object strikes

[guest]

Are most major injuries that result from object strike due to the collision with the object itself or the resultant canopy collapse and impact with the ground/talus?

How probable is a canopy collapse/deflation in the event of a head-on strike, where forward speed is reduced to zero? Is it a sure thing?

Is there real-world evidence that indicates that bottom-skin-vented canopies are more likely to maintain inflation when decelerated to zero by an object strike?

What is the vertical decent rate of a bottom-skin-vented canopy when it has zero a forward airspeed and inflation is being maintained only by vent-pressurization? Is it a decent rate that, with a good PLF, would result in few injuries?

Thanks

[crwper]

Hmm, a PLF is very difficult without some kind of horizontal motion, and wouldn't be very effective into talus, I should think.

Michael

[space]

Very situational question,
If the leading edge hangs up, air is expelled. If not, not.
take care,
space
ps, don´t do jumps like that until there is equipment designed to do that. Bottom-skin-vented canopies are designed for faster opening control, not object strikes.

[guest]

BTT

[imported_Tom Aiello]

>Is there real-world evidence that indicates that
>bottom-skin-vented canopies are more likely to
>maintain inflation when decelerated to zero by
>an object strike?

Yes. I have a video of a Vtec FOX remaining inflated through the secondary inlets while nosed into a wall with zero forward speed (it actually has some backward speed).

While this is good evidence indicating that the canopy will remain inflated under these circumstances, it is not conclusive.

--Tom Aiello
tbaiello@mac.com

[guest]

Re Tom's comment, while your video datum does support your theory that the canopy's inflation was due to air intake through the secondary inlets, as you say, it is not conclusive at all, in fact it would be very difficult, short of using smoke or colored gas in a more controlled situation, to say that the secondary inlets had anything to do with the canopy remaining inflated.

I'm not discounting potential advantages of vented canopies, and not saying that the vented canopy didn't have something to do with the inflated state of the canopy in this specific instance. Nevertheless, I have personally observed more than a 'few' data points of my own where standard non-vented canopies remained inflated surprisingly well despite being nose first into the wall (and other angles of attack too), and I would assume there are plenty of jumpers out there who have observed similar results from wall strikes with non-vented canopies. In fact any ram air canopy will tend to remain inflated during a nose first wall strike and simply descend straight down the wall remaining inflated and 'attempting' to go 'forward' into the wall, that is without pilot input and/or the canopy actually snagging on the wall. I believe it is the canopy hanging up on the wall which is most likely to result in dangerous airfoil deformations and hence canopy deflation. Maybe under these circumstances a vented canopy would recover quicker with less loss of altitude?


DT

[space]

Very situational question. If the nose is being trashed, the airfoil is gone,saw this in Norway, the canopy acted like a round, the jumper was unable to even turn it away, On the other side, i watched 3 jumpers in a row nail hop-n-pop with the dreaded 90° left, 2 vented, one not, the one not was needing rescue, but the vented could not escape the trees either..

I don´t think that a canopy snag will release without damage to the leading edge,, I´ve checked 7 cliff strike canopies,,
If the airfoil cannot produce enough lift then you have some weird version of bottomskin drag like a round and cell inflation has little effect IMHO...
take care,
space