DC93, en-route, north west of Miami USA, 1996

Summary: 

On 11 May 1996, the crew of a ValuJet DC9-30 were unable to keep control of their aircraft after fire broke out. The origin of the fire was found to have been live chemical oxygen generators loaded contrary to regulations. The Investigation concluded that, whilst the root cause was poor practices at SabreTech (the maintenance contractor which handed over oxygen generators in an unsafe condition), the context for this was oversight failure at successive levels - Valujet over SabreTech and the FAA over Valujet. Failure of the FAA to require fire suppression in Class 'D' cargo holds was also cited.

Event Details
When: 
11/05/1996
Event Type: 
Day/Night: 
Day
Flight Conditions: 
VMC

18655

Flight Details
Aircraft: 
Operator: 
Type of Flight: 
Public Transport (Passenger)
Flight Origin: 
Take-off Commenced: 
Yes
Flight Airborne: 
Yes
Flight Completed: 
No
Phase of Flight: 
Climb
General
Tag(s): 
Air Turnback, Inadequate Aircraft Operator Procedures, Ineffective Regulatory Oversight
FIRE
Tag(s): 
Dangerous Goods, Fire-Cargo origin, Fire-Underfloor origin
GND
Tag(s): 
Dangerous Goods
LOC
Tag(s): 
Airframe Structural Failure, Significant Systems or Systems Control Failure, Extreme Pitch
Outcome
Damage or injury: 
Yes
Aircraft damage: 
Hull loss
Non-aircraft damage: 
Yes
Non-occupant Casualties: 
No
Occupant Fatalities: 
Most or all occupants
Off Airport Landing: 
Yes
Ditching: 
Yes
Causal Factor Group(s)
Group(s): 
Aircraft Operation, Aircraft Technical
Safety Recommendation(s)
Group(s): 
Aircraft Operation, Aircraft Airworthiness
Investigation Type
Type: 
Independent

Description

On 11 May 1996, the crew of a Douglas DC9-30 (N904VJ) being operated by ValuJet on a scheduled domestic passenger flight from Miami to Atlanta reported fire on board during the climb out of Miami in day VMC. Although the climb was stopped approaching 11,000 feet and an air turnback was commenced, fire damage prevented completion of this plan and the aircraft crashed out of control in what was observed to have been a near-vertical attitude killing all 110 occupants.

Investigation

An Investigation was carried out by the National Transportation Safety Board (USA) (NTSB). The wreckage was located and, eventually, a substantial part of it was recovered. The 11-parameter FDR and the CVR were also recovered and successfully downloaded.

It was established that the first indication to the flight crew that there may be a problem had occurred approximately six minutes after take off from runway 09L at Miami, when an unidentified sound recorded on the CVR area microphone channel prompted the Captain to query aloud what it was. Simultaneously, FDR data recorded an anomaly in which recorded altitude and airspeed varied in a way which would be consistent with a sudden increase in static pressure of about 0.5 psi. Within twelve seconds of this, the Captain was recorded announcing a loss of electrical systems and after a further ten seconds, voices in the passenger cabin could be heard shouting "fire, fire, fire". ATC were advised of the need to return to Miami due to smoke in the cabin and began giving appropriate radar vectors and clearing descent to 7000 feet. Less than four minutes after the occurrence of the unidentified sound - approximately ten minutes after take off - the aircraft impacted the ground in a near vertical attitude approximately 17 miles north west of Miami. A 3-D plot of the flight trajectory is shown in the diagram below. The highest altitude recorded on the FDR was 10,879 feet amsl, and this occurred some 30 seconds after the indications that something abnormal had occurred - the unidentified noise.

Analysis of all the available evidence pointed to a fire originating in the forward underfloor (Class 'D') hold and that its specific origin was one or more of the chemical oxygen generators which the load and trim sheet confirmed had been loaded into that hold as part of a quantity of "COMAT" (company-owned material) in addition to baggage and mail. Documentation for this COMAT listed two main wheels fitted with tyres, one nose wheel fitted with a tyre and five boxes described as “Oxy Canisters -Empty". The contents of the boxes were chemical oxygen generators which had been removed from three MD82 aircraft recently acquired by ValuJet by maintenance contractor SabreTech under instructions issued by ValuJet. It was found that, although all the generators had exceeded their service life and were not re-usable, there was no evidence that any of them had been activated before being transported, or that any had been fitted with safety caps (which it was considered would have prevented activation) or that any of them bore warning notices which might have led to those handling them asking questions about how they should be shipped. AMM procedures were found to be valid but the work cards supposedly based on them were deficient to the extent that they were considered to have contributed to the circumstances which made the accident possible.

Reproduced from the Official Report

Fire testing during the Investigation found that a main landing gear tyre at the same inflation to the one carried in the hold ruptured 16 minutes after the activation of an oxygen generator placed in a similar relative position when the fire had destroyed nine of the twelve sidewall plies of the tyre. Since main wheels were reported to have been loaded just forward of the forward hold door, they would have been just above the position of the left hand side static ports which are the source of/input to the altitude and speed data recorded on the FDR. It was therefore concluded that the unidentified sound on the CVR, noticed by the crew and coincident with the identified FDR data anomaly, had probably been caused by the rupture of an inflated tyre in the forward cargo compartment after it had been partially burnt through by the fire.

It was apparent that the oxygen-fed fire had propagated rapidly and based on FDR evidence of continuing degradation of the flight controls and damage to cabin floorboards in the area of the flight controls, it was concluded that the eventual loss of control was "most likely the result of flight control failure from the extreme heat and structural collapse". However although there was no evidence to indicate that any significant level of smoke had entered the fight deck, the possibility that the pilots had been incapacitated by smoke or heat during the last seven seconds of the flight could not be discounted.

Because the hold where the fire occurred was a Class 'D' cargo compartment and was not equipped nor required to be equipped with a smoke detection system, the crew had no way of detecting any threat to continued flight until smoke and fumes reached the passenger cabin. And since this hold was not fitted, nor required to be fitted, with a fire suppression system, there was no way to extinguish or even limit the spread of what was an oxygen-fed fire. It was considered that "one or more of the oxygen generators likely were actuated at some point after the loading process began, but possibly as late as during the airplane's takeoff roll".

It was noted that at the time of the accident, the ValuJet Operations Manual stated that the carrier would "not engage in transportation of hazardous materials" but quoted 49 CFR section 175.10, as listing "the allowable exceptions which are required for support of ValuJet’s operations and certain items which are exempted partially or completely from the Hazardous Material Regulations". However, chemical oxygen generators, other than those provided by a carrier for medical use by a passenger, were not included in that list. Also at the time of the accident, the FAA-approved ValuJet Station Operations Manual stated that the carrier would "not engage in transportation of hazardous materials" and that "prompt recognition and refusal of such materials is essential to the safety of our passengers and employees". In case of any uncertainty about a cargo on-load, this Manual required that the Station call 'Flight Control' where relevant Dangerous Goods documentation was held. The Investigation noted that such a policy was known in the industry as a "recognition-only" or "will-not-carry" hazardous materials program and had been approved by the FAA's assigned operations inspector in accordance with prevailing procedures.

No evidence was found that either relevant airworthiness issues with the aircraft or any actions that the flight crew could have taken had any bearing on the accident outcome.

It was noted that although Class 'D' cargo compartments were designed to achieve suppression of any fire through oxygen starvation, previous experience including aircraft accidents had shown that some oxidisers were capable of generating sufficient oxygen to support combustion despite the reduced ventilation in such a compartment.

The Investigation reviewed previous accidents and incidents relevant to the accident circumstances and concluded that "had the FAA responded to prior chemical oxygen generator fires and allocated sufficient resources and initiated programs to address the potential hazards of these generators, including issuing follow-up warnings and inspecting the shipping departments of aircraft maintenance facilities, the chemical oxygen generators might not have been placed on (the accident flight)".

Considerable attention was also devoted to an examination of SabreTech's procedures and the oversight of its activities by both ValuJet and the FAA and to ValuJet’s own operational procedures and the FAA oversight of them. The Investigation noted that ValuJet was a rapidly growing operator which, having commenced operations with 2 DC9 aircraft less than 3 years earlier, had grown its fleet to 48 DC9s within two years and to 52 by the time of the accident. It was considered quite likely that "contrary to its authority, ValuJet’s practices before the accident might have included the shipment of hazardous aircraft equipment items aboard company airplanes".

The Probable Causes of the accident, "which resulted from a fire in the airplane’s class 'D' cargo compartment that was initiated by the actuation of one or more oxygen generators being improperly carried as cargo", were formally determined to have been:

  1. the failure of SabreTech to properly prepare, package, and identify unexpended chemical oxygen generators before presenting them to ValuJet for carriage.
  2. the failure of ValuJet to properly oversee its contract maintenance program to ensure compliance with maintenance, maintenance training, and hazardous materials requirements and practices.
  3. the failure of the Federal Aviation Administration (FAA) to require smoke detection and fire suppression systems in class D cargo compartments.

Contributory Factors were determined to have been:

  • the failure of the FAA to adequately monitor ValuJet’s heavy maintenance programs and responsibilities including ValuJet’s oversight of its contractors and SabreTech’s repair station certificate.
  • the failure of the FAA to adequately respond to prior chemical oxygen generator fires with programs to address the potential hazards.
  • ValuJet’s failure to ensure that both ValuJet and contract maintenance facility employees were aware of the carrier’s "no-carry" hazardous materials policy and had received appropriate hazardous materials training.

A total of 27 Safety Recommendations were made as a result of the Investigation as follows:

  • that the Federal Aviation Administration should expedite final rulemaking to require smoke detection and fire suppression systems for all class D cargo compartments. (A-97-56)
  • that the Federal Aviation Administration should specify, in air carrier operations master minimum equipment lists, that the cockpit-cabin portion of the service interphone system is required to be operating before an airplane can be dispatched. (A-97-57)
  • that the Federal Aviation Administration should issue guidance to air carrier pilots about the need to don oxygen masks and smoke goggles at the first indication of a possible in-flight smoke or fire emergency. (A-97-58)
  • that the Federal Aviation Administration should establish a performance standard for the rapid donning of smoke goggles; then ensure that all air carriers meet this standard through improved smoke goggle equipment, improved flight crew training, or both. (A-97-59)
  • that the Federal Aviation Administration should require that the smoke goggles currently approved for use by the flight crews of transport category aircraft be packaged in such a way that they can be easily opened by the flight crew. (A-97-60)
  • that the Federal Aviation Administration should evaluate the cockpit emergency vision technology and take action as appropriate. (A-97-61)
  • that the Federal Aviation Administration should evaluate and support appropriate research, including the National Aeronautics and Space Administration research program, to develop technologies and methods for enhancing passenger respiratory protection from toxic atmospheres that result from in-flight and post-crash fires involving transport-category airplanes. (A-97-62)
  • that the Federal Aviation Administration should evaluate the usefulness and effectiveness of the Douglas DC-9 procedures involving the partial opening of cabin doors and similar procedures adopted by some operators of other transport-category airplanes for evacuating cabin smoke or fumes and, based on that evaluation, determine whether these or other procedures should be included in all manufacturers’ airplane flight manuals and air carrier operating manuals. (A-97-63)
  • that the Federal Aviation Administration should require airplane manufacturers to amend company maintenance manuals for airplanes that use chemical oxygen generators to indicate that generators that have exceeded their service life should not be transported unless they have been actuated and their oxidizer core has been depleted. (A-97-64)
  • that the Federal Aviation Administration should require that routine work cards used during maintenance of Part 121 aircraft (a) provide, for those work cards that call for the removal of any component containing hazardous materials, instructions for disposal of the hazardous materials or a direct reference to the maintenance manual provision containing those instructions and (b) include an inspector’s signature block on any work card that calls for handling a component containing hazardous materials. (A-97-65)
  • that the Federal Aviation Administration should require manufacturers to affix a warning label to chemical oxygen generators to effectively communicate the dangers posed by unexpended generators and to communicate that unexpended generators are hazardous materials; then require that aircraft manufacturers instruct all operators of aircraft using chemical oxygen generators of the need to verify the presence of (or affix) such labels on chemical oxygen generators currently in their possession. (A-97-66)
  • that the Federal Aviation Administration should require all air carriers to develop and implement programs to ensure that aircraft components that are hazardous (other than chemical oxygen generators) are properly identified and that effective procedures are established to safely handle those components after they are removed from aircraft. (A-97-67)
  • that the Federal Aviation Administration should evaluate and enhance its oversight techniques to more effectively identify and address improper maintenance activities, especially false entries. (A-97-68)
  • that the Federal Aviation Administration should review the adequacy of current industry practice and, if warranted, require that Part 121 air carriers and Part 145 repair facilities performing maintenance for air carriers develop and implement a system requiring items delivered to shipping and receiving and stores areas of the facility to be properly identified and classified as hazardous or non hazardous, and procedures for tracking the handling and disposition of hazardous materials. (A-97-69)
  • that the Federal Aviation Administration should include, in its development and approval of air carrier maintenance procedures and programs, explicit consideration of human factors issues, including training, procedures development, redundancy, supervision, and the work environment, to improve the performance of personnel and their adherence to procedures. (A-97-70)
  • that the Federal Aviation Administration should review the issue of personnel fatigue in aviation maintenance; then establish duty time limitations consistent with the current state of scientific knowledge for personnel who perform maintenance on air carrier aircraft. (A-97-71)
  • that the Federal Aviation Administration should issue guidance to air carriers on procedures for transporting hazardous aircraft components consistent with Research and Special Programs Administration requirements for the transportation of air carrier company materials; then require principal operations inspectors to review and amend, as necessary, air carrier manuals to ensure that air carrier procedures are consistent with this guidance. (A-97-72)
  • that the Federal Aviation Administration should require air carriers to ensure that maintenance facility personnel, including mechanics, shipping, receiving, and stores personnel, at air carrier-operated or subcontractor facilities, are provided initial and recurrent training in hazardous materials recognition, and in proper labelling, packaging, and shipment procedures with respect to the specific items of hazardous materials that are handled by the air carrier’s maintenance functions. (A-97-73)
  • that the Federal Aviation Administration should ensure that Part 121 air carriers’ maintenance functions receive the same level of Federal Aviation Administration surveillance, regardless of whether those functions are performed in house or by a contract maintenance facility. (A-97-74)
  • that the Federal Aviation Administration should review the volume and nature of the work requirements of principal maintenance inspectors assigned to Part 145 repair stations that perform maintenance for Part 121 air carriers, and ensure that these inspectors have adequate time and resources to perform surveillance. (A-97-75)
  • that the Federal Aviation Administration should develop, in cooperation with the U.S. Postal Service and the Air Transport Association, programs to educate passengers, shippers and postal customers about the dangers of transporting undeclared hazardous materials aboard aircraft and about the need to properly identify and package hazardous materials before offering them for air transportation. The programs should focus on passenger baggage, air cargo, and mail offered by U.S. Postal Service customers. (A-97-76)
  • that the Federal Aviation Administration should instruct principal operations inspectors to review their air carriers’ procedures for manifesting passengers, including lap children, and ensure that those procedures result in a retrievable record of each passenger’s name. (A-97-77)
  • that the Research and Special Programs Administration should develop records for all approvals previously issued by the Bureau of Explosives and transferred to the Research and Special Programs Administration and ensure all records, including designs, testing, and packaging requirements are available to inspectors to help them determine that products transported under those approvals can be done safely and in accordance with the requirements of its approval. (A-97-78)
  • that the U.S. Postal Service should develop, in cooperation with the Federal Aviation Administration and the Air Transport Association, programs to educate passengers, shippers and postal customers about the dangers of transporting undeclared hazardous materials aboard aircraft and about the need to properly identify and package hazardous materials before offering them for air transportation. The programs should focus on passenger baggage, air cargo, and mail offered by U.S. Postal Service customers. (A-97-79)
  • that the U.S. Postal Service should develop a program for U.S. Postal Service employees to help them identify undeclared hazardous materials being offered for transportation. (A-97-80)
  • that the U.S. Postal Service should continue to seek civil enforcement authority when undeclared hazardous materials shipments are identified in transportation. (A-97-81)
  • that the Air Transport Association should develop, in cooperation with the U.S. Postal Service and the Federal Aviation Administration, programs to educate passengers, shippers and postal customers about the dangers of transporting undeclared hazardous materials aboard aircraft and about the need to properly identify and package hazardous materials before offering them for air transportation. The programs should focus on passenger baggage, air cargo, and mail offered by U.S. Postal Service customers. (A-97-82)

The Final Report of the Investigation was adopted by the NTSB on 19 August 1997.

Accidents & Serious Incidents involving Dangerous Goods which Resulted in a Fire

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