Special Conditions: Airbus Model A318, A319, A320, and A321 Series Airplanes; Interaction of Systems and Structures, 64025-64029 [2012-25604]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 77, Number 202 (Thursday, October 18, 2012)]
[Rules and Regulations]
[Pages 64025-64029]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-25604]



[[Page 64025]]

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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2012-1118; Special Conditions No. 25-469-SC]


Special Conditions: Airbus Model A318, A319, A320, and A321 
Series Airplanes; 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 Airbus Model A318, 
A319, and A320 series airplanes with modification 160500 and Model A321 
series airplanes with modification 160023 (Sharklet). These airplanes 
will have novel or unusual design features when compared to the state 
of technology envisioned in the airworthiness standards for transport 
category airplanes. The design features are associated with the systems 
that affect the structural performance of the airplane. 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 October 11, 
2012. We must receive your comments by December 3, 2012.

ADDRESSES: Send comments identified by docket number FAA-2012-1118 
using any of the following methods:
     Federal eRegulations Portal: Go to 
http:[sol][sol]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 http:[sol][sol]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 
http:[sol][sol]DocketsInfo.dot.gov[sol].
    Docket: Background documents or comments received may be read at 
http:[sol][sol]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/Cabin 
Safety Branch, ANM-115, Transport Airplane Directorate, Aircraft 
Certification Service, 1601 Lind Avenue SW., Renton, Washington 98057-
3356; telephone 425-227-1178; facsimile 425-227-1232.

SUPPLEMENTARY INFORMATION: The FAA has determined that notice of, and 
opportunity for prior public comment on, these special conditions are 
impracticable because these procedures would significantly delay 
issuance of the design approval and thus delivery of the affected 
aircraft. In addition, 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 April 8, 2010, Airbus applied for a change to Type Certificate 
No. A28NM to include modification 160500 on Airbus Model A318, A319, 
and A320 series airplanes and modification 160023 on Model A321 series 
airplanes for the installation of a ``Sharklet,'' a large wingtip 
device. The Model A318, A319, A320, and A321 series airplanes are short 
to medium-range, twin turbofan, transport category airplanes with a 
maximum seating capacity of 136 to 220 passengers, a maximum takeoff 
weight of 130,071 to 205,027 pounds, and a maximum operating altitude 
of 39,800 feet.
    FAA issued special conditions 25-ANM-23, effective December 15, 
1988, originally applicable to Airbus Model A320 series airplanes and 
later to the Model A318, A319, and A321 series airplanes. Those special 
conditions included requirements for interactions of systems and 
structures. Airbus requested, and FAA agrees, that these special 
conditions be updated for the Airbus Model A318, A319, and A320 series 
airplanes with modification 160500 and Model A321 series airplanes with 
modification 160023 (Sharklet) and later derivatives to be consistent 
with the latest European Aviation Safety Standards (EASA) standards and 
the latest versions of the FAA special conditions issued on this 
subject.

Type Certification Basis

    Under the provisions of Title 14, Code of Federal Regulation (14 
CFR) 21.101, Airbus must show that the Model A318, A319, A320, and A321 
series airplanes, as changed, continue to meet the applicable 
provisions of the regulations incorporated by reference in Type 
Certificate No. A28NM 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. A28NM are 14 CFR part 25, as amended 
by Amendments 25-1 through 25-56, and special conditions 25-ANM-23. In 
addition, the certification basis includes certain special conditions, 
exemptions, or later amended sections of the applicable part that are 
not relevant to these special conditions.
    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 A318, A319, A320, and A321 
series airplanes 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

[[Page 64026]]

include any other model that incorporates the same novel or unusual 
design feature, or should any other model already included on the same 
type certificate be modified to incorporate the same novel or unusual 
design feature, the special conditions would also apply to the other 
model.
    In addition to the applicable airworthiness regulations and special 
conditions, the Model A318, A319, A320, and A321 series airplanes 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.
    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.  21.101.

Novel or Unusual Design Features

    The Airbus Model A318, A319, and A320 series airplanes with 
modification 160500 and Model A321 series airplanes with modification 
160023 (Sharklet) will incorporate the following novel or unusual 
design features: Systems that, directly or as a result of failure or 
malfunction, affect structural performance. These systems include 
flight control systems, autopilots, stability augmentation systems, 
load alleviation systems, fuel management systems, and other sytems.

Discussion

    These airplanes are 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 systems on structural performance including normal 
operation and failure conditions with strength levels related to 
probability of occurrence. These special conditions define criteria to 
be used in the assessment of the effects of these systems on 
structures.

Applicability

    As discussed above, these special conditions are applicable to the 
Airbus Model A318, A319, A320 series airplanes with modification 160500 
and Model A321 series airplanes with modification 160023 (Sharklet). 
Should Airbus 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 the model series of airplanes listed above. 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, 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.

    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 Airbus Model A318, A319, and A320 
series airplanes with modification 160500 and Model A321 with 
modification 160023 (Sharklet) series 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 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. If these special 
conditions are used for other systems, it may be necessary to adapt the 
criteria to the specific system.
    (a) The criteria defined herein only address the direct structural 
consequences of the system responses and performances and 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 structure 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 in meeting 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 14 CFR 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

[[Page 64027]]

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 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 (FS) is defined in Figure 1.
[GRAPHIC] [TIFF OMITTED] TR18OC12.000

    (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). 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 and 25.491.
    (ii) For static strength substantiation, each part of the structure 
must be able to withstand the loads in paragraph 2(b)(2)(i) of the 
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 64028]]

[GRAPHIC] [TIFF OMITTED] TR18OC12.001

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 the 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] TR18OC12.002

V' = 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 14 CFR 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 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

[[Page 64029]]

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.

    Issued in Renton, Washington, on October 11, 2012.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2012-25604 Filed 10-17-12; 8:45 am]
BILLING CODE 4910-13-P