ValuJet flight 592 was a McDonnell Douglas DC-9-32 that crashed in the Florida everglades on 11 May 1996, due to an in-flight fire only ten minutes after takeoff from Miami International Airport. The fire was started by oxygen generating canisters in the aircraft’s cargo hold, and fed by three combustible spare aircraft tyres, also in the cargo hold. Only six minutes into the flight, the flight data recorder detected an air pressure spike, and the cockpit voice recorder detected a strange ‘chirp’, which the pilots commented on, likely from one of the tires exploding (Airdisaster.com, n.d.2). They did not know that a raging oxygen-fed fire was spreading through the DC-9’s cargo compartment. It was only after the pilots started to loose electronic systems and thick smoke started to enter the passenger cabin that they realised the gravity of the situation and began to turn back towards Miami. Only a few minutes later, the DC-9 plunged into the Florida everglades.
The cause of this accident is a long and complicated chain of events, with eight critical errors.
Latent error 1)
The poor safety culture at SabreTech was a major factor in this accident. If the organisation had a strong safety culture, many of the following errors may not have taken place.
Latent error 2)
The oxygen generators were removed from several ValuJet MD-80s by SabreTech employees. The canisters were removed because they had expired [reached the end of their official life]. They were told that if the canister had not been expended [used], to install plastic shipping caps over the firing pin. Confusion arose here, as the mechanics had to deal with these expired but unexpended canisters, some that were both expired and expended, some that were unexpired and expended, and replacement canisters which were unexpired and unexpended. The similarity of these two words, expended and expired, cause much subsequent confusion, and was a significant latent error in this accident. If these words were replaced with ‘used’ and ‘out of date’, the confusion and subsequent accident may not have occurred.
Latent error 3)
SabreTech did not have the plastic shipping caps. Over time, they could not be bothered to find the caps and they were either forgotten or ignored.
Active error 1)
The SabreTech employees were hurrying to complete the required tasks on the ValuJet MB-80s. They were more concerned about the new canisters being installed correctly, and did not pay too much attention to the expired canisters. As a result of this, and latent error 2, the SabreTech employees simply taped the firing cords to the canisters. While the plastic caps in latent error 3 would have prevented the canisters from activating, simply taping the cords did not. Once activated, apart from producing inflammable oxygen, the generators heat to over 200 degrees Celsius, enough to start a fire in their cardboard boxes.
Active error 2)
Due to confusion arising from latent error 1, the SabreTech employees incorrectly put a ‘repairable’ tag on the canisters. Some of the tags had ‘out of date’ written on them, and some had ‘expired, fired’ [according to SabreTech, expired did not mean fired, see latent error 1 above]. The canisters were then packed into five cardboard boxes.
Active error 3)
The SabreTech shipping clerk wrote up the paperwork so the canisters could be shipped back to ValuJet. He saw the ‘repairable’ tags on the canisters and naturally assumed this meant that the canisters were not working, but could be repaired later. Consequently, he took this to mean the canisters were empty, or at least could not be activated, hence the ‘repairable’ tag. He therefore wrote ‘oxygen canisters - empty’ on the shipping paperwork.
Active error 4)
The ValuJet ramp agent, who signed for the oxygen canisters and loaded them into flight 592, should have known that oxygen canisters were hazardous cargo. As part of his job, he had participated in a formal “hazardous goods identification course While the paperwork indeed said ‘empty’, ValuJet had specifically instructed ramp agents that maintenance contractors may send goods for shipping when in fact they are prohibited by FAA rules. FAA hazardous goods regulations prevented oxygen generators from being carried in aircraft. It would have taken the ramp agent only a few minutes to open the boxes and realise that the oxygen canisters were not expended [live], and incorrectly secured. Allowing the oxygen canister to be loaded onto the DC-9 was the final error in this chain of events, and an on-board fire was now unavoidable.
Latent error 4)
A final latent error contributed to the crash. While the fire was unavoidable, it may have been possible for the pilots to detect it earlier and return for a safe landing. There had been two similar incidents in 1986 and 1988, involving an American Trans Air DC-10 and an American Airlines MD-80. Both were destroyed by fire started by stored oxygen generators while on the ground. Even after these two incidents, the FAA had not required smoke detectors or fire suppressions system be fitted. The NTSB report criticized the FAA for this oversight. Such systems may have allowed flight 592 to land safely.
The crash of ValuJet flight 592 was a 'system accident'. These five active and latent errors formed an accident chain; if one link was missing, the accident would not have taken place. The NTSB subsequently split the blame for this accident three ways, with ValuJet, SabreTech, and the FAA being accountable.
-In 1997, ValuJet merged with Air Tran Airways, and took the latter’s name.
-In 1998, the FAA revised cargo compartment standards, requiring similar aircraft to be fitted with fire or smoke detectors (FAA, 19991).
-In 1999, SabreTech went out of business.