This is turning into a great thread, thanks for the replies everyone.
But I hope someone will answer my question (perhaps it was not clear enough)
I know that under normal circumstances most aircraft (all?) have indicators for thrust reverser deployment -when on the ground-.
But.. When you are in the air, and the reverser has deployed, for example by aerodynamic forces, or mechanical failure (parts falling off etc) - will the indicators still appear in your aircraft? Is there some kind of mechanical or electrical sensor that physically or electronically detects that the reverser door or doors are not stowed completely? Does it detect when the door is only open slightly or do the doors need to open to the stops before the sensor detects it? If the cause of the deployment is due to faulty maintenance, will the sensor (i.e. in the Airbus) still be able to detect that the door is open?
Sounds like some aircraft have a physical link to the throttles which slams the throttle lever down. That sounds like a nasty hospital bill but certainly better than crashing. What about in the Boeings and others i.e. CRJ?
And if for some reason you did not get a cockpit indicator, do you think you would still come to the conclusion that your reverser was stuck open and act appropriately? Or would you be hunting for other possible solutions and miss the obvious as the Lear crew did?