DB;
However, the point I was trying to make, that may be relevant to this accident, is that as a general practice when the pump cavitated pilots would switch the pump OFF and then acknowledge the caution. This would effectively mean that the pump ends up OFF and there are no immediate indications on the CAD to indicate this. Can we agree on this?
A combination of nose down followed by nose up (hovering), could prompt the pilot to carry out this action for both pumps. Now there is no transfer capability from the Main Tank to the Supply Tanks AND there are no visible indications (other than the switch position) to indicate this.
I am qualified to operate the EC135 but have no operating experience at this point. Hence my poor explanation of the pump logic. Please forgive me for this.
The relevant point is the pumps getting switched off and the caption acknowledged which effectively removes it from page 1 of the CAD.
I think you need to understand that with the transfer pump(s) switched off and caution acknowledged, the CAD will still be indicating
F PUMP FWD or
F PUMP AFT on the centre display column,depending on which pump has been switched off.
In normal operation, the only items displayed on the CAD would be PITOT HTR , with S\L LIGHT if switched on.
In the last many minutes of this particular flight, the CAD indications alone presented to the crew should have been PITOT HTR, F PUMP, FWD F, PUMP AFT, PRIME PUMP (1), PRIME PUMP(2), FUEL ... meaning at least three acknowledgements of the master caution. Then of course the Warning Panel indications should also be presenting themselves ...