[Federal Register Volume 61, Number 160 (Friday, August 16, 1996)]
[Proposed Rules]
[Pages 42577-42579]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-20968]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-131, Notice No. SC-96-4-NM]


Special Conditions: LET Aeronautical Works L610G Airplane

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This document proposes special conditions for the LET 
Aeronautical Works Model L610G airplane. This airplane will have a 
novel or unusual design feature associated with the use of the landing 
gear fairing as an assist means during an emergency evacuation. This 
notice contains the additional safety standards which the Administrator 
considers necessary to establish a level of safety equivalent to that 
established by the airworthiness standards of part 25 of the Federal 
Aviation Regulations (FAR).

DATES: Comments must be received on or before September 30, 1996.

ADDRESSES: Comments on this proposal may be mailed in duplicate to: 
Federal Aviation Administration, Office of the Assistant Chief Counsel, 
Attention: Rules Docket (ANM-7), Docket No. NM-131, 1601 Lind Avenue 
SW, Renton, Washington 98055-4056; or delivered in duplicate to the 
Office of the Assistant Chief Counsel at the above address. Comments 
must be marked: Docket No. NM-131. Comments may be inspected in the 
Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and 
4:00 p.m.

FOR FURTHER INFORMATION CONTACT:
Frank Tiangsing, Regulations Branch, ANM-114, Transport Airplane 
Directorate, Aircraft Certification Service, FAA, 1601 Lind Avenue SW, 
Renton, WA 98055-4056, (206) 227-121.

[[Page 42578]]

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of 
these proposed special conditions by submitting such written data, 
views, or arguments as they may desire. Communications should identify 
the regulatory docket or notice number and be submitted in duplicate to 
the address specified above. All communications received on or before 
the closing date for comments will be considered by the Administrator 
before further rulemaking action on this proposal is taken. The 
proposals contained in this notice may be changed in light of the 
comments received. All comments received will be available, both before 
and after the closing date for comments, in the Rules Docket for 
examination by interested parties. A report summarizing each 
substantive public contact with FAA personnel concerning this 
rulemaking will be filed in the docket. Commenters wishing the FAA to 
acknowledge receipt of their comments submitted in response to this 
notice must include a self-addressed, stamped postcard on which the 
following statement is made: ``Comments to Docket No. NM-131.'' The 
postcard will be date/time stamped and returned to the commenter.

Background

    On April 25, 1990, LET Aeronautical Works applied for a type 
certificate for the Model L610G airplane. On March 28, 1995, they 
applied for an extension of the original application in accordance with 
Sec. 21.17(d)(2). The L610G is a twin-engine, 40 passenger, high-wing 
airplane with a passenger emergency exit configuration consisting of 
one pair of Type I exits located at the aft end of the cabin and a pair 
of Type III exits under the wing near the middle of the cabin.
    Type III exits are typically installed over the wings of the 
airplane. They are allowed by part 25 of the FAR to have a 27-inch 
step-down from the exit sill to the wing. Additionally, if the escape 
route on the wing terminates at a point more than six feet above the 
ground, means must be provided to assist evacuees to reach the ground. 
If the termination point is less than six feet above the ground, then 
the assist means is not required.
    Since this airplane is of a high-wing configuration, it is not 
practicable to incorporate overwing Type III exits. Part 25 of the FAR 
permits non-overwing, non-floor level exits when certain conditions are 
satisfied. Included in these conditions is the requirement for an 
assist means for passengers and crew to egress from the airplane to the 
ground when the exit sill height is more than six feet. This assist 
means must be an automatically erected escape slide or equivalent, and 
must be self-supporting on the ground. The sill of the Type III exits 
on the L610G will be more than six feet above the ground; therefore, an 
assist means will be necessary.
    LET has positioned the Type III exits above the landing gear 
fairing such that the fairing will form a surface for evacuees to use 
in lieu of what would be provided by a wing. The evacuees would then 
slide or jump off the fairing to the ground in much the same manner as 
they would off a wing trailing edge.
    LET's use of the landing gear fairing as an assist means results in 
features which are characteristic of both escape slides and overwing 
evacuation routes; therefore, the requirements for either configuration 
are insufficient by themselves to assure that minimum standards are 
established.
    These special conditions will include requirements pertinent to 
both overwing and non-overwing exits, as well as additional criteria 
for this specific exit.

Type Certification Basis

    Under the provisions of Sec. 21.17, LET must show that the Model 
L610G meets the applicable provisions of part 25 as amended by 
Amendments 15-1 through 25-70 thereto, except as follows:

                                                                        
                                                                        
                                                                        
Sec.  25.365                            Amendment 25-71                 
Sec.  25.571(e)(2)                      Amendment 25-72                 
Sec.  25.729                            Amendment 25-75                 
Sec.  25.905(d)                         Amendment 25-72                 
                                                                        

    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 LET 610G because of a novel 
or unusual design feature, special conditions are prescribed under the 
provisions of Sec. 21.16.
    Special conditions, as appropriate, are issued in accordance with 
Sec. 11.49 of the FAR 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. 21.17(a)(2).
    In addition to the applicable airworthiness regulations and special 
conditions, the Model L610G must comply with the fuel vent and exhaust 
emission requirements of part 34 and the noise certification 
requirements of part 36; and the FAA must issue a finding of regulatory 
adequacy pursuant to Sec. 611 of Public Law 92-574, the ``Noise Control 
Act of 1972.''
    Special conditions are initially applicable to the model for which 
they are issued. Should the type certificate for that model be amended 
later to include any other model that incorporates 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 L610G will incorporate the following novel or unusual 
design feature: a Type III exit will be located under each wing such 
that an evacuee using the exit would step out onto the main landing 
fairing. The evacuee would then slide or jump from the landing gear 
fairing to the ground.
    Section 25.809(f) requires all non-overwing exits more than six 
feet above the ground to be equipped with an approved means to assist 
occupants in descending to the ground.
    Special 25.809(h) similarly requires all overwing exits having an 
escape route which terminates at a point more than six feet above the 
ground to be equipped with an assist means. The exit for the Model 
L610G will be more than six feet from the ground; however, the landing 
gear fairing surface will be within 27 inches of the lower exit sill. 
This distance corresponds to the allowable step-down for an overwing 
Type III exit. The distance from the landing gear fairing to the ground 
is less than six feet.
    Section 25.809(f) also requires that assist means be automatically 
erected during exit opening. Strictly speaking, the landing gear 
fairing does not satisfy this requirement since opening the exit is not 
correlated to the availability of the assist means; however, since the 
fairing is a fixed piece of airplane structure it is always available 
for use.
    The regulations also require that an assist means be self-
supporting on the ground. This requirement has been interpreted to mean 
that the assist means rests on the ground when in use such that an 
evacuee does not have to jump to the ground from the bottom of the 
assist means. In the case of an overwing exit where the terminating 
edge of the escape route is less than six feet from the ground, it is 
likely that evacuees might have to jump a short distance from the wing 
to the ground. The Model L610G incorporates aspects of both of these 
exit arrangements, which are addressed in these special conditions.
    Other features of the exit arrangement which involve both overwing 
and non-overwing exit considerations include marking, visibility, and 
width of the escape route. For the purposes of these special 
conditions, this exit will be

[[Page 42579]]

treated as an overwing exit with respect to these requirements.
    Other areas which are of particular concern for this unusual exit 
arrangement are the effectiveness of the exit in the event of landing 
gear collapse and the proximity of the escape route to the engines and 
wheel wells. Since a collapse of the landing gear could result in some 
from of collapse of the landing gear fairing, the exit must be 
demonstrated to be usable and provide for safe evacuation, considering 
all conditions of landing gear collapse.
    Since the Type III exists are directly above the main landing gear, 
it is possible that a fire originating in the landing gear assembly 
could render such an exit unusable. Due to the design of the Model 
L610G, it is considered necessary to address the possibility that a 
fire on one side of the airplane could also render the opposite side 
unusable.
    These special conditions are intended to provide requirements which 
result in an evacuation system that is as effective and safe as those 
envisioned by the regulations. Where appropriate, requirements have 
been drawn from existing regulations. In other cases, new requirements 
have been developed to preserve the level of safety which is inherent 
in the design of more conventional exit arrangements or assist means.

Conclusion

    This action affects only certain novel or unusual design features 
on one model of airplanes. It is not a rule of general applicability, 
and it affects only the manufacturer who applied to the FAA for 
approval of these features on the airplane.

List of Subjects in 14 CFR Part 25

    Air transportation, Aircraft, Aviation safety, Safety.

    The authority citation for these proposed special conditions is as 
follows:

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

The Proposed Special Conditions

    Accordingly, the FAA proposes the following special conditions as 
part of the type certification bases for the LET L610G airplanes.
    1. The landing gear fairing must be established as an escape route 
in accordance with the dimensional, reflectance, and slip resistant 
surface requirements of Sec. 25.803(e).
    2. The step-down distance from the exit sill to the surface of the 
landing gear fairing, where an evacuee would make first contact, shall 
not exceed 27 inches (ref. Sec. 25.807(a)(3)).
    3. The assist means must provide for safe evacuation of occupants, 
considering all conditions of landing gear collapse. In addition, safe 
evacuation must be afforded via the Type III exit in the event of main 
landing gear non-deployment.
    4. Exterior emergency lighting must be provided for the assist 
means and all areas of likely ground contact in accordance with 
Sec. 25.812(g)(1)(i), and (ii), and Sec. 25.812(h)(1), as amended 
through Amendments 25-58.
    5. The assist means must be demonstrated to provide an adequate 
egress rate for the number of passengers requested. The passenger 
capacity, as permitted by Sec. 25.807(c)(1), Table 1, may be reduced if 
satisfactory Type III exit performance cannot be demonstrated.
    6. It must be shown that a landing gear fire occurring on one side 
of the airplane is unlikely to render the opposite exit unusable.
    7. The assist means must be shown to be as reliable as an escape 
slide following exposure to the emergency landing conditions that may 
be encountered in service. In addition, safe evacuation from the 
airplane must be afforded following the crash conditions specified in 
Sec. 25.561(b).

    Issued in Renton, Washington, on August 8, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service, ANM-100
[FR Doc. 96-20968 Filed 8-15-96; 8:45 am]
BILLING CODE 4910-13-M