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

SUMMARY: The document proposes special conditions 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 proposed 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: Comments must be received on or before August 14, 1995.

ADDRESSES: Comments on this proposal may be mailed in duplicate to:

Federal Aviation Administration, Office of the Assistant Chief Counsel,

Attn: Rules Docket (ANM-7), Docket No. NM-112, 1601 Lind Avenue SW.,

Renton, Washington, 98055-4056; or delivered in duplicate to the Office

of the Assistant Chief Counsel at the above address. Comments must be

marked: Docket No. NM-112. Comments may be inspected in the Rules

Docket weekdays, except Federal holidays, between 7:30 a.m. and 4:00

p.m.

FOR FURTHER INFORMATION CONTACT:

Robert L. Salas, FAA, Standardization Branch, ANM-113, Transport

Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue

SW., Renton, Washington 98055-4056.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of

these proposed special conditions by submitting such written data,

views, or arguments as they may desire. Communications should identify

the regulatory docket or notice number and be submitted in duplicate to

the address specified above. All communications received on or before

the closing date for comments will be considered by the Administrator

before further rulemaking action is taken on these proposals. The

proposals contained in this notice may be changed in light of comments

received. All comments submitted will be available in the Rules Docket

for examination by interested persons, both before and after the

closing date for comments. A report summarizing each substantive public

contact with FAA personnel concerning this rulemaking will be filed in

the docket. Persons wishing the FAA to acknowledge receipt of their

comments submitted in response to this notice must submit with those

comments a self-addressed, stamped postcard on which the following

statement is made: ``Comments to Docket No. NM-112.'' The postcard will

be date stamped and returned to the commenter.

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 Rolls-Royce BR710-48 turbofan engines mounted on pylons

extending from the aft fuselage. Each engine will be capable of

delivering 14,750 pounds thrust. The flight 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, 1965,

as amended by Amendments 25-1 through 25-75. 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, and part 36 effective December 1, 1969, as amended by

Amendment 36-1 through the amendment in effect at the time of

certification. No exemptions are anticipated. The special conditions

that may be developed as a result of this notice will form an

additional part of the type certification basis. In addition, the

certification basis may include other special conditions that are not

relevant to these proposed 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 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 [[Page 33367]] 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 have 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, special

conditions are proposed for the Gulfstream V which would 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 growth

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 would require airplane

interior 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 24,000 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 27,000 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. The proposed

special condition therefore requires 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, the proposed special conditions would be

applicable initially to the Model Gulfstream V. Should Gulfstream apply

at a later date for a change to the type of certificate to include

another model incorporating the same novel or unusual design feature,

the special conditions would apply to that model as well, under the

provisions of Sec. 21.101(a)(1).

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, 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 Proposed Special Condition

Accordingly, the Federal Aviation Administration (FAA) proposes the

following special conditions as part of the type certification basis

for the Gulfstream 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).

(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: [[Page 33368]]

(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 donnning 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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Issued in Renton, Washington, on June 15, 1995.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service, ANM-100.

[FR Doc. 95-15890 Filed 6-27-95; 8:45 am]

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