The final analysis of the TAM accident is months away; however, the raw data is shedding considerable light on the catastrophe.
After any aircraft accident the investigation is a painstakingly slow process. All the aircraft, airline, manufacturer, meteorological, air traffic control and crew data is gathered. Furthermore, on-site information is collected from as many sources as possible. Once this is completed the long arduous task of interpreting and combining this data is undertaken and causes are named. This article will present that basic data in the TAM Flight 3054 accident.
There is more to an investigation than simply naming a cause. Investigators desire to understand why those causes resulted in the accident. A primary cause will definitely be named but contributing factors will also be addressed: those factors, if absent, that would have prevented the accident from occurring. This determination and the subsequent report are the most time consuming events of the analysis. But there were 4 extremely good pieces of data that gives an excellent early picture of the sequence of events that occurred in São Paulo, Brazil.
Digital Flight Data Recorder:
The DFDR, also called the “black box,” records hundreds of individual parameters of the aircraft in all stages of movement. This data gives acceleration information, servo positions and pilot input to mention a few. The accident data shows a series of important factors.
- The aircraft touched down normally in the proper touchdown zone on the runway.
- The auto-brakes and auto-spoilers were armed.*
- The #2 engine was not in idle detent.
- The aircraft failed to decelerate.
- The aircraft left the runway at 99kts (approximately 114 mph or 182 kph.)
Cockpit Voice Recorder:
The CVR, the other black box, consists of a highly sensitive area microphone located in the cockpit. It records all sounds in the area including human speech as well as aircraft noises. When combined with the DFDR data investigators gain insight to events. The CVR data in this accident revealed several things:
- The pilots were aware of the mechanical limitations of their aircraft.
- The pilots were aware of the airport and runway conditions and expressed concern.
- The pilots were aware the auto-spoilers did not deploy.
- The pilots were aware the aircraft was not slowing down.
- 10.8 seconds prior to the impact the pilots realized the aircraft absolutely would not slow down.
Maintenance Logs:
These records provide a complete link of all aircraft specific problems the airplane has had since it was built. The most vital records are the last several flights. The accident aircraft's logs revealed extenuating conditions.
- The aircraft was released under MEL** conditions.
- The #2 engine Thrust Reverses* (TR) was under MEL.
External Information:
A significant piece of information, which is not always available, was the actual landing video tapes of the aircraft accident.
- The tapes show the aircraft was not decelerating.
- The tapes show the aircraft departed the runway at a high rate of speed.
Results:
The data shows important information that will most likely be listed as a primary contributor to the cause of the accident.
- The aircraft failed to decelerate due to failure of the brakes and ground spoilers to actuate early in the landing roll. This was caused by failure to retard the #2 engine to idle thrust.
Additional failure of the spoilers to place “weight on wheels” early resulted in ineffectual manual braking by the pilots late in the landing roll. There was insufficient runway to stop the aircraft by this means.
Certainly additional factors will be attributed to the accident. Potential hydroplaning caused by a wet, ungroved runway played a significant role. The runway length played a major role as did ATC procedures. The fact that a thrust reverser was on MEL was crucial in both aircraft performance and human factors; but for this accident the raw data is quite compelling.
* Devices to slow the aircraft after landing located on the wings, brakes and engines.
** MEL (minimum equipment list) which allows an aircraft to operate with certain items not working.
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