Report shows Boeing 747-400 incident was caused by take-off weight transcription error and pilot misconduct

The crew of a Singapore Airlines (SIA) Boeing 747-400 that suffered a severe tailscrape on take-off from Auckland for Singapore made basic errors that could have led to a serious accident, according to New Zealand investigators.

The Transport Accident Investigation Commission (TAIC) says in a final report into the tailscrape on 12 March 2003 that a take-off weight transcription error led to a take-off data miscalculation. This resulted in a low thrust setting "and excessively slow take-off reference speeds".

On the load sheet for this aircraft (9V-SMT), which was embarking on a 9h flight, the take-off and the landing weights were almost the same - 247.4t for take-off and 247.04t for landing. The actual take-off weight was 347.4t, says the report, but the pilots did not carry out independent comparison checks - as required by standard procedures - on the various calculated weights: fuel on board, estimated fuel usage, zero fuel weight and take-off weight. The report says although the "bug" speed settings the crew used were far lower than they were accustomed to, they did not query them.

Rotation speed was calculated as 33kt (61km/h) less than the 163kt required. At rotation the tail struck the runway "and scraped for some 490m until the aeroplane became airborne", says the report. Compounding the situation, the crew reacted inadequately to the developing problems.

The report says: "During the take-off the aircraft moved close to the runway edge and the pilots did not respond correctly to a stall warning. Had the aeroplane moved off the runway or stalled, a more serious accident could have occurred." The TAIC says the aircraft was almost at stalling speed as it lifted off, and the stickshaker had been operating for 6s, but none of the crew called for extra power.

The captain, who has since left SIA, had 12,475h flying but only 54h on the 747-400. The first officer in the right-hand seat had 223h on type and 1,309h in total, and an additional first officer on the flightdeck had around 3,400h on type.

The TAIC observes: "The system defences did not ensure the errors were detected, and the aeroplane flight-management system itself did not provide a final defence against mismatched information being programmed into it." The TAIC has recommended that SIA use this flightdeck scenario "as a topic for pilot recurrency training or line-oriented flight training in simulators to enhance pilot awareness and crew resource management skills."

The crew returned the aircraft to Auckland and made an overweight emergency landing. None of the 369 passengers or 20 crew was injured. SIA says "lessons have been learned and several procedural changes already implemented".

Source: Flight International