# How does wake turbulence affect parachutists?

If one were to parachute out of a jumbo jetliner, would wake turbulence from the plane be an issue?

A 747 for instance produces much more wake turbulence than the smaller planes usually used to drop parachutists. Would that make a difference, or does the trajectory of a parachutist stay clear of wake turbulence in any case?

• Just be sure to jump behind the wings (and the engines). – SQB Oct 15 '14 at 19:45

Qualification: I am a master parachute rigger and I taught sport parachuting for 10 years.

The back door of a 747 is actually in a pretty good position - the tail is above the door and the fuselage is narrowing at that point so it's not a complete side exit.

A freefall jumper will drop out of the aircraft's wake in under a second so that's not really an issue. If we pick a theoretical worst-case where a jumper goes straight through a huge vortex they might get flipped over. Remember that a human does not have large surfaces like wings to interact with. Any jumper that can't recover from that won't be doing freefall jumps anyway. Seriously, this is in the Jump #1 stability lesson, and if you haven't got it sorted by jump #6 any reputable school will send you home.

Exit speed is a consideration - sport gear is meant for < 200km/h. If we are going out at 747 cruise speeds I would tighten everything right up1, wrap some tape around the riser covers2 and tuck the pilot chute handle completely into the pouch. Maybe also tack the closing flap cover down. Yes guys, it will still open if you sew it to the proper flap. If the plane is at approach speeds with flaps and gear down then you're fine - not much different than a King Air.

So in conclusion, yes, you can jump out of a 747. Rent one and you will have every jumper in the state lining up for tickets.

To reply to the comment of the pilot chute going over the tail, that happened at our place too (and to me once, but mine went under the tail). It's got nothing to do with turbulence - the pilot chute got pulled mostly out of the pouch, most likely snagging something, and the air picked it up from there. Our guy actually hit the tail. He had nasty bruises and needed a few lines changed, the pilot needed new underwear, and the Cessna needed a bunch of rivets and sheet metal work. When it happened to me I had a surprise deployment at 9,500 feet and a longer than usual ride down.

1 to the point where you will need my tools to close it.
2 it will break away after opening, and won't be more than an annoyance if it doesn't

• This is similar to what I would have written if I had more time before you got to it. Great answer! – Lnafziger Oct 16 '14 at 0:21
• every jumper in the state try country! – Matthew Peters Oct 16 '14 at 0:42

Paratroopers are sometimes dropped from large cargo carriers planes out of the backdoor (or side door) with little trouble. (right in the wake turbulence)

However by the time you open your parachute you will already be well clear of any turbulence caused by the large airplane.

• And note that dropping paratroopers ranges from static line and very low altitude (like couple hundred feet) to HALO jumps from 30-40 thousand feet. – Jan Hudec Oct 15 '14 at 18:49

Wake turbulence is caused by an aircraft as it moves through the air, so the turbulence is in the trail of the aircraft. A parachutist isn't going to be behind the aircraft after jumping out of a jumbo jet as there's only doors on the side. Say the airplane has a rear ramp like a 727, the parachutist is very quickly going to drop below the level of any wake turbulence.

This doesn't mean jumping out of a jumbo jet is anything but extremely hazardous though, the slipstream would make any attempt foolhardy.

• They used to (and maybe still do) use a 727 for skydiving during the annual World Freefall Convention here in the US. They did a "low speed" pass near its minimum airspeed, and a "high speed" pass at 250 KIAS. People keep coming back for it every year, so it must not be too bad! – Lnafziger Oct 15 '14 at 14:44
• @Lnafziger: But I suppose they jump from the rear door. – Jan Hudec Oct 15 '14 at 15:31
• @JanHudec They do indeed, but I was simply addressing his last sentence. :) – Lnafziger Oct 15 '14 at 18:34
• @Lnafziger: Yes, but that last sentence is based on the assumption that you'd have to jump from the side door of the 747 that are rather badly positioned for that purpose. So it does not apply to 727 with the tail door. – Jan Hudec Oct 15 '14 at 18:41
• @JanHudec Ummm, I didn't take it that way since it is a stand-alone paragraph/sentence, and if that's what he meant then perhaps it can be clarified. Which is ultimately what my comment was for in the first place. :) – Lnafziger Oct 15 '14 at 19:31

Bottom line is that there is very little effect on the parachutist/skydiver.

The case where there would be the largest concern would be in the event of a static line jump (which we seldom teach civilian-wise) where the jumper's pilot chute is deployed on exiting the aircraft. However, as you can see below, gravity is pulling you down faster than you are being pulled back thus you are essentially out of the turbulence cone.

In the event of non-static line jumps, the process is just faster (because of less drag).

Also, many times an aircraft will be at a slight climb and near stall speed (but this is manly for safety not turbulence related issues).

• Note that wake turbulence is stronger in slower flight. – Jan Hudec Oct 15 '14 at 15:33
• Also, I have been looking out the window of a jump place (from the back) and have seen a pilot chute go over the tail of the airplane, so it is possible (and NOT fun). One drop zone that I used to jump at even had it happen and tear 1/2 of the elevator off of the airplane. It put it into quite a dive, but the pilot was able to recover and land the airplane safely (good thing that the DeHavilland Beaver has such a large tail)! – Lnafziger Oct 15 '14 at 19:34
• Isn't wake turbulence mainly caused by the two vortices spilling from the wing tips? To quote NASA: "When viewed from in front of an aircraft, or from behind, the circulation of vortices is outward, upward, and around the wing tip.". So for that 747 example, it would be quite a bit away from the doors. – MSalters Oct 15 '14 at 19:36
• @Lnafziger, that accident was most likely caused by an improper deployment procedure, not turbulence... – Matthew Peters Oct 15 '14 at 20:48
• @MSalters the wake vortex does indeed form due to the difference of pressure between the top and the bottom of the wing at the tip of each wing. But each vortex grows and the turbulent area ends up being as wide as the plane. – usernumber Oct 15 '14 at 22:25