Baling out at high altitude.

[Hudson]

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?)

[eggplantwalking]

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.

[Capt Pit Bull]

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

[Sheep Guts]

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

[reynoldsno1]

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 ....

[galaxy flyer]

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.

[wiggy]

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 .

[SilsoeSid]

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

http://members.tripod.com/matt1125_1125/spaceman.gif

[jimgriff]

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.

:ok: Jim's ejection seat website (http://www.ejectorseats.co.uk)

[Pontius Navigator]

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.

[HSWL]

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.

[Onan the Clumsy]

I think you are correct on the TAS thing as well. Your terminal TAS is higher at altitude. Why would this make a difference?

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 :8 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 :ugh:



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. :ooh:

[jammydonut]

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.

[PAXboy]

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. :confused:

--------------------
"I tell you, we are here on Earth to fart around, and don't let anybody tell you any different." Kurt Vonnegut, Jr.

[Coastrider26]

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

[jammydonut]

In these common [if you are special forces] doing HiAlt LowOpening known as HALO you would use an automatic drogue deployment just in case you went comotose.

[Onan the Clumsy]

Similar thread running in Military (http://www.pprune.com/forums/showthread.php?s=&threadid=168638)

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.

[Say again s l o w l y]

Didn't he actually go supersonic on that drop. I believe he is the only human to break the speed of sound without a vehicle!

Scary stuff!!

[John Farley]

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

[John Farley]

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

[Capt Pit Bull]

OK, I guess Shock isn't a defined physical term anyway which is probably at the root of this issue.

Since drag is proportional to IAS I'd agree that the peak acceleration will not change with altitude.

However, the faster moving object (TAS) will take longer to slow down, so the deceleration profile will be 'stretched out', in regards to time, at higher altitude.

Given that injury is related to acceleration and duration, then altitude has to be a factor.

I know sweet FA about parachutes, but basic physics tells us that surviving a rapid deceleration is all about transferring Kinetic energy to some other form. If your TAS is higher, thats more Kinetic energy, and therfore it HAS to be more of a problem. Regardless of the actual mechanisms involved, and regardless of whether the Parachute or the person is the limiting factor.

Using Reducto ad Absurbum what would happen if you bailed out in orbit?

mmmm... tasty. OK, I'll bite.

Well, with density zero, you are already below your terminal velocity. And your terminal velocity with a parachute is still fatal !

But lets say we fire a retro rocket to get us back into the upper fringes of the atmosphere, and preemptively spread our parachute out behind us ready to catch the first whisps of air. Why can't the parachute just deliver us safely back to terra firma?

Because power = force times velocity (yes, TAS again).

We might not have much drag, but if we are doing 8 Km.s-1 we are going to burn up. (i.e. too much collision energy to transfer to something else without getting all crispy). Our cloth parachute isn't up to the job, so we need a better one - an ablative heat shield will do quite nicely. That is just a more robust drag producer after all.

[John Farley]

Capt Pit Bull

If you want to talk about 'drag' then in that language one would have to say say that a parachute Cd 'effectively' varies with altitude due to porosity effects. But that is a bad way to think of things because drag is an aero concept and porosity is not - hence the use of the term porosity

The opening shock loads are merely the peak loads measured during the opening process and depend on how the canopy is designed, whether it uses taschengerts to control the incidence of the peripheral hem during opening and so on. Complex issues.

JF

[Milt]

Isn't the question regarding the OPENING SHOCK of the canopy?

My logic says that the canopy always opens/deploys at a rate proportional to TAS - not IAS considering the canopy's lightness and hence low inertia.

Having opened with a bang and hopefully not ruptured the deployed canopy should then produce drag in relation to half rho v squared - ie related to IAS.

[Blacksheep]

That changing the Barostatic Release Units business sounds like a good idea.

Back on the 'V' Force, I spent some time encarcerated in Waddington's 'Gin Palace' working in the Instrument Calibration Laboratory. One of my incredibly boring tasks was testing the Barostatic Release Units for the ejection seats and the rear crew parachute packs. The parachute BRUs were all set the same - a 10,500' +/- 500' barostatic trigger initiated a three second timer. The device then fired a spring loaded plunger that pulled the ripcord. Ejection seats had a separate BRU that triggered separation from the seat at 12,500' +/- 500' The user could always override the devices by pulling either the seat release and/or the ripcord handle manually if he was conscious and so inclined.

BTW, in a high altitude abandonment, rear crew members would have had difficulty finding the holes in the snow made by their pilots, due to the difficulty of climbing out of their own great smoking hole in the ground. The chances of being able to get out at high altitude and ride silk were extremely remote.

After alighting on Mother Earth, any surviving pilots would of course have to face the Crew Chief and explain what happened to his beautiful piece of aeronautical machinery. Most would have preferred death to that... ;)

[SASless]

Colonel Joe Kittinger

1928 -

First To Fly Solo Across The Atlantic Ocean In A Helium Balloon, 1984

Inducted in 1998

Joe Kittinger, a native of Orlando, Florida, and eventually a Colonel in the Air Force, began flying aircraft in 1949. Kittinger qualified in practically all types of flying machines including hang gliders, hot air and gas balloons, propeller driven aircraft, and jet aircraft.

On August 16, 1960, he set three world records: the highest parachute jump (102,800 feet), the longest parachute free fall (4 minutes 36 seconds), and the first person to exceed the speed of sound without an aircraft or space vehicle (714 mph during free fall). In September 1984, Kittinger set a world record for the longest distance flown in a 3,000 cubic meter helium balloon. This first solo transatlantic balloon flight from Caribou, Maine, to Montenotte, Italy, covered 3,543 miles in 86 hours.

Colonel Kittinger received the Distinguished Flying Cross on five occasions, two for his balloon experiments and three for his combat tours in Southeast Asia. During his last combat tour as Commander of the 555th Fighter Squadron, his aircraft was shot down and he was imprisoned in a North Vietnamese POW camp.

[ChristopherRobin]

I can't find the video after a quick search, but I have seen it and it is extraordinary...he just hops off and disappears tumbling because he is going so fast. Here's a picture (http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=h_kitt_02,0.jpg&cap=Air%20Force%20Captain%20Joseph%20Kittinger,%20Jr.%20jump s%20from%20Excelsior%20III%20balloon%20gondola%20in%201960%2 0test,%20freefalling%20toward%20Earth%20for%20over%204%20min utes.) though -

And although the intrepid Colonel did jump from a very great height, it wasn't orbital altitude, although it is likely that the same could be done from that level.

The problem would come is if you actually were orbiting in which case you would re-enter at approx 15000 mph and then burn up. Coming straight down like Joe Kittinger did is not a problem up to a point; Apollo astronauts travelling to the moon left earth orbit at approx 25000 mph, but on their coast to the moon were continually being slowed down by the earth's gravity.

So much so, in fact, that by the time they crossed over the point where the moon's gravity was a greater influence than the earth's, they were "only" doing 1000 mph!

So if you jumped from that height I imagine the reverse would be true and you would accelerate towards the earth until you re-entered at approx 24000 mph.

So I suppose there is some upper limit to what height one can jump from, but I can't be @rsed to work it out.

[HSWL]

Thanks for replies. John Farley, especially. I flew Mustangs countless years ago and I recall we were warned about the shock of high altitude bale-outs and your reply John now bears that out. Where I am uncertain, however, is the TAS/IAS question.

If the shock of opening is dependant on the volume or pressure of air particles filling out the canopy, then at high altitude it would be the IAS that counts, wouldn't it? If not, I am at loss to understand where TAS comes into it at high altitude. If you jump at say 40,000 ft and open the chute at 230 IAS vertical speed (if you had a speedo on your body), then would not the opening shock be the same as opening the chute at 230 IAS at say 10,000 ft?

The porosity of the silk at high (cold?) altitudes is something I never thought about. And just to confirm part of my original question and that is assume that temperature and oxygen aspects are a different story -so ignore their effect on the pilot.

[John Farley]

HSWL

The way I think of it the amount of energy stored in your pink body as you go over the side is related to your TAS not IAS. That being so whatever force the chute applies to slow you down would have to be applied longer. Toss in the porosity and high altitude effects which make the chute snatch harder as it opens and you have a double whammy of a bigger initial load that also stays applied longer. So a hard time would be had by all.

JF

[Capt Pit Bull]

Thanks for the whole porosity issue input JF. As you say, its a complex issue.

I was also pondering on the peak deceleration experienced by the body versus the 'chute. It occured to me that as the chute opens you carry on falling for a bit as the lines extend, and then as the snatch bites, you have an element of elasticity in the lines.

Which means the deceleration profile of the person is likely to look quite a bit different to the canopy. Its a bit like the old 'why don't we put a nice soft cushion on that Bang seat' question.

I do love to chew on this stuff ;)

CPB

[gravity victim]

Sport canopies have used reefing systems for years. The faster you're going, the stronger the resistance to the canopy spreading, with the reefng force directly proportional, so the part-open canopy slows you until a speed when the spreading force overcomes the reefing. (If a modern, aerodynamic 'square' canopy opened without any reefing it would generate instant drag and lift, which would not be good for it or you.) I guess that a reefing system is impractical because of the need to cater for for a very low ejection, though.

[SASless]

Round canopys have been put into sleeve assemblys to slow the opening.....doesn't creat much delay but does soften the opening shock. Low Porosity canopies....feel very slick and solid next to other materials....definitely have a higher shock loading at time of deployment.

A sport jumper I knew at the Sunderland airport years ago...broke his back when his square canopy opened abruptly when someone had rigged the slider improperly. When I suggested that must have hurt....he smiled and said...."Not as bad as the landing did!" He went on to compete in the international championships that year after being told in hospital that he would probably not be able to walk. Quite a guy!

[MovinWings]

Interesting Argument, Interesting Physics, Interesting Parachute Theory. But..... Out of what present a/c is anybody going to need a 'High Level' Ejection! Oh, I forgot, Typhoon when the Engines both Stop..... Silly Me!

MW

[Pontius Navigator]

Blacksheep, fascinating. If what you say is true and as far as I remember my 10k/12.5k is also true, then someone was telling porkies.

I would not put is passed the system to have convinced the poor sods with only low level barastats that the other poor sod in the bang seat had them <g>.

Beags your shout.

[Blacksheep]

I think you've read it wrong Pontius - the parachutes were all the same, but the seat separation units chucked an unconscious pilot out of his seat at 12,500 so he fell clear of the seat before the chute opened. He could always leave earlier if he was awake and felt like it.

One thing always bothered me. That three second delay - said to be to allow time to clear the aircraft. Did they teach aircrew not to wait for auto-deployment at lower levels? I mean, imagine a low level ejection. Three seconds for auto-deploy wouldn't have been much good to you below about a thousand feet, would it?

[Pontius Navigator]

Blacksheep, no what I understood you to say was that the pilot barastat worked at 12.5 and the rear crew at 10k. That was the reverse of my understanding which was why the Akrotiri units bang seat barastats were the 5km version.

As far as the 3 second delay I think a pilot will need to answer that one.

[Perfect PFL]

Just a few points to add to the discussions here. I don't know whether the professional pilots among you know just how much work is continually on going in the development of military aircraft escape systems? Any advances that can be made to better ensure the safety of aircrew are looked at daily by a number of experts at a number of different companies.

All the different points mentioned here on ejection sequence timings, parachute opening shock at different altitudes etc are in constant development, and quite often with each new aircraft entering service comes a whole new range of systems - from a new seat, a new parachute, through to better designed clothing. Retrofits are also made, and a lot of work goes into ensuring the systems on current in service aircraft are enhanced where possible, the focus is not just on future aircraft.

With the latest ejections seats all the pilot needs to do is pull the handle, and some time later, depending on the conditions on ejection, he will land safely on the ground. Have a quick read here about the latest Mk16E seat being developed for use in JSF:
http://www.martin-baker.com/eject_mk16E.htm
The parachutes are constantly developed too by a company called IrvinGQ:
http://www.irvingq.co.uk/products/ees.asp

As well as the emergency escape system being there to save the life of the pilot, we in the research, development and testing world also want to make the whole sequence as safe as possible. If possible we want the aircrew to land following the ejection sequence in a fit state to go and fly again the next day. To aid this a lot of research is done in a number of areas including harness design, limb restraint, and even posture on ejection.

All systems go through a rigorous testing phase before they can be used in service - including live jumping of new parachute canopies, where there are a group of brave (crazy??) people who risk themselves to test these things.

Although these manufacturers do a lot of there own equipment testing, of course there is also independent testing and verification, as well as seperate research work done by other companies, such as QinetiQ (formerly DERA, DRA, RAE...):
http://www.qinetiq.com/

Hopefully some of that information is new / interesting to some people.

[Load Toad]

Read that page mate - cheers for that; one quote to catch the eye:-

'..that is based on the NASA T-38N design to ensure accommodation of the larger aircrew'


Snigger.

[wiggy]

Blacksheep
The USAF, I believe, used to teach beating the seat on it's non-Martin Baker types ( seem to remember seeing a USAF film on the subject in around 1980), and certainly when Neil Armstrong ejected from the Lunar Landing Training Vehicle in late 68/early 69 he is on record as trying to beat the seat :

"I always thought I might be able to match the automatic system, but I found out that when I was reaching for the D ring the automatic system had already fired"

As a user of one of Martin Bakers older models IMHO on those it was a non-starter - on ejection you are, in sequence, kicked very hard in the backside, have your head rammed between your knees as umpteen g are applied by the rocket pack and in all probability thrust into a roaring gale....and also generally smacked around a lot. It would be the rare individual who could sit there immediately after burn out and go straight into the manual separation drill. Added to which on the older MB seats the first action in the drill (pulling the manual separation handle) neatly disconnects you from the drogue chute (which is attached to the top of the seat) which you need to extract the main chute PDQ if at low level. So in a nutshell, on the older RAF seats you were not taught to beat the seat, with good reason.

[L J R]

Its a pity that all the so called R&D companies (especially Qinetic - Sp?) never actually take into account 'Normal' and 'Operational' military flying activities when they come up with new gear. I have found as time goes by, all the latest stuff is more uncomfortable, more restrictive, hotter, more expensive and more delicate - Often to the point that most aircrew either wear it wrongly (in order to get more comfortable for that 8 hour trip over Baghdad) or dont wear it at all!

[Perfect PFL]

L J R - what kit are you talking about specifically? And what role do you think QinetiQ had in it's development?