Special Conditions: Learjet Inc., Model LJ-200-1A10 Airplane; Crashworthiness, Emergency Landing Conditions, 65235-65237 [2013-25841]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 78, Number 211 (Thursday, October 31, 2013)]
[Proposed Rules]
[Pages 65235-65237]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2013-25841]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2013-0857; Notice No. 25-13-08-SC]


Special Conditions: Learjet Inc., Model LJ-200-1A10 Airplane; 
Crashworthiness, Emergency Landing Conditions

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions for the Learjet Model 
LJ-200-1A10 airplane. This airplane will have novel or unusual design 
features when compared to the state of technology envisioned in the 
airworthiness standards for transport category airplanes. These 
features are associated with a hybrid construction that uses both 
composite and metallic materials in the structure for which the 
crashworthiness responses for occupant safety may not be equivalent to 
current all-metallic airplanes. The applicable airworthiness 
regulations do not contain adequate or appropriate safety standards for 
the crashworthiness of this design feature. These proposed 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: Send your comments on or before December 16, 2013.

ADDRESSES: Send comments identified by docket number FAA-2013-0857 
using any of the following methods:
     Federal eRegulations Portal: Go to https://www.regulations.gov/ and follow the online instructions for sending 
your comments electronically.
     Mail: Send comments to Docket Operations, M-30, U.S. 
Department of Transportation (DOT), 1200 New Jersey Avenue SE., Room 
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
     Hand Delivery or Courier: Take comments to Docket 
Operations in Room W12-140 of the West Building Ground Floor at 1200 
New Jersey Avenue SE., Washington, DC, between 8 a.m. and 5 p.m., 
Monday through Friday, except federal holidays.
     Fax: Fax comments to Docket Operations at 202-493-2251.
    Privacy: The FAA will post all comments it receives, without 
change, to https://www.regulations.gov/, including any personal 
information the commenter provides. Using the search function of the 
docket Web site, anyone can find and read the electronic form of all 
comments received into any FAA docket, including the name of the 
individual sending the comment (or signing the comment for an 
association, business, labor union, etc.). DOT's complete Privacy Act 
Statement can be found in the Federal Register published on April 11, 
2000 (65 FR 19477-19478), as well as at https://DocketsInfo.dot.gov/.
    Docket: Background documents or comments received may be read at 
https://www.regulations.gov/ at any time. Follow the online instructions 
for accessing the docket or go to the Docket Operations in Room W12-140 
of the West Building Ground Floor at 1200 New Jersey Avenue SE., 
Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, 
except federal holidays.

FOR FURTHER INFORMATION CONTACT: Mark Freisthler, FAA, Airframe/Cabin 
Safety, ANM-115, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, Washington 98057-3356; telephone 
(425) 227-1119; facsimile (425) 227-1320.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite interested people to take part in this rulemaking by 
sending written comments, data, or views. The most helpful comments 
reference a specific portion of the special conditions, explain the 
reason for any recommended change, and include supporting data.
    We will consider all comments we receive on or before the closing 
date for comments. We may change these special conditions based on the 
comments we receive.

Background

    On February 9, 2009, Learjet Inc. applied for a type certificate 
for their new Model LJ-200-1A10 airplane (hereafter referred to as the 
``Model LJ-200''). The Model LJ-200 is a business class airplane 
powered by two high-bypass turbine engines with an estimated maximum 
takeoff weight of 35,550 pounds and an interior configuration for up to 
10 passengers.
    The current design includes a skin-stringer fuselage and aft 
fuselage configuration. The pressure fuselage will consist of 
monolithic carbon fiber reinforced plastic (CFRP) skin, with CFRP and 
metallic frames above floor level, and CFRP longerons and stringers. 
All substructure will be mechanically fastened to the skin. Fasteners 
for stringers aligned along the length of the co-cured splice will 
provide fail-safe capability for the splice. Cabin entry door frames, 
over-wing exit door frames, and frames below floor level will be 
metallic. Attachment of pressure bulkheads, windshield frame, and 
splicing concepts will be adjusted for any skin thickness variation 
that occurs. The wing consists of resin transfer infusion (RTI) skins 
with composite spars and metallic ribs. The empennage consists of 
composite sandwich skins with metallic spars and ribs. The airframe has 
a sandwich construction for the nose and empennage structures.
    There are no existing regulations that adequately address the 
potential difference between metallic fabricated airplanes and 
composite fabricated airplanes with regards to impact response 
characteristics for what are considered survivable crash conditions. 
The CFRP fuselage constitutes a novel and unusual design feature for a 
transport category airplane. These special conditions are necessary to 
ensure a level of safety equivalent to that provided by Title 14, Code 
of Federal Regulations (14 CFR) part 25.

Type Certification Basis

    Under the provisions of 14 CFR 21.17, Learjet Inc. must show that 
the Model LJ-200 meets the applicable provisions of part 25, as amended 
by Amendments 25-1 through 25-127 thereto, and 14 CFR part 26, as 
amended by Amendment 26-1 through 26-2 thereto.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Model LJ-200 because of a novel or 
unusual design feature, special conditions are prescribed under the 
provisions of Sec.  21.16.
    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 or similar 
novel or unusual design feature, the special conditions would also 
apply to the other model under Sec.  21.101.
    In addition to the applicable airworthiness regulations and special 
conditions, the Model LJ-200 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, and the FAA must issue a finding of 
regulatory adequacy under Sec.  611 of Public Law 92-574, the ``Noise 
Control Act of 1972.''
    The FAA issues special conditions, as defined in 14 CFR 11.19, in 
accordance with Sec.  11.38, and they become part of

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the type-certification basis under Sec.  21.17(a)(2).

Novel or Unusual Design Features

    The Model LJ-200 will incorporate the following novel or unusual 
design features: Hybrid construction using both composite and metallic 
materials in the structure for which the crashworthiness responses for 
occupant safety may not be equivalent to current all-metallic 
airplanes.

Discussion

    The Model LJ-200 fuselage is fabricated using carbon fiber 
reinforced plastic (CFRP) skins with aluminum ribs and stringers. This 
hybrid construction may behave differently from similar, fully-metallic 
structure due to differences in material ductility, stiffness, failure 
modes, and energy absorption characteristics. Therefore, the impact 
response characteristics of the Model LJ-200 must be evaluated to 
ensure the survivable crashworthiness characteristics are not 
significantly different than those of a similarly sized airplane 
fabricated from traditionally used metallic materials.
    The FAA and industry have been working together for many years to 
understand how transport airplane occupant safety can be improved for 
what are considered survivable accidents. This work has involved 
examining airplane accidents, conducting tests to simulate crash 
conditions, and developing analytical modeling of a range of crash 
conditions, all with the purpose of providing further insight into the 
factors that can influence occupant safety. Results of this on-going 
effort have enabled specific changes to regulatory standards and design 
practices to improve occupant safety. This evolution is reflected in 
changes to the part 25 emergency landing condition regulations. For 
example, airplane emergency load factors in Sec.  25.561, General, have 
been increased, and passenger seat dynamic load conditions have been 
added (Sec.  25.562, Emergency landing dynamic conditions).
    The seat dynamic load conditions were added to the regulations 
based on FAA and industry tests and a review of accidents. They reflect 
horizontal and vertical accelerations/time environment generated by 
previously certificated airplane designs given conditions that were 
survivable. These tests also demonstrated that the performance of the 
airframe was acceptable in a dynamic impact event. In the evolution of 
the regulations, there is at present no specific dynamic regulatory 
requirement for airplane-level crashworthiness. However, the FAA 
requires an assessment of each new model airplane to ensure that the 
airplane will not significantly depart from typical dynamic 
characteristics found in previously certificated designs.
    The nature of the assessment is largely dependent on the 
similarities and differences between the new type design and previously 
certificated airplanes. Such an assessment ensures that the level of 
safety of the new composite designs corresponds to the level of safety 
achieved with similar metallic designs around which the existing 
regulations were written. If significant trends in industry warrant 
change to the existing regulations, the FAA and industry rulemaking 
process may be used to develop an appropriate dynamic regulatory 
requirement for airplane level crashworthiness.
    The FAA and industry have collected a significant amount of 
experimental data as well as data from crashes of transport category 
airplanes that demonstrate a high occupant survival rate at vertical 
descent velocities up to 30 ft/sec (on a single-aisle airplane). Based 
on this information, the FAA finds it appropriate and necessary for an 
assessment of the Model LJ-200 to span a range of airplane vertical 
descent velocities (up to 30 ft/sec, or that appropriate for a 
comparable size airplane).
    The FAA expects the Model LJ-200 to exhibit similar crashworthiness 
capabilities under foreseeable survivable impact events as achieved by 
previously certificated transport category airplanes of similar size 
and configuration. In order to make this assessment, criteria need to 
be established by which the similarities and differences between new 
type designs and previously certificated airplanes may be analytically 
evaluated. Based on the FAA's evaluation of the intent of existing 
regulations, the following areas need to be evaluated to demonstrate 
comparable behavior of the Model LJ-200 design to currently 
certificated transport category airplanes:
     Retention of items of mass. It must be shown that the 
occupants, i.e., passengers, flight attendants, and flight crew, will 
be protected during the impact event from release of seats, overhead 
bins, and other items of mass due to the impact loads and resultant 
structural deformation of the supporting airframe and floor structures.
     Maintenance of occupant emergency egress paths. The 
airframe must not deform such that rapid evacuation of occupants is 
impeded.
     Maintenance of acceptable acceleration and loads 
experienced by the occupants.
     Maintenance of a survivable volume. All areas of the 
airplane occupied for takeoff and landing must be shown to provide a 
survivable volume during and after the impact event.

Applicability

    As discussed above, these special conditions are applicable to the 
Learjet Model LJ-200-1A10. Should Learjet Inc. 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.

Conclusion

    This action affects only certain novel or unusual design features 
on one model of airplanes. It is not a rule of general applicability.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

    The authority citation for these special conditions is as follows:

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

The Proposed Special Conditions

    Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions as part of the type certification basis 
for Learjet Model LJ-200-1A10 airplanes.
    In order to demonstrate an equivalent level of occupant safety and 
survivability to that provided by previously certificated transport 
category airplanes of similar size and configuration under foreseeable 
survivable impact events, Learjet must demonstrate that the Model LJ-
200-1A10 meets the following criteria for a range of airplane vertical 
descent velocities up to 30 ft/sec:
    1. Retention of items of mass. The occupants, i.e., passengers, 
flight attendants, and flightcrew, must be protected during the impact 
event from release of seats, overhead bins, and other items of mass due 
to the impact loads and resultant structural deformation of the 
supporting airframe and floor structures. The applicant must show that 
loads due to the impact event and resultant structural deformation of 
the supporting airframe and floor structure at the interface of the 
airplane structure to seats, overhead bins, and other items of mass are 
comparable to those of previously certificated transport category 
airplanes of similar size for the

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range of descent velocities stated above. The attachments of these 
items need not be designed for static emergency landing loads in excess 
of those defined in Sec.  25.561 if impact response characteristics of 
the Model LJ-200-1A10 yield load factors at the attach points 
comparable with those expected for a previously certificated transport 
category airplane of similar size.
    2. Maintenance of acceptable acceleration and loads experienced by 
the occupants. The applicant must show that the vertical acceleration 
levels experienced at the seat/floor interface and loads experienced by 
the occupants during the impact event are consistent with those found 
in Sec.  25.562(b) or with the levels expected for a previously 
certificated comparable transport category airplane of similar size.
    3. Maintenance of a survivable volume. The applicant must show that 
all areas of the airplane occupied for takeoff and landing provide a 
survivable volume comparable to that of previously certificated 
transport category airplanes of similar size during and after the 
impact event. This means that structural deformation will not result in 
infringement of the occupants' normal living space significantly 
affecting their survivability or egress.
    4. Maintenance of occupant emergency egress paths. The applicant 
must show that the airframe deformation after the vertical impact event 
does not impede the rapid evacuation of occupants comparable to 
previously certified transport category airplanes of similar size.

    Issued in Renton, Washington, on September 19, 2013.
Ross Landes,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2013-25841 Filed 10-30-13; 8:45 am]
BILLING CODE 4910-13-P