
90-4 should be deferred to the Aviation Rulemaking Advisory Committee
(ARAC). The ARAC is a committee of safety experts chartered by the FAA
on
[[Page 57951]]
February 5, 1991, to develop future proposed safety standards by using
a systems-type analysis. Although much of the future proposed
rulemaking of this nature will be developed by ARAC, it is not
considered appropriate to defer this particular subject to ARAC since
the proposed rulemaking has already been developed and published for
public comments.
The international airline organization forwarded comments from two
foreign airlines. One airline supports the proposed rulemaking, stating
that it clarifies the existing rules and has the potential for
increased flexibility in aircraft design. The other airline has
reservations concerning the proposed slide erection times but supports
the other aspects of the proposed rulemaking. The latter airline did
not elaborate on its reservations.
Three commenters support the proposed change concerning assist
space in the apparent belief that it introduced a new requirement for
assist space at exits other than Type A exits. Actually, all exits
other than Type A are already required to have such assist space if
they are required by Sec. 25.810(a) to have assist means. The only
change proposed in this regard was simply a conforming change to add
consideration of Type B emergency exits. The recent consolidation of
all assist space requirements in Sec. 25.813(b) should preclude further
confusion in that regard.
The three commenters also propose that the dimensions of the
required assist space should be defined more precisely. Any change of
that nature would be beyond the scope of Notice 90-4 and could not be
considered at this time; nevertheless, it is being considered for
future rulemaking.
Type and Number of Emergency Exits
One commenter believes the passenger ratings of all exit types
should be reconsidered. According to the commenter, the ratings are
based on obsolete assumptions and are not verified with data from
actual evacuations. In particular, the commenter notes that the egress
rate of an exit is dependent on the presence and type of assist means.
In the same vein, another commenter believes that additional credit
should be given for exits not requiring assist means. In light of the
successful evacuations that have been accomplished under actual
emergency conditions, the FAA does not concur that the present
passenger ratings of all exit types are inappropriate as suggested by
the first commenter. The FAA does, however, concur that the egress rate
of an exit type may be dependent on the presence and type of assist
means. Although not specifically stated by either commenter, the egress
rate for exit types not requiring assist means is undoubtedly dependent
also on the distance from the exit sill to the ground. Nevertheless,
any changes beyond those proposed in Notice 90-4 would have to be
deferred for future rulemaking. It must be recognized that extensive
additional testing would have to be conducted before any changes of
this nature could be proposed.
The commenter also suggests that credit should be given for
unpaired exits because, according to the commenter, it is quite rare
that one side of the airplane is blocked by fire, and usable exits are
distributed in a less predictable manner over both sides and the length
of the airplane. The FAA does not consider any change in that regard to
be appropriate. The unpredictability of fire or other circumstance that
might render an exit unavailable is the very reason why credit can not
be given for an exit that does not have a counterpart on the opposite
side of the airplane. Whether one complete side would be likely to be
blocked by fire is not relevant. It is necessary to have a
corresponding exit on the opposite side if only one exit is blocked.
Contrary to the first commenter's assertion, there have been many
instances in which an exit on one side was blocked by fire while its
counterpart on the opposite side was clear and usable. The commenter
also implies that exits should be distributed over the length of the
airplane. It is recognized that there is a practical limit to the
lengthwise distribution of exits in smaller airplanes; however, exits
are already required to be distributed along the length of the cabin,
as well as on either side, to the greatest extent practicable. In
regard to the second comment, part 25 does not require the number of
exits on both sides to be equal. Due to practical considerations, such
as normal passenger entry, service access, etc., the designer may
choose to install more openings in one side than the other; however,
any opening that does not have a counterpart on the other side is not
credited as an emergency exit.
Section 25.807(f)(2) presently states that, unless another location
affords a more effective means of passenger evacuation or the airplane
has a ventral or tail cone exit, an airplane is only required to have
one pair of floor-level exits must have that exit pair located in the
rearward part of the passenger compartment. The commenter believes that
Sec. 25.807(f)(2) should be removed or amended to emphasize locating
the sole pair of floor-level exits in the forward part of the passenger
cabin. The FAA concurs that there are some circumstances in which that
would be preferable, but not that the forward end of the cabin is a
preferable location in general. Several factors must be considered for
any particular design, including proximity of the propeller plane,
engine inlet or engine exhaust, potential sources of fires, potential
fuselage impact damage, etc. Another consideration is that the flight
attendant must be stationed near those exits to direct the evacuation.
Having the exit pair, and the associated flight attendant, at the rear
of the cabin is advantageous in situations where the flightcrew can
assist the flight attendant by directing the evacuation from the
forward end of the cabin. The FAA does not concur that the commenter's
proposed change is appropriate since the rule already permits locating
the exits at the forward end of the cabin when that location would, in
fact, afford a more effective means of evacuation. Furthermore, it is
arguable whether the forward end is predominantly the preferable
location, as the commenter believes. In any event, a change of this
nature would be beyond the scope of Notice 90-4 and could not be
adopted at this time even if it were deemed to have merit.
The same commenter asserts that ventral and tail-cone exits have
not contributed to the rapid evacuation of occupants from airplanes
during life-threatening situations and questions whether they should
remain in part 25 as creditable emergency exits. Contrary to the
commenter's assertion, service experience has shown that ventral and
tail-cone emergency exits can provide valuable means of emergency
egress and should remain as creditable exits.
The commenter further questions whether the current passenger
ratings for those exits are appropriate. Another commenter recommends
that the passenger rating of ventral emergency exits should be reduced
by 50%. That commenter assets the ventral exit would probably be usable
only half the time because of possible landing gear failure. This too
would go beyond the scope of the notice; however, it must be noted that
a change of this nature would be based on flawed logic. The percentage
of emergency evacuations in which an exit is usable has no bearing on
how many persons can safely pass through it when it is usable.
Nevertheless, the commenter's apparent concern is already addressed by
current Sec. 25.807(d)(3). That section, which now becomes
Sec. 25.807(g)(9), specifies that a ventral exit must provide the same
rate of egress as a Type III exit with the airplane in the most adverse
exit
[[Page 57952]]
opening condition that would result from the collapse of one or more
landing gear legs. If the geometry of the airplane is such that the
exit would not provide this rate of egress with the most adverse
landing-gear failure-condition, no credit is given for the exit.
There is, of course, no assurance that any particular exit,
regardless of its type and location, will be available for use in every
accident that may occur. As noted above, the standards of part 25 are
based on the assumption that only half of the required exits will be
usable due to fire, crash damage or other adverse circumstance. There
is no need evident at this time to change the passenger rating of
either ventral or tail-cone exits, nor any basis on which to establish
new ratings. Any future change involving either an increase or a
decrease in the passenger ratings for those exit types would have to be
based on considerable additional testing.
One commenter expresses concern that the requirement of
Sec. 25.807(c)(7) concerning the maximum distance between exits would
be removed. (This requirement was contained in Sec. 25.807(d)(7) at the
time Notice 90-4 was published; however, it was moved to
Sec. 25.807(c)(7) with the adoption of Amendment 25-72.) The omission
of this requirement from proposed Sec. 25.807 was actually inadvertent.
There was no intention to remove this requirement, and the final rule
has been corrected accordingly.
Another commenter recommends that all non-floor level passenger
emergency exits should be eliminated (i.e., Types III and IV, ventral
and some tail cone exits) and that, in particular, Type III exits
should not be used in airplanes with more that 299 passenger seats. The
FAA does not concur with the commenter that they should be eliminated
altogether. Type III exits were previously permitted in airplanes with
as many as 299 seats; and, as discussed above, they can now be used in
larger airplanes provided the overall evacuation capability is not
diminished. They have proven to be effective means of egress. Due to
structural weight and cabin space considerations, it would be
impractical to require the use of larger exit types exclusively in lieu
of those exits.
As noted above, service experience has shown that ventral and tail-
cone exits can provide valuable means of emergency egress and should
remain as creditable exits.
As also noted above, Type IV exits are permitted in airplanes with
nine or fewer passengers; however, Sec. 25.785(h) requires each
passenger entry door in the side of the fuselage to qualify as a Type
II or larger emergency exit. Although it can only be considered a Type
IV exit when the corresponding exit on the opposite side is also at
least a Type IV exit, the opening in one side of the fuselage of an
airplane with nine or fewer seats is already required by Sec. 25.783(h)
to meet the requirements of at least a Type II exit. It would be
extremely impractical from the standpoints of structural weight and
lost cabin space to require the exits on both sides of the cabins of
airplanes with nine or fewer seats to be Type II or larger exits.
Furthermore, the FAA is not aware of any service history indicating
that these small exits are not satisfactory for the smaller transport
category airplanes.
The rationale given by the commenter for not permitting the use of
Type III exits in airplanes with more than 299 passengers is that the
floor-level exits may be unusable and that it would be necessary to
evacuate more than 299 passengers through a Type III exit. As noted
above, the largest passenger rating for any exit pair (Type A) is 110
passengers. An airplane with more than 299 passengers would, therefore,
have to have a minimum of three floor-level exit pairs in addition to
the pair of Type III exits. As noted earlier, the standards of part 25
are based on the assumption that half of the required exits may be
unusable due to fire or crash damage. It is unrealistic to believe that
not half, but all six floor-level exits would be rendered unusable in
an otherwise survivable crash, as the commenter suggests, leaving only
a pair of Type III exits usable. As noted above, the original concern
was not the use of Type III exits in the larger airplanes per se; it
was actually whether they would be effective in airplanes with twin
aisles. As also noted above, experience with Airbus Model A310 and
Boeing Model 767 airplanes has shown that Type III exits can be
effective in twin-aisle airplanes. (Another commenter states that those
exits in the Airbus Model A310 are derated Type I exits rather than
Type III exits. Actually the exits provided at the same location in
some A310 airplanes are fully qualified as Type I exits. Those provided
at that location in other A310 airplanes can only be considered Type
III by definition since they fail to meet all of the qualifications of
a larger exit type. In any event, the experience gained with those
exits is pertinent regardless of how they are identified.)
The commenter supports the establishment of the new Type B exit,
but questions whether it is effective enough to support the proposed
passenger rating of 75. The commenter expresses concern that the exit
may cause a bottleneck in passenger flow, since it could be four inches
narrower than the passageway leading to it, and suggests that the
passengers rating should be reduced from 75 to 65. Another commenter
believes that the difference would cause a bottleneck but, instead of
recommending that the passenger rating be reduced, suggests that the
width of the passageway should be reduced to 30 inches.
As noted above, the effectiveness of Type B exits has already been
demonstrated with such passageways to support passenger ratings of 80
and 75 for Douglas DC-10's and Boeing 757's, respectively; and the more
conservative passenger rating of the two was selected for the proposed
rule. As shown by previous tests, the effectiveness of a Type B exit is
maintained by having two uniform parallel lines of evacuees leading to
the exit. Although the exit is not as wide as a Type A exit, the two
parallel lines merge at the exit only to the limited extend needed to
pass through the exit before continuing as two parallel lines down the
assist means (i.e. the inflatable slide). Typically, the evacuees twist
their shoulders a few degrees for the moment in which they are passing
through the exit side-by-side. The delay due to this momentary merging
is reflected in the proposed passenger rating of 75-68% of that of Type
A exits. There is no basis to support arbitrarily reducing it further
to 65.
Contrary to the second commenter's assertion, reducing the width of
the passageway to less than 36 inches would actually be
counterproductive. The evacuees could not be expected to maintain two
uniform parallel lines in a narrow passageway if doing so would
necessitate keeping their shoulders twisted for the entire length of
the passageway. The use of a narrower passageway would, therefore,
disrupt the orderly flow of parallel lines of evacuees to the exit and
result in greatly reduced flow through it.
One commenter believes that an additional exit type should be
defined. The proposed additional type would be similar to proposed Type
B exits except for the use of a single-lane slide. In the absence of
additional test data showing otherwise, it appears that an exit of this
nature might provide egress capability no greater than that of the
proposed Type C exit. In any event, defining this or any other
additional exit type would be beyond the scope of Notice 90-4 and could
not be implemented at this time.
A commenter requests that the capacity of a Type B exit be
demonstrated by any air carrier
[[Page 57953]]
requesting an increase in the number of passenger seats. Compliance
with the emergency evacuation requirements of Sec. 25.803 is already
required for any increase in maximum seating capacity over that
previously shown satisfactory in accordance with that section.
One commenter notes that the proposed maximum corner radii of six
inches is inconsistent with the corresponding requirements for other
exit types that are functions of the exit width. The commenter further
questions whether the maximum corner radii for other exit types is
based on the actual width of the exit or on the minimum required width
for that particular exit type. The commenter then raises the
possibility that the standards should be expressed in terms of minimum
sill width, i.e. door width less the corner radii.
In answer to the commenter's question, the corner radii currently
specified for other exit types are based on the minimum required width
rather than the actual width of the exit. The FAA recognizes that the
current presentation could be misinterpreted in that regard and concurs
that expressing the maximum corner radii in absolute dimensions is
preferable. Although the pertinent parameters are actually the sill
width, as the commenter suggests, and corresponding dimension at the
top of the exit, it appears that requirements expressed in those terms
could easily be misinterpreted, particularly if the door is a
nonstandard oval or trapezoidal shape. After carefully considering the
three methods of presentation, the FAA has concluded that expressing
the requirement in terms of actual corner radii is preferable because
it is least likely to be misinterpreted. Accordingly, Sec. 25.807(a) is
amended to specify maximum corner radii of 8 inches for Type I exits, 7
inches for Type II, Type III and Type A exits, and 6.3 inches for Type
IV exits. For the same reason, Sec. 25.807(g)(9)(ii) specifies corner
radii of 7 inches for tail cone exits. The maximum corner radii for
Type B exits is 6 inches as proposed and 10 inches for Type C exits.
There changes are nonsubstantive because they simply state the same
values in a way less likely to be misinterpreted.
The same commenter asserts that maximum corner radii based on the
minimum exit width are not consistent with structural design principles
(i.e. corner radii should be increased for large cutouts in order to
reduce the stress levels). It must be emphasized that the dimensions
specified in Sec. 25.807 describe the minimum openings. As stated in
Sec. 25.807(d)(5), openings larger than those specified, whether or not
of rectangular shape, may be used if the specified rectangular opening
can be inscribed within the actual opening. The designer can,
therefore, increase corner radii as much as needed for structural or
other considerations simply by increasing the overall size of the exit
opening sufficiently to allow an opening with the specified length,
width and corner radii to be inscribed within the actual opening.
One commenter asserts that the testing conducted by CAMI to support
the passenger rating of proposed Type C exit pairs is invalid because a
dual lane slide was used. As discussed above, Type B exits are wide
enough for the two parallel lines of evacuees to partially merge
momentarily while passing through the exit, then continue down the
assist means in two parallel lines. Type C exits, on the other hand,
are not wide enough for evacuees to form two parallel lines after
passing through the exit. No matter how wide the slide is, evacuees
continue down the slide in one single file. The width of the assist
means, i.e. the slide, used in the CAMI testing of Type C exits is,
therefore, irrelevant.
Three commenters do not believe there is justification for
requiring Type C exits to have assist means regardless of how close
they are to the ground. All of the data presently available to support
the passenger rating for Type C exit pairs are based on tests conducted
with assist means. In the absence of additional test data showing
otherwise, it appears that exits of the dimensions of proposed Type C
exits without assist means would not perform any better than Type I
exits. In any event, defining exits of those dimensions without assist
means would be beyond the scope of Notice 90-4 and could not be
undertaken at this time. Designers would be free to install exits of
those dimensions without assist means; however, the exits would be
considered Type I exits and credited accordingly.
Another commenter supports the development of the Type C exit, but
recommends that the passenger rating be reduced from 55, as proposed,
to 50. The commenter bases this recommendation on the assertion that
more than half of the emergency exits would probably be unavailable in
an actual emergency. As noted earlier, the standards in part 25, and
those proposed in Notice No. 90-4, are based on the assumption that
half of the exits are unusable due to fire, structural damage or other
adverse circumstance. The validity of the commenter's assertion that
more than half would be unusable has not been established: however, it
would be an issue common to all emergency exit types. There is,
therefore, no reason to single out Type C exits and to arbitrarily
reduce the rating of those exits. Any change based on the assertion
that more than half of the exits would be unavailable would be beyond
the scope of Notice 90-4 and could not be adopted at this time.
The commenter also makes a number of recommendations in other areas
that are beyond the scope of this rulemaking, such as minimizing
jamming of exits, dispatch with inoperative doors, optimal width of
passageways to exits and assist space for flight attendants. The
commenter's recommendation concerning width of passageways leading to
exits was addressed, in part, by recently adopted Amendments 25-76,
121-228 and 135-43 (57 FR 19220, May 4, 1992). Any other
recommendations, if found to have merit, would have to be the subject
of future rulemaking.
One commenter believes that the passenger ratings should be
increased for several combinations of Type I, Type II and Type III
exits. The commenter cites consistency with the rest of the proposed
changes in passenger ratings, apparently in the belief that any exit
type should be given the highest passenger rating previously permitted
for that type under any circumstances or with any combination of other
exit types. The FAA does not concur. The fact that ratings would be
changed to remove inconsistencies does not imply that the
inconsistencies must be resolved by simply granting the highest rating
previously given for an exit type under any circumstance. By the same
token, this does not imply that the inconsistencies must be resolved by
arbitrarily granting the lowest rating previously given, as other
commenters seem to believe.
In order to resolve the inconsistencies, preference was generally
given to the more reliable passenger ratings contained in the second
table of Sec. 25.807(d)(1). Where substituting the passenger ratings of
the second table would have resulted in significant increases for
certain combinations of exit types shown in the first table, specific
constraints on their use were proposed in Sec. 25.807(g). As a result,
there was no significant increase in any instance, an insignificant
increase of one passenger seat in three instances, and significant
decreases of 14 and 24 seats in two others. As noted above, the
increase of one seat would be negligible insofar as the egress
capability of the exits is concerned; however, it would be more than
compensated for by the proposed
[[Page 57954]]
improvement in escape slide deployment time in any event. Although most
transport category airplanes are required to have escape slides, some
have exits located close enough to the ground that slides are not
needed. For those, even more time would be afforded for egress since no
time would be needed for slide deployment. No supporting data were
presented to justify either greater or lower passenger ratings;
therefore, the various exit types are rated as proposed.
Two commenters support the proposed reduction in passenger ratings
of closely located Type III exits in proposed Sec. 25.807(g)(7).
Another commenter opposes the proposed reduction and believes that the
primary considerations are integrity of the access and optimized
opening mechanism and hatch weight. The FAA concurs that those are both
important considerations; however, they are not relevant to the
proposal. As noted above, actual demonstrations show that the rate of
egress through one exit is consistently less because some evacuees must
bypass the first exit they reach to use that exit.
A third commeter does not support the proposed reduction in
passenger ratings of closely located Type III exits because, according
to the commenter, extensive full scale evacuation tests have justified
the 70 passenger rating of Type III exits regardless of their spacing
and the exit flow is determined by the exit opening rather than the
aisle flow rate. Again, the comments are not relevant to the proposal.
The issue is not whether the aisle is capable of feeding enough
evacuees to maintain maximum flow nor whether the rating for Type III
exits in general is justified. Instead, the proposed reduction
recognizes that some persons, who must bypass the first exit they reach
and egress through the other exit for maximum total flow to occur,
choose to join the line of evacuees waiting to use the first exit.
Spacing exits farther apart and having more passengers seated between
them reduces or eliminate altogether the number of passengers who must
bypass an exit for maximum total flow.
One commenter believes that the criteria for reduction in the
ratings should be 84 inches between exit centerlines rather than three
passenger seat rows, based on an assumed minimum seat row pitch of 28
inches. As noted above, three passenger seat rows would typically
result in approximately 80 to 90 inches between adjacent vertical edges
of the two exits, or 100 or 120 inches between exit centerlines.
Regardless of the value chosen, the FAA does not concur because the
pertinent parameter is not the measured distance between the exits, per
se, but the number of rows (i.e., the number of passengers) located
between the exits. The comment does, however, raise the possibility
that the phrase `` * * * two Type III exits located within three
passenger seat rows of each other * * * '' could be misinterpreted. To
preclude any confusion in that regard, Sec. 25.807(g)(7), as adopted,
reads`` * * * two Type III exits that are separated by fewer than three
passenger seat rows * * * ''
One commenter does not concur that the combined credit for all Type
III exits should be limited to 70 passengers, i.e., no or very limited
credit given for more than two pairs of Type III exits. The commenter
notes that it is possible to distribute more than two pairs of Type III
exits in airplanes with exceptionally long wing chord, such as
supersonic transports.
The FAA is not aware of any previously type-certificated transport
category airplane with more than two pairs of Type III exits.
Generally, designers have elected to utilize Type III exits only when
they can be located over the wing, inherently limiting airplanes to
only two such exits because of the limited wing chord length available.
As the commenter suggested, it is possible that there may be future
airplanes with extremely long wing chords over which more than two
pairs of Type III exits could be distributed. Also, it is possible to
utilize Type III exits at non-overwing locations. Nevertheless, the use
of more than two pairs of Type III exits would be a novel or unusual
design feature not envisioned at the time the standards for such exits
were developed. Based on information presently available, there are
serious doubts as to the viability of multiple pairs of such exits in
regard to both access within the cabin and orderly escape from them
outside the airplane. In addition, the advisability of fewer larger
exits in favor of having more than two pairs of Type III exits is
questionable. In the absence of extensive additional testing, the FAA
does not concur that the combined credit for all Type III exit pairs
should exceed 70 passengers.
One commenter believes that a 42 inch wide escape route is needed
for two adjacent Type III exits only when the two exits share a common
escape route. (This requirement was proposed as Sec. 25.803(e)(1);
however, it would become Sec. 25.810(c)(1) due to the change in
editorial structure that resulted from Amendment 25-72.) That was, in
fact, the intent of the proposal; however, it appears in light of the
comment that ``adjacent'' may result in varying interpretations. To
preclude any confusion in this regard, Sec. 25.810(c)(1) refers to a
common escape route from two Type III exits rather than an escape route
from adjacent Type III exits.
A commenter believes that there is confusion in proposed
Sec. 25.785(h) between ``near'' and ``adjacent'' in regard to the
proximity of flight attendant seats to Type B exits. Actually, the
proposed rule is the same as current Sec. 25.785(h) insofar as use of
those terms is concerned.
Contrary to the commenter's assertion that the terms are presently
considered interchangeable, the distinction in terminology is used
because Type A and, as proposed, Type B exits must meet a higher
standard than other floor-level exits. Any flight attendant seats
provided must be located in the general vicinity of required floor-
level exits; however, there is no requirement to provide a separate
flight attendant seat for each floor-level exit other than a Type A
exit or, as proposed, a Type B exit. In some instances, the number of
required floor-level exits may exceed the number of flight attendant
seats provided; in that case, one seated flight attendant would be
expected to serve more than one exit, e.g., exits located on opposite
sides of the cabin. The seat provided for that flight attendant can be
located ``near,'' i.e., in the general vicinity of, both exits, but it
would not generally be considered to be located ``adjacent,'' or next
to, both exits--particularly if the exits are located on opposite sides
of the cabin. For Type A and, as proposed, Type B exits, a flight
attendant seat must be provided for each exit and must generally be
located next to the exit, not just in the general vicinity. The
distinction provided by the terms ``near'' and ``adjacent'' is,
therefore, correct.
The same commenter note that proposed Sec. 25.807(e) would require
exits to be distributed as uniformly as `possible,' while earlier
language required them to be distributed as uniformly as practicable.''
Actually, the word ``practicable'' was replaced with ``practical'' when
the requirement was moved to Sec. 25.813 in Amendment 25-72. The FAA
has carefully considered the definition of each of the three terms, as
well as the intent of the rule, and has concluded that the present term
``practical'' is appropriate and should be retained. Advisory Circular
25.807-1 provides guidance material concerning compliance with this
section.
One commenter objects to the proposed requirement that if a Type A,
Type B or Type C exit is installed, there must be at least two Type C
or larger exits installed in each side of the
[[Page 57955]]
fuselage. The commenter asserts that the requirements for uniformity of
passenger exit distribution and the ``certification process'' would
ensure that the loss of one exit would not have a critical impact on
the evacuation capability of the airplane. As noted above, this
requirement was proposed to ensure that adequate evacuation capability
would be maintained in the event a primary exit became unusable. In the
absence of this proposal, it would be possible for a 145 passenger
airplane, for example, to be type certificated with one Type A exit and
one Type III exit in each side of the fuselage. If one of the Type A
exits was unusable due to fire, structural damage or other adverse
circumstance, 38% of the total egress capability would be lost.
Similarly, if both Type A exits were unusable, only 24% of the egress
capability would remain. Contrary to the commenter's assertion, the
requirements for uniformity of passenger exit distribution would not
ensure that the loss of one exit would not have a critical impact on
the evacuation capability of the airplane.
Escape Slide Deployment
Several commenters object to the times specified for erection of
the assist means serving proposed Type C exits; however, none present
any factual data to support their apparent contention that more time
should be permitted for erection. As discussed above, the proposed
erection time is based on the demonstrated capability of current state-
of-the-art devices.
One commenter supports the proposed reduction in erection times,
but notes that essential equipment should not be relocated to the
airplane to achieve those reductions. Since the assist means remains
attached to the airplane, there would be no reason to require any
essential equipment to be attached to the device insofar as it
functions as an assist means. It appears, however, that the commenter
is actually referring to dual-purpose inflatable devices, sometimes
referred to as slide rafts. Slide rafts are designed to remain attached
to the airplane and serve as assist means during an emergency
evacuation on land, or to be detached from the airplane and serve as
liferafts following a ditching. Section 25.1415(c) currently requires
approved survival equipment to be attached to each liferaft, and that
requirement would not be affected by any of the changes proposed in
Notice 90-4.
Some commenters also object to initiating the measurement of
erection time when the means for opening the exit is actuated rather
than when erection is begun, as is currently specified for other exit
types. It is not clear whether their intent is to achieve a more
relaxed total deployment interval by specifying that the device must be
fully erect within 10 seconds after erection is begun, or whether they
simply object to including exit opening in the time interval regardless
of the total time permitted. In contrast, another commenter, a foreign
airworthiness authority, recommends that the erection duration and
starting time requirements for other types of exits should also be
consistent with those proposed for new Type C exits.
As noted above, the proposed erection time is based on current
state-of-the-art, and the FAA does not concur that a more relaxed total
deployment interval is justified. Including exit actuation time in the
total deployment interval actually provides the designer more
flexibility in achieving the desired goal. If the exit opening time is
especially rapid, there would be more time available for erection of
the assist device. On the contrary, if the erection time is especially
rapid, there would be more time available for exit opening. The other
commenter's recommendation that the erection duration and starting time
requirements for other types of exits should be consistent with those
proposed for Type C exits appears to have merit. Although it is beyond
the scope of Notice 90-4, it will be considered for possible future
rulemaking.
One commenter, a manufacturer of inflatable assist means, questions
what constitutes when ``deployment is begun'' and suggests the phrase
``actuation of the inflation controls is begun'' be used instead. The
commenter notes that the latter phrase is used in Technical Standard
Order (TSO) C69b which contains design standards for off-wing escape
slides.
Generally, the two phrases are interchangeable since the assist
means are inflatable devices. Since TSO-C69b pertains specifically to
inflatable devices, the phrase ``actuation of the inflation controls is
begun'' is appropriate in that document. Unlike the TSO, part 25 does
not require the assist means to be an inflatable device. It would,
therefore, be inappropriate to use that phrase in part 25 since the
assist means may, in fact, not be an inflatable device. For the same
reason, the FAA concurs with another commenter that the phrase
``actuation of the inflation system'' in proposed Sec. 25.809(h) is
inappropriate. This requirement, now contained in Sec. 25.810(d)(4),
has been changed to read, ``actuation for the erection system.''
Adoption of the Final Rule
As noted above, the editorial structure of certain portions of part
25 was changed considerably subsequent to the publication of Notice 90-
4. Except for the substantive changes discussed above and a number of
non-substantive changes made for conformity with part 25 as it is not
structured, the amendments are adopted as proposed in Notice 90-4.
Final Regulatory Evaluation, Final Regulatory Flexibility
Determination, and Trade Impact Assessment
Proposed changes to Federal Regulations must undergo several
economic analyses. First, Executive Order 12866 directs that each
Federal agency propose or adopt a regulation only upon a reasoned
determination that the benefits of the intended regulation justify its
costs. Second, the Regulatory Flexibility Act of 1980 requires agencies
to analyze the economic effect of regulatory changes on small entities.
Third, the Office of Management and Budget directs agencies to assess
the effects of regulatory changes on international trade. In conducting
these analyses, the FAA has determined that this rule: (1) will
generate benefits that justify its costs but because of the public
interest is a ``significant regulatory action'' as defined in the
Executive Order; (2) is ``significant'' as defined in DOT's Regulatory
Policies and Procedures; (3) will not have a significant impact on a
substantial number of small entities; and (4) will not constitute a
barrier to international trade. These analyses, available in the
docket, are summarized below.
Regulatory Evaluation Summary
Exits
Overall, changes to the types and number of required passenger
emergency exits will not likely result in significant modifications to
cabin interiors nor result in significant cost differentials, either
positive or negative. Part 25 airplane exit configurations are variable
and are seldom at the maximum limit in terms of passengers per exit.
Any increases in costs would be far outweighed by the benefits of
enhanced design flexibility, consistency in standards, and improved
evacuation capabilities.
The addition of Type B and Type C exits will provide manufacturers
with increased design flexibility. Configurations with Types B and C
exits will likely cost no more, and potentially less, than
configurations without these exits since manufacturers will most
[[Page 57956]]
likely not utilize them unless it is cost-effective to do so.
The revisions relating to Type I exits could increase costs in
certain instances. The current standards allow an increase in passenger
seating configuration ranging from 45 to 70 for each additional Type I
exit pair, depending on airplane exit configuration and total passenger
seating capacity. The revisions will limit the allowed increase for
Type I exit pairs to 45 passengers for all exit configurations and
seating capacities.
Limiting Type I exit pairs to 45 passengers will improve safety. It
is clear that 45 passengers can evacuate through a pair of Type I exits
more expeditiously than can a greater number. An aircraft having two
pairs of Type I exits and two pairs of Type III exits can have 179
passengers under the current standards but only 155 passengers under
the revised standards, a reduction of 13 percent. However, a
manufacturer of a design which includes 179 passengers (with two pairs
each of Type I and Type III exits) that desires to maintain that
capacity could, under the revised standards, replace the two Type I
exit pairs with Type C exit pairs (the two new Type C pairs allow 110
passengers and the two Type III pairs another 70 for a total of 180
passengers). Evacuation from an airplane with the modified
configuration would be easier since the Type C exit is six inches wider
than the Type I exit. Benefits resulting from this safety enhancement
would easily exceed any incremental design/manufacturing costs.
While it is difficult to estimate the number of fatalities or
injuries that might be avoided by the revised rule, studies have shown
that exit flow rates are proportional to exit widths within the 24 to
42 inch range. In one study, the evacuation rate increased by one
occupant every 12 seconds for each six inch increase in exit width
(``Study of FAR Sec. 25.807(c) Emergency Exits,'' FAA Aeronautical
Center, May 1975, Project Report No. 70-597-120A). In another study,
the National Bureau of Standards (NBS) (since renamed the National
Institute for Standards and Technology), analyzed accidents involving
fire and fatalities that occurred between 1965 and 1982 and estimated
the number of fatalities that could have been avoided if passengers had
additional time to escape as a result of reduced seat cushion
flammability (`Decision Analysis Model for Passenger-Aircraft Fire
Safety with Application to Fire Blocking of Seats,'' National Bureau of
Standards, March 1984, NBSTR 84-2817, DOT/FAA/CT/84-8). NBS estimated
that of 712 fire fatalities during the period analyzed, 109 could have
been avoided if there had been 20 additional seconds of evacuation time
(a rate of 3 lives saved per 100 million passenger enplanements). While
having more time to evacuate an airplane is not the same as being able
to evacuate an airplane faster, it can nevertheless serve as a proxy
for estimating benefits, because the end result is the same--more
passengers can egress before fire or explosion makes egress impossible.
Reduced crowding at exits and the consequent decrease in evacuation
time resulting from the revised exit standards could potentially save
several lives in just one accident.
Escape Slides
The reduced time allowed for escape slide erection will provide
faster emergency evacuation rates and potentially prevent some
fatalities or injuries that otherwise might be sustained. The
technology to meet the revised standard is available and will not add
to the cost of slides. The rule changes basically update slide
requirements to current technology. Since costs will be unaffected and
safety enhanced, the revisions are cost beneficial.
Regulatory Flexibility Determinations
The Regulatory Flexibility Act of 1980 (RFA) was enacted by
Congress to ensure that small entities are not unnecessarily and
disproportionately burdened by Government regulations. The FRA requires
agencies to assess whether rules would have ``a significant economic
impact on a substantial number of small entities,'' and in cases where
they would, to conduct a Regulatory Flexibility Analysis. The FAA size
threshold for a small aircraft manufacturer is 75 or fewer employees
(per FAA Order 2100.14A, Regulatory Flexibility Criteria and Guidance).
Since there are no manufacturers of part 25 airplanes with 75 or fewer
employees, the rule will not have ``a significant economic impact on a
substantial number of small entities.''
International Trade Impact Assessment
The rule will have no effect on the sale of U.S. airplanes in
foreign markets or the sale of foreign airplanes in the U.S.
Federalism Implications
The regulations adopted herein will not have substantial direct
effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government. Therefore, in
accordance with Executive Order 12612, it is determined that this final
rule will not have sufficient federalism implications to warrant the
preparation of a Federalism Assessment.
Conclusion
For the reasons given earlier in the preamble, the FAA has
determined that this is a ``significant'' regulation as defined in
Executive Order 12866 and is ``significant'' as defined in Department
of Transportation Regulatory Policies and Procedures (44 FR 11034;
February 26, 1979) because of the public interest involved. In
addition, it is certified under the criteria of the Regulatory
Flexibility Act that this regulation will not have a significant
economic impact, positive or negative, on a substantial number of small
entities.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting and recordkeeping
requirements.
Adoption of Amendment
Accordingly, the FAA amends 14 CFR part 25 of the Federal Aviation
Regulations (FAR), as follows:
PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES
1. The authority citation for part 25 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701, 44702 and 44704.
2. By amending Sec. 25.783 by revising paragraph (h) to read as
follows:
Sec. 25.783 Doors.
* * * * *
(h) Each passenger entry door in the side of the fuselage must meet
the applicable requirements of Secs. 25.807 through 25.813 for a Type
II or larger passenger emergency exit.
* * * * *
3. By amending Sec. 25.785 by revising paragraph (h)(1) to read as
follows:
Sec. 25.785 Seats, berths, safety belts, and harnesses.
* * * * *
(h) * * *
(1) Near a required floor level emergency exit, except that another
location is acceptable if the emergency egress of passengers would be
enhanced with that location. A flight attendant seat must be located
adjacent to each Type A or B emergency exit. Other flight attendant
seats must be evenly distributed among the required floor-
[[Page 57957]]
level emergency exits to the extent feasible.
* * * * *
4. By amending Sec. 25.807 by revising paragraphs (a)(1) through
(a)(4), (a)(7), and (d) through (f) and by adding paragraphs (a)(8),
(a)(9), and (g) through (i) to read as follows:
Sec. 25.807 Emergency exits.
(a) * * *
(1) Type I. This type is a floor-level exit with a rectangular
opening of not less than 24 inches wide by 48 inches high, with corner
radii not greater than eight inches.
(2) Type II. This type is a rectangular opening of not less than 20
inches wide by 44 inches high, with corner radii not greater than seven
inches. Type II exits must be floor-level exits unless located over the
wing, in which case they must not have a step-up inside the airplane of
more than 10 inches nor a step-down outside the airplane of more than
17 inches.
(3) Type III. This type is a rectangular opening of not less than
20 inches wide by 36 inches high with corner radii not greater than
seven inches, and with a step-up inside the airplane of not more than
20 inches. If the exit is located over the wing, the step-down outside
the airplane may not exceed 27 inches.
(4) Type IV. This type is a rectangular opening of not less than 19
inches wide by 26 inches high, with corner radii not greater than 6.3
inches, located over the wing, with a step-up inside the airplane of
not more than 29 inches and a step-down outside the airplane of not
more than 36 inches.
* * * * *
(7) Type A. This type is a floor-level exit with a rectangular
opening of not less than 42 inches wide by 72 inches high, with corner
radii not greater than seven inches.
(8) Type B. This type is a floor-level exit with a rectangular
opening of not less than 32 inches wide by 72 inches high, with corner
radii not greater than six inches.
(9) Type C. This type is a floor-level exit with a rectangular
opening of not less than 30 inches wide by 48 inches high, with corner
radii not greater than 10 inches.
* * * * *
(d) Asymmetry. Exits of an exit pair need not be diametrically
opposite each other nor of the same size; however, the number of
passenger seats permitted under paragraph (g) of this section is based
on the smaller of the two exits.
(e) Uniformity. Exits must be distributed as uniformly as
practical, taking into account passenger seat distribution.
(f) Location. (1) Each required passenger emergency exit must be
accessible to the passengers and located where it will afford the most
effective means of passenger evacuation.
(2) If only one floor-level exit per side is prescribed, and the
airplane do not have a tail-cone or ventral emergency exit, the floor-
level exits must be in the rearward part of the passenger compartment
unless another location affords a more effective means of passenger
evacuation.
(3) If more than one floor-level exit per side is prescribed, and
the airplanes does not have a combination cargo and passenger
configuration, at least one floor-level exit must be located in each
side near each end of the cabin.
(g) Type and number required. The maximum number of passenger seats
permitted depends on the type and number of exits installed in each
side of the fuselage. Except as further restricted in paragraphs (g)(1)
through (g)(9) of this section, the maximum number of passenger seats
permitted for each exit of a specific type installed in each side of
the fuselage is as follows:
Type A 110
Type B 75
Type C 55
Type I 45
Type II 40
Type III 35
Type IV 9
(1) For a passenger seating configuration of 1 to 9 seats, there
must be at least one Type IV or larger overwing exit in each side of
the fuselage or, if overwing exits are not provided, at least one exit
in each side that meets the minimum dimensions of a Type III exit.
(2) For a passenger seating configuration of more than 9 seats,
each exit must be a Type III or larger exit.
(3) For a passenger seating configuration of 10 to 19 seats, there
must be at least one Type III or larger exit in each side of the
fuselage.
(4) For a passenger seating configuration of 20 to 40 seats, there
must be at least two exits, one of which must be a Type II or larger
exit, in each side of the fuselage.
(5) For a passenger seating configuration of 41 to 110 seats, there
must be at least two exits, one of which must be a Type I or larger
exit, in each side of the fuselage.
(6) For a passenger seating configuration of more than 110 seats,
the emergency exits in each side of the fuselage must include at least
two Type I or larger exits.
(7) The combined maximum number of passenger seats permitted for
all Type III exits is 70, and the combined maximum number of passenger
seats permitted for two Type III exits in each side of the fuselage
that are separated by fewer than three passenger seat rows in 65.
(8) If a Type A, Type B, or Type C exit is installed, there must be
at least two Type C or larger exits in each side of the fuselage.
(9) If a passenger ventral of tail cone exit is installed and that
exit provides at least the same rate of egress as a Type III exit with
the airplane in the most adverse exit opening condition that would
result from the collapse of one or more legs of the landing gear, an
increase in the passenger seating configuration is permitted as
follows:
(i) For a ventral exit, 12 additional passenger seats.
(ii) For a tail cone exit incorporating a floor level opening of
not less than 20 inches wide by 60 inches high, with corner radii not
greater than seven inches, in the pressure shell and incorporating an
approved assist means in accordance with Sec. 25.810(a), 25 additional
passenger seats.
(iii) For a tail cone exit incorporating an opening in the pressure
shell which is at least equivalent to a Type III emergency exit with
respect to dimensions, step-up and step-down distance, and with the top
of the opening not less than 56 inches from the passenger compartment
floor, 15 additional passenger seats.
(h) Excess exits. Each emergency exit in the passenger compartment
in excess of the minimum number of required emergency exits must meet
the applicable requirements of Sec. 25.809 through Sec. 25.812, and
must be readily accessible.
(i) Ditching emergency exits for passengers. Whether or not
ditching certification is requested, ditching emergency exits must be
provided in accordance with the following requirements, unless the
emergency exits required by paragraph (g) of this section already meet
them:
(1) For airplanes that have a passenger seating configuration of
nine or fewer seats, excluding pilot seats, one exit above the
waterline in each side of the airplane, meeting at least the dimensions
of a Type IV exit.
(2) For airplanes that have a passenger seating configuration of 10
of more seats, excluding pilot seats, one exit above the waterline in a
side of the airplane, meeting at least the dimensions of a Type III
exit for each unit (or part of a unit) of 35 passenger seats, but no
less than two such exits in the passenger cabin, with one on each side
of the airplane. The passenger seat/
[[Page 57958]]
exit ratio may be increased through the use of larger exits, or other
means, provided it is shown that the evacuation capability during
ditching has been improved accordingly.
(3) If it is impractical to locate side exits above the waterline,
the side exits must be replaced by an equal number of readily
accessible overhead hatches of not less than the dimensions of a Type
III exit, except that for airplanes with a passenger configuration of
35 or fewer seats, excluding pilot seats, the two required Type III
side exits need be replaced by only one overhead hatch.
5. By amending Sec. 25.810 by revising paragraphs (a) introductory
text, (a)(1) introductory text, (a)(1)(ii), (b), (c)(1), and (d) to
read as follows:
Sec. 25.810 Emergency egress assist means and escape routes.
(a) Each non over-wing Type A, Type B or Type C exit, and any other
non over-wing landplane emergency exit more than 6 feet from the ground
with the airplane on the ground and the landing gear extended, must
have an approved means to assist the occupants in descending to the
ground.
(1) The assisting means for each passenger emergency exit must be a
self-supporting slide or equivalent; and, in the case of Type A or Type
B exits, it must be capable of carrying simultaneously two parallel
lines of evacuees. In addition, the assisting means must be designed to
meet the following requirements--
* * * * *
(ii) Except for assisting means installed at Type C exits, it must
be automatically erected within 6 seconds after deployment is begun.
Assisting means installed at Type C exits must be automatically erected
within 10 seconds from the time the opening means of the exit is
actuated.
* * * * *
(b) Assist means from the cabin to the wing are required for each
type A or Type B exit located above the wing and having a stepdown
unless the exit without an assist-means can be shown to have a rate of
passenger egress at least equal to that of the same type of non over-
wing exit. If an assist means is required, it must be automatically
deployed and automatically erected concurrent with the opening of the
exit. In the case of assist means installed at Type C exits, it must be
self-supporting within 10 seconds from the time the opening means of
the exits is actuated. For all other exit types, it must be self-
supporting 6 seconds after deployment is begun.
(c) * * *
(1) The escape route from each Type A or Type B passenger emergency
exit, or any common escape route from two Type III passenger emergency
exits, must be at least 42 inches wide; that from any other passenger
emergency exit must be at least 24 inches wide; and
* * * * *
(d) Means must be provided to assist evacuees to reach the ground
for all Type C exits located over the wing and, if the place on the
airplane structure at which the escape route required in paragraph (c)
of this section terminates is more than 6 feet from the ground with the
airplane on the ground and the landing gear extended, for all other
exit types.
(1) If the escape route is over the flap, the height of the
terminal edge must be measured with the flap in the takeoff or landing
position, whichever is higher from the ground.
(2) The assisting means must be usable and self-supporting with one
or more landing gear legs collapsed and under a 25-knot wind directed
from the most critical angle.
(3) The assisting means provided for each escape route leading from
a Type A or B emergency exit must be capable of carrying simultaneously
tow parallel lines of evacuees; and, the assisting means leading from
any other exit type must be capable of carrying as many parallel lines
of evacuees as there are required escape routes.
(4) The assisting means provided for each escape route leading from
a Type C exit must be automatically erected within 10 seconds from the
time the opening means of the exit is actuated, and that provided for
the escape route leading from any other exit type must be automatically
erected within 10 seconds after actuation of the erection system.
6. By amending Sec. 25.811 by revising the introductory texts of
paragraphs (e)(2) and (e)(4) to read as follows:
Sec. 25.811 Emergency exit marking.
* * * * *
(e) * * *
(2) Each Type A, Type B, Type C or Type I passenger emergency exit
operating handle must--
* * * * *
(4) Each Type A, Type B, Type C, Type I, or Type II passenger
emergency exit with a locking mechanism released by rotary motion of
the handle must be marked--
* * * * *
7. By amending Sec. 25.812 by revising paragraph (g)(1)(ii) to read
as follows:
Sec. 25.812 Emergency lighting.
* * * * *
(g) * * *
(1) * * *
(ii) Not less than 0.05 foot-candle (measured normal to the
direction of incident light) along the 30 percent of the slip-resistant
portion of the escape route required in Sec. 25.810(c) that is farthest
from the exit for the minimum required width of the escape route; and
* * * * *
8. By amending Sec. 25.813 by revising paragraphs (a) introductory
text, (a)(1), and (b) to read as follows:
Sec. 25.813 Emergency exit access.
* * * * *
(a) There must be a passageway leading from the nearest main aisle
to each Type A, Type B, Type C, Type I, or Type II emergency exit and
between individual passenger areas. Each passageway leading to a Type A
or Type B exit must be unobstructed and at least 36 inches wide.
Passageways between individual passenger areas and those leading to
Type I, Type II, or Type C emergency exits must be unobstructed and at
least 20 inches wide. Unless there are two or more main aisles, each
Type A or B exit must be located so that there is passenger flow along
the main aisle to that exit from both the forward and aft directions.
If two or more main aisles are provided, there must be unobstructed
cross-aisles at least 20 inches wide between main aisles. There must
be--
(1) A cross-aisle which leads directly to each passageway between
the nearest main aisle and a Type A or B exit; and
* * * * *
(b) Adequate space to allow crewmember(s) to assist in the
evacuation of passengers must be provided as follows:
(1) The assist space must not reduce the unobstructed width of the
passageway below that required for the exit.
(2) For each Type A or Type B exit, assist space must be provided
at each side of the exit regardless of whether a means is required by
Sec. 25.810(a) to assist passengers in descending to the ground from
that exit.
(3) Assist space must be provided at one side of any other type
exit required by Sec. 25.810(a) to have a means to assist passengers in
descending to the ground from that exit.
* * * * *
Issued in Washington, D.C., on November 1, 1996.
David R. Hinson,
Administrator.
[FR Doc. 96-28650 Filed 11-7-96; 8:45 am]
BILLING CODE 4910-13-M