[Federal Register Volume 59, Number 31 (Tuesday, February 15, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-3449]
[[Page Unknown]]
[Federal Register: February 15, 1994]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 25
[Docket No. NM-89; Special Conditions No. 25-ANM-80]
Special Conditions; Cessna Aircraft Company, Model 750 (Citation
X) Airplane, High Altitude Operation
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final special conditions.
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SUMMARY: These special conditions are issued for the Cessna Aircraft
Company (Cessna), Model 750 (Citation X) airplane. This new airplane
will have a novel and unusual design feature associated with an
unusually high operating altitude (51,000 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: March 17, 1994.
FOR FURTHER INFORMATION CONTACT:
Mark Quam, FAA, Standardization Branch, ANM-113, Transport Airplane
Directorate, Aircraft Certification Service, 1601 Lind Avenue SW.,
Renton, Washington, 98055-4056; telephone (206) 227-2145.
SUPPLEMENTARY INFORMATION:
Background
On October 15, 1991, Cessna Aircraft Company (Cessna), 6030 Cessna
Blvd., P.O. Box 7704, Wichita, KS 67277-7704, applied for a new type
certificate in the transport airplane category for the Model 750
(Citation X) airplane. The Cessna Model 750 is a T-tail, low swept
wing, medium sized business jet powered by two GMA-3007C turbofan
engines mounted on pylons extending from the aft fuselage. Each engine
will be capable of delivering 6,000 pounds thrust. The flight controls
will be powered and capable of manual reversion. The type design of the
Cessna Model 750 series airplanes contains a number of novel and
unusual design features for an airplane type certificated under the
applicable provisions of part 25 of the FAR. Those features include the
relatively small passenger cabin volume and a high operating
altitude.The applicable airworthiness requirements do not contain
adequate or appropriate safety standards for the Cessna 750 series
airplanes; 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, Cessna must show,
except as provided in Sec. 25.2, that the Model 750 (Citation X) meets
the applicable provisions of part 25, effective February 1, 1965, as
amended by Amendments 25-1 through 25-74. In addition, the
certification basis for the Model 750 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. No exemptions are anticipated. These special conditions
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 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 Cessna Model 750 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).
Novel or Unusual Design Feature
The Cessna Model 750 will incorporate an unusual design feature in
that it will be certified to operate up to an altitude of 51,000 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, and Cessna Model 560. The special conditions for the Cessna Model
650 are considered the most applicable to the Model 750 and its
proposed operation and are therefore used as the basis for the special
conditions described below.
Damage tolerance methods are proposed to be used to assure 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 cabin
altitude after failure must not exceed the cabin altitude/time curve
limits shown in Figures 3 and 4.
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. 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 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 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 pilots receive
oxygen will provide a safety margin against being incapacitated and can
be accomplished by the use of mask-mounted regulators. This 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.
Discussion of Comments
Notice of proposed special conditions No. SC-93-5-NM was published
in the Federal Register on November 10, 1993 (14 CFR 59689). No
comments were received.
Conclusion
This action affects only certain unusual or novel design features
on one model of 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 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, pursuant to the authority delegated to me by the
Administrator, the following special conditions are issued as part of
the type certification basis for the Cessna Model 750 (Citation X)
series airplanes:
Operation to 51,000 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
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
prescribed.
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 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. 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 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) 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.
TR15FE94.085
TR15FE94.086
TR15FE94.087
TR15FE94.088
Issued in Renton, Washington, on January 31, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate Aircraft Certification
Service, ANM-100.
[FR Doc. 94-3449 Filed 2-14-94; 8:45 am]
BILLING CODE 4910-13-M