posted 05-19-2018 07:02 AM               

I compare this with Ted Freeman's accident in 1964. When Freeman's T-38 lost power, Freeman also had to make a low altitude ejection. But apparently, his parachute did not fully open and he perished.

posted 05-19-2018 08:08 AM               

That's about what I found in a couple of sources for the altitude of Freeman's ejection, while some newspaper accounts at the time had witnesses estimating it at 300 feet.

My very-amateurish guess for the difference in the outcome is that the LLRV, at the instant of ejection, was barely descending. (It was, however, practically sideways - it's always seemed to me that the ejection system launched him upwards despite that.) Freeman's plane was descending rapidly, and was traveling at jet-plane speed.

posted 05-19-2018 10:31 PM               

With any ejection, the seat upward velocity needs to raise the crew member to a height that will allow the drogue chute to deploy and withdraw the main chute, which then needs airflow to inflate with sufficient time to allow the deceleration of velocity prior to landing.

If the aircraft has a high rate of decent, the downward velocity can be subtracted from the upward velocity (for a vertical ejection), meaning even a Zero / Zero seat may not deploy in time if your going downward fast enough.

In Armstrong's ejection, the LLTV did not have a high downward velocity at the time of ejection, giving the seat time to self right and gain some height. This video of the Canadian Super Hornet crash demonstrates a similar event.

posted 05-21-2018 01:04 AM               

I know that NASA and Bell Aircraft knew that potential instability problems could happen with the LLRV and the LLTV. If the engines gave out, it would drop like a brick. Therefore necessitating a zero/zero (or better) ejection capability.

posted 05-21-2018 02:10 AM            

The entire philosophy of abandoning aircraft evolved over time. The first ejection seats were replacements for manual bale out under high speed (read combat) conditions. Aircraft were getting too fast for humans to overcome the airloads, or avoid subsequently hitting parts of the structure. Originally no-one envisaged jumping out of airplanes on the runway, just after take-off etc, because that was never a consideration with a manual parachute. When pilots started using seats they also made "Hail Mary" attempts outside seat performance envelope — so the performance was gradually improved. It wasn't an easy thing to do without the seat killing it's occupant. Some of this is covered in an old British book with a memorable title — "The Man in The Hot Seat," about a guy named Doddy Hay, can't remember who wrote it.

posted 05-21-2018 11:25 AM               

quote:

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Originally posted by David C:
It was not self righting or vertical seeking.

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posted 05-21-2018 02:31 PM            

This is a picture of the Weber zero zero live demonstration. The direction of the rocket thrust is seen clearly as not being vertical.

If you look very closely at the Armstrong film you'll see ejection is not initiated in a wings level pitch up, but with a large bank angle present as well. The seat initially translates up and forward relative to the LLRV attitude (not the ground) at time of seat exit. The trajectory then curves because of the "pitch up sweep" during the burn. This curving is perhaps better seen in the footage of Algranti's ejection.

Finally, part of the seeming vertical ascent is an optical illusion caused by bank/yaw angles and a lack of suitable background visual references.

posted 05-22-2018 02:14 AM               

A related question concerns the ejection seats of the Gemini spacecraft and the issue of high speed ejections:

What is the maximum speed a vehicle can be traveling at that allows for a survivable ejection? To be precise, the Titan II would been ascending at a speed of at least 4,000 miles per hour to reach orbit (anyone — please correct me on this number if you know it. 4,000 mph I believe is only a suborbital flight speed. Orbital flight speed I believe is closer to 5,000 mph). So could the astronauts have survived an ejection at 4,000 plus miles per hour?

posted 05-22-2018 07:10 AM            

Perhaps surprisingly, the Gemini seat was not designed for really high speed bale outs like the A-12/SR-71 and of course the incomparable X-15. It's "party trick," if you like, was a very long throw from a prospective fireball on the launch pad. The idea was to escape both the blast and thermal pulse (which could have melted the nylon parachute).

During a Titan launch the ejection seats were the primary means of escape for a Mode I abort which covered a seat altitude range of 100 to just 15,000 feet, and a speed range of zero to only Mach 0.75. Beyond that they were a back up for aborts that utilised the spacecraft, up to 45,000 feet and near Mach 2 (roughly 1300 mph). Now there's nothing to prevent a seat occupant from pulling the handle above those parameters, but survival becomes progressively less likely.

A speed of 4,000 mph in itself doesn't mean anything. What are important are dynamic pressure (or equivalent airspeed), Mach number and altitude. If you ejected at 4,000 mph at sea level (if a vehicle capable of achieving that existed), you'd be very dead indeed from the initial air blast. If you tried that at 200,000 feet altitude the initial air blast would be survivable. However, there are other threats. These include skin friction heating and lack of stability producing body rotational rates that can incapacitate or kill, or result in failure to deploy the parachute satisfactorily.

The highest Mach (not dynamic pressure) mishap survived by any human outside of an aircraft or spacecraft that I am aware of is the 1966 Article 135 loss. The Lockheed M-21/D-21 combination.

posted 05-23-2018 03:14 AM               

And it sounds like the SR-71 broke up at Mach 3.18.

And about the Weber T-37 seat? How many feet could the Weber T-37 propel a pilot out of the aircraft? And how does the seat balance out to be vertically level if a pilot's ejection angle is sideways and nearly horizontal? I assume the seat is weighted to be vertically level. But in a zero/zero ejection, does the seat have time to level out on weighted characteristics alone?

And was the height/feet range that the T-37 could propel a pilot comparable or better in height range than other ejection seats of the day?

posted 05-23-2018 05:38 AM               

Astronauts were skeptical of the ejection seats' usefulness. STS-1 pilot Robert Crippen stated:

"In truth, if you had to use them while the solids were there, I don't believe you'd — if you popped out and then went down through the fire trail that's behind the solids, that you would have ever survived, or if you did, you wouldn't have a parachute, because it would have been burned up in the process. But by the time the solids had burned out, you were up to too high an altitude to use it. ...So I personally didn't feel that the ejection seats were really going to help us out if we really ran into a contingency."

posted 05-23-2018 05:38 AM            

quote:

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Originally posted by Jim_Voce:
How many feet could the Weber T-37 propel a pilot out of the aircraft? And how does the seat balance out to be vertically level if a pilot's ejection angle is sideways and nearly horizontal?

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These seats had absolutely no vertical seeking or self righting capability, no "weighting" or anything else. The "pitch sweep" provided some statistical compensation for non-zero pitch attitude at ejection initiation. However, if you went out sideways due to bank then that's it. You're going out sideways and you need to be a lot higher up. Aircrew take all this stuff into account when making an ejection decision.

The LLRV seat was optimised for the high sink rate, low level, low speed case. My guess is that it was better than other seats in that region, worse elsewhere.

quote:

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Any idea how the Shuttle Orbital Flight Test ejection seats and abort procedures compare to the Gemini ejection seats?

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posted 05-23-2018 06:44 AM               

I have also found a reference for the shuttle test flight that states:

During ascent, the capcom made the call 'negative seats.' This occurred as the shuttle climbed above 80,000 feet. At that altitude the ejection seats would still work, and the pressure suit had sufficient oxygen get back down so you may ask, why was that a limit? Because an analysis of the speed and trajectory above that point resulted in enough air friction heating to melt the plastic faceplate of the helmet. And probably other things we didn’t analyse.

quote:

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Originally posted by David C:
I don't think the seats were just a placebo for the crew.

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posted 05-23-2018 09:20 AM            

quote:

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Originally posted by oly:
I do think, like Gemini, they served more use during decent.

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51F was a straight forward intact abort. 93 and 107 weren’t detected in time to take any action. Personally I suspect that if the 51L incident had occurred during OFT, both crew could have survived. To a lesser degree the same may be the case with 107.

posted 05-23-2018 08:08 PM               

quote:

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Originally posted by Skylon:
Had See managed to actually eject from the aircraft, or was he thrown totally clear somehow and attempted to open his chute?

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During an accident, the head box closure flaps can be torn open, allowing the contents to be released. There are many other ways the contents can be torn free from their container.

In Armstrong's LLTV ejection, he can be seen swinging in an arc during the ejection sequence as the chutes are deployed and inflated, washing off his velocity. He only gets a few swings as he floats down, drifting past the fireball of the exploding vehicle. I have often wondered how close he came to the burning wreckage during his descent. I have not seen another film angle to determine how far behind the wreckage he passed.

posted 05-24-2018 12:25 AM               

One last "summing it up" question is do we have a firm answer on the question of what is the highest speed a pilot can eject from an aircraft (or rocket launch) and survive? And the answers in this thread have been -

1. Below Mach 2.7 for Shuttle ejection seats

2. The M-21/D-21 accident in 1966. The crash occurred when the plane was at Mach 3 but the pilots waited to eject. So the actual speed was not known.

3. The SR-71 accident (also in 1966) in which the plane broke apart when the plane was traveling at Mach 3.18.

posted 05-24-2018 01:53 AM               

There are varying designs of seat, suit, helmet and system that make a true answer of altitude survivability difficult. Banging out at 80,000 feet at Mach 3 may be survivable. You also may die of hypoxia, broken neck, have your limbs ripped off, or luck out and fall to a safe altitude. Bear in mind, an ejection at Mach 3 will result in some serious aerodynamic heating issues. Joseph Kittinger II, Felix Baumgartner and others have demonstrated that high altitude parachute jumps are survivable from higher altitudes, and the examples above show that high speed and high altitude ejections are possible. However, putting a number on the limit is not so easy.

posted 05-24-2018 01:59 AM               

And on page 48 of the document it states that the HS-1 (X-15 ejection seat) can be used safely at a speed of Mach 2.2 in an altitude range of 30,000 to 70,000 feet.

So it appears that there is a critical number between a vehicle's speed and the relative air pressure at certain altitudes that must be the common number that equates to the limits of survivability at the time of ejection. And I would assume that is a G force number. Is that correct?

And would anyone know what that number is?

posted 05-24-2018 02:58 AM            

If you want numbers to get a feel for it, then John Stapp's work is the place to go. He survived minus gx (i.e. deceleration in a forward facing seat) values of 45.4 applied at 493 g/second, and 38.6 at 1100 g/second. The latter higher onset rate and lower peak caused the more severe effects.

It is impossible to say what true airspeed Mach 3.18 at 78,000 feet equated to on the day of the SR-71 mishap, because the atmospheric conditions are unknown. On a standard day that would be around 2,100 mph, but a completely standard day never happens.

quote:

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Originally posted by oly:
In general, ejection seat drogue and main parachutes are stowed in the head box unit...

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posted 05-24-2018 08:39 AM               

quote:

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Originally posted by Jim_Voce:
So it appears that there is a critical number between a vehicle's speed and the relative air pressure at certain altitudes that must be the common number that equates to the limits of survivability at the time of ejection. And I would assume that is a G force number. Is that correct?

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And q would determine the "wind blast" and subsequent g loads.

posted 05-25-2018 10:32 PM               

So these higher risk regimes are where Ejection Seat manufacturers focus a lot of design attention. Zero/zero capability, self righting, rapid action and other design traits are priorities. There have been several designs of ejection system specifically catering for high altitude or high speed.

The F-111 ejection module and the B-58 ejection capsule come to mind. These systems are designed for high speed and altitude survivability for aircraft expected to fly into war zones in combat conditions, perhaps under fire, with a high risk of something going wrong that may require crew ejection.

The SR-71 was not designed for such missions. It was envisioned that it could out climb and out run most things thrown at it.

There have been some exceptions to this, including the F-104 downward ejection seat on early models.

So the designers probably weighed up the pro's and con's and decided that the weight and size options favoured a seat over a capsule and that if a high speed ejection was required, luck became a major player.

This runs true with the Gemini escape system. Theoretically an ejection on the pad was possible, and lower speed and altitude ejection was considered safer than higher speed and altitude.

If your passing through max Q and suffer a rocket failure, you run the risk assessment thru your own mind and decide if ejection is the preferred option. The designers have given you helmets, suits and systems to increase your survivability factor, but all bets are off.

Imagine the weight and size penalty if rockets and military aircraft were built with safety protection systems that protected the manufacturers from liability cases should the pilot get bumped or bruised during catastrophic structural failure at Mach 3 and 70,000 feet.

So ejection seats are no guarantee of escape survival, they are designed to give the crew another option. An aircraft doing a carrier launch or landing runs a high risk of some kind of failure, the seat may provide a second chance.

Ejection seats are like the spare wheel in your car, They sit there waiting to be used, will only work if you use them, need to be maintained, and may not get you home.

posted 05-26-2018 05:45 AM            

quote:

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Originally posted by Jim_Voce:
Was the Weber T-37 seat used on the LLRV in 1968 a self-righting seat?

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I have answered this question here twice already quite plainly. We, myself and others, have also repeatedly tried to introduce you to a few other concepts including dynamic pressure, frictional heating and ejection philosophies. However, we appear to be going round in a frustrating series of ever decreasing circles. I don't know what your personal situation is, and I'm not trying to be nasty, but can you either please read our replies properly or explain if there is some other difficulty. I can be patient if there is a reason.

posted 05-26-2018 12:04 PM               

quote:

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Originally posted by David C:
Jim, I'm not trying to be funny here, but the reason I stopped participating in your threads is that you do not seem to read the replies that people take their time to write to you.

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posted 05-28-2018 04:38 AM               

quote:

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Originally posted by David C:
These seats had absolutely no vertical seeking or self righting capability, no "weighting" or anything else.

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quote:

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Originally posted by oly:
In Armstrong's ejection, the LLTV did not have a high downward velocity at the time of ejection, giving the seat time to self right and gain some height.

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posted 05-28-2018 07:45 AM            

quote:

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Originally posted by Jim_Voce:
you might understand why I was seeking some additional clarity.

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quote:

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Originally posted by oly:
I am not sure what type of seats were installed...

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posted 05-28-2018 08:32 AM               

quote:

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Originally posted by Jim_Voce:
It sounded contradictory. So you might understand why I was seeking some additional clarity.

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Your original question, "Does anyone know at what altitude Armstrong ejected at?" was answered, details of Ted Freeman's case can be found here and this from The New York Times (of the time):

Witnesses said the craft was 300 to 500 feet high when the canopy left the aircraft. It was not clear whether Captain Freeman had ejected or had been thrown from the plane on impact.

quote:

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Originally posted by Jim_Voce:
I just wonder why Northrop didn't build that in to the T-38 aircraft. Any thoughts on this?

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quote:

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Originally posted by David C:
There were no zero zero seats when the T-38 entered service.

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quote:

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Originally posted by Jim_Voce:
Was the Weber T-37 seat used on the LLRV in 1968 a self-righting seat?

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