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

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

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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.

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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