[Federal Register: April 7, 2004 (Volume 69, Number 67)]
[Rules and Regulations]
[Page 18246-18250]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr07ap04-2]
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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