Hacker News new | ask | show | jobs
by voldacar 1699 days ago
I was about to leave a snarky "glide ratio = 0" comment until I saw the note about the ballistic parachute. Wish they included the effective altitude though. I assume it would be effective from a lower altitude than the Cirrus, as this thing weighs only ~400 lbs with a human in it.
2 comments

Parachute opening needs to balance between speed of deployment (because the ground is coming up) and G-force shock (because humans are squishy, and even the aircraft structure they're attached to has a limit).

Cirrus flies fast, so its parachute has a slider / limiter on it to reduce the speed of opening to keep the G shock manageable. On the other hand, since the top speed of this Jetson device is pretty low at 63mph, their parachute must have no slider and can probably be deployed from as little as 200 ft in ideal conditions. Depends on the exact model, your decision/reaction time, aircraft speed, attitude, and stability at time of deploy, etc.

The parachute should cost less than $5K, and its weight is not included in the 255lb weight limit (it's an FAA part 103 aircraft), so it's pretty much a no-brainer to add it to this aircraft, even if it's not very useful in very low level flights.

The official number is 400ft but I've heard anecdotes that there have been successful deployments lower. That said, I see this being operated in the "dead mans curve", ie well below any effective height, for a significant portion of it's flight
Surely there are flight patterns that can minimize this risk: ie diagnostic hover at 10ft for X seconds to rule out start up failures, followed by an ascend to 500ft, flight path maintains that height, similar pause prior to descent on landing...
This is usually done in helicopters, but it's not straight up and hover but instead a departure over the runway with forward speed. You can use that speed/energy in an emergency like losing an engine.
There are also enough false deployments that caused harm with these parachutes (edit: instances where pilots didn’t deploy when they should have) that the jury is out on how much of an improvement these are to safety, overall. Operator skill and training is a big factor and this product isn’t targeted at highly trained pilots.
I haven't heard of any deaths as a result but I'm sure there are a few. Usually it's just a hull loss.

That said, this looks like another Icon A5 situation...

I don’t have great sources, so take my claim with a grain of salt. But overall this analysis of Cirrus incidents over 25 years [0] was interesting to read.

In response to fatalities and pilots choosing not to use the parachute when that could have saved lives, Cirrus improved training and saw significant safety record improvements.

> By then, Cirrus had already upgraded its training twice, eventually pulling it entirely in-house. All new-aircraft buyers take it.

They also have training for the used market, and saw owners that didn’t do it often had worse safety records.

Since a Cirrus has a wing, the parachute is primarily a super last resort.. the passenger safety training I took even said it’s mainly to be used if the pilot passes out and a passenger engages it.

The jetson doesn’t have a wing, so I’m happy they have this parachute. I hope they can offer great training too.

[0] https://www.aviationconsumer.com/safety/cirrus-at-25-a-safer...

The new Garmin Autonomi system is designed so that a passenger can push one button to land the airplane if the pilot passes out.

https://discover.garmin.com/en-US/autonomi/