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Aircraft rejector seat

  [vote for,

Ejector seats have saved the lives of many pilots.

However, "banging out" is a far from pleasant experience, and can cause spinal damage.

This is because the pilot must leave the aircraft with substantial vertical velocity to clear the airframe, particularly the tail; thus extreme acceleration is necessary.

However, a little consideration of relativity leads to a startling conclusion. For a passenger on a train, it is impossible to determine if the train leaves the station, or the station leaves the train.

Thus the answer is not to eject the pilot's seat, but for the seat to reject the aircraft.

In an emergency, the cockpit cover is "blown" in the usual way, but instead of the seat being launched upward on rails, a small charge simply imparts a gentle vertical acceleration to the seat. As the seat starts to rise, very much larger propellant charges mounted at critical locations drive the entire aircraft very fast in the opposite direction, i.e. downwards. After all, if the pilot has been forced to eject, the airframe's a total loss anyway.

So the pilot retains their forward momentum, and rises gently upward, while the aircraft is hurled away from them fast enough that they don't hit any part of it.

BorgCo are currently accepting applications from prospective testers of this amazing new technology, which has the potential to be a great advance in aviation safety, once we iron out one or two very minor problems.

8th of 7, Jul 12 2017

American Airlines Flight 587 https://en.wikipedi...Airlines_Flight_587
"aggressive use of the rudder controls by the co-pilot caused the vertical stabilizer to snap off the plane" ... [8th of 7, Jan 17 2018]

Rudder problems, an industry standard. https://en.wikipedi...g_737_rudder_issues
[bs0u0155, Jan 17 2018]


       This is pretty damned clever, but why not replace the charges with air foils that pop up to push the plane down? Getting a 250 pound man / seat combo to pop up doesn't need a lot of explosive but getting that multi ton plane to move in the opposite direction would require many times more explosives. Getting the aircraft to hold together once you pop these things might make a bad situation worse.   

       Might be able to get the plane to nosedive out from under the pilot with a simple flap on the nose that pops up, both pushing the plane downwards and affording the ejecting pilot a temporary wind screen to keep him from getting blown back into the plane until it gets out of the way.   

       In faaaact, you could have that flap just pull the pilot and seat out like a crane. He gets flipped up while the plane gets pushed down.
doctorremulac3, Jul 12 2017

       What about blowing the tail off first? In fact, not just the sticking-up part of the tailplane, but the entire rear part of the aircraft from immediately behind the pilot backwards. Gone, ejected. Luggage, cargo, fuel, passengers and all.   

       To aid airofoil stability the remaining rear fuselage could be recycled in mid-air, if mid-air recycling were to be quickly invented. Then the small pile of aluminium atoms would simply stream their way down to earth harmlessly.   

       Then the pilot could simply nudge their seat backward slightly and they'd be free of the nosey part of the plane, and can gently and serenely descend to the pile of mattresses on the ground.
Ian Tindale, Jul 13 2017

       You're close, but with enough mattresses already in the cockpit you could just skip the exiting the plane part and just bounce on the mattresses when the plane de-airs.
normzone, Jul 14 2017

       I like it, aside from the glaring flaw that the seat would still have its previous momentum making low altitude ejections impossible.
DIYMatt, Jul 14 2017

       Not impossible, just fatal.
pocmloc, Jul 15 2017

       Don't say that, it puts off potential testers ... it's hard enough to recruit as it is.
8th of 7, Jul 15 2017

       //However, a little consideration of relativity leads to a startling conclusion.//   

       I was really hoping for a consideration of ejection at v/c approaching 1. Your next statement applies only to constant velocity.   

       These days, survival after ejection from ground level is also considered important. I would recommend that a drilling rig is attached to the aircraft to allow for this situation.
TomP, Jul 15 2017

       What if you simply blew the vertical tail off the plane, faster than the pilot was rising?
Vernon, Jul 16 2017

       If so much of the plane needs to be removed before the pilot can eject, perhaps landing it would the more practical option.
MaxwellBuchanan, Jul 16 2017

       This apparently makes complete sense. I wonder if the autorejection act could cause the plane to go into drone- mode, flying the damaged remains in ways that a human passenger would not permit.
beanangel, Jan 14 2018

       Needs brass and mahogany.
21 Quest, Jan 15 2018

       A suitable way forward would be to invent in-flight maintenance and repairing. Upon hearing a squawk suggesting serious trouble, simply launch another aircraft which will speedily arrive alongside, or underneath the stricken aircraft. The in-flight repair garage will, using robots, rapidly assess the damage, issue air inversely through teeth, and proceed to get to work according to the time available, after first putting the kettle on.
Ian Tindale, Jan 16 2018

       In most cases the pilot is free to move on with her life and see other aircraft, but sometimes the rejected aircraft becomes fixated and embittered.
pertinax, Jan 16 2018

       There are documented cases where an aircraft continues to find themselves rejected by any further pilots they are involved with. The problem can often be traced to a deep seated problem with the aircraft itself, and not each consecutive pilot. Deep seats are often the cause of rejection.
Ian Tindale, Jan 16 2018

       If there's anyone who's going to be able to speak about rejection on the basis of a wealth of personal experience, it's you, [IT].
8th of 7, Jan 16 2018

       I did offer, but they turned me down.
Ian Tindale, Jan 16 2018

       Life's just full of these little ironies, isn't it ?
8th of 7, Jan 16 2018

       I like this idea. I wonder if, to some extent this is already in use. It would be pretty trivial for example to use canards and elevons to provide a lot of down force to a Typhoon for example.   

       I thought a while ago that a switch to engage a somewhat attenuated ejection might be desirable. There's a big difference between loosing all pitch control while lawn darting at the ground from 1000ft and say, running out of fuel. In the latter, you could flip the switch, pitch up to slow and get the vertical stab out of the way and punch out with a little less violence.   

       I think though, ejection is one of those places where a brutal simplicity is preferred. They used to have two handles for options, but it introduced decision time between the two. Linking the seat action to the aircraft in an ejection scenario is asking a known damaged component to perform. Do you really want additional electrical dodads in an active electronic warfare environment or even EMP?
bs0u0155, Jan 17 2018

       The solution, surely, is either to put the vertical stabiliser at the front, or put the plane into reverse before banging out.
MaxwellBuchanan, Jan 17 2018

       // put the vertical stabiliser at the front, //   

       Been tried. Didn't end well ...   

       // put the plane into reverse before banging out. //   

       Been tried. REALLY didn't end well ...   

       // It would be pretty trivial for example to use canards and elevons to provide a lot of down force to a Typhoon for example. //   

       Yes, but you counter your own point ... for whatever reason, you've lost control and the die-by-wire FCS has wandered off into the tall grass.   

       But pyrotechnics, linked mechanically (det cord) via multiple paths to the bang handle, are ultra-reliable.
8th of 7, Jan 17 2018

       //But pyrotechnics, linked mechanically (det cord) via multiple paths to the bang handle, are ultra-reliable.//   

       So how does this work? If your large charge drives the front of the airframe down, you may end up with the aircraft rotating in pitch and the vertical stab moving forwards in a... stabbing motion. You could drive down the rear, then the violent pitch-up would drive the seat into the cockpit, contrary to what you want. Doing both at once requires two coordinated charges, these would be HUGE compared to the seat charge and necessarily distributed around the aircraft. The explosives are already a huge hazard, more and larger charges multiply the danger and modes of failure.   

       I wonder if the charge could extend a telescopic tube upwards to act as a guide for the seat to follow designed to miss the vertical stabilizer? Or, deploy a much larger section, canopy + significant surrounding structure. Just the mass ratios will drive the airframe down. Getting the timing right would be tough.
bs0u0155, Jan 17 2018


       Thinking about this, it seems clear that the pilot will be wearing an ejector seat at the time of egress. It's also clear that his (or, indeed, her) forward speed relative to the airframe will be zero initially. Unless the pilot has left a foot on the throttle, the plane will not be accelerating. Therefore, it is only the relative wind (admittedly, perhaps 500mph) driving the pilot into the vertical stabiliser.   

       Given a horizontal distance of, say, 6 metres between the cockpit and the tail, the pilot should not be doing more than 40-60mph by the time they hit the tail. So, simply design the ejector seat to be able to withstand a 60mph impact, and/or make the upper leading edge of the vertical stabiliser crumplable. The main aerodynamic forces on the vertical stabiliser must be lateral, so fore-aft crumplability seems feasible.
MaxwellBuchanan, Jan 17 2018

       Not explosives, propellants. H.E. will cause supersonic fragmentation. Think vertically-orientated JATO bottles.   

       Initiate the pushers at the rear of the airframe slightly before the mid and front, causing it to pivot around the C of G, then "drop".   

       At the point of separation the aircraft and pilot have the same velocity. Due to mass/area factors, as the pilot hits the slipstream they start to lose velocity due to drag. If the aircraft then accelerates rapidly downwards, the pilot will clear the empennaged without needing too much vertical speed themselves.   

       // a telescopic tube upwards to act as a guide for the seat to follow //   

       Semi-baked on the Space Shuttle.   

       // The main aerodynamic forces on the vertical stabiliser must be lateral, so fore-aft crumplability seems feasible. //   

       Airbus provide lateral crumplability too - just hit the rudder a bit too hard, and Wheee ! Say bye-bye, tailfin ...   

8th of 7, Jan 17 2018

       //Given a horizontal distance of, say, 6 metres between the cockpit and the tail, the pilot should not be doing more than 40-60mph by the time they hit the tail.//   

       Aero drag at sea level is F=1/2 air density*velocity squared*drag coefficient*frontal area. I get an initial force of 29,500N for an acceleration of 266 m/s/s or 27G for 500mph ejection. It's close. That v-squared really gets you, especially at 600mph. After that the drag goes all squiffy and trans sonic, not my pay grade.
bs0u0155, Jan 17 2018

       // not be doing more than 40-60mph //   

       So, your day has gone seriously pear-shaped, you've had to abandon a rather expensive bit of kit belonging to someone else (probably because unpleasant people are shooting at you with evil intent) that you've signed for and they expect you to bring back, and now your comfy chair has slammed into a big lump of titanium ...   

       Good game, good game ...
8th of 7, Jan 17 2018

       They said I was mad, shooting at a $40m fighter plane with a revolver. And indeed, it would have been futile but for the large propellant charges pre-positioned in the airframe ...
pertinax, Jan 18 2018

       Small target, easily protected by a kevlar jacket. Plenty of other big, vulnerable targets to go at ...
8th of 7, Jan 18 2018

       //very much larger propellant charges//   


       //Small target//   

pertinax, Jan 18 2018


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