Years ago I was flying Trislanders. Because a failure of the centre engine wasn't that obvious, there was a light on the panel marked "No. 2 Engine Fail". The system was switched on before takeoff, and subsequently the light began to flash. Bearing in mind that the first pax row is directly behind the pilot, and we frequently had a passenger in the RHS, it was common to get the dig in the back of the neck and.."Ere, pilot".