[Federal Register Volume 60, Number 200 (Tuesday, October 17, 1995)]
[Rules and Regulations]
[Pages 53691-53697]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-25676]



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  Federal Register / Vol. 60, No. 200 / Tuesday, October 17, 1995 / 
Rules and Regulations  

[[Page 53691]]


DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-112; Special Conditions No. 25-ANM-108]


Special Condition: Gulfstream Aerospace Corporation, Model 
Gulfstream V, High Altitude Operations

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final special conditions.

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

SUMMARY: These special conditions are for the Gulfstream Model 
Gulfstream V airplane. This new airplane will be capable of operating 
at a maximum altitude of 51,000 feet. The applicable regulations do not 
contain adequate or appropriate safety standards for the protection of 
the fuselage structure or passengers and crew from the effects of high 
altitude operations. 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: November 16, 1995.

FOR FURTHER INFORMATION CONTACT:
Gerald Lakin, FAA, Standardization Branch, ANM-113, Transport Airplane 
Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., 
Renton, Washington, 98055-4056, (206) 227-1187.

SUPPLEMENTARY INFORMATION: 

Background

    On February 26, 1992, Gulfstream Aerospace Corporation, P.O. Box 
2206, Savannah, GA 31402-2206, applied for an amended type certificate 
in the transport airplane category for the Model Gulfstream V airplane. 
The Gulfstream V is a T-tail, low swept wing, business jet airplane 
powered by two BMW Rolls-Royce BR700-710A1-10 turbofan engines mounted 
on pylons extending from the aft fuselage. Each engine will be capable 
of delivering 14,750 pounds thrust. The controls will be powered and 
capable of manual reversion. The airplane has a seating capacity of up 
to nineteen passengers, and a maximum takeoff weight of 89,000 pounds. 
Gulfstream has requested certification for operations up to 51,000 
feet.

Type Certification Basis

    Under the provisions of Sec. 21.101 of the FAR, Gulfstream must 
show, except as provided in Sec. 25.2, that the Model Gulfstream V 
meets the applicable provisions of part 25, effective February 1, 1995, 
as amended by Amendments 25-1 through 25-81. In addition, the proposed 
certification basis for the Model Gulfstream V includes part 34, 
effective September 10, 1990, plus any amendments in effect at the time 
of certification; part 36, effective December 1, 1969, as amended by 
Amendment 36-1 through the amendment in effect at the time of 
certification; and certain exceptions and special conditions that are 
not relevant to these special conditions. No exemptions are 
anticipated. These special conditions form an additional part of the 
type certification basis.
    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 Gulfstream V because of a novel or 
unusual design feature, special conditions are prescribed under the 
provisions of Sec. 21.16 to establish a level of safety equivalent to 
that established in the regulations.
    Special conditions, as appropriate, are issued in accordance with 
Sec. 11.49 of the FAR after public notice, as required by Secs. 11.28 
and 11.29, and become part of the type certification basis in 
accordance with Sec. 21.101(b)(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 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(a)(1).

Novel or Unusual Design Features

    The Model Gulfstream V will be certificated for operations at a 
maximum altitude of 51,000 feet. This unusually high operating altitude 
constitutes a novel or unusual design feature for which the applicable 
airworthiness regulations do not contain adequate or appropriate safety 
standards.
    There are no specific regulations that address protection 
requirements for the airplane fuselage pressure vessel or passengers 
and crew, in the event of a rapid decompression, during high altitude 
operations. The potential adverse impact from rapid decompression at 
high altitudes has made it necessary to provide adequate protection.
    To ensure that a level of safety is achieved equivalent to that 
intended by the regulations incorporated by reference, these special 
conditions require compliance with additional requirements to provide 
protection from the direct and indirect effects of high altitude 
operations.
    Damage tolerance methods are proposed to be used to ensure pressure 
vessel integrity while operating at the higher altitudes. Crack grown 
data are used to prescribe an inspection program which will detect 
cracks before an opening in the pressure vessel would allow rapid 
decompression. Initial crack sizes for detection are determined under 
Sec. 25.571, Amendment 25-72. The cabin altitude after failure may not 
exceed the limits specified in Figures 3 and 4.
    In order to ensure that there is adequate fresh air to crewmembers 
to perform their duties, to provide reasonable passenger comfort, and 
to enable occupants to better withstand the effects of decompression at 
high altitudes, the ventilation system must be designed to provide 10 
cubic feet of fresh air per minute per person during normal operations. 
Therefore, these special conditions require that crewmembers and 
passengers be provided with 10 cubic feet of fresh air per minute per 
person. In addition, during the development of the supersonic transport 
special conditions, it was noted that certain pressurization failures 
resulted in hot ram or bleed air being used to maintain pressurization. 
Such a measure can lead to cabin temperatures that exceed human 
tolerance. Therefore, these special conditions require airplane 
interior 

[[Page 53692]]
temperature limits following probable and improbable failures.
    Continuous flow passenger oxygen equipment is certificated for use 
up to 40,000 feet; however, for rapid decompressions above 34,000 feet, 
reverse diffusion leads to low oxygen partial pressure in the lungs, to 
the extent that a small percentage of passengers may lose useful 
consciousness at 35,000 feet. The percentage increases to an estimated 
60 percent at 40,000 feet, even with the use of the continuous flow 
system. To prevent permanent physiological damage, the cabin altitude 
must not exceed 25,000 feet for more than two minutes. The maximum peak 
cabin altitude of 40,000 feet is consistent with the standards 
established for previous certification programs. In addition, at these 
altitudes the other aspects of decompression sickness have a 
significant detrimental effect on pilot performance (for example, a 
pilot can be incapacitated by internal expanding gases).
    Decompression above 37,000 feet can result in cabin altitudes that 
approach the physiological limits of the average person; therefore, 
every effort must be made to provide the pilots with adequate oxygen 
equipment to withstand these severe decompressions. Reducing the time 
interval between pressurization failure and the time the pilot receives 
oxygen will provide a safety margin against being incapacitated and can 
be accomplished by the use of mask-mounted regulators. These special 
conditions therefore require pressure demand masks with mask-mounted 
regulators for the flightcrew. This combination of equipment will 
provide the best practical protection for the failures covered by the 
proposed special conditions and for improbable failures not covered by 
the special conditions, provided the cabin altitude is limited.
    As discussed above, these special conditions are applicable 
initially to the Model Gulfstream V. 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 feature, these special 
conditions would apply to that model as well, under the provisions of 
Sec. 21.101(a)(1).

Discussion of Comments

    Notice of Proposed Special Conditions No. ANM-95-5-NM for the 
Gulfstream Aerospace Corporation, Model Gulfstream V, was published in 
the Federal Register on June 28, 1995 (60 FR 33366). One commenter, the 
applicant, submitted four comments as follows:
    (1) The commenter states that the current nomenclature for the 
turbofan engine is BMW Rolls-Royce BR700-710A1-10 in lieu of Rolls-
Royce BR710-48. The FAA agrees with the commenter and has incorporated 
the change in this document.
    (2) The commenter states that the presently accepted Certification 
Basis for the Gulfstream V is part 25, effective February 1, 1965, as 
amended by Amendments 25-1 through 25-81 in lieu of Amendment 25-75. 
The FAA agrees with the commenter and has incorporated the change in 
this document.
    (3) The commenter asks the question whether certain wording 
discrepancies under the ``Novel or Unusual Design Features'' portion of 
the notice are typographical errors or if there has been a change in 
philosophy. The wording has to do with the value of ``rapid 
decompressions above 24,000 feet,'' and ``decompression above 27,000 
feet.'' In numerous preceding publications over the years of such high 
altitude special conditions, these altitudes have been stated as 34,000 
and 37,000 feet respectively. The FAA confirms that these discrepancies 
are typographical errors made by the Federal Register when they 
published the notice. The correct values are 34,000 feet and 37,000 
feet respectively, and those values are reflected in this document.
    (4) The commenter asks the question whether a change in Figure 3, 
Cabin Altitude Vs Time, is an error or a change in philosophy/
requirements. The question has to do with the fact that the horizontal 
portion of the 25,000 foot altitude line begins to break downward at 
the 6 minute point of the figure. In numerous preceding publications 
over the years of such high altitude special conditions, this break 
point in the graph has been at 7 minutes. The FAA confirms that the 6 
minute break point is in error and the 7 minute break value is correct. 
Figure 3 is corrected in this document to reflect the 7 minute break 
value point.

Conclusion

    This action affects certain design features only on the Gulfstream 
V airplane. It is not a rule of general applicability and affects only 
the manufacturer who applied to the FAA for approval of these features 
on the airplane.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Federal Aviation Administration, 
Reporting and recordkeeping requirements.

    The authority citation for these proposed special conditions is as 
follows:

    Authority: 49 U.S.C. app. 1344, 1348(c), 1352, 1354(a), 1355, 
1421 through 1431, 1502, 1651(b)(2), 42 U.S.C. 1857f-10, 4321 et 
seq.; E.O. 11514; and 49 U.S.C. 106(g).

The Special Conditions

    Accordingly, the following special conditions are issued as part of 
the type certification basis for the Gulfstream Aerospace Corporation, 
Model Gulfstream V series airplanes.

1. Pressure Vessel Integrity

    (a) The maximum extent of failure and pressure vessel opening that 
can be demonstrated to comply with paragraph 4 (Pressurization) of this 
special condition must be determined. It must be demonstrated by crack 
propagation and damage tolerance analysis supported by testing that a 
larger opening or a more severe failure than demonstrated will not 
occur in normal operations.
    (b) Inspection schedules and procedures must be established to 
assure that cracks and normal fuselage leak rates will not deteriorate 
to the extent that an unsafe condition could exist during normal 
operation.
    (c) With regard to the fuselage structural design for cabin 
pressure capability above 45,000 feet altitude, the pressure vessel 
structure, including doors and windows, must comply with 
Sec. 25.365(d), using a factor of 1.67 instead of the 1.33 factor 
described.

2. Ventilation

    In lieu of the requirements of Sec. 25.831(a), the ventilation 
system must be designed to provide a sufficient amount of 
uncontaminated air to enable the crewmembers to perform their duties 
without undue discomfort or fatigue, and to provide reasonable 
passenger comfort during normal operating conditions and also in the 
event of any probable failure to any system which could adversely 
affect the cabin ventilating air. For normal operations, crew members 
must be provided with at least 10 cubic feet of fresh air per minute 
per person, or the equivalent in filtered, recirculated air based on 
the volume and composition at the corresponding cabin pressure altitude 
of not more than 8,000 feet.

3. Air Conditioning

    In lieu of the requirements of Sec. 25.831, paragraphs (b) through 
(e), the cabin cooling system must be designed to meet the following 
conditions during flight above 15,000 feet mean sea level (MSL).

[[Page 53693]]

    (a) After any probable failure, the cabin temperature-time history 
may not exceed the values shown in Figure 1.
    (b) After any improbable failure, the cabin temperature-time 
history may not exceed the values shown in Figure 2.

4. Pressurization

    In addition to the requirements of FAR 25.841, the following apply:
    (a) The pressurization system, which includes for this purpose 
bleed air, air conditioning, and pressure control systems, must prevent 
the cabin altitude from exceeding the cabin altitude-time history shown 
in Figure 3 after each of the following:
    (1) Any probable malfunction or failure of the pressurization 
system. The existence of undetected, latent malfunctions, or failures, 
in conjunction with probable failures must be considered.
    (2) Any single failure in the pressurization system combined with 
the occurrence of a leak produced by a complete loss of a door seal 
element, or a fuselage leak through an opening having an effective area 
2.0 times the effective area that produces the maximum permissible 
fuselage leak rate approved for normal operation, whichever produces a 
more severe leak.
    (b) The cabin altitude-time history may not exceed that shown in 
Figure 4 after each of the following:
    (1) The maximum pressure vessel opening resulting from an initially 
detectable crack propagating for a period encompassing four normal 
inspection intervals. Mid-panel cracks and cracks through skin-stringer 
and skin-frame combinations must be considered.
    (2) The pressure vessel opening or duct failure resulting from 
probable damage (failure effect) while under maximum operating cabin 
pressure differential due to a tire burst, engine rotor burst, loss of 
antennas or stall warning vanes, or any probable equipment failure 
(bleed air, pressure control, air conditioning, electrical source(s), 
etc.) that affects pressurization.
    (3) Complete loss of thrust from all engines.
    (c) In showing compliance with paragraphs d.1. and d.2. of these 
special conditions (Pressurization), it may be assumed that an 
emergency descent is made by approved emergency procedure. A 17-second 
crew recognition and reaction time must be applied between cabin 
altitude warning and the initiation of an emergency descent.

5. Oxygen Equipment and Supply

    (a) A continuous flow oxygen system must be provided for the 
passengers.
    (b) A quick donning pressure demand mask with mask-mounted 
regulator must be provided for each pilot. Quick donning from the 
stowed position must be demonstrated to show that the mask can be 
withdrawn from stowage and donned within 5 seconds.

BILLING CODE 4910-13-M

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BILLING CODE 4910-13-C
    Issued in Renton, Washington, on October 5, 1995.
Gary L. Killion,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service, ANM-100.
[FR Doc. 95-25676 Filed 10-16-95; 8:45 am]
BILLING CODE 4910-13-M