Minimum effective altitude for parachutes on light aircraft is about 400 ft agl, but the exact number varies depending on the flight regime. For powered lift aircraft there is likely a small "dead zone" in the flight envelope: too high to survive a crash, too low for the parachute to be effective. This may or may not be acceptable depending on mission risk tolerance and the reliability of other systems.

https://www.aopa.org/news-and-media/all-news/2018/march/flig...

> too high to survive a crash, too low for the parachute to be effective

This is probably a silly question, but couldn't the pilot just wait until the plane dropped below the dead zone before deploying the parachute?

You're thinking about the dead zone in the wrong way: There's a height X where you can drop the aircraft and it'll absorb all the forces to have the people live. There's a height Y where the parachute has enough time to deploy and bring the aircraft to terminal velocity. If X is less than Y, there's a height where there's nothing to save you.

Options to resolve this are: make X higher by making the structure able to absorb more energy, or make Y lower by having it deploy faster.

The lower the craft drops, the deader the zone.

The Cirrus SR22 needs ~1000ft above ground to effectively deploy the airframe parachute in a spin.