[Federal Register Volume 62, Number 112 (Wednesday, June 11, 1997)]
[Rules and Regulations]
[Pages 31707-31708]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-15311]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM-131, Special Conditions No. 25-ANM-128]
Special Conditions: LET Aeronautical Works Model L610G Airplane
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions.
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SUMMARY: These final special conditions are issued 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. 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 airworthiness standards of 14 CFR
part 25.
EFFECTIVE DATE: July 11, 1997.
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, (425) 227-121.
SUPPLEMENTARY INFORMATION:
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
14 CFR 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. The are allowed by part 25 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 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 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 14 CFR 21.17, LET must show the Model L610G
meets the applicable provisions of part 25 as amended by Amendments 15-
1 through 25-70 thereon, 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 610G because of a novel or
unusual design feature, special conditions are prescribed under the
provisions of 14 CFR 21.16. In addition to the applicable airworthiness
regulation and special conditions, the LET Aeronautical Works Model
L610G must comply with the fuel vent and exhaust emission requirements
of 14 CFR part 34 and the noise certification requirements of 14 CFR
part 36.
Special conditions, as appropriate, are issued in accordance with
14 CFR 11.49 after public notice, as required by 14 CFR 11.28 and
11.29(b), and become part of the type certification basis in accordance
with 14 CFR 21.17(a)(2).
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 14 CFR 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
gear fairing. The evacuee would then slide or jump from the landing
gear fairing to the ground.
14 CFR 25.809(f) requires all non-overwing exits more than six feet
above
[[Page 31708]]
the ground to be equipped with an approved means to assist occupants in
descending to the ground.
14 CFR 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
Typing III exit. The distance from the landing gear fairing to the
ground is less than six feet.
14 CFR 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 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
form 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 exits 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 provided 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.
Discussion of Comments
Notice of Proposed Special Conditions No. SC-96-4-NM for the LET
Aeronautical Works Model L610G airplane, was published in the Federal
Register on August 16, 1996. No comments were received.
Applicability
As discussed above, these special conditions are applicable to the
LET Aeronautical Works Model L610G airplane. Should LET Aeronautical
Works apply at a later date for a change to the type certificate to
include another model incorporating the same novel or unusual design
feature, the special conditions would apply to that model as well under
the provisions of 14 CFR 21.101(a)(1).
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 applicant 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 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 the LET Aeronautical Works L610G
airplane.
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
Secs. 25.812(g)(1) (i) and (ii), and Sec. 25.812(h)(1), as amended
through Amendment 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 June 3, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service, ANM-100.
[FR Doc. 97-15311 Filed 6-10-97; 8:45 am]
BILLING CODE 4910-13-M