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cited few cases of rotor burst in cruise. In one such instance, the crew of a DC-10 crossing New
Mexico reported several cases of initial decompression sickness, apparently with no permanent
injuries.
Airbus supplied data for the A380, using estimated values of airplane rate of descent for several
failure scenarios, as required in published FAA policy on this subject. In addition, Airbus
provided information on the likelihood of various failure events. In its decompression analysis,
Airbus included a measure of the severity of exposure for occupants, based on a
Depressurization Exposure Integral (DEI) from the MSHWG report. The petitioner used the
relationship between cabin pressure and the Depressurization Severity Indicator (DSI), which is
a measure of the partial pressure of oxygen, as was proposed by the MSHWG. The petitioner
showed that for all the failures modes reviewed for this exemption, the resultant DSI levels were
much less than the critical value specified by the MSHWG. The analysis considers certain
1 The Final Report of the MSHWG, dated August 2003, was approved by a majority of the members of ARAC’s
Transport Airplane Engine Issues Group (TAEIG). Seven members of TAEIG voted to submit the report as a
recommendation to the FAA, two members voted against submitting the report, and one member abstained.
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design and operational features of the A380-800 which would mitigate the effects of an increase
in cabin pressure altitude. One of these design features is the cabin pressurization control system
(CPCS) which was designed to minimize system failures that would lead to loss of cabin
pressurization events.
The petitioner’s Statement of Public Interest:
“The A380 aircraft fully complies with the requirements of 14 CFR 25.841, (a)(2)(i) and
(ii) and (3) for all system and structural failure events. An exemption is requested for
cabin depressurization that can occur from uncontained engine rotor failures that result in
large holes in the fuselage (i.e., those holes with a geometric area exceeding 0.225 m2).
Airbus believes, based on fleet service experience, that these are rare events…The new
aircraft complies with the latest FAA requirements and, therefore, offers a significantly
higher basic level of safety than previously certified transport category aircraft.
“Approval for operation at FL 430 would enable the air traffic system to provide more
capacity, and hence more aircraft separation and safety, without adversely affecting the
safety of the passengers.
“Approval for flight at FL 430 would enable the A380 to compete fairly with other
existing aircraft that are not subject to the same requirements, without causing any
adverse effects to the passengers.
“Approval for operation at FL 430 would also serve the public interest via the use of the
newest generation of engines available today, and permit them to operate where they
offer lower emissions, and higher fuel efficiency.
“Approval for flight at FL 430 provides for more economical operation of the A380,
reducing the cost to the traveling public.”
Notice and Opportunity for Public Comment
A Notice of Petition for Exemption was published in the Federal Register on January 13, 2005.
Four comments were received.1 Two of the commenters—the Boeing Company and a pilot for
the Airbus Model A300-600F—support a grant of exemption. The pilot suggests a restriction to
“require provisions of the relief within the Master Minimum Equipment List (MMEL).
Operations could be limited to a maximum of FL390 if any component of the CPCS (Cabin
Pressure Control System) is inoperable or deferred for a flight.”
The FAA does not agree with this suggestion because the A380’s CPCS is designed so that—in
the event of the loss of one air generation unit (AGU)—cabin pressure altitude will remain at or
below the maximum permitted by the regulations. The design capability of the A380 is such that
1 Copies of all comments may be found in the Department of Transportation’s Docket Management System at
http://dms.dot.gov/ in Docket FAA-2005-20139.
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the loss of one means of providing pressurized air to the cabin does not affect compliance with
the normal cabin pressure limit specified in 14 CFR part 25.
Two other commenters—the Association of Flight Attendants (AFA) and the Airline Pilots
Association (ALPA)—oppose a grant of exemption. Their comments address the following
topics:
1. Physiological effects of decompression
One commenter, AFA, states that the Airbus petition seems to be built upon the framework of
the FAA’s Interim Policy on Amendment 25-87 Requirements and the MSHWG’s Final Report
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