B737-when is it safe to switch off the anti-collision light?
Aircraft stops at aerobridge and starts levers selected to cut-off. Some operators require that the anti-collision light should not be turned off until the engines have run down by 20 seconds - or 20% N2. The idea being that ground staff should not move towards the cargo holds until it is safe to do so.
The ear protectors worn by ground staff don't cut all noise, but simply reduce it to non-dangerous levels. So why can't they listen to the engine noise running down rather than watch for the anti-collision light to stop rotating? Is 20% N2 sufficiently low thrust to prevent someone being blown over?