I noticed this initially when learning to fly Robinson Helicopters but fail to remember the reason my instructor gave me; this again came up when watching a video about the ISS.
- In helicopters (Robinson R22/44), the main rotor typically operates at 104% RPM.
- On the space shuttle, after max q, they throttle back up to 104%.
What is the significance of 104%? If this is the maximum, why is this not called 100%, and everything scaled back to fit? This seems the most fit place to ask this, as I have only seen this in aviation / aerospace.