Engines Auxiliary Power Unit (APU) Practice Exam

The amber REV indicator is a caution signal that shows the thrust reverser is not in its stowed position. When you move the reverser away from the stowed position, this amber light comes on to alert you that the reverser is now out of its normal safe position and status needs monitoring (retraction or deployment as appropriate).

It isn’t signaling deployed as a normal full reverse is active, and it isn’t indicating a fault (fault warnings are typically red). It also doesn’t relate to engine idle—idle status is shown by N1 and other engine parameters, not this reverser annunciator. So the amber REV light specifically tells you the reverser has been moved from the stowed position.