A good question.
What kind of aircraft? Are you just lowering the collective or are you pulling the "trigger" and lowering the collective? Are you manipulating the trim switch on the collective?
The " Hollywood " answer is that the helicopter would explode in a fireball that would put the Bikini nuclear tests to shame.
"Humour" answer - 7 of 10 captains would slap you upside the head with the OPS manual.
reality depending on the aircraft is that probably the collective trim would go to full travel and then the collective trim would give up and alt should decouple.
In a 225 you will descend and you will get advisory chevrons on the FND. until you release the colective - order will be restored and the ac will return to the altitude selected the autopilot will not decouple..
Last edited by albatross; 21st Nov 2013 at 03:51.