Subject: Calculated Air Release Point (CARP)
Hi,
dropping guys and it's all worked out by the talking GPS who sits behind me.
I'm all for keeping it simple as some of the replies to your thread seem to suggest but if you have a large stick and / or a small DZ there has to be some better method of coming up with the goods.
CARP for freefall is made up of:
Green-on to Off-Sill (GOS) - how long it takes the guys to get out of the aircraft.
Still Air Forward Throw (SAFT) - distance travelled by the jumper, due to the forward airspeed of the aircraft.
F/eefall Drift - depends on time in the air from end of SAFT to opening height and mean windspeed for that height range.
Canopy Drift - depends on time under canopy and mean wind speed for that height range
We have made up an Excell programme that takes 101+ variables into account and comes up with an offset in yards and bearing from the impact point.
(For static line we miss out Freefall Drift and use Canopy Drive as an equation function)
Taking into account the size of the DZ we also come up with a Parachute Cut-Off Time (PCOT). If the last guy isn't out of the aircraft by that time, in seconds, after the "Green-on" then the Red goes back on.
If you haven't much down view from the aircraft, either because of superstructure or higher drop heights it's simply a case of listening to the Nav or flying to the GPS position and getting them out.
As the driver I'm not fully sure of the numbers used but I'll look into it and see if I can come up with some ballparks, or if you can come back with some of your numbers as examples I'll give the problem to one of my guys as a project.
Rgds
Art
Hello Art!
Sorry i couldn't reply to your mail, i just got it bounced back as undeliverable...
From your response i'm gathring you're a military driver, Herc i suppose ?
You're right we don't have much of a down view from the Skyvan , especially considering that our standard jumprun is at 15.000 feet. And due to the fact that most skydivers are used to side exit a/c they don't get the spotting right at most of times... GPS drop is the best approach i think, and as far as i got from Leviathan in his response they are using the same procedure in their Casa.
But as you said the difficultie lies in the number of varibles !
You guys do mostly round canopies i suppose ?
I've been to germany 2 month back and we did some dropping on an airfield that had also a Transall from the german AF dropping sticks of 20 round canopies, they get out pretty fast which is a good thing, we do have the problem that in a load of up to 25 folks you can have as many as 25 exits! Having that many is somewhat unusual tho
but 10-12 exits is a normal number. The seperation is supposed to be in the 5-7 seconds range between exits.
For an example:
Jumprun at FL150
85 KIAS
12 exits
DZ allignment 27/09
say 1000 yards long and 100 wide
Winds on the ground:
180/15
5000 feet to 15000 feet
360/30
I actually had that situation.
Really looking forward to what you and your guys come up with ! I'd be especially interested on what variables you take into account.
Cheers
Phil
a.k.a MB