Special Conditions: Cessna Aircraft Company, Model 525A, High Altitude Operation.

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 23

[Docket No. CE154; Notice No. 23-99-01-SC]

Special Conditions: Cessna Aircraft Company, Model 525A, High

Altitude Operation.

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This notice proposes special conditions for the Cessna

Aircraft Company Model 525A airplane. This airplane will have novel or

unusual design features associated with high altitude operation. The

applicable airworthiness regulations do not contain adequate or

appropriate safety standards for this design feature. 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 October 13, 1999.

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

Federal Aviation Administration, Regional Counsel, ACE-7, Attention:

Rules Docket, Docket No. CE154, 601 East 12th Street, Kansas City,

Missouri 64106, or delivered in duplicate to the Regional Counsel at

the above address.

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Comments must be marked: CE154. 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: Lowell Foster, Federal Aviation

Administration, Aircraft Certification Service, Small Airplane

Directorate, ACE-111, 601 East 12th Street, Kansas City, Missouri, 816-

426-5688, fax 816-426-2169.

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.

The proposals described in this notice may be changed in light of the

comments received. All comments received 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 include with those

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

statement is made: ``Comments to CE154.'' The postcard will be date

stamped and returned to the commenter.

Background

On May 14, 1998, Cessna Aircraft Company applied to amend the Model

525 Type Certificate to add a new Model 525A. The Model 525A is a

derivative of the Model 525 currently approved under Type Certificate

Data Sheet A1WI.

The Cessna Model 525A, a derivative of the Model 525, will be

certified for operation to a maximum altitude of 45,000 feet. This will

be the first of this series to be approved above 41,000 feet. The

certification basis of the Model 525 was primarily 14 CFR part 23, as

amended by Amendments 23-1 through 23-40, plus special conditions. 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. Therefore, it is

necessary to develop special conditions that provide the level of

safety to that established by the regulations.

The FAA has previously issued Special Conditions No. 23-ACE-87, to

another small turbojet airplane model with requested approval for

operation up to 49,000 feet.

The FAA policy is to apply special conditions to part 23 airplanes

when the certified altitude exceeds the capability of the oxygen system

(in this case, the passenger system). This was the situation for a part

23 turbojet airplane. Thus, the special conditions were deemed to be

appropriate for the Cessna Model 525A and provide the basis for

formulating the special conditions described below:

Damage tolerance methods are proposed to assure pressure vessel

integrity while operating at the higher altitudes. Crack growth data is

used to prescribe an inspection program, which should detect cracks

before an opening in the pressure vessel would allow rapid

depressurization. Initial crack sizes for detection are determined

under 23.571 as amended by Amendment 23-48.

The cabin altitude after failure may not exceed the cabin altitude/

time history curve limits shown in Figures 3 and 4.

Continuous flow passenger oxygen equipment is certified 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. To prevent permanent physiological damage, the cabin altitude

must not exceed 25,000 feet for more than 2 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 the 37,000 foot limit of Figure 4 approaches

the physiological limits of the average person; therefore, every effort

must be made to provide the pilot 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 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

special conditions and for improbable failures not covered by the

special conditions, provided the cabin altitude is limited.

Type Certification Basis

Under the provisions of 21.101, Cessna Aircraft Company must show

that the Cessna Model 525A meets the applicable provisions of the

regulations incorporated by reference in Type Certificate Data Sheet

A1WI or the applicable regulations in effect on the date of application

for the change to the Cessna Model 525A. 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 Data Sheet A1WI are as follows:

(1) Part 23 of the Federal Aviation Regulations effective February

1, 1965, as amended by Amendments 23-1 through 23-40;

(a) In addition, if the regulations incorporated by reference do

not provide adequate standards with respect to the change, the

applicant must comply with certain regulations in effect on the date of

application for the change. The FAA has determined that the Cessna

Model 525A must also be shown to comply with the following sections of

part 23:

Federal Aviation Regulations Secs. 23.331, 23.351, 23.421, 23.423,

23.425, 23.427, 23.939, and 23.1163 as amended by Amendments 23-1

through 23-42;

Federal Aviation Regulations Secs. 23.943, 23.951, 23.957, 23.961,

23.967, 23.991, 23.993, 23.997, 23.999, 23.1001, 23.1011, 23.1019,

23.1041, 23.1061, 23.1189, 23.1322, 23.1357, 23.1391, 23.1393, 23.1395,

and 23.1445 as amended by Amendments 23-1 through 23-43;

Federal Aviation Regulations Secs. 23.305, 23.321, 23.361, 23.397,

23.479, 23.485, 23.613, 23.615, 23.621, 23.731 and 23.1549 as amended

by Amendments 23-1 through 23-45;

Federal Aviation Regulations Secs. 23.335, 23.337, 23.341, 23.343,

23.345, 23.347, 23.371, 23.393, 23.399, 23.415, 23.441, 23.443, 23.455,

23.457, 23.473, 23.499, 23.561, 23.571, 23.572, 23.611, 23.629, 23.673,

and 23.725 as amended by Amendments 23-1 through 23-48;

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Federal Aviation Regulations Secs. 23.677, 23.723, 23.785, 23.787,

23.791, 23.853, 23.855, 23.1303, 23.1307, 23.1321, 23.1351, 23.1353,

23.1361, and 23.1401 as amended by Amendments 23-1 through 23-49;

Federal Aviation Regulations Secs. 23.233, 23.235, 23.1555, and

23.1589 as amended by Amendments 23-1 through 23-50;

Federal Aviation Regulations Secs. 23.901, 23.903, 23.929, 23.963,

23.965, 23.1013, 23.1043, 23.1143, 23.1183, 23.1191, and 23.1337 as

amended by Amendments 23-1 through 23-51;

(2) Federal Aviation Regulations part 36 effective December 1,

1969, as amended by Amendments 36-1 through the amendment in effect at

the time of TC issuance.

(3) Federal Aviation Regulations part 34 effective September 10,

1990, as amended by Amendment 34-1, Fuel Venting and Exhaust Emission

Requirements for Turbine Engine Powered Airplanes.

(4) Special Conditions as follows:

(a) 23-ACE-55, additional requirements for engine location,

performance, characteristics, and protection of electronic systems from

lightning and high intensity radiated electromagnetic fields (HIRF).

(b) Special conditions adopted by this rulemaking action.

(5) Exemption: Exemption number 5759 granted. Model 525A to use

Federal Aviation Regulations Sec. 25.181 in lieu of damping criteria of

Federal Aviation Regulations Sec. 23.181(b).

(6) Compliance with ice protection will be demonstrated in

accordance with Federal Aviation Regulations Sec. 23.1419.

If the Administrator finds that the applicable airworthiness

regulations (i.e., part 23) do not contain adequate or appropriate

safety standards for the Cessna Model 525A because of a novel or

unusual design feature, special conditions are prescribed under the

provisions of Sec. 21.16.

In addition to the applicable airworthiness regulations and special

conditions, the Model 525A must comply with the part 23 fuel vent and

exhaust emission requirements of 14 CFR part 34 and the part 23 noise

certification requirements of 14 CFR part 36, and the FAA must issue a

finding of regulatory adequacy pursuant to Sec. 611 of Public Law 92-

574, the ``Noise Control Act of 1972.''

Special conditions, as appropriate, are issued in accordance with

Sec. 11.49 after public notice, as required by Secs. 11.28 and

11.29(b), and become part of the type certification basis in accordance

with 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 21.101(a)(1).

Novel or Unusual Design Features

The Model 525A will incorporate the following novel or unusual

design features:

The methods used to ensure pressure vessel integrity and to provide

ventilation, air conditioning, and pressurization will be unique due to

the operating altitude of this airplane.

Applicability

As discussed above, these special conditions are applicable to the

Cessna Model 525A. Should the Cessna Aircraft Company apply at a later

date for a change to the type 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

21.101(a)(1).

Conclusion

This action affects only certain novel or unusual design features

on one model of airplane. It is not a rule of general applicability,

and it affects only the applicant who applied to the FAA for approval

of these features on the airplane.

List of Subjects in 14 CFR Part 23

Aircraft, Aviation safety, Signs and symbols.

Citation

The authority citation for these special conditions is as follows:

Authority: 49 U.S.C. 106(g), 40113 and 44701; 14 CFR 21.16 and

21.17; and 14 CFR 11.28 and 11.29(b).

The Proposed Special Conditions

Accordingly, the Federal Aviation Administration (FAA) proposes the

following special conditions as part of the type certification basis

for the Cessna Aircraft Company Model 525A airplane.

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.

2. Ventilation

In addition to the requirements of Sec. 23.831(b), 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 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

no more than 8,000 feet.

3. Air Conditioning

In addition to the requirements of Sec. 23.831, 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 Sec. 23.841, 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, in conjunction with any undetected, latent malfunctions or

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

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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 4a and 4b of these

special conditions (Pressurization), it may be assumed that an

emergency descent is made by an 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 Cessna 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) In addition to the requirements of Sec. 23.1441(d), the

following applies: A quick-donning oxygen mask system with a pressure-

demand, mask mounted regulator must be provided for the flightcrew. It

must be shown that each quick-donning mask can, with one hand and

within 5 seconds, be placed on the face from its ready position,

properly secured, sealed, and supplying oxygen upon demand.

(b) In addition to the requirements of Sec. 23.1443, the following

applies: A continuous flow oxygen system must be provided for each

passenger.

(c) In addition to the requirements of Sec. 23.1445, the following

applies: If the flightcrew and passengers share a common source of

oxygen, a means to separately reserve the minimum supply required by

the flightcrew must be provided.

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Issued in Kansas City, Missouri on August 31, 1999.

Michael Gallagher,

Manager, Small Airplane Directorate, Aircraft Certification Service.

[FR Doc. 99-23719 Filed 9-10-99; 8:45 am]

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