Per request in another forum I am posting information on jump run from one of Skydive Arizona's "whuzzup" educational clinics. This writing is only in-part. If you would like a copy of it in its entirety please PM me.
Indicated airspeed for practical purposes is the rate that the aircraft is moving through the air, and will be roughly 85-90 nautical miles per hour on jump run almost always in otters, skyvan and king air. The porter flies with a slightly slower airspeed on jump run, 75-80 knots. The airspeed during jump run will always be fairly consistant in any given day and is more or less the industry standard for these particular aircraft.
Wind velocity at the jump run altitude can and will be variable throughout the day and definitely from day to day. The wind acting against the aircraft does not effect the indicated airspeed but will effect the speed that the aircraft will travel across the ground.
Ground Speed is the rate that the aircraft is traveling across the ground. If the aircraft is flown consistantly at 90 knots indicated airspeed then it will be the wind velocity that will affect the ground speed. The air is thinner at 13,000 feet than on the ground so if there is no wind affecting the aircraft on jump run and the indicated speed is 90 knots then normally the ground speed will be between 105 and 110 knots depending on the actual atmospheric conditons. So with this in mind its fairly simple to determine the wind acting against the aircraft on jump run by the ground speed. Ground speed of 80 knots means that the aircraft has a head wind of 20 knots. Ground speed of 125 knots means that the aircraft has a tail wind of 20 knots.
Exit separation
When there are multiple groups exiting the same aircraft then there must be a certain amount of distance between each groups exit order to have enough airspace to do what they have planned, break off, and open safely and not enter the airspace needed by the other groups exiting the same aircraft.
A group of 16 people will require more airspace than a group of 3.
For all practical purposes it is a safe distance that is required between groups. If you were to follow out the same 16 way on every jump, everyday for a month, the distance required to remain safe would stay the same every time you exit. However the time it takes to achieve that same distance would change because of the wind affecting the ground speed of the aircraft from day to day, or even form jump to jump in some conditions.
If the ground speed is high it requires less time between groups to obtain safe distance. If the ground speed is low it requires more time between groups.
Visual information is more effective than using time or seconds between exits but either way you must develop a feel for how much distance to put between your group and others. And you should be aware of whether you are accurate or not, by checking the results from jump to jump. Simply opening up without colliding with someone from another group is not enough. You could be leaving way too much distance between groups, which has an affect on your skydiving whether you realize it or not. Or you could be opening up right in the middle of the group that exited right before you and just get lucky enough not to collide with anyone.
