Fire in the engine

This happened to one of the Squadron test pilots, after he had completed the typical test flight to one of the airplanes after coming out of an inspection, as he came up to the field and making the initial turn at 1500 feet and deploying the landing gear, he saw the FIRE light flashing.   

Immediately he declares an emergency and as he reached the runway he noted that the light had stopped flashing and now was on permanently. The reaction of the pilot should have been to launch the parachute according to the procedures with the consequences of the loss of the airplane, but the pilot remained calm and after waiting for a bit to see what would happen was god sent.

Once on land, and following immediate check, it was found that the identical lens caps for the FIRE and LANDING lights, located on the left side of the front panel, were interchanged.

For this reason, the light FIRE was flashing when the landing gear was deployed and it was steady on when the landing gear was locked.