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South Africa - Aircraft Stalls as Skydivers Prepare to Jump

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South Africa - Aircraft Stalls as Skydivers Prepare to Jump

Old 6th Nov 2021, 19:35
  #41 (permalink)  
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Overweight, center of gravity problems, skydivers/passengers that don’t understand weight and balance…

https://diverdriver.com/accidents/be...tober-17-1982/

Beech C-45 Fatal (14) Taft, CA October 17, 1982

The aircraft was on a local flight involving a parachute jumping activity. In addition to the pilot, there were 12 parachutists and an observer on board. The pilot initiated his takeoff on runway 18. A witness stated that shortly after takeoff, the engine power was reduced to climb power, followed by the gear retraction. Reportedly, the aircraft had climbed to about 150 ft agl when the nose pitched up, th plane rolled to the left and then it crashed in a steep left bank, nose down attitude. An investigation revealed that the aircraft was loaded well beyond its maximum gross weight and aft cg limits. The amount of fuel on board was not verified, but even with no fuel, the plane would have been about 580 lbs over the maximum limit. With 100 gallons, the estimated gross weight would have been about 9939 lbs with the cg at about 121 inches. The maximum certificated gross weight was 8750 lbs with an aft cg limit of 117.6 inches. Extensive ground fire damage, but no preimpact, mechanical discrepancies evident.
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Old 6th Nov 2021, 19:43
  #42 (permalink)  
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Originally Posted by pchapman View Post
You got a better idea? Ok, it is a turbine aircraft with good altitude performance, so maybe that's only a small difference in altitude, fair enough.
The pilot report stated, "The stall and subsequent spin happened when we allowed too many jumpers on the outside step, " ... but that doesn't say whether it was "more than usual" or just "too much for the given conditions".
Because it was a special event, maybe the number of people for that group was larger than usual or more focused than usual in keeping tightly packed near the doorway -- while at the same time perhaps the DZ's rules on the number of floaters wasn't that well established or perhaps communicated.

But it doesn't matter in the end too much here to us out on the internet. The drop zone would know "what factor changed", why a normal everyday jump run procedure didn't work this particular time.
16 or 13K doesn’t really matter.”

Aren’t you required to use oxygen above a certain altitude? At least for the pilot.

Inadequate oxygen can lead to stupid decisions by both the pilot and the passengers/skydivers, especially as the higher you fly, the longer it takes to get to altitude, so the more time you spend with inadequate oxygen, especially if you are used to the amount of oxygen available at sea level and your body is not acclimated to low oxygen conditions.

And obviously a plane is far more likely to lose lift and stall the higher you fly, as the air thins and lift is reduced.
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Old 6th Nov 2021, 20:41
  #43 (permalink)  
 
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Abuse of the airframe.

The basic premise of this shit is that somehow itís ok to get out of the aircraft, and not part company with it.

I am reminded of many video clips where the hard of thinking are seen crashing a motorcycle they have been trying to wheely at high speed for a long distance.

jumping out of the door, in a pre planned sequence is just about safe. Clambering out onto the airframe is crazy, allowing it is worse.

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Old 8th Nov 2021, 16:23
  #44 (permalink)  
 
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Originally Posted by Pilot DAR View Post
....supect that the large pack they provided to me was really not intended for pilot use, as it fit terribly with the seat, and was entirely uncomfortable!
You might check for the compact parachute once used by USNavy pilots. Ripstop nylon for strength at high deployment speed.

Perhaps a modification to seat padding, on a spare set of cushions.
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Old 8th Nov 2021, 16:34
  #45 (permalink)  
 
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Pilot should use oxygen that high, jumpers will just get dozy.
Oh! wait, they have to be on the ball to pull deployment cords and maneuver. :-o)

Every person should test their blood oxygen at altitude to see if there lungs are functioning well, before spending time at altitude while needing to be alert. Small airplane pilots have been surprised at deterioration of their body with aging/health problems. (Cheap ones readily available, Nonin is the class one but can be hard to find as distributors are bureaucracies, AeroMedix sells a clip-on-finger one, Nonin also makes a recording one with low-profile sensor and wrist recorder.

(Accident over eastern BC, airplane had temporary oxygen system while regular one was being fixed, experienced pilot had to take mask off temporarily to use radio, probably forgot to put it back on, IIRC was flying at 15,000 feet ASL to clear huge rocks sticking up.)

Do airliner pilots test regularly? Should be done by doctor on periodic review.

Last edited by RationalKeith; 8th Nov 2021 at 17:02.
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Old 8th Nov 2021, 17:04
  #46 (permalink)  
 
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Does anyone have a link to the South African report on the case in question? (You linked to an Australian report on different case.)

Last edited by RationalKeith; 8th Nov 2021 at 20:56.
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Old 9th Nov 2021, 05:26
  #47 (permalink)  
 
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Does anyone have a link to the South African report on the case in question
No record of a report on the Authorities site, here is what Russ Niles of Avweb says the pilot had to say.
The pilot of a King Air C90 that went into a spin while skydivers prepared to jump over South Africa on Oct. 14 says the plane departed controlled flight because too many jumpers got out of the rear exit at the same time. The dramatic video of the incident has gone viral and been featured on network news shows but it was all in a day’s work for the pilot, who identified himself as Xei. “The stall and subsequent spin happened when we allowed too many jumpers on the outside step, causing an aft center of gravity and excessive blocking of the airflow to the left horizontal stabilizer. The nose then pitched up beyond the controllability of the elevator,” he said in a post that accompanied the video on YouTube.He said he quickly ran out of rudder and elevator and after the right wing came over he chopped power to both engines and began the recovery. “The aircraft behaved very well, and the recovery was surprisingly easy,” Xei wrote. “I pulled out as gently as possible as I did not want to stress the airframe. There was some additional instability when I pulled out of the dive and pushed the throttles forward to power up, as the one engine spooled up much quicker than the other and caused another asymmetrical moment.”

He also said the aircraft is intentionally flown with asymmetrical power for the release of jumpers to prevent them from being blasted by the propwash from the left engine. “Power is kept on the right engine to maintain altitude during the jump run, which typically takes 60 seconds,” he wrote. “A fair amount of right rudder is required to fly a straight line in this configuration. Pilot to maintain 95-90 kts IAS.” He said the incident was reported to authorities and the aircraft inspected. He said the operation has now limited the number of jumpers outside to five at a time and skydivers will be briefed to let go if the aircraft suddenly pitches up.
Avwebs Paul Bertorelli, an experienced skydiver,
Last week, my various inboxes filled up with links to the video posted here, attached to the question, “have you seen this?” How could I not? Shortly after it was posted, it rocketed around the skydiving village like a rubber check in a tile bathroom. I spent a couple of days last week doing intensive wind-tunnel training and we discussed it during our breaks. Suffice to say it’s one of a kind only to the extent that the stall/spin was dramatically captured by a videographer. It is hardly a first and as much as I might wish that publishing it here will make it the last, I know that this passing thought gives futility a bad name. My reaction to these things is often, “the things we get away with in this sport that don’t kill us.” It might deserve firsties for pinning five skydivers inside the airplane during the spin, however.

There’s a lot wrong here related to decision making, judgment and execution of what planning may have been in place. That means there’s a takeaway related not just to skydiving flight operations, but flying in general. It relates to just saying no sometimes. As described in the video summary, this was a workup jump to a 20-way event at a South African drop zone. Presumably those would have been with two-aircraft formations since a King Air won’t carry but about 14.

To my eye, the first thing that went wrong is that they took off in the first place. The exit was above a broken to overcast layer and although it was thin, the videographer’s footage shows it was right at the altitude where the skydivers broke off to gain some separation for canopy deployment. In freefall, I don’t like being in clouds, being near clouds, or going through them, period, much less with a large group. Deploying with zero visibility invites a canopy collision, especially if the break-off tracking happens in cloud with no visual reference.

When this jump unraveled, the organizer did the standard pull-it-out-the-bag salvage by signaling for a round formation. He may or may not have known five jumpers never got out of the airplane due to the stall/spin. Carrying on with some semblance of the dive made sense because that was the plan and keeping a group together for an orderly break-off is preferable to everyone careening around the sky looking for separation to deploy.

Jumping in other than perfectly clear conditions requires judgment on the part of the drop zone operator, the pilots and the skydivers themselves. In my experience, the latter have the least ability to make a wise call because doing so means, at best, you may have to go around for another pass or just land with the airplane, usually losing the cost of the jump ticket. Horrors. So skydivers want to exit no matter what and many will. Sometimes, the pilot—who is on the enforcement hook for jumpers busting clouds—just has to say no to taking off in the first place.

This video reminds me of why I don’t like jumping King Airs. They are not a common jump ship, but because they’re relatively cheap, some drop zones use them in lieu of Twin Otters or Caravans. For aircraft, skydiving is a utility operation and Otters and Caravans, with big doors, fixed gear and hell-for-strong structure, are utility airplanes. King Airs are really business airplanes, with smaller doors and retractable landing gear which increases operational and maintenance complexity. One weakness of King Airs is a relatively narrow, aft-tending CG that means the airplane isn’t tolerant of six or seven people hanging off the bars and maybe a videographer perched out near the tail close to a CG station Beechcraft never figured was relevant.

Skydivers know bupkis about center of gravity. They just assume if they can crawl out there and hang on until exit, the airplane will shrug it off. So the smarter dropzones and organizers who have been through stalls, brief the jumpers on how to do these exits. For every jump, we dirt dive the plan on the ground and set up and practice the exit in a ground aircraft mock-up. Sometimes several times. This is the point where the skydivers in the front of the airplane need to be reminded to stay there until that instant when the outside people are just departing and they can rush the door without causing a stall. In an Otter, you can put six outside and three close in to the door inside and the rest spaced out in the airplane and some forward. It is true that the forward-most skydivers will be delayed diving down to the formation by a few seconds, but better that than being slammed into the cabin walls during a spin entry.

I have been through two stalls in Otters, albeit no spins. I was standing outside for one and departing from the inside for the other. I knew what was happening, even if my fellow skydivers did not. I’ve seen this from both sides. (Sounds like a song.) I’m hardly a Twin Otter expert but I’ve flown enough Otter loads to understand what happens and it’s challenging to deal with it. The usual drill is to reduce power on the left engine and trim up for 90 to 95 knots indicated. When a big group gets out of the door—say eight or 10 perched for exit—the pitch moment starts heading north and it will continue to do that until they exit. If they’re slow about it, you know what’s coming when there’s no more elevator authority left. In this case, the pilot told authorities he reduced the left engine to idle and the prop to coarse pitch, otherwise the jumpers would have too much prop blast to set up the exit.

There’s not necessarily universal agreement on how to fly these jump runs. Some pilots don’t do asymmetric thrust in any twins, some do. For the King Air, www.diverdriver.com recommends flaps and flight idle for the exit, but some power on the right side if the pilot wants to minimize altitude loss. Extreme asymmetrical power seems to be asking for trouble, especially if power isn’t available quickly on the left side if needed.

So skydivers have to be briefed about all this. Hang out there long enough and you’ll cause a stall. Or put too many out there and you’ll cause a stall. And that’s what happened here, along with a rolling moment and enough yaw to initiate a spin. The recovery was quick; it’s only about a turn and a half. I can’t tell for certain, but once the spin stops, there may be some secondary stalling going on during the recovery. King Airs build speed rapidly and the pilot said he wanted to avoid that and may have commanded pitch up too aggressively during the pull out. The pilot attributed the unstable rolling to one engine spooling up faster than the other, but I’m not so sure about that.

The jump organizer can and should have avoided this. The DZO and pilot should have made sure he knew not to put so many people outside and not to keep whoever was out there in place for so long. These guys didn’t discover this on their own. This has happened before and King Air operators know about it. Still, when skydivers get all amped up with adrenaline before an exit, they sometimes ignore the briefing. More than a handful of times, I’ve grabbed jumpers by the collar to haul them back from the door until a bigger group exits.

The most egregious example of this I ever saw was during the 400-way record skydives in Thailand in 2006. We had 410 people in five C-130s. The plan had been for two passes with 200-ish formations on each one, as practice set-ups. These were from 24,000 feet. So it was suggested when the first group exited, the second would walk to the back of the airplanes, pick up the oxygen tubes from the departed jumpers and await the second pass. No, don’t even, said one of the organizers with experience in high-altitude exits. Stay on your butt and stay on oxygen until exit time and then go.

But we did exactly the opposite of that and it was a near catastrophe. One of the jumpers picked up a disconnected oxygen line and became hypoxic enough to fall flat on his back right in front of me. Wisely, the ramps were closed up and we rode the airplanes down—all 200 of us—proving once again that something as risky as skydiving requires unrelenting discipline. The challenge of it is often just learning to think straight with a quart of adrenaline gushing through your veins.

As is obvious here, sometimes you can’t.


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Old 9th Nov 2021, 08:16
  #48 (permalink)  
 
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Orinally Posted by RationalKeith
Does anyone have a link to the South African report on the case in question? (You linked to an Australian report on different case.).

The OP simply stated that the event was reported to the SA CAA. I'd be surprised if that resulted in an investigation.
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Old 9th Nov 2021, 10:59
  #49 (permalink)  
 
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And obviously a plane is far more likely to lose lift and stall the higher you fly, as the air thins and lift is reduced.
Nope. Lift is proportional to the square of the air speed and will occur at the same IAS no matter what the density of the local atmosphere. It is the TAS that will change with height - and not many aircraft I know fly on TAS.

It is lack of thrust that is the snag at high level.

Mog
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Old 9th Nov 2021, 11:22
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Originally Posted by Mogwi View Post
And obviously a plane is far more likely to lose lift and stall the higher you fly, as the air thins and lift is reduced.
Nope. Lift is proportional to the square of the air speed and will occur at the same IAS no matter what the density of the local atmosphere. It is the TAS that will change with height - and not many aircraft I know fly on TAS.

It is lack of thrust that is the snag at high level.

Mog
Mog,

Not quite. Dynamic pressure is a function of EAS not IAS and as altitude increases the IAS for a given EAS will increase slightly. Therefore, the IAS for stall speed will increase slightly as altitude increases.
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Old 9th Nov 2021, 12:59
  #51 (permalink)  
 
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LOMCEVAK, I don't think we need to be that fussy, 90 CAS at 16,000 ISA is 89.827 EAS, 115.109 TAS. I don't think .173 ktots is some thing to to get the knickers in a twist.
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Old 9th Nov 2021, 15:51
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megan,

Hence why I said ‘not quite’. I think that Mog knows me well enough to realise that I was not criticising him but adding a little so that if anyone on here was interested they would have an accurate understanding that would be applicable to other conditions where the difference may be significant.
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Old 9th Nov 2021, 19:23
  #53 (permalink)  
 
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Gotcha Can be significant as you say, SR-71 ISA 75,000 3.2M 842CAS 393EAS 1,847TAS
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Old 9th Nov 2021, 20:00
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And then there is the variation in the maximum coefficient of lift for a given wing as a function of Mach number and Reynolds number but let’s not dig the rabbit holes too deep in this thread.
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Old 9th Nov 2021, 21:45
  #55 (permalink)  
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To keep the topic relevant, should I delete the preceding six posts? Jump runs from SR-71's are a stretch!

From my Piper Cheyenne days, I recall that the plane seems more twitchy to fly higher than the high 'teens, but I don't have a lot of experience up there. I accept that the King Air pilot was pushing the bounds by approaching a messy stall at 16,000 feet, and my limited experience has me thinking that maybe the less dense air resulted in delayed recovery.
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Old 10th Nov 2021, 08:31
  #56 (permalink)  
 
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megan,

Can you tell me more about those two photos you posted - the circumstances, the dates, who did it, etc. A friend of mine who used to drop skydivers from a DH Dragon Rapide and an Antonov An-2 is interested.
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Old 11th Nov 2021, 00:09
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From the web Bergerie, came across them when looking for a similar photo taken by Andy Keech, no details re what, when, where.
To keep the topic relevant, should I delete the preceding six posts? Jump runs from SR-71's are a stretch
Yout train set DAR, post #49 should remain as Mogwi was correcting an incorrect statement, jumps have been made from the -71, but out of necessity.
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Old 11th Nov 2021, 03:16
  #58 (permalink)  
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jumps have been made from the -71, but out of necessity.
I'm sure they have! But, were they may during a jump run? Okay, I'll bite... Could you even jump from a fast Jet? Or, would you have to eject to get out?
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Old 11th Nov 2021, 05:01
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What constitutes a fast jet DAR? 727, DC-9 fast enough?

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Old 11th Nov 2021, 06:02
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One of the members of the dublin gliding club recounted a story about removing the canopy on his Blanic and taking a parachutist up. The parachutist gave his camera to the pilot then climbed onto the wing but decided that the Kodac moment would be more spectacular sitting on the wingtip. He didn’t quite get to the end as on the verge of loosing control of the glider the pilot lobed the camera at him and the parachutist followed in an attempt to retrieve the camera.
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