Tijd voor een motorstoring

Trainen in de luchtvaart is gerelateerd aan tijd. Acties die we in de simulator trainen zijn gebaseerd op een evaluatie van een probleem. Die evaluatie kost tijd. Daarna nemen we actie op wat we denken dat er aan de hand is. Soms kan die actie uitgesteld worden. In een ander geval is snel handelen geboden. Vaste rituelen leren we daarbij, gestructureerde handelingen die vlot maar niet overhaast gedaan moeten worden.

N-1 at Vrotate

From the Captains report:

Due to a small technical problem with the brakes  our pre-flight preparation took longer than normal at Schiphol Airport.  For this reason we arrived late at our Boeing 767 and hence the passengers were already boarding the plane. The period from pre-flight until taxiing to our take-off runway were uneventful with the First Officer (F/O) as pilot flying.

Weather conditions were good and we made a de-rated thrust take-off with a rather high take-off weight. The take-off was made during nighttime conditions and just when we passed  V1 (only about 3 Kts below Vr), we experienced a rapid drop in N1 on one of the engines from 100% to 60% together with vibration.

First you almost do not believe it at this point but rapidly the engine instruments tell you the truth. At 400 ft we started the memory items and while retarding the Thrust Levers, the vibration vanished and all the indications of the engine parameters were like those of a normally running engine at idle thrust. At this point we decided to leave the engine running in idle instead of switching it off, contrary to our AOM procedures and memory items. Both the unknown cause of the failure together with normal engine indications (the situation seemed under control) prompted us to make this decision (we were aware of the fact that FMS presentation and switching is affected by the position of the fuel control switch).

The moment we gave ATC a PAN PAN call, Schiphol Tower gave excellent support on our own discrete frequency and by means of radar vectors we were put in a holding pattern over the ADF beacon "OA" for runway 19R.
The event was also out of the ordinary for the cabin crew. As we did not see all the crewmembers before our departure, same of them did not even know which pilots were sitting in the cockpit. The first time I contacted the purser was after the clean-up of the aircraft, which took quite same time due to the high TOW. I expected that our purser would explain the situation to the other cabin staff, however, here something went wrong so some of our Cabin Attendants got the first information about what happened via the Public Address announcement. In my opinion it would be wiser in this case to ask the purser to brief the cabin staff before starting the PAS announcement.

After the approach preparations we started our approach for runway 19R and the F/O made a perfect landing. After turning off the landing runway, we switched off the damaged engine and taxied to the gate. After trying to arrange support for our passengers and informing various persons about what had transpired, we exited the aircraft, together with our cabin crew, to look at the engine. For the first time the damage was visible to us and it was clearly more damaged than we had evaluated from our cockpit instruments. Several engine parts were propelled into the flaps and ailerons, which made it obvious that more serious damage was not at all unrealistic.
This made it also very clear to us that it is hard to make sound judgements about the extent of the inflicted damage to engines and aircraft by only observing your instruments. Besides this, it also proved to us that most of the damage to engines in the take-off phase can probably better be interpreted as severe damage and also that most actual engine failures do not resemble the failures that are trained in the simulator.

Post script:

An actual engine failure at the most critical point of the takeoff ( a so-called V1 engine failure ) is a extremeley rare event. When this engine failure took place on a KLM B767 it was the first recorded case for almost 20 years. It shows that engine failures of this type are rare but since it is the most critical event during takeoff it is still a requirement to train and assess this scenario on the simulator.