How much of a factor is weight of the pilot in ejections?

Factual Questions
1

This articlewhich caught my eye this afternoon is about the USAF’s first female F35 fighter pilot. She is also the only female F35 pilot for now since; (emphasis supplied)

136 pounds, 62 kg is a bit on the heavier side for most women (5’4 inches is the USAF minimum and its at about maximum healthy weight for females of that height), but is too light for men (minimum healthy weight for a man of that height 66 kg, 145 pounds).

So how much of a factor is weight going to be in ejections and are woman in much greater danger during ejections then men?

2

Semi-informed WAGs to follow.

From the seat’s POV what matters are that the pilot weight not be too much or too little and be geometrically distributed within the expected envelope.

Additional potential factors depending on the installation would be the pilot not being so tall his/her head was taller than the seat top/headrest. As well, all else equal long slender arms are more prone to disabling wind-flail injuries than short stubby ones. Last of all, people who are heavily muscled are more likely not to break or dislocate something than folks who are mostly skin & bones.

Surely a seat could be designed for the, e.g. 90th percentile ergonomic 20-something human, not merely the 90th percentile ergonomic 20-something male.

It seems the seat actually was designed for both the male & female body models, but it looks like they screwed that up.
Speaking as somebody who was at the bottom 10%ile of the weight range and was definitely of the wiry skin & bones design. …

While riding such a seat (ACES II or earlier models in my case) I never gave it much thought. IMO the incremental statistical risk isn’t zero. But of all the things to worry about killing you, that one was real low on my list. Besides, there wasn’t much I could do about it.
I’ve not seen anything in the trade press on this. I’d be *real *curious to learn the back-story. Did they have an event, or is somebody just doing engineering analysis? If so, why now? With what parameters. If clearly the thing will rip any 103# human in half their concern is well-founded. If, OTOH, there’s a 2% incremental chance, they’re being penny-wise and pound-foolish. If the actual goal was to increase safety 2 percent across the board they could simply tighten other ergonomic rules. E.g. no lanky people.

3

An ejection is basically a reverse hanging isn’t it? At least Russian ones see, to be.

[QUOTE=LSLGuy]
Surely a seat could be designed for the, e.g. 90th percentile ergonomic 20-something human, not merely the 90th percentile ergonomic 20-something male]
[/QUOTE]

Would such a seat be practical though? I believe there is no modern ejection seat which permits ejection through all aspects of a fighter’s potential performance (you can’t eject at Mach 2 on an F16) but rather an envelope. Would that not reduce the envelope or require a rebuild of the whole plane?

4

I’ve worked on an ejector seat trainer for an F-15 back in the late 80’s and I think the part about getting your neck broken if the weight is too small is a bit far fetched since the neck and back go into compression when you eject. But I can imagine that studies have taken into account the dynamics of ejecting from an actual plane that may put more sideways stress on the body when ejecting; this stuff is always being revised.

Pilots are generally fairly small, compact guys, still 135 seems kind of low end for a male. Still it would be possible for a 5 foot tall female to achieve 135 lbs, she would just be strong as hell; which is kind of necessary when you are pulling high g-loads.

I knew one male fighter pilot who couldn’t swim very well because his body fat was so low he sank like a rock without constantly moving.

5

Judging from this article (paywall):

It appears that the problem was driven by the parachute loading portion of the ejection seat deployment (combined with a rather heavy helmet)- where the neck may be in tension.

They also added an airbag to the neck region, to help under low speed ejections

6

The old F-111 had an ejection capsule and the pilot and weapon systems officer sat side-by-side. They had to weigh within a few pounds of each other. If they didn’t the lighter person brought along some ballast to even up the weight.

7

No it’s not. 145 lbs is nearly overweight (BMI of 24.9 @ 5’4"). I’m 5’6" @ 125 lbs and no doctor has ever said that I’m underweight. On the contrary; they’ve all said to keep up whatever I’m doing, diet-wise.

8

The USAF disagrees with you.
Their minimum weight for a 5’4" man is 110 lbs and the max healthy weight is 150-160 lbs depending on age.
It seems like the Army has a bit more detail based on age.

9

YamatoTwinkie (awesome handle BTW) seems to have nailed it.

An issue I’d forgotten about was the bulky heavy magic helmet the F-35 folks wear. The engineers have done a marvelous job making that helmet as small, conformal, and light as possible. But it’s still bigger than the former standard stuff.

There’s only so much throttling of the rocket motors and adjusting of the parachute deployment timing that can practically be done. The lighter the person, the more acceleration you get from whatever forces are applied.

10

What happens if the ejector seat is activated when the plane isn’t upright? If it’s spiraling down out of control and the ejection profile is downwards, say?

11

The seat leaves the aircraft at about 90 degrees relative to however it’s pointed at that moment. A couple seconds and a couple hundred feet away the parachute deploys and is pulled “downwind” versus whichever way the seat is traveling. Which is a vector sum of however it was being carried by the aircraft plus its own vector ~90 degrees to that.

As the parachute deploys and slows versus the airstream, gravity pendulums the pilot towards “down”, rotating the chute towards “up”. Within a couple more seconds the pilot is descending at a safe rate.

if there’s enough distance and time between where this whole process started and the ground the pilot lives. If not, then not.

The general rule of thumb is that in an out of control situation it’s best to eject 10,000 feet = 2 miles above the ground. By that low you’ve almost certainly run out of space / time to recover control and you’re increasingly likely to run out of room to jump out successfully too. IOW, quit while you’re only a little behind.
Bottom line, the whole point of the seat is to get the pilot away from the airplane, not above the airplane. For the vanilla case of jumping out while flying more or less upright *away *is above. For less vanilla cases that’s increasingly less true.

12

Just curious, what would happen? Ruptured internal organs?

13

What Happens When You Eject Out Of A Jet At 800 MPH

Altitude (air density) matters, of course; the more altitude you have, the higher the safe ejection speed. There’s the case of an SR-71 breaking up in mid-flight, pitching its 2-man crew into a Mach 3 slipstream. Stilll, only one of them survived the incident.

14

Great story, but a bad ending for the flight engineer.

Some love for the second flight - “Bill! Bill! Are you there?”

15

On some early jet aircraft, the ejection seat fired downward. That way you didn’t have to worry about hitting the rudder and vertical stabilizer. Of course you better more than a few feet off the ground when you eject. :eek:

16

This is one of the ideas behind the ejection capsule on the F-111. There were successful ejections at supersonic speeds.

17

There are a lot of situations wherein ejecting is termed “Probably committing suicide to avoid being killed.” Every fairy tale doesn’t have a happy ending. War stories are even more so.

18

Aren’t most ejection seats zero-zero, so that the pilot can eject even from aircraft sitting on the ground and have enough space for parachute to deploy and cushion his fall?

19

Sure, but that’s not best. If (for example) your primary chute gets tangled, you don’t have enough altitude to jettison and deploy your reserve.

20

See below.

All true. Malfunctions are always a material risk.

In your specific example, there is no such thing as a reserve chute; it’s one and done. We expect to cure tangles, line-overs, etc., by cutting enough risers with the handy knife we carry for just that purpose. And hoping the remaining partial canopy gives a survivable descent rate.

Other sources of malfunctions are the aircraft canopy doesn’t leave the aircraft, the seat doesn’t fire at all, the seat fires half-assedly or the rocket explodes instead, the seat tumbles madly breaking your limbs and or neck, the device that separates you from the seat doesn’t fire, the parachute doesn’t separate from its container in the seat.

That’s a partial list. About 30 discrete things happen in 4 seconds when everything goes right. Each one has at least one failure mode. You can expect to be stunned from the experience for several seconds. For any medium-low altitude ejection there probably won’t be time for you to address the addressable malfunctions before the ground arrives. And there was already nothing you can do about the non-addressable ones.
Back to Velocity …

The actual process is “Recognize the problem/situation, decide ejection is the least bad solution, assume the position, pull the handle(s), hope for the best”. Each of those steps takes time and therefore, in a fast moving vehicle, distance.

“Zero-zero” means as you say. But there’s a third, fourth, fifth, and sixth term to the survival equation.

  1. Zero descent rate. If you are diving straight to the ground at 500 knots and pull the eject handle 50 feet before the nose touches the Earth you’re still screwed. As a practical matter at even a fairly mild 300 knots closure with the ground you’d better have the seat departing/departed the aircraft by 1000 feet to survive. Which means you need to decide by 2000 feet above the ground which means recognition starts at 2500+ feet above the ground.

  2. Little pitch or roll. If you’re inverted, or descending near vertically, or whatever, then the boost the seat provides, although still away from the aircraft, is not as much away from the Earth. Or maybe it’s even towards the Earth. That situation adds additional altitude to the safe minimum.

  3. Little gyrating. If the airplane is damaged and flailing about in the sky or is an aerodynamic spin state the centrifugal forces may preclude you reaching or pulling the handle. It may preclude you assuming a good body position. It may interfere with how the ejection sequence works or the orientation of you vs. the seat at separation time. All of which increase the odds you’re injured and increase the odds of a parachute opening malfunction to boot.

  4. Moderate speed. Ejecting at 150 knots airspeed is not too risky for the properly dressed pilot. At a more typical 300 knots wind blast injuries such as dislocated limbs and damaged eyes are common and should be expected as just part of the ride. At 450+ knots the odds on incapacitating injuries approaches 100%. As well, above 450 the odds on parachute malfunctions from overload, or bodily injury from the opening shock, begins to approach 100%. This despite all sorts of engineering features intended to mitigate these risks as far as possible.
    Then we get to the next phase of the problem: On the ground. If the seat delivers you into a good parachute and the parachute delivers you at a survivable speed to 10 feet of altitude, you need to successfully land on whatever is there. Which might be an ocean, a forest, a swamp, a desert, a cliff face, or a powerline. It may be day or night, 100F or -40F, windy or calm. If this is wartime you may be in friendly territory, empty territory, or enemy territory. Or even amongst enemy formations.

And now you’re alone with your injuries in whatever the environment is. Equipped with some training and 25 lbs of survival gear (unless that got lost in the ejection).
In all, zero-zero was a huge improvement over what came before. And saved a great many pilots back in the early 1960s when low altitude engine or flight control failure during takeoff and landing was causing about 3/4ths of USAF’s fighter fatalities. But that does not mean that current or near future seats are magic Star Trek transporters that give you a riskless, painless do-over on today’s mission.