Jumper / Aircraft collisions

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stratostar

Do you know more details about (1), the collision with the C-130?

Reginald

It matters if in FF or under canopy... as I am trying to make sense of said theory that only applies for freefall. If that theory is sound, then freefalling through clouds would be acceptable. Its no way acceptable under canopy in my opinion.

Your other point is about acceptable losses. It may sound strange, but I can understand the concept. For example, the aircraft you fly to altitude with has certainly been build with similar considerations in mind. The wings I think are only designed to bear 1.5 times the maximum allowable load. Beyond that, they might snap off. To prevent this they would have to be sturdier and the aircraft would be heavier, therefore need stronger engines, consume more fuel, ... so the question is in my opinion not if it is acceptable, but what the chances are. If it is a 1 in a billion chance, I might be inclined to take the risk, a 1:100,000 chance might keep me from jumping through clouds for that reason.

BMFin

Agreed, I have only 300 jumps so far and yet have had some scary moments where it surely helped to see all my fellow jumpers.

mrbiceps

We might well have been at the same dropzone last weekend. I didn't mean to slack off Aussie rules, just chose some pointed words to stimulate responses I've learned that from today's news media haha

billvon

I have spotted airplanes that way too, but I have also been surprised by aircraft although there was someone, me or others, spotting. What I want to say is that one will probably miss at least some planes due to speed, direction, light conditions etc. Apart from the jump plane I have only been aware of other planes oncer under canopy, so far.

Thanks all participants for this discussion, I've already learned something so far.

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pchapman

Thanks for bringing this up, this is indeed what the aussie pilot was referring to.

Here is the direct link to the spreadsheet:

http://www.apf.asn.au/documents/pdf/CloudJumping/CJPMuncontrolled_Airspace_Model.xls

Very interesting to play around with. I have to admit that I'm too lazy right now to dive into the mathematic model, maybe later.

I hope Tom Buchanan will see this topic, I would be very interested to hear his opinion on that model.

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I hope Tom Buchanan will see this topic, I would be very interested to hear his opinion on that model.

I have been watching the thread, and it’s interesting. The spreadsheet looks a bit over my head, and I’m not sure I buy into all the assumptions, but I’m going to address the issue from another direction.

I have been in many close calls, but only two very, very, very close calls that really could have gone either way. Fortunately in both cases luck was on my side.

The first was an RW jump that exited directly over the flight path of a commuter airplane. As I recall, the plane went under us at about 7,000 doing a hard avoidance bank. The vertical distance between the formation (about 10 jumpers) and the airplane was cut in half in the time it took the airplane to cross under the formation. We were probably within 100 feet of impact and could feel the turbulence from the plane under our formation.

The second was a near collision with a brown Cessna 172 with two occupants. It too did a significant avoidance turn to miss me just as my canopy opened, easily within 50 feet of the aircraft. I’ve told that story here before, and I will take a good deal of responsibility for what almost happened. Crap, I was an idiot.

I’ve watched dozens of close calls, but just two that I would describe as very, very, very close, either one of which could just as easily have resulted in multiple fatalities.

The first was a C-130 that spooled up its engines, initialed a climb, and then banked super hard to avoid a tandem pair and cameraman under canopy. It missed by less than 100 feet. I doubt the avoidance maneuvers had anything to do with survival.

The second was a passenger 737 inbound for landing at an airport about 12 miles away. It too did an aggressive maneuver to avoid a tandem and missed by less than 100 feet, due entirely to luck and not the avoidance effort.

In each of these cases the aggressive avoidance maneuver itself was a threat to aircraft control and safety. From a pilots standpoint a near collision can be as serious of a threat as an actual collision. I’m guessing that according to the spreadsheet those would qualify as non-events, but they absolutely put pilots and passengers at risk.

The second point I always like to make about this issue is that when an aircraft/jumper collision happens it threatens our access to the airspace, and that’s especially true if it is a passenger airplane. We can argue probability and responsibility and fault and regulation, but the reality of aviation politics, at least in this country, is that a single collision with a commercial (or military) aircraft could dramatically change our status within the airspace. The best designed and peer reviewed spreadsheet in the world won't change that.

I also always note that in the United States it is incumbent upon the skydivers not to create “a hazard to air traffic or to persons or property on the surface” (105.5), and we can’t reasonably comply with that regulation if we can’t see other aircraft.

So given the way we manage our airspace and the politics of aviation in this country, I think jumping through clouds is foolish unless it occurs in class “B” airspace to the surface. I’ve done it, and I’ll almost certainly get myself caught in that situation again, but it’s not a good idea to rely on probability alone to stay safe.

As for why collisions are a bigger threat under canopy than in freefall, and ways to avoid them, please Articles 1 and 19 which I wrote quite a while ago for The Ranch web site at: http://theblueskyranch.com/STA.php

Thanks for pulling me in off the sidelines...

Tom Buchanan
Instructor Emeritus
Comm Pilot MSEL,G
Author: JUMP! Skydiving Made Fun and Easy