[Federal Register Volume 69, Number 67 (Wednesday, April 7, 2004)]
[Rules and Regulations]
[Pages 18246-18250]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-7877]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM275; Special Conditions No. 25-258-SC]


Special Conditions: Gulfstream Model GIV-X Airplane; Interaction 
of Systems and Structures

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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SUMMARY: These special conditions are issued for the Gulfstream Model 
GIV-X 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 are associated with new or modified flight control systems, 
including the yaw damper and hard-over prevention system, that affect 
the structural performance of the airplane. The applicable 
airworthiness regulations do not contain adequate or appropriate safety 
standards for these systems and their effect on structural performance. 
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 applicable airworthiness 
standards.

DATES: The effective date of these special conditions is March 29, 
2004. Comments must be received on or before May 7, 2004.

ADDRESSES: Comments on these special conditions may be mailed in 
duplicate to: Federal Aviation Administration, Transport Airplane 
Directorate, Aircraft Certification Service, Attention: Rules Docket 
(ANM-113), Docket No. NM275, 1601 Lind Avenue SW., Renton, Washington 
98055-4056; or delivered in duplicate to the Transport Airplane 
Directorate at the above address. All comments must be marked: Docket 
No. NM275. Comments may be inspected in the Rules Docket weekdays, 
except Federal holidays, between 7:30 a.m. and 4 p.m.

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 98055-
4056; telephone (425) 227-1178; facsimile (425) 227-1320.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA has determined that notice and opportunity for prior public 
comment is impracticable, because these procedures would significantly 
delay certification and, thus, delivery of the airplane. The FAA, 
therefore, finds that good cause exists for making these special 
conditions effective upon issuance; however, the FAA invites interested 
persons to participate in this rulemaking by submitting 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 ask that you send 
us two copies of written comments.
    We will file in the docket all comments we receive as well as a 
report summarizing each substantive public contact with FAA personnel 
concerning these special conditions. The docket is available for public 
inspection before and after the comment closing date. If you wish to 
review the docket in person, go to the address in the ADDRESSES section 
of this preamble between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal holidays.
    We will consider all comments we receive on or before the closing 
date for comments. We will consider comments filed late if it is 
possible to do so without incurring expense or delay. We may change 
these special conditions in light of the comments we receive.
    If you want the FAA to acknowledge receipt of your comments on 
these special conditions, include with your comments a pre-addressed, 
stamped postcard on which the docket number appears. We will stamp the 
date on the postcard and mail it to you.

Background

    On August 22, 2000, Gulfstream applied for an amendment to Type 
Certificate No. A12EA to include an updated version of the Model GIV 
airplane. The Model GIV-X, which is a derivative of the GIV airplane 
currently approved under Type Certificate No. A12EA, is a pressurized, 
low-wing, ``T'' tail transport category airplane with tricycle landing 
gear. It is powered by two Rolls-Royce model Tay 611-8C engines and 
will carry a maximum of 19 passengers.

[[Page 18247]]

    The primary differences between the existing GIV and the new GIV-X 
are the installation of an advanced avionics and flight deck display 
suite, airframe aerodynamic changes to increase performance, range and 
economics, derivative Tay 611-8C engines with GV nacelles and thrust 
reversers, and a new Full Authority Digital Engine Control (FADEC). 
Additionally, the GIV-X includes a modified yaw damper and a new hard-
over prevention system (HOPS) which serve to alleviate loads in the 
airframe but, when in a failure state, can create loads in the 
airframe. The current regulations do not adequately account for the 
effects of these systems and their failures on structural performance. 
These special conditions will require Gulfstream to substantiate the 
strength capability and freedom from aeroelastic instabilities after 
failures in yaw damper and HOPS systems.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Gulfstream must show that 
the Model GIV-X airplane meets the applicable provisions of the 
regulations incorporated by reference in Type Certificate No. A12EA 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. A12EA are 14 CFR part 25, effective February 1, 
1965, including Amendments 25-1 through 25-56, except for the following 
sections which are limited to showing compliance with the amendments 
indicated: part 25 effective February 1, 1965, Sec.  25.109, 25.571, 
and 25.813; part 25 Amendment 25-22, Sec.  25.571; and part 25 
Amendment 25-15, Sec.  25.807(c)(2). In addition, the certification 
basis includes certain special conditions, exemptions, and equivalent 
safety findings that are not relevant to these special conditions.
    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 GIV-X airplane 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 regulations and special 
conditions, the Model GIV-X airplane 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 defined in Sec.  11.19, are issued in 
accordance with Sec.  11.38 and become part of the type certification 
basis in accordance with Sec.  21.101.
    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, 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 under the provisions of Sec.  21.101.

Novel or Unusual Design Feature

    The Model GIV-X airplane will have systems that affect the 
structural performance of the airplane, either directly or as a result 
of a failure or malfunction. These novel or unusual design features are 
systems that can serve to alleviate loads in the airframe but, when in 
a failure state, can create loads in the airframe. The current 
regulations do not adequately account for the effects of these systems 
and their failures on structural performance. These special conditions 
provide the criteria to be used in assessing the effects of these 
systems on structures.

Conclusion

    This action affects only certain novel or unusual design features 
on the Gulfstream Model GIV-X airplane. It is not a rule of general 
applicability and 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

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.


0
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

Interaction of Systems and Structure

    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 subparts C and D of part 25. 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, flutter control 
systems, and fuel management systems. 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 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 modes are not 
provided in these special conditions.
    (b) Depending upon the specific characteristics of the airplane, 
additional studies that go beyond the criteria provided in these 
special conditions may be required 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, lower 
flutter margins, or change the response of the airplane to inputs such 
as gusts or pilot actions).
    2. Effects of Systems on Structures. The following criteria will be 
used in

[[Page 18248]]

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, 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] TR07AP04.000

    (ii) For residual strength substantiation, the airplane must be 
able to withstand two thirds of the ultimate loads defined in paragraph 
(b)(1)(i) above.
    (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 speed increases 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 at speeds up to 
Vc, or the speed limitation prescribed for the remainder of the flight, 
must be determined:
    (A) The limit symmetrical maneuvering conditions specified 
Sec. Sec.  25.331 and 25.345.
    (B) The limit gust and turbulence conditions specified in 
Sec. Sec.  25.341 and 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.  
2.473 and 25.491.
    (ii) For static strength substantiation, each part of the structure 
must be able to withstand the loads defined in paragraph (2)(i) above, 
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 18249]]

[GRAPHIC] [TIFF OMITTED] TR07AP04.001

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)(ii) above.
    (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 VI 
and VII 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] TR07AP04.002


V \I\ = Clearance speed as defined by Sec.  25.629(b)(2).
V \II\ = Clearance speed as defined by Sec.  25.629(b)(1).
Q J = (T j)(P j) where:
T j = Average time spent in failure condition j (in hours).
P j = 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 \II\


    (vi) Freedom from aeroelastic instability must also be shown up to 
V \I\ 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 2-9, criteria other than those specified in 
this paragraph may be used for structural substantiation to show 
continued safe flight and landing.
    (c) Warning considerations. For system failure detection and 
warning, 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. The flightcrew 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 
warning systems, to achieve the objective of this requirement. These 
certification maintenance requirements must be limited to components 
that are not readily detectable by normal warning 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 flightcrew. 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 \II\, 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

[[Page 18250]]

structural performance, then the provisions of these special conditions 
must be met for the dispatched condition and for subsequent failures. 
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 March 29, 2004.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 04-7877 Filed 4-6-04; 8:45 am]
BILLING CODE 4910-13-M