Special Conditions: Israel Aircraft Industries Model Galaxy Series Airplane, High Altitude Operation

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-111; Special Conditions No. 25-ANM-106]

Special Conditions: Israel Aircraft Industries Model Galaxy

Series Airplane, High Altitude Operation

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are for the Israel Aircraft

Industries (IAI) Ltd. Model Galaxy airplane. This new airplane will

have an unusual design feature associated with an unusually high

operating altitude (45,000 feet), for which the applicable

airworthiness regulations do not contain adequate or appropriate safety

standards. 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.

EFFECTIVE DATE: October 13, 1995.

FOR FURTHER INFORMATION CONTACT:

Timothy Dulin, FAA, Standardization Branch, ANM-113, Transport Airplane

Directorate, Aircraft Certification Service, 1601 Lind Avenue SW.,

Renton, Washington, 98055-4056, telephone (206)227-2141.

SUPPLEMENTARY INFORMATION:

Background

On July 29, 1992, IAI Ltd., Ben-Gurion International Airport,

70100, Israel, applied for a new type certificate in the transport

airplane category for the Model Galaxy airplane. The IAI Model Galaxy

airplane is a derivative of the IAI Model 1125 Westwind Astra and is

designed to be a long range, high speed swept low wing airplane with

two aft-fuselage mounted Pratt & Whitney PW 306A engines and a

conventional empennage.

The type design of the Model Galaxy contains a number of novel and

unusual design features for an airplane type certificated under the

applicable provisions of part 25 of the Federal Aviation Regulations

(FAR). Those features include a high maximum operating altitude. The

applicable airworthiness requirements do not contain adequate or

appropriate safety standards for the IAI Galaxy; therefore, special

conditions are necessary to establish a level of safety equivalent to

that established in the regulations.

Type Certification Basis

Under the provisions of Sec. 21.17 of the FAR, IAI Ltd. must show

that the Galaxy meets the applicable provisions of part 25, effective

February 1, 1965, as amended by Amendments 25-1 through 25-77. The

certification basis may also include later amendments to part 25 that

are not relevant to these special conditions. In addition, the

certification basis for the Galaxy 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

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

certification. These special conditions 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 special

conditions.

If the Administrator finds that the applicable airworthiness

regulations (i.e., part 25, as amended) do not contain adequate or

appropriate safety

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standards for the Galaxy 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. 21.17(a)(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 features, the special conditions would also apply to the

other model under the provisions Sec. 21.101(a)(1).

Novel or Unusual Design Feature

The IAI Galaxy will incorporate an unusual design feature in that

it will be certified to operate up to an altitude of 45,000 feet.

The FAA considers certification of transport category airplanes for

operation at altitudes greater than 41,000 feet to be a novel or

unusual feature because current part 25 does not contain standards to

ensure the same level of safety as that provided during operation at

lower altitudes. Special conditions have therefore been adopted to

provide adequate standards for transport category airplanes previously

approved for operation at these high altitudes, including certain

Learjet models, the Boeing Model 747, Dassault-Breguet Falcon 900,

Canadair Model 600, Cessna Model 650, Israel Aircraft Industries Model

1125 Westwind Astra, and Cessna Model 560. The special conditions for

the Learjet Model 45 are considered the most applicable to the Galaxy

and its proposed operation and are therefore use as the basis for the

special conditions described below.

Damage tolerance methods are proposed to be used to ensure pressure

vessel integrity while operating at the higher altitudes, in lieu of

the 1/2-bay crack criterion used in some previous special conditions.

Crack growth data are used to prescribe an inspection program that

should detect cracks before an opening in the pressure vessel would

allow rapid depressurization. Initial crack sizes for detection are

determined under Sec. 25.571, as amended by Amendment 25-72. The

maximum extent of failure and pressure vessel opening determined from

the above analysis must be demonstrated to comply with the

pressurization section of the proposed special conditions, which state

that the cabin altitude after failure must not exceed the cabin

altitude/time curve limits shown in Figures 3 and 4.

In order to ensure that there is adequate fresh air for 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 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 pressures 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. Therefore, to prevent permanent physiological damage, the cabin

altitude must not exceed 25,000 feet for more than 2 minutes, or 40,000

feet for any time period. The maximum peak cabin altitude of 40,000

feet is consistent with the standards established for previous

certification programs. In addition, at high 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 resulting in cabin altitudes above the 37,000-foot

limit depicted in Figure 4 approaches 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 receive 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 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 to the

IAI Model Galaxy. Should IAI Ltd. 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. SC-95-4-NM for the Israel

Aircraft Industries Model Galaxy Series Airplane, was published in the

Federal Register on June 7, 1995 (60 FR 30019). No comments were

received.

Conclusion

This action affects only certain design features on the IAI Ltd.

Model Galaxy 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 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 Israel Aircraft Industries, Ltd.

Model Galaxy series airplanes:

Operation to 45,000 Feet

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

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ensure that cracks and normal fuselage leak rates will not deteriorate

to the extent that an unsafe condition could exist during normal

operation.

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 of any system that could adversely affect

the cabin ventilating air. For normal operations, crewmembers and

passengers 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 addition to the requirements of

Sec. 25.831, paragraphs (b) through (e), the cabin cooling systems 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 Sec. 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 4(a) and 4(b) 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.

Note: For the flight evaluation of the rapid descent, the test

article must have the cabin volume representative of what is

expected to be normal, such that IAI Ltd. must reduce the total

cabin volume by that which would be occupied by the furnishings and

total number of people.

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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Issued in Renton, Washington, on August 31, 1995.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service, ANM-100.

[FR Doc. 95-22740 Filed 9-12-95; 8:45 am]

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