> New York City could be a prime market but there are only a few heliports.

Afaik rooftop helipads have been banned in NYC ever since an accident in 1977 killed five people.

There are three heliports on the rivers around Manhattan. There’s plenty of space to build more but noise complaints prevent that from happening. Bezos wanted to build one on the Queens waterfront (LIC) but the city killed the idea.

Any idea what the minimum height for the parachute to be effective as a life saving device?

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.