Canadair push back collision
There are situations pilots will not encounter, but are encountered by maint. personel.
I can think of at least 3 of them, that could have led to this accident.
One is to make sure the ADG squibb will fire after loosing the last generator( in the air).
The procedure was to disconnect the squibb connector, and hook it up to another connector with a 15ma fuse.
After starting the engines and APU, the weight- on- wheel breakers were pulled, then the gen. switched off one at the time; the fuse would blow after the last gen. failed. You have to realise, the brakes will go off with WOW.
Another test was to make sure the ACU would go to "HIGH" mode if the other failed "in the air". This required a similar procedure.
A third, is to make sure the ground spoilers (once deployed) will snap shut when the throttles are advanced above idle, again "in the air". This one was brought out following the crash of a DC-8, in Toronto, in 1970, where the ground spoilers did not retract during a touch-and-go scenario.
Of course, this test is usually done in the hangar, but nothing stops you from doing during a run-up, along with a number of other tests following a maint. check or simply a repair to a system.
Following a check list is fine ( step 1: apply parking brakes) when everything is serviceable and all the breakers are "in", like a pilot going to fly.
Maint. tests are often done with some breakers pulled, on systems still being worked on, making it difficult to "find" them in a panic situation.
Of course, I'm speculating until more is known, but I suspect one of these scenario was being performed, not realising the brakes would be released while WOW, and when they realised they were moving, they would have stepped on the brakes as the first reaction, then panic, then if they realised the breakers were pulled, find them and push them in; by then, they're moving...
As for safety procedures, that tractor should have been nowhere near in front of the a/c;that's an absolute no-no; it is to be parked well away from the a/c, and to the side of it; there should never be anyone standing in front of a running engine: to the side and well clear of the wing, with the a/c in his sight at all times.
Lastly, when performing testing similar to the above mentioned, we always carried a heavy rubber set of chucks with us before leaving the hangar.
The old phrase: There is never time to do it right, but there's always time to do it twice.
I also realise some of these checks may have been modified or discontinued by now, but I did lots of them, always requiring total concentration.