The Hong Kong Air Accident Investigation Authority (AAIA) has released its preliminary report on the airACT 747 freighter that veered off the runway on 20 October, striking a security vehicle and pushing it into the sea, killing both occupants.
The 747 also went through the airport perimeter fence into the sea. The aircraft’s crew of four were able to safely evacuate, while the aircraft was damaged beyond repair.
As with all preliminary accident investigation reports, the AAIB only provides factual information. The final report, usually available approximately 12 months after an accident, will detail what investigators believe to be the probable cause.
Notable findings
The preliminary report notes that the aircraft was dispatched per the Minimum equipment list with Engine number 4 thrust reverse inoperative. The first officer was the pilot flying, the captain was the pilot monitoring.
Upon landing the speed brake lever was extended “with the appropriate crew call.” Reverse thrust was deployed on engines 2 & 3 at approximately 95% of N1. Engine 1 was selected to idle reverse.
The crew received an AUTOBRAKES message on the Engine-indicating and crew-alerting system (EICAS) screen (exact time is not noted in the report), and the autobrake was disarmed, with the crew calling “manual braking.” The captain took control of the aircraft at this time.
The time stamps in the image above are taken from the preliminary report based on the aircraft’s Flight Data Recorder. We have collated those times to the ADS-B data sent from the aircraft’s transponder to provide a visual reference.
At 19:52:30 UTC (03:52:30 local time), Engine number 4 “accelerated to 90% N1 forward thrust.” The selected thrust reversers (ENG 2 & 3) were stowed at 19:52:35.
Engine number 4 continued to accelerate, achieving 106% of N1 at 19:52:36 and reaching 107% of N1 by 19:52:42.
Reverse thrust was applied on Engine number 2 at 19:52:41. Thrust reversers on Engines 1 & 3 were also deployed, but no specific time is noted on the deployment of these in the report.
Investigative next steps
The AAIA says it will continue collecting data with particular focus on aircraft systems and performance, maintenance records, flight crew qualifications and experience, human factors, and Safety Management Systems.
Specifically, investigators note a focus on “technical issues related to aircraft systems and performance, including the aircraft’s speed, system status and operational control at the time of the accident, as well as conditions and performance of the aircraft engines, the forward movement of the Number 4 engine thrust lever, the landing gears and the associated brake systems, etc.”
18 Responses
In the good old days on the 747-200 the Flight Engineer, after touch down, was holding the four thrust levers in idle position and, in case of one reverse inoperative, both (#1 and #4 in this case) reverse levers into stowed position…
Cdl and suggested to be a technical issue on eng 4 which keep accelerating power and three engines deployed reverse thrust! That finally push flight to sharply turn left…..
What’s the final decision on Air lndia
Flight which crashed in Ahmedabad
Can I buy the cockpit of this aircraft?
Clearly a case of uncommented auto throttle failure. With engines reverse thrust. Doubt pilots spooled it. Auto throttle failure
Uncommanded instead of uncommented I guess
Not possible due the way autothrottle work on B747
How come the A/C was even allowed to take off with one reverser known to be inoperative?
This is because reversers are not very important for slowdown. Passengers might think they play a big role, but actually, it is mainly the brakes that stop the plane. Generally, when calculating the distance for a plane to fully stop at landing, reversers are not considered at all! They are just a “bonus”. So it is not surprising if some airlines decide that planes can be allowed to take off without any working reverser.
yes agree – its just an issue for the accelerate stop case…… MTOW reduction !
It is possible to depart with a reverser locked out. The MEL ( min equipment list) will state the conditions which have to be met!!
How was the a/c even allowed to depart with one reverser inoperative?
As noted in the report, the Minimum Equipment List provides for dispatch of the aircraft when certain equipment ins inoperative. The MEL notes what steps must be taken to ensure continued safe flight when that equipment is inoperative.
Exactly. I see Ian P explains how the MEL works but that doesn’t address your question. To have a nonfunctioning thrust reverser seems like a critical deficiency. I’m sure the MEL points out what needs to be done to compensate, but I still don’t see how anything that interferes with normal landing procedure should ever be tolerated.
Be interesting to know what the MEL was exactly for this particular aircraft, and whether it was allowed to fly under the laws of the country of registration with certain equipment ‘disabled’.
It is possible to depart with a reverser locked out. The MEL ( min equipment list) will state the conditions which have to be met!!
Whatever happened to #4 eng fuel control shutoff or #4 eng fire switch pulled?
Völlig normal das ein Reverser Inop gesetzt werden darf. Gem MEL