[Federal Register Volume 64, Number 176 (Monday, September 13, 1999)]
[Proposed Rules]
[Pages 49413-49418]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-23719]


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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

[[Page 49416]]

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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