Special Conditions: Gulfstream Model GVI Airplane; Interaction of Systems and Structures, 36865-36869 [2011-15704]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 76, Number 121 (Thursday, June 23, 2011)]
[Rules and Regulations]
[Pages 36865-36869]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-15704]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM442; Special Conditions No. 25-434-SC]


Special Conditions: Gulfstream Model GVI Airplane; Interaction of 
Systems and Structures

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Gulfstream GVI 
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 design features 
include systems that affect the structural capability 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: Effective Date: July 25, 2011.

FOR FURTHER INFORMATION CONTACT: Carl Niedermeyer, FAA, Airframe/Cabin 
Safety Branch, ANM-115, Transport Standards Staff, Transport Airplane 
Directorate, Aircraft Certification Service, 1601 Lind Avenue, SW., 
Renton, Washington 98057-3356; telephone (425) 227-2279; electronic 
mail carl.niedermeyer@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

    On March 29, 2005, Gulfstream Aerospace Corporation (hereafter 
referred to as ``Gulfstream'') applied for an FAA type certificate for 
its new Gulfstream Model GVI passenger airplane. Gulfstream later 
applied for, and was granted, an extension of time for the type 
certificate, which changed the effective application date to September 
28, 2006. The Gulfstream Model GVI airplane will be an all-new, two-
engine jet transport airplane. The maximum takeoff weight will be 
99,600 pounds, with a maximum passenger count of 19 passengers.

Type Certification Basis

    Under provisions of Title 14, Code of Federal Regulations (14 CFR) 
21.17, Gulfstream must show that the Gulfstream Model GVI airplane 
(hereafter referred to as ``the GVI'') meets the applicable provisions 
of 14 CFR part 25, as amended by Amendments 25-1 through 25-119, 25-
122, and 25-124. 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 GVI because of a novel 
or unusual design feature, special conditions are prescribed under the 
provisions of Sec.  21.16.
    In addition to complying with the applicable airworthiness 
regulations and special conditions, the GVI 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 must also issue a 
finding of regulatory adequacy pursuant to section 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).
    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 features, the special conditions would also apply to the 
other model under provisions of Sec.  21.101.

Novel or Unusual Design Features

    The Gulfstream Model GVI airplane will incorporate novel or unusual 
design features. These features are systems that may 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. These systems include the GVI's flight 
control systems, autopilots, stability augmentation systems, load 
alleviation systems, and fuel

[[Page 36866]]

management systems. Such systems represent a novel and unusual feature 
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 are identical or nearly identical to those 
previously required for type certification of other transport airplane 
models. These special conditions were derived initially from 
standardized requirements developed by the Aviation Rulemaking Advisory 
Committee (ARAC), comprised of representatives of the FAA, Europe's 
Joint Aviation Authorities (now replaced by the European Aviation 
Safety Agency), and industry.
    These special conditions require that the airplane meets the 
structural requirements of Subparts C and D of 14 CFR part 25 when the 
airplane systems are fully operative. These 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.
    In these special conditions and in the current standards and 
regulations, the term ``any'' is used. Use of this term has 
traditionally been understood to require that all items covered by the 
term are addressed, rather than addressing only a portion of the items. 
The use of the term ``any'' in these special conditions continues this 
traditional understanding.

Discussion of Comments

    Notice of proposed special conditions No. 25-11-02-SC for 
Gulfstream GVI airplanes was published in the Federal Register on 
February 14, 2011 (76 FR 8316). Only one comment was received.

Clarification of GVI Fuel Management System

    The commenter, Gulfstream, agreed with the content of the special 
conditions, but provided a clarification regarding the GVI airplane's 
fuel management system. The Novel or Unusual Design Features section of 
the proposed special conditions referenced the fuel management system 
as an example of a system or function that could affect the airplane's 
structural performance. Gulfstream stated that the GVI airplane has a 
simple and conventional two-tank fuel system design so no unusual 
consideration is required for the fuel management system. Gulfstream 
did not propose any changes to the special conditions.
    We agree with Gulfstream's statement regarding the fuel management 
system. No change is required and these special conditions are adopted 
as proposed.

Applicability

    As discussed above, these special conditions are applicable to the 
Gulfstream Model GVI airplane. Should Gulfstream apply at a later date 
for a change to the type certificate to include another model 
incorporating the same novel or unusual design features, these special 
conditions would apply to that model as well.

Conclusion

    This action affects only certain novel or unusual design features 
of the GVI. 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 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 Gulfstream GVI airplanes.

A. General

    The GVI is 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 Title 14, Code of Federal 
Regulations (14 CFR), part 25, Subparts C and D.
    1. 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.
    2. The criteria defined herein only address the direct structural 
consequences of the system responses and performance. 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 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.
    3. Depending upon the specific characteristics of the airplane, 
additional studies may be required that go beyond the criteria provided 
in this special condition 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.
    4. The following definitions are applicable to these special 
conditions.
    (a) Structural performance: Capability of the airplane to meet the 
structural requirements of 14 CFR part 25.
    (b) 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.).
    (c) 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).
    (d) Probabilistic terms: The probabilistic terms (probable, 
improbable, extremely improbable) used in these special conditions are 
the same as those used in Sec.  25.1309.
    (e) 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).

B. Effects of Systems on Structures

    1. General. The following criteria will be used in determining the 
influence of a system and its failure conditions on the airplane 
structure.
    2. System fully operative. With the system fully operative, the 
following apply:
    (a) Limit loads must be derived in all normal operating 
configurations of the

[[Page 36867]]

system from all the limit conditions specified in Subpart C (or used 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.
    (b) The airplane must meet the strength requirements of 14 CFR 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.
    (c) The airplane must meet the aeroelastic stability requirements 
of Sec.  25.629.
    3. System in the failure condition. For any system failure 
condition not shown to be extremely improbable, the following apply:
    (a) 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 the failure.
    (1) 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] TR23JN11.001

    (2) For residual strength substantiation, the airplane must be able 
to withstand two thirds of the ultimate loads defined in subparagraph 
B.3(a)(1) of these special conditions. For pressurized cabins, these 
loads must be combined with the normal operating differential pressure.
    (3) 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.
    (4) 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.
    (b) 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:
    (1) The loads derived from the following conditions (or used 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:
    (i) The limit symmetrical maneuvering conditions specified in Sec.  
25.331 and in Sec.  25.345.
    (ii) The limit gust and turbulence conditions specified in Sec.  
25.341 and in Sec.  25.345.
    (iii) 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).
    (iii) The limit yaw maneuvering conditions specified in Sec.  
25.351.
    (iv) The limit ground loading conditions specified in Sec.  25.473 
and Sec.  25.491.
    (2) For static strength substantiation, each part of the structure 
must be able

[[Page 36868]]

to withstand the loads in paragraph B.3(b)(1) 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.
[GRAPHIC] [TIFF OMITTED] TR23JN11.002

    Qj = (Tj)(Pj)

Where:

Qj = Probability of being in failure condition j
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.

    (3) For residual strength substantiation, the airplane must be able 
to withstand two thirds of the ultimate loads defined in paragraph 
B.3(b)(2) of this special condition. For pressurized cabins, these 
loads must be combined with the normal operating differential pressure.
    (4) 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.
    (5) 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).

[[Page 36869]]

[GRAPHIC] [TIFF OMITTED] TR23JN11.000

V'' = Clearance speed as defined by Sec.  25.629(b)(1).
V' = Clearance speed as defined by Sec.  25.629(b)(2).
Qj = (Tj)(Pj) where:
Qj = Probability of being in failure condition j
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''.

    (6) 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).
    (c) 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.
    4. Failure indications. For system failure detection and 
indication, the following apply:
    (a) The system must be checked for failure conditions, not 
extremely improbable, that degrade the structural capability below the 
level required by 14 CFR 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.
    (b) 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.
    5. Dispatch with known failure conditions. If the airplane is to be 
dispatched in a known system failure condition that affects structural 
performance, or that 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 B.2 for 
the dispatched condition and paragraph B.3 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 1E-3 per hour.

    Issued in Renton, Washington, on June 13, 2011.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2011-15704 Filed 6-22-11; 8:45 am]
BILLING CODE 4910-13-P