[Federal Register Volume 65, Number 197 (Wednesday, October 11, 2000)]
[Rules and Regulations]
[Pages 60343-60347]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-26016]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM176; Special Conditions No. 25-165-SC]


Special Conditions: British Aerospace Jetstream 4101 Series 
Airplanes; Seats with Inflatable Lapbelts

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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SUMMARY: These special conditions are issued for British Aerospace 
(BAE) Systems Jetstream Model 4101 series airplanes, modified by BAE 
Systems to include seats with inflatable lapbelts. The applicable 
airworthiness regulations do not contain adequate or appropriate safety 
standards for this design feature. These special conditions contain the 
additional safety standards that the Administrator considers necessary 
to establish a level of safety equivalent to that established by the 
existing airworthiness standards.

DATES: The effective date of these special conditions is September 28, 
2000. Comments must be received on or before November 13, 2000.

ADDRESSES: Submit comments in duplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114,

[[Page 60344]]

Attention: Rules Docket No. NM176, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056. Comments may be inspected at this location 
between 7:30 a.m. and 4 p.m., Monday through Friday, except Federal 
holidays. Comments may be submitted via fax to (425) 227-1232. Comments 
may also be sent via the Internet using the following address: [email protected]. Comments sent via fax or the Internet must contain 
``Docket No. NM176'' in the subject line and need not be submitted in 
triplicate. Comments sent via the Internet as attached electronic files 
must be formatted in Microsoft Word 97 for Windows or ASCII text.

FOR FURTHER INFORMATION CONTACT: Todd Thompson, International Branch, 
ANM-116, Transport Airplane Directorate, Aircraft Certification 
Service, FAA, 1601 Lind Avenue SW., Renton, Washington, 98055-4056; 
telephone (206) 227-1175; facsimile (425) 227-1149.

SUPPLEMENTARY INFORMATION: The FAA has determined that notice and 
opportunity for prior public comment hereon are impracticable because 
these procedures would significantly delay issuance of the approval 
design and thus delivery of the affected airplanes.

Comments Invited

    Interested persons are invited to submit such written data, views, 
or arguments as they may desire. Communications should identify the 
Rules Docket number identified above and be submitted in duplicate to 
the address specified above. All communications received on or before 
the closing date for comments specified above will be considered. The 
special conditions may be changed in light of the comments received.
    All comments received will be available in the Rules Docket for 
examination by interested persons, both before and after the closing 
date for comments. A report summarizing each substantive public contact 
with FAA personnel concerning this rulemaking will be filed in the 
Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this request must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number NM176.'' The postcard will be date stamped and 
returned to the commenter.

Background

    On April 28, 1999, British Aerospace Systems applied for a change 
to Type Certificate No. A41NM for the installation of an Amsafe 
inflatable airbag-seatbelt for the front row passenger seats in the 
British Aerospace System Jetstream 4101 series airplane. The Model 4101 
series airplane is a straight-wing, conventional-tail, twin-engine, 
turboprop-powered transport. The inflatable lapbelt is designed to 
limit occupant forward excursion in the event of an accident. This will 
reduce the potential for head injury, thereby reducing the Head Injury 
Criteria (HIC) measurement. The inflatable lapbelt behaves similarly to 
the fixed mounted airbag, but in this case the airbag is integrated 
into the lapbelt, and deploys away from the seated occupant. While 
airbags are now standard in the automotive industry, the use of an 
inflatable lapbelt is novel for commercial aviation.
    Title 14 Code of Federal Regulations (14 CFR) Sec. 25.785 requires 
that occupants be protected from head injury by either the elimination 
of any injurious object within the striking radius of the head, or by 
padding. Traditionally, this has required a set back of 35" from any 
bulkhead or other rigid interior feature or, where not practical, 
specified types of padding. The relative effectiveness of these means 
of injury protection was not quantified. With the adoption of Amendment 
25-64 to part 25, a new standard that quantifies required head injury 
protection was created.
    Section 25.562 specifies that dynamic tests must be conducted for 
each seat type installed in the airplane. In particular, the 
regulations require that persons not suffer serious head injury under 
the conditions specified in the tests, and that a HIC measurement of 
not more than 1000 units be recorded, should contact with the cabin 
interior occur. While the test conditions described in this section are 
specific, it is the intent of the requirement that an adequate level of 
head injury protection be provided for crash severity up to and 
including that specified. In addition HIC is the only available 
quantifiable measure of head injury protection. Therefore, the FAA will 
require that a HIC of less than 1000 be demonstrated for occupants of 
seats incorporating the inflatable lapbelt.
    Because Sec. 25.562, Sec. 25.785, and associated guidance do not 
adequately address seats with inflatable lapbelts, the FAA recognizes 
that appropriate pass/fail criteria need to be developed that do fully 
address the safety concerns specific to occupants of these seats.
    The inflatable lapbelt has two potential advantages over other 
means of head impact protection. First, it can provide significantly 
greater protection than would be expected with energy absorbing pads, 
for example, and second, it can provide essentially equivalent 
protection for occupants of all stature. These are significant 
advantages from a safety standpoint, since such devices will likely 
provide a level of safety that exceeds the minimum standards of the 
Federal Aviation Regulations (FAR). Conversely, airbags in general are 
active systems, and must be relied upon to activate properly when 
needed, as opposed to an energy absorbing pad or upper torso restraint 
that is passive, and always available. These potential advantages must 
be balanced against the potential disadvantages in order to develop 
standards that will provide an equivalent level of safety to that 
intended by the regulations.
    The FAA has considered the installation of inflatable lapbelts to 
have two primary safety concerns: first, that they perform properly 
under foreseeable operating conditions, and second, that they do not 
perform in a manner or at such times as would constitute a hazard to 
the airplane or occupants. This latter point has the potential to be 
the more rigorous of the requirements, owing to the active nature of 
the system. With this philosophy in mind, the FAA has considered the 
following as a basis for the special conditions.
    The inflatable lapbelt will rely on electronic sensors for 
signaling and pyrotechnic charges for activation so that it is 
available when needed. These same devices could be susceptible to 
inadvertent activation, causing deployment in a potentially unsafe 
manner. The consequences of such deployment must be considered in 
establishing the reliability of the system. BAE Systems must 
substantiate that the effects of an inadvertent deployment in flight 
are either not a hazard to the airplane, or that such deployment is an 
extremely improbable occurrence (less than 10-9 per flight 
hour). The effect of an inadvertent deployment on a passenger or 
crewmember that might be positioned close to the airbag should also be 
considered. The person could be either standing or sitting. A minimum 
reliability level will have to be established for this case, depending 
upon the consequences, even if the effect on the airplane is 
negligible.
    The potential for an inadvertent deployment could be increased as a 
result of conditions in service. The installation must take into 
account wear and tear so that the likelihood of an inadvertent 
deployment is not increased to an unacceptable level. In this context, 
an appropriate inspection interval and self-test capability are 
considered

[[Page 60345]]

necessary. Other outside influences are lightning and high intensity 
electromagnetic fields (HIRF). Since the sensors that trigger 
deployment are electronic, they must be protected from the effects of 
these threats. Existing Special Conditions No. 25-ANM-48 regarding 
lightning and HIRF are therefore applicable. For the purposes of 
compliance with those special conditions, if inadvertent deployment 
could cause a hazard to the airplane, the airbag is considered a 
critical system; if inadvertent deployment could cause injuries to 
persons, the airbag should be considered an essential system. Finally, 
the airbag installation should be protected from the effects of fire, 
so that an additional hazard is not created by, for example, a rupture 
of the pyrotechnic squib.
    In order to be an effective safety system, the airbag must function 
properly and must not introduce any additional hazards to occupants as 
a result of its functioning. There are several areas where the airbag 
differs from traditional occupant protection systems, and requires 
special conditions to ensure adequate performance.
    Because the airbag is essentially a single use device, there is the 
potential that it could deploy under crash conditions that are not 
sufficiently severe as to require head injury protection from the 
airbag. Since an actual crash is frequently composed of a series of 
impacts before the airplane comes to rest, this could render the airbag 
useless if a larger impact follows the initial impact. This situation 
does not exist with energy absorbing pads or upper torso restraints, 
which tend to provide protection according to the severity of the 
impact. Therefore, the airbag installation should be such that the 
airbag will provide protection when it is required, and will not expend 
its protection when it is not needed. There is no requirement for the 
airbag to provide protection for multiple impacts, where more than one 
impact would require protection.
    Since each occupant's restraint system provides protection for that 
occupant only, the installation must address seats that are unoccupied. 
It will be necessary to show that the required protection is provided 
for each occupant regardless of the number of occupied seats, and 
considering that unoccupied seats may have lapbelts that are active.
    Since a wide range of occupants could occupy a seat, the inflatable 
lapbelt should be effective for a wide range of occupants. The FAA has 
historically considered the range from the fifth percentile female to 
the ninety-fifth percentile male as the range of occupants that must be 
taken into account. In this case, the FAA is proposing consideration of 
a larger range of occupants, due to the nature of the lapbelt 
installation and its close proximity to the occupant. In a similar 
vein, these persons could have assumed the brace position, for those 
accidents where an impact is anticipated. Test data indicate that 
occupants in the brace position may not require supplemental 
protection, and so it would not be necessary to show that the 
inflatable lapbelt will enhance the brace position. However, the 
inflatable lapbelt must not introduce a hazard in that case by 
deploying into the seated, braced occupant.
    Another area of concern is the use of seats so equipped by children 
whether lap-held, in approved child safety seats, or occupying the seat 
directly. Similarly, if a pregnant woman occupies the seat, the 
installation needs to address such usage, either by demonstrating that 
it will function properly, or by adding appropriate limitation on 
usage.
    Since the inflatable lapbelt will be electrically powered, there is 
the possibility that the system could fail due to a separation in the 
fuselage. Since this system is intended as crash/post-crash protection 
means, failure due to fuselage separation is not acceptable. As with 
emergency lighting, the system should function properly if such a 
separation occurs at any point in the fuselage. A separation that 
occurs at the location of the inflatable lapbelt would not have to be 
considered.
    Since the inflatable lapbelt is likely to have a large volume 
displacement, the inflated bag could potentially impede egress of 
passengers. Since the bag deflates to absorb energy, it is likely that 
an inflatable lapbelt would be deflated at the time that persons would 
be trying to leave their seats. Nonetheless, it is considered 
appropriate to specify a time interval after which the inflatable 
lapbelt may not impede rapid egress. Ten seconds has been chosen as a 
reasonable time since this corresponds to the maximum time allowed for 
an exit to be openable. In actuality, it is unlikely that an exit would 
be prepared this quickly in an accident severe enough to warrant 
deployment of the inflatable lapbelt, and the inflatable lapbelt will 
likely deflate much quicker than ten seconds.
    Finally, it should be noted that the special conditions are 
certification requirements applied to the inflatable lapbelt system as 
installed. The special conditions are not an installation approval. 
Therefore, while the special conditions relate to each such system 
installed, the overall installation approval is a separate finding and 
must consider the combined effects of all such systems installed.

Type Certification Basis

    Under the provisions of Sec. 21.101, BAE Systems must show that the 
Model 4101 series airplanes, as changed, continue to meet the 
applicable provisions of the regulations incorporated by reference in 
Type Certificate No. A41NM or the applicable regulations in effect on 
the date of application for the change. The regulations incorporated by 
reference in the type certificate are commonly referred to as the 
``original type certification basis.'' The regulations incorporated by 
reference in Type Certificate No. A41NM are as follows: Amendments 25-1 
through 25-66 with exceptions. The U.S. type certification basis for 
the Model 4101 is established in accordance with Secs. 21.29 and 21.17, 
and the type certification application date to the United Kingdom Civil 
Aviation Authority. The U.S. type certification basis is listed in Type 
Certificate Data Sheet No. A41NM.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., part 25 as amended) do not contain adequate or 
appropriate safety standards for the Model 4101 series airplanes 
because of a novel or unusual design feature, special conditions are 
prescribed under the provisions of Sec. 21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Model 4101 must comply with the fuel vent and exhaust 
emission requirements of part 34 and the noise certification 
requirements of part 36.
    Special conditions, as appropriate, are issued in accordance with 
Sec. 11.49 after public notice, as required by Secs. 11.28 and 
11.29(b), and become part of the type certification basis in accordance 
with Sec. 21.101(b)(2).
    Special conditions are initially applicable to the model for which 
they are issued. Should the applicant apply for a supplemental type 
certificate to modify any other model included on the same type 
certificate to incorporate the same novel or unusual design feature, 
the special conditions would also apply to the other model under the 
provisions of Sec. 21.101(a)(1).

Novel or Unusual Design Features

    The Model 4101 series airplanes will incorporate the following 
novel or unusual design features. BAE Systems plans to install an 
Amsafe Inc, inflatable lapbelt on the front row passenger seats

[[Page 60346]]

of the Model 4101 series airplanes, in order to reduce the potential 
for head injury in the event of an accident. The inflatable lapbelt 
works similarly to an automotive airbag, except that the airbag is 
integrated with the lap belt of the restraint system.
    The CFR states the performance criteria for head injury protection 
in objective terms. However, none of these criteria are adequate to 
address the specific issues raised concerning seats with inflatable 
lapbelts. The FAA has therefore determined that, in addition to the 
requirements of part 25, special conditions are needed to address 
requirements particular to installation of seats with inflatable 
lapbelts.
    Accordingly, in addition to the passenger injury criteria specified 
in Sec. 25.785, these special conditions are adopted for the BAE Model 
4101 series airplanes equipped with inflatable lapbelts. Other 
conditions may be developed, as needed, based on further FAA review and 
discussions with the manufacturer and civil aviation authorities.

Discussion

    From the standpoint of a passenger safety system, the airbag is 
unique in that it is both an active and entirely autonomous device. 
While the automotive industry has good experience with airbags, the 
conditions of use and reliance on the airbag as the sole means of 
injury protection are quite different. In automobile installations, the 
airbag is a supplemental system and works in conjunction with an upper 
torso restraint. In addition, the crash event is more definable and of 
typically shorter duration, which can simplify the activation logic. 
The airplane-operating environment is also quite different from 
automobiles and includes the potential for greater wear and tear, and 
unanticipated abuse conditions (due to galley loading, passenger 
baggage, etc.); airplanes also operate where exposure to high intensity 
electromagnetic fields could affect the activation system.
    The following special conditions can be characterized as addressing 
either the safety performance of the system, or the system's integrity 
against inadvertent activation. Because a crash requiring use of the 
airbags is a relatively rare event, and because the consequences of an 
inadvertent activation are potentially quite severe, these latter 
requirements are probably the more rigorous from a design standpoint.

Applicability

    As discussed above, these special conditions are applicable to the 
Model 4101 series airplanes. Should BAE Systems apply at a later date 
for modification of any other model included on Type Certificate No. 
A41NM to incorporate the same novel or unusual design feature, the 
special conditions would apply to that model as well under the 
provisions of Sec. 21.101(a)(1).

Conclusion

    This action affects only certain novel or unusual design features 
on the BAE Systems Model 4101 series airplanes. It is not a rule of 
general applicability, and it affects only the applicant who applied to 
the FAA for approval of these features on the airplane.

Immediate Adoption of Special Conditions

    The substance of these special conditions has been subject to the 
notice and comment period in two prior instances and has been derived 
without substantive change from those previously issued. It is unlikely 
that prior public comment would result in a significant change from the 
substance contained herein. For this reason, and because a delay would 
significantly affect the certification of the airplane, which is 
imminent, the FAA has determined that prior public notice and comment 
are unnecessary and impracticable, and good cause exists for adopting 
these special conditions upon issuance. The FAA is requesting comments 
to allow interested persons to submit views that may not have been 
submitted in response to the prior opportunities for comment described 
above.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

Authority Citation

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type certification basis for British Aerospace (BAE) Systems Model 
4101 series airplanes equipped with Amsafe inflatable lapbelts.
    1. Seats With Inflatable Lapbelts. It must be shown that the 
inflatable lapbelt will deploy and provide protection under crash 
conditions where it is necessary to prevent serious head injury. The 
means of protection must take into consideration a range of stature 
from a two-year-old child to a ninety-fifth percentile male. The 
inflatable lapbelt must provide a consistent approach to energy 
absorption throughout that range. In addition, the following situations 
must be considered:

    a. The seat occupant is holding an infant.
    b. The seat occupant is a child in a child restraint device.
    c. The seat occupant is a child not using a child restraint 
device.
    d. The seat occupant is a pregnant woman.

    2. The inflatable lapbelt must provide adequate protection for each 
occupant, regardless of the number of occupants of the seat assembly, 
considering that unoccupied seats may have active seatbelts.
    3. The design must prevent the inflatable lapbelt from being either 
incorrectly buckled or incorrectly installed such that the airbag would 
not properly deploy. Alternatively, it must be shown that such 
deployment is not hazardous to the occupant and will provide the 
required head injury protection.
    4. It must be shown that the inflatable lapbelt system is not 
susceptible to inadvertent deployment as a result of wear and tear, or 
inertial loads resulting from in-flight or ground maneuvers (including 
gusts and hard landings), likely to be experienced in service.
    5. Deployment of the inflatable lapbelt must not introduce injury 
mechanisms to the seated occupant, or result in injuries that could 
impede rapid egress. This assessment should include an occupant who is 
in the brace position when it deploys, and an occupant whose belt is 
loosely fastened.
    6. It must be shown that an inadvertent deployment, that could 
cause injury to a standing or sitting person, is improbable.
    7. It must be shown that inadvertent deployment of the inflatable 
lapbelt, during the most critical part of the flight, will either not 
cause a hazard to the airplane or is extremely improbable.
    8. It must be shown that the inflatable lapbelt will not impede 
rapid egress of occupants 10 seconds after its deployment, considering 
the requirements of Special Conditions No. 25-NM-45, issued July 9, 
1991, and Special Conditions No. 25-NM-45A, issued November 8, 1994, 
concerning cabin aisle width.
    9. The system must be protected from lightning and high-intensity 
radiated fields (HIRF). The threats specified in Special Condition No. 
25-ANM-48 are incorporated by reference for the purpose of measuring 
lightning and HIRF protection. For the purposes of

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complying with HIRF requirements, the inflatable lapbelt system is 
considered a critical system if its deployment could have a hazardous 
effect on the airplane; otherwise it is considered an essential system.
    10. The inflatable lapbelt must function properly after loss of 
normal aircraft electrical power, and after a transverse separation of 
the fuselage at the most critical location. A separation at the 
location of the lapbelt does not have to be considered.
    11. It must be shown that the inflatable lapbelt will not release 
hazardous quantities of gas or particulate matter into the cabin.
    12. The inflatable lapbelt installation must be protected from the 
effects of fire such that no hazard to occupants will result.
    13. There must be a means for a crewmember to verify the integrity 
of the inflatable lapbelt activation system prior to each flight or it 
must be demonstrated to reliably operate between inspection intervals.

    Issued in Renton, Washington, on September 28, 2000.
Dorenda D. Baker,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-26016 Filed 10-10-00; 8:45 am]
BILLING CODE 4910-13-U