Baling out at high altitude.
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Baling out at high altitude.
In another life when I flew Mustangs, if for some reason the aircraft had to be abandoned, we were advised to wait until passing through 10,000 ft agl before pulling the rip-cord. I presumed that this was because of oxygen requirements.
However, I also recall that the shock of the parachute opening was purported to be much more severe at high altitudes (20,000 ft plus?) than at lower altitudes and that the parachute might even be damaged during opening.
Question: Why would be the shock of opening be more severe at high altitudes? Is it something to do with falling at a faster rate at high altitudes (TAS factor?)
However, I also recall that the shock of the parachute opening was purported to be much more severe at high altitudes (20,000 ft plus?) than at lower altitudes and that the parachute might even be damaged during opening.
Question: Why would be the shock of opening be more severe at high altitudes? Is it something to do with falling at a faster rate at high altitudes (TAS factor?)
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Hudson,
Your assumption that oxygen was a reason for not bailing out above 10,000ft. is partially correct. However, the best reason for waiting until reaching lower altitudes is for higher temperatures. If you took the example of going over the side at 35,000ft, the standard temperature at this altitude is -34degs. By the time you reached the earth you would be a "frozen Hudson", forget the oxygen concern. As the altitudes decrease, the temperatures increase and so do your chances of survival. You can ascertain the temperature at any altitude (approximately) with the formula for the dry adiabatic lapse rate which is 3.5F degrees per 1000ft or 2deg.C. per 1000ft. of altitude. Simply start with the surface temperature and work up. Then, the "wind chill" factor (falling at 135mph through cold air) must be taken into account. On the ejection seats I am now using, the berostat is set to start the opening sequence at 10,000ft if the ejection is made at a higher level. But, we do have oxygen during the decent, something the Mustang and other types of that period did dot have. Having flown the Mustang, I remember that if you forgot to duck your head while pulling the red canopy release lever under the RH canopy rail, you could forget getting out anyway.
Your assumption that oxygen was a reason for not bailing out above 10,000ft. is partially correct. However, the best reason for waiting until reaching lower altitudes is for higher temperatures. If you took the example of going over the side at 35,000ft, the standard temperature at this altitude is -34degs. By the time you reached the earth you would be a "frozen Hudson", forget the oxygen concern. As the altitudes decrease, the temperatures increase and so do your chances of survival. You can ascertain the temperature at any altitude (approximately) with the formula for the dry adiabatic lapse rate which is 3.5F degrees per 1000ft or 2deg.C. per 1000ft. of altitude. Simply start with the surface temperature and work up. Then, the "wind chill" factor (falling at 135mph through cold air) must be taken into account. On the ejection seats I am now using, the berostat is set to start the opening sequence at 10,000ft if the ejection is made at a higher level. But, we do have oxygen during the decent, something the Mustang and other types of that period did dot have. Having flown the Mustang, I remember that if you forgot to duck your head while pulling the red canopy release lever under the RH canopy rail, you could forget getting out anyway.
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epw
I think you are correct on the TAS thing as well. Your terminal TAS is higher at altitude. So (approx figures here) if say your terminal IAS is perhaps 120 KIAS and you need to decelerate to say 30 KIAS that represents much more than a 90 kts TAS change, an effect amplified the higher you are.
Oxygen and Temperature are obviously survival issues as well, but I'm pretty sure I remember some mention of parachute opening shock as being a reason mentioned, in groundschool, for the function of the Barometric release unit on the Martin Baker seat we were using.
Course, I might be befuddled, It was a while back.
CPB
I think you are correct on the TAS thing as well. Your terminal TAS is higher at altitude. So (approx figures here) if say your terminal IAS is perhaps 120 KIAS and you need to decelerate to say 30 KIAS that represents much more than a 90 kts TAS change, an effect amplified the higher you are.
Oxygen and Temperature are obviously survival issues as well, but I'm pretty sure I remember some mention of parachute opening shock as being a reason mentioned, in groundschool, for the function of the Barometric release unit on the Martin Baker seat we were using.
Course, I might be befuddled, It was a while back.
CPB
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Maybe some Modern Jet Jocks could answer what happens when they eject at 35,000ft etc?
Does the parachute deployimediately or is it altimeter activated , also do Jet pilots have oxygen after they eject or is it disconnected?
Sheep
Does the parachute deployimediately or is it altimeter activated , also do Jet pilots have oxygen after they eject or is it disconnected?
Sheep
AFAIK, there is a separate oxygen supply on the seat. A small drogue deploys immediately to stabilise the seat, and then you stick with it (and the oxygen), until a barometric release operates at a safe altitude that disconnects the seat straps and deploys the main 'chute for you ....
Yes, most seats (ACES II, for me) do have a "bailout" bottle that provides oxygen to the normal O2 mask. It is activated by a green knob that is part of the harness. It is about 2 inches by 10 inches, as I remember. More than enough to get to the baro parachute activation altitude of around 10,000 + or - some tolerance.
Also, correct on the TAS problem, opening shock is very severe at altitude, all seats delay opening 'til about 10,000 MSL. Don't know about bailing out above high terrain, that was never discussed in Life Support class. Guess the assumption was you would be smart enough to open the chute manually. Memory is fading on the details.
My ejection gave me about two swings to treetops, but ejection seats are fascinating bits of technology.
Gf says.
Oops, just remembered the bottle is part of the harness, not the seat. The seat goes away from quickly.
Also, correct on the TAS problem, opening shock is very severe at altitude, all seats delay opening 'til about 10,000 MSL. Don't know about bailing out above high terrain, that was never discussed in Life Support class. Guess the assumption was you would be smart enough to open the chute manually. Memory is fading on the details.
My ejection gave me about two swings to treetops, but ejection seats are fascinating bits of technology.
Gf says.
Oops, just remembered the bottle is part of the harness, not the seat. The seat goes away from quickly.
Re the high terrain - One solution is to have two or more barostats the ("altimeters" that used to trigger seat separation ).
Seats I sat in (RAF) were usually set up with a 10,000' barostat in the UK ( no high terrain), however when we flew to,say, Deci. or Cyprus and were going to overfly the Alps the barostats were changed for a 5000 metre model .
Seats I sat in (RAF) were usually set up with a 10,000' barostat in the UK ( no high terrain), however when we flew to,say, Deci. or Cyprus and were going to overfly the Alps the barostats were changed for a 5000 metre model .
Purveyor of Egg Liqueur to Lucifer
I am presently reading 'Two sides of the Moon' by David Scott and Alexei Leonov.
This book is about the concurrent lives and experiences of both the astronauts and cosmonauts during the cold wars 'race to the moon'.
Interestingly, Since the SL-3 booster was severely power limited due to the weight of the Vostok spacecraft, the first cosmonauts would eject from the craft at an altitude of 23,000 feet.
After ejection, the cosmonaut would separate from his seat and parachute to earth landing at a speed of about 5m/sec (16.5 ft/sec).
(To qualify internationally as the first orbital flight, this had to be kept secret, as the Cosmonaut was supposed to land safely IN the spacecraft. Never the less, Yuri Gagarin WAS the first man to circle the Earth.)
Also the Gemini program used ejection seats for emergency egress.
Found these;
http://www.ejectionsite.com/vostok.htm
http://www.ejectionsite.com/gemini.htm
This book is about the concurrent lives and experiences of both the astronauts and cosmonauts during the cold wars 'race to the moon'.
Interestingly, Since the SL-3 booster was severely power limited due to the weight of the Vostok spacecraft, the first cosmonauts would eject from the craft at an altitude of 23,000 feet.
After ejection, the cosmonaut would separate from his seat and parachute to earth landing at a speed of about 5m/sec (16.5 ft/sec).
(To qualify internationally as the first orbital flight, this had to be kept secret, as the Cosmonaut was supposed to land safely IN the spacecraft. Never the less, Yuri Gagarin WAS the first man to circle the Earth.)
Also the Gemini program used ejection seats for emergency egress.
Found these;
http://www.ejectionsite.com/vostok.htm
http://www.ejectionsite.com/gemini.htm
Guess I get to plug my (not for profit) website again!!
The 02 bottle on most ejection seats is about 10litres capacity. More than enough for the ride to 10,000 feet and man/seat seperation.
Jim's ejection seat website
The 02 bottle on most ejection seats is about 10litres capacity. More than enough for the ride to 10,000 feet and man/seat seperation.
Jim's ejection seat website
I don't own this space under my name. I should have leased it while I still could
Wiggy is quite right when he mentions changing the bang-seat bottle from 10k to 5km. When we flew over Turkey and Iran we always joked with the pilots that we would be OK and would find them by looking for the hole in the snow. The rear crew, free-fall, barastats were set to 12.5k, just enough for a HALO drop <g>.
One thing we never dressed for was a high altitude bailout. It was just something we did not want to consider. The chances of the jet breaking up was beyond consideration. At 40k to 56k we would have been into the pressure breathing regime as well as all the discomfort of the cold. The 2 mile drop would, I guess, have taken something like a minute or more and the temperature would still have been -56 when the pressure breathing came off. Then we would have had a further 4 mile or 2 minutes until the parachute opened.
Warming up at 12k would have been a slow process.
It did happen. I believe a Canberra disintegrated when its 8 inch flare ignited under the tail. The two-man crew, I understand, did not so much eject from the jet as the jet disintegrated around them. This was in the late 50s or early 60s.
One thing we never dressed for was a high altitude bailout. It was just something we did not want to consider. The chances of the jet breaking up was beyond consideration. At 40k to 56k we would have been into the pressure breathing regime as well as all the discomfort of the cold. The 2 mile drop would, I guess, have taken something like a minute or more and the temperature would still have been -56 when the pressure breathing came off. Then we would have had a further 4 mile or 2 minutes until the parachute opened.
Warming up at 12k would have been a slow process.
It did happen. I believe a Canberra disintegrated when its 8 inch flare ignited under the tail. The two-man crew, I understand, did not so much eject from the jet as the jet disintegrated around them. This was in the late 50s or early 60s.
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Baling out at high altitude.
If you bale out of an aircraft at high altitude (say 35,000 ft) and pull the rip cord immediately, is the opening shock any greater than if you free-falled (or is it free-fell!) and delayed opening the parachute to say 5000 ft? Disregard any question of use of oxygen etc. This is purely a question on the dynamics of high altitude versus low altitude opening of a parachute.
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I think you are correct on the TAS thing as well. Your terminal TAS is higher at altitude.
Your terminal velocity is only higher because there are fewer air molecules to slow you down. Therefore there are equally fewer air mollecules available to create an opening shock.
Using Reducto ad Absurbum
what would happen if you bailed out in orbit?In short, TV and any opening shock is dependent on IAS and not TAS.
I think the temp reason is more plausible, plus, don't forget they were jumping rounds, so if you open over the mess at 20,000ft and can see your labrador frolicking with the ground crew, with a North Wind, you'll still end up having schnapps for a night cap along with a couple of rousing choruses of the Horst Wessel song
Here's another reason: You might want to take a delay because your a/c was going faster than you will at Terminal Velocity. Now THAT could shred your canopy.
Last edited by Onan the Clumsy; 28th Mar 2005 at 12:37.
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No problem opening the chute at terminal velocity [125 mph]
but why would you want to hang around at that altitude at very minus temperatures [-35C etc]
Far more interesting to free fall from 100,000ft plus - break the sound barrier at 800mph plus, warm up as you enter atmosphere slowing down - and all in 4 minutes.
but why would you want to hang around at that altitude at very minus temperatures [-35C etc]
Far more interesting to free fall from 100,000ft plus - break the sound barrier at 800mph plus, warm up as you enter atmosphere slowing down - and all in 4 minutes.
Paxing All Over The World
Hmmm, interesting. I know this was an academic question but if your body is frozen by the -35C, will you be killed by the temp before the lack of oxygen? You would certainly be unconcious before death. However, a post mortem would not have enough of your body left to examine to determine wot got you first. 
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"I tell you, we are here on Earth to fart around, and don't let anybody tell you any different." Kurt Vonnegut, Jr.
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"I tell you, we are here on Earth to fart around, and don't let anybody tell you any different." Kurt Vonnegut, Jr.
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Years ago I heard about an pilot that ejected around 35K Feet in the back than still Soviet Union. From what the newspaper was telling he survived and landed safely. Than again this was in the old days.
So I guess it's possible to survice minus (Very Cold)C
Coastrider26
So I guess it's possible to survice minus (Very Cold)C
Coastrider26
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Similar thread running in Military
If you dumped imediately, then the shock may well be greater...depending on how fast the aircraft was (and therefore you were) going.
Otherwise, why would it? it's all related to the number of air molecules you displace anyway, so I don't see why the dynamics would be any different.
35,000' pah! Col Joe Kittinger (?) jumped from 108,000' or thereabouts. He took a five minute delay and used a drogue to check his speed.
If you dumped imediately, then the shock may well be greater...depending on how fast the aircraft was (and therefore you were) going.
Otherwise, why would it? it's all related to the number of air molecules you displace anyway, so I don't see why the dynamics would be any different.
35,000' pah! Col Joe Kittinger (?) jumped from 108,000' or thereabouts. He took a five minute delay and used a drogue to check his speed.
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HSWL
Back in 1954 I was working on parachute flight testing at RAE. Then the opening load depended on what we would all think (size and speed at deployment) BUT there was another factor that was very important and that was the porosity of the fabric. The porosity of any fabric can be shown to reduce with altitude. This means that unless a parachute is designed to be used at high altitude then it will very likely split (or otherwise fail) if opened way above its design ceiling. There is also the IAS/TAS issue which will certainly affect the opening shock loads and again at 40k the TAS is twice the IAS so any forces related to inertia will be doubled.
JF
Back in 1954 I was working on parachute flight testing at RAE. Then the opening load depended on what we would all think (size and speed at deployment) BUT there was another factor that was very important and that was the porosity of the fabric. The porosity of any fabric can be shown to reduce with altitude. This means that unless a parachute is designed to be used at high altitude then it will very likely split (or otherwise fail) if opened way above its design ceiling. There is also the IAS/TAS issue which will certainly affect the opening shock loads and again at 40k the TAS is twice the IAS so any forces related to inertia will be doubled.
JF
Do a Hover - it avoids G
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Hudson
You remember right. The opening shock loads induced in any canopy increase markedly with height due to porosity effects. You might like to check a similar topic running on Questions.
JF
You remember right. The opening shock loads induced in any canopy increase markedly with height due to porosity effects. You might like to check a similar topic running on Questions.
JF