The thrust reverser may be deployed: * Inflight when the thrust lever is at idle * When either radio altimeter is sensing less than 10 feet altitude * When the air/ground safety sensor is in the ground mode * All of the above

Yes, no and maybe :( "* Inflight when the thrust lever is at idle"A thrust lever must be at idle because there is a mechanical interlock preventing the reverse lever being lifted if the corresponding forward lever isn't fully back. In flight, you are, however, restricted by the logic "When either radio altimeter is sensing less than 10 feet radio height""* When either radio altimeter is sensing less than 10 feet altitude"Yes, but not if the throttles aren't at idle : P"* When the air/ground safety sensor is in the ground mode"Well, there is more than one air/ground safety sensor, but yes, if the appropriate sensors are registering that the aircraft is on the ground (irrespective of what the Rad Altimeters are telling you), then you will be able to deploy the reversers if your forward thrust levers are at idle.Note that if the reversers do start deploying by accident in flight, that the Engine ECU's will tell the engine/s to go to idle (irrespective of thrust lever position).Do I pass? Cheers.Qavion.

Q: I enjoy the complexity you can bring to table. What kind of failure would result in a reverser deployment in flight? Seem like several things would have to go wrong.

Well, Murphy's Law tells us that if anything can go wrong, it will ; )Fortunately, aircraft that have been around as long as the 737 usually have most of the bugs sorted out (I'm talking about real world bugs here). It's usually only the very bizarre circumstances which bypass all the safety systems. But it's usually a combination of human error, airplane defects and weather which is required to trigger a catastrophe. On the 737, for example, if only one faulty Rad Alt (say, reading zero feet*) has the ability to allow the deployment of the reverser in flight at any altitude, then it opens the door for human error and environmental effects to deploy the reverser at the wrong time. *We know it can do this from the relatively recent accident where a 737 fell out of the sky because the flight crew didn't notice that their faulty Rad Alt had caused the A/T to go into a somewhat premature flare idle mode.Unfortunately, I've seen the effect that airline cost-cutting can do on the level of maintenance carried out these days. If you start cutting staff, reduce training and generally making it more difficult for people to do their jobs, then accidents are more likely to happen. I could even give you a few personal examples, but this is not really the time and place for it ; )You may have heard of the recent near-accident involving a British Airways 747-400 out of Johannesburg. Part of the reverser logic caused the Leading Edge Flaps to retract during takeoff. Some folks are putting this down to human (maintenance) error, but the adjustment of this system has long been known to be too critical (i.e. a position sensor for a large and somewhat flexible part of the aircraft (subjected to aerodynamic forces), requires millimeter precision). This should not be allowed in the design. Anyway, we (the flying public) won't have to worry about this anymore, aircraft have already been modified to prevent this happening again.Hope this helps)CheersQ>

Very interesting, thanks!I know all too well how insightful Maj. Murphy (USAF) was with his observation. I've seen safety systems in industry bypassed because they have annoying alarms :(

I would say that the most correct answer would be that the A/C has to be in ground mode for the reversers to be actuated.