A sound like that of a stall-warning stick-shaker was recorded during the last 2min 46s of flight of the West Caribbean Airways Boeing MD-82 that crashed in Venezuela on 16 August, says an initial factual report published by the Venezuelan accident investigation agency CIAA.
The crew reported having lost power on both engines, but the aircraft hit the ground in a slightly nose-up attitude with both engines turning at high speed on impact, and it took only 205m (670ft) ground travel for the wreckage to come to a halt. All 160 people on board were killed.
The flight data recorder (FDR) provided good information, but the channel for the left engine’s data was not operating, says the US National Transportation Safety Board (NTSB), which has been charged with publishing the report for the CIAA.
The starboard engine data shows that its power never reduced below flight idle at any time during the descent, which took about 3min 30s from flight level 330 (33,000ft/10,060m). The cockpit voice recorder (CVR) sound quality was not good, but investigators say it was useful.
The aircraft, operating a charter from Panama City to Fort de France, Martinique in the French Caribbean, had climbed to FL330 and accelerated to its cruise Mach number of 0.76 without any anomalies.
After reaching FL330 the crew began “discussing weather concerns that included possible icing conditions”, says the NTSB transcript, but there is no record of whether they selected any engine or airframe anti-icing. Some 90s after stabilising at 0.76, the Mach number began to reduce until it reached M0.6, when the autopilot was disengaged and the descent began.
During the speed reduction of FL330, the stabiliser pitch trim had moved from two units nose-up to four units up.
The time to impact from the beginning of the descent was about 3min 30s, but the report records that the right-engine pressure ratio (EPR) never reduced below idle EPR, and “even increased several times including shortly before the end of the recording”.
Upon leaving FL330, the crew at first requested clearance to FL310, then made subsequent requests for FL290, FL240, and finally 14,000ft. About 2min 40s before impact “a sound similar to stick-shaker” began, followed by an aural stall warning, and the stick-shaker did not stop for the rest of the recording. It was not until 1min after the stick-shaker sound began that the crew first reported double power loss and, the report says, the pilots were not heard carrying out any checklist routine.
When the aircraft hit the ground its horizontal stabiliser was trimmed for maximum nose-up pitch.
DAVID LEARMOUNT/LONDON
Source: Flight International
