The US National Transportation Safety Board (NTSB) is strongly urging the FAA to adopt new regulations specific to Boeing MD-11 aircraft to stave off a raft of hard landings that began in 1993 and continued through 2010.
"Although it is not uncommon for jet transport aircraft to experience a small skip or bounce during landing, since it was entered into service in 1990, the MD-11 has had at least 14 events of such severity that the aircraft sustained substantial damage," said NTSB in a recommendation letter to the FAA. Four of those events were complete hull losses while seven events have occurred during the last two years, the board stressed, including five in 2009.
"The number and severity of these events raise concerns that the MD-11 flight crews are not effectively trained to recognise and arrest high sink rates during landing to properly control pitch attitude following a hard landing," the board concluded.
To drive home its point to the FAA the board focused primarily on a 27 July 2010 incident involving a Lufthansa Cargo MD-11F that caught fire after a hard landing at King Khalid International airport in Riyadh, Saudi Arabia.
The captain, who was the pilot monitoring the approach, "did not call out the high sink rate or call for a go-around as suggested in the Lufthansa Cargo operating manual", said NTSB.
Following initial touchdown, the aircraft bounced 1.4m (4.7ft) off the runway and touched down a second time at 3.0G. After the second touchdown, explained NTSB, the aircraft reached a pitch attitude of 13 degrees and on third touchdown the main landing gear exceeded 4G. Flight data indicated two large forward and aft column inputs were made between the first and final touchdown, said NTSB.
The first officer operating the aircraft has completed bounced recovery landing training that entails an instructor demonstrating a hard landing during a simulator session, with the trainee taking control and maintaining 7.5 degrees of pitch, and applies go-around thrust to recover.
"The company's MD-11 chief flight instructor stated the simulator was limited in its ability to capture the true sensation of a bounced landing," said the board.
NTSB also referenced a 13 September 2009 Lufthansa Cargo hard landing incident in Mexico City. The board stated the aircraft did not begin flare until 6.1m (20ft) agl, and the sink rate was roughly 311 metres [1,020 ft per minute] during the last five seconds before touchdown.
The board highlighted that MD-11s are certified to land at maximum weight at a sink rate of 182m [600 ft] per minute, with an ultimate sink rate of 3.7m [12.3ft] per second.
Despite corrective action taken in the past, "MD-11 crews continue to have difficulty in judging the flare manoeuvre and in making appropriate pitch and power changes after hard landings", said NTSB.
The two latest recommendations sent to FAA by NTSB would require Boeing to revise the MD-11 flight crew operating manuals to re-emphasise high sink rate awareness and to stress the importance of momentarily maintaining landing pitch attitude after touchdown, and using proper pitch attitude to cushion sink rate in the fare, and to perform a go-around after a bounced landing.
NTSB's second recommendation states FAA should require all MD-11 operators to incorporate Boeing-recommended bounce recognition and recovery procedures in its operating manuals and in recurrent simulator training.
Source: Air Transport Intelligence news
