Forums: Skydiving: General Skydiving Discussions:
Re: [JohnSherman] The Z-hills Double Fatal Speculation Thread

 


robinheid  (D 5533)

Apr 3, 2013, 12:39 PM
Post #1 of 10 (1466 views)
Shortcut
Re: [JohnSherman] The Z-hills Double Fatal Speculation Thread Can't Post

In reply to:
You know, some things do happen faster,but the overall result is more distance due to more speed.
I find that to deploy a canopy in 300 feet at terminal you had better be able to do it in 200 feet at cutaway speeds. Apply that to what we are seeing. Unsure

John

Very astute of you, John, or should I say, thanks for reminding everyone of basic physics.

Faster speed, longer stopping time. Period.

Planes, trains, automobiles or parachutes.

Story to illustrate:

Guy is flying a Mig-21 doing supersonic threat scenarios against a Canadian aircraft carrier.

After one run, he pulls up and hits 12,000 feet. Don't know his supersonic speed but 1500 f/s = 1000mph, so it takes him about 8 seconds to get that high.

then (as the investigation discovered) something came loose on the wing (pylon, tank, can't remember) and increased the drag on one side, throwing the plane out of control.

By the time the ship's radar dish rotated around, the MiG was off the screen.

Found the wreckage, found the body, and found the parachute streamered but not open.

Pilot was former Navy Top Gun instructor, thousands of hours of jet fighter time, hundreds of MiG-21 hours, and I can't remember the exact numbers, but we worked it out in terms of reaction time to the precipitating event in relation to the presumed speed and IIRC came up with a he-did-everything-right-and-fast ejection altitude of about 8,000 feet and he still hit the water before the parachute fully deployed.

Yes, there is aircraft clearance, seat separation, etc, which adds to deployment time, but the bottom line is, he was going so fast that even 8,000 feet wasn't enough to get the reserve out and open before impact.

This is a big deal to think about these days of freeflying were everyone's going so much faster, even at pull time, than the AAD firing altitude can comfortably accommodate. The same goes for RW, too; the suits are so much tighter that the actual freefall speeds are faster than they were back in the 1970s when jumpsuits were much bigger and baggier.

And if the assumed scenario here - incapacitation on the student's part - holds true, then we have two guys going way faster than the AAD firing altitude could accommodate.

Which brings us to raising the AAD firing altitude, which them bumps against the two-out problem --- which brings us to guess what: the obsolescence of USPA's 2,000 feet pack opening altitude BSR.

As you remember, John, this BSR was created in the mid-1970s when most peeps were still jumping surplus rounds with and without sleeves, and a lot of them were pulling at 500-600 feet because the parachutes opened in 200 feet and they were all nuts anyway. Wink

So let's do the math: When this BSR was created, your parachute was completely open -- or not -- by 1,800 feet, and then you acted accordingly. If it was a total, you had 90 percent of your 2,000 feet left to take care of it. If it was a partial, you had 90 percent of your 2,000 feet left to take care of it.

Granted, back then, you have more complex release systems so it took longer to do EPs, but still, you had that 1,800 feet or 90 percent of the 2,000 feet to observe, orient, decide and act.

Fast forward to today: Many commonly used parachutes open in 400 to 700 feet, so suddenly you have to wait until you've used up 20-35 percent of you 2,000 feet before you even know what your next move is, yet IIRC correctly, USPA still has a "decision altitude" of 1,800 feet.

So that's where we are today: Everyone's falling faster, and most of their parachutes are taking longer to open than they did when the 2,000-foot BSR was put in place -- but it's still in place and people don't think critically about the consequences of pulling at that altitude given these changes in the math and physics.

And you know, back when that BSR was put in place, most skydives were from 7,500 to 10,500 feet, so the 2K was a reasonable compromise between opening altitude safety and cutting the skydive too short.

Well, now almost everyone goes to 12,500 or higher, so they're all getting several more seconds of freefall time per jump, so, you know, I think maybe instead of having stupid discussions and wasting BOD time about wingsuit BSRs, that discussion and BOD time would be far far FAR better spent revisiting the pack opening altitude BSR and see if it's maybe time to raise those altitudes by 500 to 1000 feet.

One final data point in support of that notion: When that BSR was put in place, there were almost no "resort" DZs; everything was kind of gnarly, and rough and tumble (literally) and when you were skydiving you never forgot that you were dancing on the edge of the envelope. Plus, you could only make a few jumps a day because the airplanes were so slow, so you thought more about each one and focused more on what you were doing.

Now with all the resorts and high-tech electronics and cameras and cool gear and trust fund baby social scene, it's more like a big party at the amusement park, and now you can make 10 jumps a day easy at most places, all of which means when you have a problem, almost everyone is going to burn through a second or two or three of their "life saving time" shifting their mental gears from amusement park to dealing with the Reaper right in their faces.

So the math doesn't add up any more, and even with ADDs (Anti-Darwin Devices) reducing the carnage significantly, we're still seeing a lot more body bags than we should be seeing.

So thanks again for the reminder, John. Speed affects distance and if you change one, then you better understand its effect on the other.

Cool
44


airtwardo  (D License)

Apr 3, 2013, 1:26 PM
Post #2 of 10 (1384 views)
Shortcut
Re: [robinheid] The Z-hills Double Fatal Speculation Thread [In reply to] Can't Post

So that's where we are today: Everyone's falling faster, and most of their parachutes are taking longer to open than they did when the 2,000-foot BSR was put in place --

In reply to:

Yeah Robin, but these days they're usually more sober so they have faster reaction times! Wink


jonstark  (D 8298)

Apr 3, 2013, 3:00 PM
Post #3 of 10 (1330 views)
Shortcut
Re: [airtwardo] The Z-hills Double Fatal Speculation Thread [In reply to] Can't Post

In reply to:
Yeah Robin, but these days they're usually more sober so they have faster reaction times! Wink

and mad skillz Laugh


weaverd  (C License)

Apr 3, 2013, 8:51 PM
Post #4 of 10 (1225 views)
Shortcut
Re: [robinheid] The Z-hills Double Fatal Speculation Thread [In reply to] Can't Post

In reply to:
In reply to:
You know, some things do happen faster,but the overall result is more distance due to more speed.
I find that to deploy a canopy in 300 feet at terminal you had better be able to do it in 200 feet at cutaway speeds. Apply that to what we are seeing. Unsure

John

Very astute of you, John, or should I say, thanks for reminding everyone of basic physics.

Faster speed, longer stopping time. Period.

Planes, trains, automobiles or parachutes.

Story to illustrate:

Guy is flying a Mig-21 doing supersonic threat scenarios against a Canadian aircraft carrier.


Cool
44

Canada doesn't have aircraft carriers!


JohnSherman  (D 2105)

Apr 4, 2013, 7:57 AM
Post #5 of 10 (1132 views)
Shortcut
Re: [weaverd] The Z-hills Double Fatal Speculation Thread [In reply to] Can't Post

Quote:
Canada doesn't have aircraft carriers!

Good story Robin but the math/physics don't work either.

If he ejected at 8000 feet he would slow down immediately to an equalized velocity and have pleanty of time to deploy.
If this is an official story they got it wrong.

We don't go any faster today than we did yesterday!
Remember "Style"


pchapman  (D 1014)

Apr 4, 2013, 8:44 AM
Post #6 of 10 (1089 views)
Shortcut
Re: [robinheid] The Z-hills Double Fatal Speculation Thread [In reply to] Can't Post

Looks like we could get into a whole other thread about MiG 21 parachuting!

The original eastern equipment does have an ejection seat to which the canopy attaches, specifically designed as a windbreak for high speed ejection. (The Indian Air Force still has those ejection seats installed, or at least did a couple years ago) I don't know what the seat's envelope is though, whether he would have ejected within the envelope. Sherman is right that the deceleration would be pretty rapid.

Anyway, no big deal, but I think other things went wrong on that day of the ejection...



The incident you reported intrigued me so I looked it up a little more. Not much seems to be out there. The accident took place in 1999 and I wonder if he really did eject. Who knows. One report:

Quote:
> Doug Schultz, 53, of Francestown, N.H., was flying the plane in radar
> tracking drills for the HMCS Algonquin, a Canadian Navy ship, at the time
> of the crash.
>
> The MIG-21 belonged to Air USA, a Quincy, Ill., based contractor that buys
> and refurbishes airplanes for resale.
>
> Schultz logged more hours flying Russian-built MIGs than anyone else
> outside the former Soviet Union, said Don Kirlin, Air USA president.
>
[..]>
> Canadian Air Force Capt. Dennis Johnston said the Navy warship last
> plotted the MIG at 12,000 feet. The plane crashed about a mile from the
> last known position.
>
> ``The evidence indicates he impacted at a very high speed,'' Johnston
> said. A parachute and some of Schultz' personal items, but no body, were
> found.


jumpwally  (D License)

Apr 4, 2013, 11:45 AM
Post #7 of 10 (1020 views)
Shortcut
Re: [JohnSherman] The Z-hills Double Fatal Speculation Thread [In reply to] Can't Post

Thanks, John,,I love it when you straighten things out here,,,,ca chink,,,bingo ! Cool love it....


robinheid  (D 5533)

Apr 4, 2013, 1:48 PM
Post #8 of 10 (960 views)
Shortcut
Re: [pchapman] The Z-hills Double Fatal Speculation Thread [In reply to] Can't Post

In reply to:
Looks like we could get into a whole other thread about MiG 21 parachuting!

The original eastern equipment does have an ejection seat to which the canopy attaches, specifically designed as a windbreak for high speed ejection. (The Indian Air Force still has those ejection seats installed, or at least did a couple years ago) I don't know what the seat's envelope is though, whether he would have ejected within the envelope. Sherman is right that the deceleration would be pretty rapid.

Anyway, no big deal, but I think other things went wrong on that day of the ejection...



The incident you reported intrigued me so I looked it up a little more. Not much seems to be out there. The accident took place in 1999 and I wonder if he really did eject. Who knows. One report:

Quote:
> Doug Schultz, 53, of Francestown, N.H., was flying the plane in radar
> tracking drills for the HMCS Algonquin, a Canadian Navy ship, at the time
> of the crash.
>
> The MIG-21 belonged to Air USA, a Quincy, Ill., based contractor that buys
> and refurbishes airplanes for resale.
>
> Schultz logged more hours flying Russian-built MIGs than anyone else
> outside the former Soviet Union, said Don Kirlin, Air USA president.
>
[..]>
> Canadian Air Force Capt. Dennis Johnston said the Navy warship last
> plotted the MIG at 12,000 feet. The plane crashed about a mile from the
> last known position.
>
> ``The evidence indicates he impacted at a very high speed,'' Johnston
> said. A parachute and some of Schultz' personal items, but no body, were
> found.

Thanks for doing your homework (and mine too!) Good thing I included "IIRC" in my post. Obviously I mis-remembered the ship type (but I got the country and last plot altitude right!)...

...and John, the 8K figure was for a did-everything-fast-and-right scenario... at those speeds, you cover a lot of airspace during a standard OODA loop (observe, orient, decide, act), so, sorry if I wasn't more clear, but if he even took just one extra second to solve the problem instead of just bailing, he would have been closer to 6,000 feet - and accelerating.

Something else on which I apparently didn't elaborate enough for math wonks: the MiG-21 can climb sustained at more than 500mph (44,000 fpm), and it can go 1,500 mph in level flight, so given a supersonic start, he hit 12K in about ten seconds and he obviously sustained that speed or accelerated because he was off the radar in one turn of the dish.

So when he started down, he probably went a lot faster -- a lot faster and may well have hit the water at closer to 2,000 mph than 1,000 mph so, sorry, but I don't buy the rapid deceleration profile you outline.

It wouldn't be too hard to figure but if he and his seat go out of the plane at either 1K or 2K mph, and the forward throw is straight down, no matter what your drag profile is, it's gonna take you quite a while and a lot of distance to slow down and, again, if he delayed his ejection even a second or two beyond an immediate OODA loop to get out (because he may have thought he could solve the problem and save the airplane), even a few thousand feet of air would not be enough distance given the time he had left.

And of course, this is all academic pissing in the wind anyway because he went off the scope at 12K and no one knows or will ever know what all these numbers were even though they did finally figure out the proximate cause and (IIRC from a conversation I had with Don) the fact that he most likely did get out at some point on the way down but was too low for the canopy to open. That was kind of the whole point about mentioning the MiG incident in this thread, you know, John? To buttress your contention with a real-life extreme example that the faster you go the more distance you need to get a parachute open.

Your S&A thing doesn't track, either, and for the same reason; yes, they did and still do go faster than flat flyers, but their canopies were/are not taking 400-700 feet to open either.

That was my point -- the combination of generally (if slightly) faster freefall speeds and generally I (and significantly) slower opening parachutes makes the 2k pack opening altitude BSR arguably obsolete so it should be revisited instead of wasting any more time on a wingsuiting BSR that is a solution in search of a problem.

So let's stay on task and not nitpick numbers that were meant to be illustrative, not absolute and as a coda for the MiG-21 portion of this thread, here's some basic performance data on this magnificent bird:

General characteristics
Crew: 1
Length: 14.5 (with pitot) m (47 ft 6.86 in)
Wingspan: 7.154 m (23 ft 5.66 in)
Height: 4.125 m (13 ft 6.41 in)
Wing area: 23.0 m2 (247.3 ft2)
Gross weight: 8,825 kg (19,425 lb)
Powerplant: 1 Tumanskiy R25-300, 40.21 kN (9,040 lbf) thrust dry, 69.62 kN (15,650 lbf) with afterburner each

Performance
Maximum speed: 2,228 km/h (1,468 mph)
Maximum speed: Mach 2.00
Range: (internal fuel) 1,210 km (751 miles)
Service ceiling: 17,800 m (58,400 ft)
Rate of climb: 225 m/s (44,280 ft/min)

Armament
1x internal 23 mm GSh-23 cannon, plus
2x R-27R1 or R-27T or 4x Vympel R-77

or 4x R-60M or R-73E AAM or
2x 500 kg (1,102 lbs) bombs


More here.

Cool
44


Andy9o8  (D License)

Apr 4, 2013, 3:34 PM
Post #9 of 10 (856 views)
Shortcut
Re: [robinheid] The Z-hills Double Fatal Speculation Thread [In reply to] Can't Post

In reply to:
Good thing I included "IIRC" in my post.

Bwahaha!

Blush

Oops!


pchapman  (D 1014)

Apr 4, 2013, 4:14 PM
Post #10 of 10 (810 views)
Shortcut
Re:The Z-hills Double Fatal Speculation Thread [In reply to] Can't Post

REMINDER:
This is the MiG 21 thread cut out of the Z hills speculation thread that's in S&T, not the speculation thread itself.

So if you have no opinions about MiG-21's and their ejection seats, stay the hell out. SmileSmile


P.S. Robin, since we aren't intruding on another thread now: Someone on one site suggested that the MiG accident might have been related to stores clearance envelopes -- that the supersonic speed he was at, the G loads he was using, and the centerline fuel tank were not compatible. Still, I'd be surprised that a single centerline fuel tank wouldn't be approved for maneuvering, as internal fuel on older fighters can be pretty marginal. Who knows; I certainly don't know the answers.



Forums : Skydiving : General Skydiving Discussions

 


Search for (options)