Special Conditions: Learjet Inc., Learjet Model LJ-200-1A10; Interaction of Systems and Structures, 6945-6949 [2012-3077]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 77, Number 28 (Friday, February 10, 2012)]
[Rules and Regulations]
[Pages 6945-6949]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-3077]


=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2012-0154; Special Conditions No. 25-457-SC]


Special Conditions: Learjet Inc., Learjet Model LJ-200-1A10; 
Interaction of Systems and Structures

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

-----------------------------------------------------------------------

SUMMARY: These special conditions are issued for the Learjet Model LJ-
200-1A10 airplane. This airplane will have novel or unusual design 
features associated with systems that, directly or as a result of 
failure or malfunction, affect structural performance. The applicable 
airworthiness regulations do not contain adequate or appropriate safety 
standards for these design features. 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 February 3, 
2012. We must receive your comments by March 26, 2012.

ADDRESSES: Send comments identified by docket number FAA-2012-0154 
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: Todd Martin, FAA, Airframe and Cabin 
Safety Branch, ANM-115, Transport Airplane Directorate, Aircraft 
Certification Service, 1601 Lind Avenue SW., Renton, Washington 98057-
3356; telephone (425) 227-1178; facsimile (425) 227-1320.

SUPPLEMENTARY INFORMATION: The FAA has determined that notice of, and 
opportunity for public comments on, these special conditions are 
unnecessary. The substance of these special conditions has been subject 
to the public comment process in several prior instances with no 
substantive comments received. The FAA therefore finds that good cause 
exists for making these special conditions effective upon issuance.

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 by 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 (hereafter referred to as ``Model LJ-
200'') airplane. The Model LJ-200 is a business class aircraft powered 
by 2 high bypass turbine engines with an estimated maximum takeoff 
weight of 36,000 pounds and an interior configuration for up to 10 
passengers.
    The airplane is equipped with systems that, directly or as a result 
of failure or malfunction, affect its structural performance. Current 
regulations do not take into account loads for the aircraft due to the 
effects of system failures on structural performance. These special 
conditions define criteria to be used in the assessment of the effects 
of these systems on structures. The general approach of accounting for 
the effect of system failures on structural performance would be 
extended to include any system whose partial or complete failure, alone 
or in combination with other system failures, would affect structural 
performance.

Type Certification Basis

    Under the provisions of Title 14, Code of Federal Regulations (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.
    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, these special conditions would also 
apply to the other model.
    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 pursuant to 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 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

[[Page 6946]]

features: systems that affect the airplane's structural performance, 
either directly or as a result of failure or malfunction. That is, the 
airplane's systems affect how it responds in maneuver and gust 
conditions, and thereby affect its structural capability. These systems 
may also affect the aeroelastic stability of the airplane. Such systems 
include flight control systems, autopilots, stability augmentation 
systems, load alleviation systems, and fuel management systems. Such 
systems represent novel and unusual features when compared to the 
technology envisioned in the current airworthiness standards.

Discussion

    Special conditions are needed to require consideration of the 
effects of systems on the structural capability and aeroelastic 
stability of the airplane, both in the normal and in the failed state, 
because these effects are not covered by current regulations.
    These special conditions require that the airplane meet the 
structural requirements of subparts C and D of 14 CFR part 25 when the 
airplane systems are fully operative. The special conditions also 
require that the airplane meet these requirements considering failure 
conditions. In some cases, reduced margins are allowed for failure 
conditions based on system reliability.
    These special conditions establish a level of safety that neither 
raises nor lowers the standard set forth in the applicable regulations.

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 features, 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.
    The substance of these special conditions has been subjected to the 
notice and comment period in several 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. Therefore, 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.

    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 Learjet Model LJ-200-1A10 airplanes.

1. General

    For airplanes equipped with systems that affect structural 
performance, either directly or as a result of a failure or 
malfunction, the influence of these systems and their failure 
conditions on structural performance must be taken into account when 
showing compliance with the requirements of 14 CFR part 25, subparts C 
and D. The following criteria must be used for showing compliance with 
these special conditions for airplanes equipped with flight control 
systems, autopilots, stability augmentation systems, load alleviation 
systems, fuel management systems, and other systems that either 
directly or as a result of failure or malfunction affect structural 
performance.
    (a) The criteria defined herein only address the direct structural 
consequences of the system responses and performances. They cannot be 
considered in isolation but should be included in the overall safety 
evaluation of the airplane. These criteria may in some instances 
duplicate standards already established for this evaluation. These 
criteria are only applicable to structures whose failure could prevent 
continued safe flight and landing. Specific criteria that define 
acceptable limits on handling characteristics or stability requirements 
when operating in the system degraded or inoperative mode are not 
provided in these special conditions.
    (b) Depending upon the specific characteristics of the airplane, 
additional studies may be required that go beyond the criteria provided 
in these special conditions in order to demonstrate the capability of 
the airplane to meet other realistic conditions such as alternative 
gust or maneuver descriptions for an airplane equipped with a load 
alleviation system.
    (c) The following definitions are applicable to these special 
conditions.
    Structural performance: Capability of the airplane to meet the 
structural requirements of part 25.
    Flight limitations: Limitations that can be applied to the airplane 
flight conditions following an in-flight occurrence and that are 
included in the flight manual (e.g., speed limitations, avoidance of 
severe weather conditions, etc.).
    Operational limitations: Limitations, including flight limitations, 
that can be applied to the airplane operating conditions before 
dispatch (e.g., fuel, payload and Master Minimum Equipment List 
limitations).
    Probabilistic terms: The probabilistic terms (probable, improbable, 
extremely improbable) used in these special conditions are the same as 
those used in Sec.  25.1309.
    Failure condition: The term failure condition is the same as that 
used in Sec.  25.1309; however, these special conditions apply only to 
system failure conditions that affect the structural performance of the 
airplane (e.g., system failure conditions that induce loads, change the 
response of the airplane to inputs such as gusts or pilot actions, or 
lower flutter margins).

2. Effects of Systems on Structures

    The following criteria will be used in determining the influence of 
a system and its failure conditions on the airplane structure.
    (a) System fully operative. With the system fully operative, the 
following apply:
    (1) Limit loads must be derived in all normal operating 
configurations of the system from all the limit conditions specified in 
subpart C (or defined by special condition or equivalent level of 
safety in lieu of those specified in Subpart C), taking into account 
any special behavior of such a system or associated functions or any 
effect on the structural performance of the airplane that may occur up 
to the limit loads. In particular, any significant nonlinearity (rate 
of displacement of control surface, thresholds, or any other system 
nonlinearities) must be accounted for in a realistic or conservative 
way when deriving limit loads from limit conditions.
    (2) The airplane must meet the strength requirements of part 25 
(static strength, residual strength), using the specified factors to 
derive ultimate loads from the limit loads defined above. The effect of 
nonlinearities must be

[[Page 6947]]

investigated beyond limit conditions to ensure the behavior of the 
system presents no anomaly compared to the behavior below limit 
conditions. However, conditions beyond limit conditions need not be 
considered when it can be shown that the airplane has design features 
that will not allow it to exceed those limit conditions.
    (3) The airplane must meet the aeroelastic stability requirements 
of Sec.  25.629.
    (b) System in the failure condition. For any system failure 
condition not shown to be extremely improbable, the following apply:
    (1) At the time of occurrence, starting from 1-g level flight 
conditions, a realistic scenario including pilot corrective actions 
must be established to determine the loads occurring at the time of 
failure and immediately after failure.
    (i) For static strength substantiation, these loads, multiplied by 
an appropriate factor of safety that is related to the probability of 
occurrence of the failure, are ultimate loads to be considered for 
design. The factor of safety is defined in Figure 1.
[GRAPHIC] [TIFF OMITTED] TR10FE12.000

    (ii) For residual strength substantiation, the airplane must be 
able to withstand two thirds of the ultimate loads defined in 
subparagraph 2(b)(1)(i) of these special conditions. For pressurized 
cabins, these loads must be combined with the normal operating 
differential pressure.
    (iii) Freedom from aeroelastic instability must be shown up to the 
speeds defined in Sec.  25.629(b)(2). For failure conditions that 
result in speeds beyond VC/MC, freedom from 
aeroelastic instability must be shown to increased speeds, so that the 
margins intended by Sec.  25.629(b)(2) are maintained.
    (iv) Failures of the system that result in forced structural 
vibrations (oscillatory failures) must not produce loads that could 
result in detrimental deformation of primary structure.
    (2) For the continuation of the flight. For the airplane, in the 
system failed state and considering any appropriate reconfiguration and 
flight limitations, the following apply:
    (i) The loads derived from the following conditions (or defined by 
special condition or equivalent level of safety in lieu of the 
following conditions) at speeds up to VC/MC, or 
the speed limitation prescribed for the remainder of the flight, must 
be determined:
    (A) The limit symmetrical maneuvering conditions specified in Sec.  
25.331 and in Sec.  25.345.
    (B) The limit gust and turbulence conditions specified in Sec.  
25.341 and in Sec.  25.345.
    (C) The limit rolling conditions specified in Sec.  25.349 and the 
limit unsymmetrical conditions specified in Sec.  25.367 and Sec.  
25.427(b) and (c).
    (D) The limit yaw maneuvering conditions specified in Sec.  25.351.
    (E) The limit ground loading conditions specified in Sec. Sec.  
25.473, 25.491, 25.493(d) and 25.503.
    (ii) For static strength substantiation, each part of the structure 
must be able to withstand the loads in paragraph 2(b)(2)(i) of these 
special conditions multiplied by a factor of safety depending on the 
probability of being in this failure state. The factor of safety is 
defined in Figure 2.

[[Page 6948]]

[GRAPHIC] [TIFF OMITTED] TR10FE12.001

Qj = (Tj)(Pj)

Where:

Tj = Average time spent in failure condition j (in hours)
Pj = Probability of occurrence of failure mode j (per 
hour)


    Note: If Pj is greater than 10-3 per 
flight hour, then a 1.5 factor of safety must be applied to all 
limit load conditions specified in Subpart C.

    (iii) For residual strength substantiation, the airplane must be 
able to withstand two thirds of the ultimate loads defined in paragraph 
2(b)(2)(ii) of these special conditions. For pressurized cabins, these 
loads must be combined with the normal operating differential pressure.
    (iv) If the loads induced by the failure condition have a 
significant effect on fatigue or damage tolerance, then their effects 
must be taken into account.
    (v) Freedom from aeroelastic instability must be shown up to a 
speed determined from Figure 3. Flutter clearance speeds V' and V'' may 
be based on the speed limitation specified for the remainder of the 
flight using the margins defined by Sec.  25.629(b).
[GRAPHIC] [TIFF OMITTED] TR10FE12.002

V1' = Clearance speed as defined by Sec.  25.629(b)(2).
V'' = Clearance speed as defined by Sec.  25.629(b)(1).
Qj = (Tj)(Pj)

Where:

Tj = Average time spent in failure condition j (in hours)
Pj = Probability of occurrence of failure mode j (per 
hour)


    Note:  If Pj is greater than 10-\3\ per 
flight hour, then the flutter clearance speed must not be less than 
V''.

    (vi) Freedom from aeroelastic instability must also be shown up to 
V' in Figure 3 above for any probable system failure condition combined 
with any damage required or selected for investigation by Sec.  
25.571(b).' ''
    (3) Consideration of certain failure conditions may be required by 
other sections of part 25 regardless of calculated system reliability. 
Where analysis shows the probability of these failure conditions to be 
less than 10-\9\, criteria other than those specified in 
this paragraph may be used for structural substantiation to show 
continued safe flight and landing.
    (c) Failure indications. For system failure detection and 
indication, the following apply:
    (1) The system must be checked for failure conditions, not 
extremely improbable, that degrade the structural capability below the 
level required by part 25 or significantly reduce the reliability of 
the remaining system. As far as reasonably practicable, the flight crew 
must be made aware of these failures before flight. Certain elements

[[Page 6949]]

of the control system, such as mechanical and hydraulic components, may 
use special periodic inspections, and electronic components may use 
daily checks, in lieu of detection and indication systems to achieve 
the objective of this requirement. These certification maintenance 
requirements must be limited to components that are not readily 
detectable by normal detection and indication systems and where service 
history shows that inspections will provide an adequate level of 
safety.
    (2) The existence of any failure condition, not extremely 
improbable, during flight that could significantly affect the 
structural capability of the airplane and for which the associated 
reduction in airworthiness can be minimized by suitable flight 
limitations, must be signaled to the flight crew. For example, failure 
conditions that result in a factor of safety between the airplane 
strength and the loads of Subpart C below 1.25, or flutter margins 
below V'', must be signaled to the crew during flight.
    (d) Dispatch with known failure conditions. If the airplane is to 
be dispatched in a known system failure condition that affects 
structural performance, or affects the reliability of the remaining 
system to maintain structural performance, then the provisions of these 
special conditions must be met, including the provisions of paragraph 
2(a) for the dispatched condition, and paragraph 2(b) for subsequent 
failures. Expected operational limitations may be taken into account in 
establishing Pj as the probability of failure occurrence for 
determining the safety margin in Figure 1. Flight limitations and 
expected operational limitations may be taken into account in 
establishing Qj as the combined probability of being in the 
dispatched failure condition and the subsequent failure condition for 
the safety margins in Figures 2 and 3. These limitations must be such 
that the probability of being in this combined failure state and then 
subsequently encountering limit load conditions is extremely 
improbable. No reduction in these safety margins is allowed if the 
subsequent system failure rate is greater than 10-\3\ per 
hour.
    For each system for which these special conditions are applied, the 
following must be identified for showing compliance:
    (a) The system that either directly or as a result of failure or 
malfunction affects structural performance;
    (b) The failure condition of the system and the probability of that 
failure;
    (c) The structure whose performance is affected directly or as a 
result of failure or malfunction of the system; and,
    (d) The loading condition(s) on the structure affected by the 
system.

    Issued in Renton, Washington, on February 3, 2012.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2012-3077 Filed 2-9-12; 8:45 am]
BILLING CODE 4910-13-P