G2,
In FAA AC 27-1B, Look for AC 27.79, (b) (6) (i), Landing Gear Loads, High Hover (around page B-40). It specifies a one second delay between recognizing the engine failure, and lowering the collective. I've done the test a few times, that's a long second!
Otherwise, I'm not aware of a similar standard for engine failures on airplanes, though AC 23-8B would be a good place to look. I have had long discussions with Transport Canada Aircraft Certification about the required delays for pilots to recognize electrical system failures, and we have agreed on some benchmarks, depending on the nature of the annunciation. That presumes a failure which does not make itself apparent though...