Autorotation vs Parachute

Two-seat R22 and four-seat R44 helicopters.

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tanglefoot
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Autorotation vs Parachute

Unread post by tanglefoot » Thu Jul 18, 2013 3:44 pm

Watching the FALA Cirrus thread unfold and came across this interesting statement.

viewtopic.php?f=9&t=118114&start=45#p1291629
sdbeach wrote:.....................So, you become a passenger in a vehicle descending at 17 knots (1700 fpm or 20 mph). Much lower impact energy than hitting something at flying speed, which in an SR20 is above about 60 knots.

That's a 12-times greater impact energy if you hit something -- like a rock, stump, fence, ditch, tree, etc.

Rick
The descent rate of a Cirrus under parachute is not much different (higher actually) than an R44 in full stable autorotation and you pancake the aircraft into the ground at that speed :shock: I'd have a good look at the survival statistics before I invest in a parachute. I'm confident that a goodly percentage of the survivors crashed on sloping ground and didn't take the full impact and the rest all had major back trauma and probably never walked again.

Imagine forgetting to flair at the bottom of an auto. 8-[

These fixed wing pilots, they are crazy :smt119
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Re: Autorotation vs Parachute

Unread post by sdbeach » Fri Jul 19, 2013 9:02 pm

tanglefoot wrote:Watching the FALA Cirrus thread unfold and came across this interesting statement.

viewtopic.php?f=9&t=118114&start=45#p1291629
sdbeach wrote:.....................So, you become a passenger in a vehicle descending at 17 knots (1700 fpm or 20 mph). Much lower impact energy than hitting something at flying speed, which in an SR20 is above about 60 knots.

That's a 12-times greater impact energy if you hit something -- like a rock, stump, fence, ditch, tree, etc.

Rick
The descent rate of a Cirrus under parachute is not much different (higher actually) than an R44 in full stable autorotation and you pancake the aircraft into the ground at that speed :shock: I'd have a good look at the survival statistics before I invest in a parachute. I'm confident that a goodly percentage of the survivors crashed on sloping ground and didn't take the full impact and the rest all had major back trauma and probably never walked again.

Imagine forgetting to flair at the bottom of an auto. 8-[

These fixed wing pilots, they are crazy :smt119
Those Cirrus fixed-wing pilots have the benefit of a whole set of energy absorbing features, starting with the flexing main landing gear and ending with 3-inch honeycomb seat pads. Cirrus designed to reduce injuries from a vertical impact.

Survival statistics are amazing. When the airframe parachute has fully deployed, no one has died -- 72 people survived. Some have had serious injuries including compression fractures of the vertabrae in the lower back, a fractured ankle, and a couple of cuts requiring stitches. The worst back injuries happened when the parachute snagged on a 600 foot communications mast and dropped the plane from higher up. However, to my knowledge, none of the injuries were permanent. (And that's unlike some off-airport landings that involved paralysis, but that's for the other thread . . . :wink: )

Cheers
Rick
Safety Liaison, Cirrus Owners and Pilots Association (COPA)
www.cirruspilots.org
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Re: Autorotation vs Parachute

Unread post by tanglefoot » Fri Jul 19, 2013 9:42 pm

I don't think that many aircraft are equipped to handle a vertical impact better than a helicopter. Skid deformation, seat deformation (much more than 8").

A 1700ft/m approach to the ground is still scary as all hell, even after practising it for 7yrs. Good thing about doing it in a fixed wing is that your viz is restricted so you can't see the ground rushing up :D

1700ft/m is more or less equivalent to being dropped vertically from 30ft which is considered survivable by the Robbie manufacturers.

Still wouldn't want to hit the ground at 1700ft/m, thank you very much #-o

As I said, fixed wing pilots are crazy :shock:
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