"First I heard a big explosion. Then I saw flames come out from behind the plane. And then a whole wing with the engine fell off." - Antonio Villela, a construction worker.
F.O.D. kills (foreign object damage)
You must work for the airlines. I'll bet it was another frayed wire in the belly fuel tank?
Actually, no, I don't work for an airline. I used to be in the Air Force. I spent ten years as a jet engine mechanic on the F-15 and the F-16 as my primary airframe. I helped with the Field Service Evaluation on the F100-PW-220 and the 229, picked up numerous aircraft that pilots managed to lose, and worked in several crash investigations. So, now that we know a little bit more about my background, how long were you working in jet engine maintenance?
Ok. So they left a wrench in the cowling, fifteen feet above the pilot's head. That implies that the wrench is inside the nacelle, away from the airflow. The lower lip of the intake is within the pilot's view. So, now they have this wrench inside the nacelle, where the pilot can't see it on inspection. This means that it is out of the primary gaspath, and since the lip of the compressor is sealed to the front of the nacelle, that means the wrench is stuck inside...or did they rig a trap door that would suddenly drop the wrench into the airflow, allowing it to be ingested?
Now, assuming that there was no trap door, and the wrench was loose in the flowpath, what kept it from being ingested on engine start? I've seen items get ingested before at 75% power on an engine with lower thrust ratings than these. Once the item is ingested, it doesn't just sit there, damage begins immediately, starting at the inlet fan, and working its way back through the compressor. Big shards would get caught up against the combustion chamber and fuel nozzles. Smaller bits of debris would work their way through and shell out the turbine...now, this would be on the start, not at taxi or take off. So now the pilots are taxiing out with a FODded engine, and despite the noise, vibration and smoke, as well as the FTIT (Fan Turbine Inlet Temperature) and EGT (Exhaust Gas Temperature) gauges going nuts in the cockpit, they elect to take off anyways.
It's all starting to make sense now.....