Aug 30, 2006, 12:52 AM
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round canopy, pucker vent question
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Did pucker vents actually do anything useful on C 9 canopies? It was an elastic banded thing that closed the apex hole if pressure was low. I kept mine but everyone else I know cut them out. Maybe they helped in high speed ejections, but sure didnt seem to do much in a skydiving jump. My C 9 was so worn out and porous that I never had one standup jumping it over a hundred times. It was BRUTAL, but I was too poor to get anything better at that time. I'd probably be an inch taller today if I could have afforded a PC back then.
Pucker vents probably made a difference on new C9 canopies at higher velocities. A lot of weird things (i.e. rubber bands dumping lines, post-inflation slump, etc.) happen at velocities faster than 250 knots that have been forgotten by skydivers.
OK, here's what I think (and mine was cut out). Remember that round canopies open because of a low pressure area created on the TOP of the parachute by the high speed flow of air, not because of air blowing up from the bottom (recall all the photos of rounds with the top mushroomed out, but the skirt still mostly gathered). That pucker vent should have staged the opening somewhat, which would have decreased opening shock and increased reliability by allowing for more line stretch before skirt separation. Very important at higher velocities. Blue skies, Tom
Somewhere on the Internet there was a video of a C 9 high speed opening shot by a VERY high speed film camera camera for some govt project. That canopy did things during deployment that looked like the laws of physics were being violated. I think it blew up but I may be recalling some other video. Is the C 9 still used in ejection seats today? I liked mine, well... at least I liked how it looked with the sun lighting it up. The performance was more likely to benefit orthopedic surgeons than the jumper.
(This post was edited by 377 on Aug 30, 2006, 6:14 PM)
When I worked for AERO I was involved in a test program to replace the GQ-1000 canopy in the F-18 head box with a C-9.
Here is an article about a test we did at China Lake. Fired the seat at 600 KEAS at 500 feet AGL. This was my first time packing the head box myself. Talk about a rush. We were only about 200 yards off of flight line when it went.
The C-9 is about the only canopy in the inventory that can take that kind shot and still set a pilot down safely with an all up weight of 400 pounds.
WOW!! I have new respect for the time proven C 9. How does it deploy from a head box? Just a pilot chute extracting the bare C 9 or is there a bag or sleeve of some kind to slow inflation? Wonder what would have happened to a Navy conical under those conditions? Confetti?
WOW!! I have new respect for the time proven C 9. How does it deploy from a head box? Just a pilot chute extracting the bare C 9 or is there a bag or sleeve of some kind to slow inflation? Wonder what would have happened to a Navy conical under those conditions? Confetti?
It takes 2 days to pack it. It has a small PC than a 5-foot stabilizer drogue. It has reefing controlled by finger cutters initiated by a lazy leg from the head box. When I get home I will check and see if I have some pictures of it on the table. It ended up being one of the most interesting programs I have worked on and I didn’t even get to do any test jumps.
As for the Navy conical, don't sell it short. It is one hell of a canopy. Built stout. I am not sure but I think it was only used for Aircrew and not ejection.
