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From:
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NTSB
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To:
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FAA
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Date:
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9/11/1997
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Response:
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Notation 6901: The National Transportation Safety Board has reviewed the Federal Aviation Administration's (FAA's) Notice of Proposed Rulemaking (NPRM), "Revised Standards for Cargo or Baggage Compartments in Transport Category Aircraft," Docket No. 28937, Notice No. 97-10, which was published at 62 Federal Register 32411 on June 13, 1997. The notice proposes to upgrade the fire safety standards for cargo and baggage compartments in certain transport category aircraft by eliminating class D compartments as an option for future type certification. Compartments that could no longer be designated as class D would have to meet the standards for class C or class E compartments. Class D compartments on aircraft manufactured under existing type certificates and used in passenger service would have to meet the fire detection and suppression standards for class C compartments by early 2001 for use in air carrier, commuter, on-demand, or most other commercial service. The class D compartments in certain transport category aircraft manufactured under existing type certificates and used only for the carriage of cargo would have to meet such standards for class E compartments by that same date. The purpose of these changes is to increase protection from possible in-flight fires.
As long ago as 1981 with Safety Recommendations A-81-12 and -13, the Safety Board expressed concern about the adequacy of class D compartments, which are not required to be equipped with fire detection or suppression systems, but are designed to contain fire damage by the use of flame-resistant compartment liners and to control a fire by limiting the oxygen available to support combustion. On October 9, 1984, the Safety Board commented on an NPRM (Notice 84-11, dated August 8, 1984) that proposed a new testing method for determining the flame penetration resistance of compartment liners. In its comments, the Safety Board advised the FAA that, although the proposed flame penetration tests were more stringent than previous ones, a fire should not be allowed to persist in any state of intensity in an airplane without the flightcrew's knowledge. The Board further stated that a fire detection system should be required in class D cargo compartments. While the final rule issued on May 16, 1986, required improved flame penetration resistance for compartment liners, it did not require fire detection systems.
On October 24, 1988, as a result of a February 3, 1988, in-flight fire involving a hydrogen peroxide solution (an oxidizer) aboard an American Airlines DC-9-83 (flight 132) en route to Nashville Metropolitan Airport, Nashville, Tennessee, the Safety Board recommended that the FAA require fire/smoke detection systems and a fire extinguishment system for all class D cargo compartments (Safety Recommendations A-88-122 and -123). The Board also recommended that the FAA consider the effects of authorized hazardous materials in fires for all types of cargo compartments and require appropriate safety systems to protect the aircraft and occupants (Safety Recommendation A-88-127). On August 10, 1993, the FAA responded by stating that it did not believe that fire/smoke detection and fire extinguishment systems would provide a significant degree of protection to airplane occupants and that it had terminated its rulemaking action to require such systems. On October 14, 1993, Safety Recommendations A-88-122 and -123 were classified "Closed-Unacceptable Action." Safety Recommendation A-88-127 was classified "Closed-Unacceptable Action" on March 17, 1994, after the FAA failed to take any positive action.
The Safety Board concluded from its investigation of the in-flight fire and crash of a ValuJet Airlines DC-9-32 (flight 592) on May 11, 1996, that the activation of one or more chemical oxygen generators in the forward cargo compartment, a class D compartment, initiated the fire; that a smoke/fire warning device would have more quickly alerted the crew to the fire and may have allowed more time to land the aircraft; and that a fire suppression system may have delayed the spread of fire and, in conjunction with an early warning, would likely have provided time for the crew to land the aircraft safely. The Safety Board also concluded that had the FAA required fire/smoke detection and/or fire extinguishment systems in class D cargo compartments, as the Safety Board recommended in 1988, ValuJet flight 592 likely would not have crashed.
The ValuJet accident prompted the Air Transport Association of America (ATA) to announce with Vice President Gore in December 1996 that its members would voluntarily retrofit existing class D cargo compartments with smoke detectors. As of the date of this letter, with the exception of one aircraft that has been retrofitted by Delta Air Lines, the Safety Board is unaware that any other aircraft in scheduled passenger service have been modified.
The Safety Board strongly supports the FAA's proposal to convert class D cargo compartments to class C compartments on passenger aircraft and to convert class D cargo compartments to class E compartments on cargo aircraft. However, more than 1 year after the ValuJet crash and 9 years after the American Airlines accident at Nashville, the class D cargo compartments on most passenger aircraft still lack fire/smoke detection or suppression equipment, and no requirement for such equipment is in place. The Safety Board believes that the FAA should expedite final rulemaking to require smoke detection and fire suppression systems for all class D cargo compartments.
Although the NPRM discusses the potential hazards from aerosol cans that use a mixture of propane, butane, and isobutane as propellants, the effect of fires initiated from other chemical sources still is not being addressed. The in-flight fires in the American Airlines and the ValuJet accidents were caused by the reaction of oxidizing materials that generate heat and liberate oxygen. In both accidents, the design features of the class D compartment (the flame-resistant capabilities of the compartment liners and the restriction of the air supply to the compartment) were not sufficient to control the fire or prevent flames from penetrating beyond the compartment. The Safety Board will provide comments on this issue in its letter on the Research and Special Programs Administration NPRM "Prohibition of Oxidizers Aboard Aircraft," Docket HM-224A, issued on August 20, 1997.
The Safety Board appreciates the opportunity to comment on this NPRM.
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