Side by side ejection seat question
 

On aircraft such as the A6, B52 even the B2 with side by side ejection seats
do both crewmembers always eject simultaneously ?


And if not, what prevents the second 'ejectee' being eviscerated in the rocket plume from the first ?

Even the dear the old JP was side by side, though no rocket pack, it was a purely gun seat, so no rocket plume, as I suspect is at least one type on your list (the B52?) There was presumably a risk of mechanical interference between the seats on ejection if you went purely simultaneously but no one ever really mentioned it.

As far as seats with rocket packs, firstly on all the ones I knew of the rocket didn't fire until the seat was well up the rails thanks to the gun which gave the seat the initial push.. I however do know of an almost simultaneous double ejection on an F4 (obviously tandem rather than side by side but as a crew you are still quite proximate) with the pilot just going first and as a result the nav suffered superficial burns from the rocket plume from the pilots seat as they both left the aircraft in very close formation with the nav trailing the pilot...not nice for the nav but he certainly wasn't eviscerated.

They are also biased to boost you in opposite directions. Left to left, right to right (hopefully).

Canberra rear seats ditto

Is there any compensation for the divergent seat vectors if the aircraft is banked and close to the ground? Are there any mechanisms to take account of similar factors?

AFAIK, the side-by-side ones I sat on (JP, Vampire T11, Hunter T7/T8) all had parallel rails. Anyone know better?

IIRC... On many MB products Sequencing (Either mechanical or electronic) prevents confliction. Divergence is often built into the airframe on seat installation. For the MB upgrade to Cessna A/T 37 historics in Oz, a guide device was retro-fitted to the cockpit structure to make sure the seat did not impact the cockpit canopy framework on exit and also ensured separation.

I know nothing about other manufactures but if its a Chinese seat it will probably have features remarkably like those made by MBA. If you know what I mean....

Not strictly an ac but on the US Gemini spacecraft which used ejector seats instead of an escape rocket the seats were angled at 12 degs from the vertical to ensure that the 2 astronauts diverged during an ejection.

In their case they were departing from a closed pressurised cabin full of 100% oxygen which might have reacted unfavourably with the rocket exhaust! In at least one test the doors also failed to open in sequence & the test manikins went through them on their seats which would've killed any human occupants, this might explain the reluctance of the astronauts to pull the handle on Gemini 6: the engines shutdown after ignition but with a cockpit indication that the rocket had started to lift off. Wally Schirra should've pulled the handle, would've had he been in the sim, but went with his gut instinct that the rocket hadn't moved. The 'right stuff' indeed.

Kenp, like you I don't recall there being obvious divergence on the JP seats, and I don't recall it ever being mentioned to me as either a stude or an instructor. Certainly if there was one it wasn't big enough to be obvious when you did the seat checks. Of course canting the seats would have resulted in one or both being sat "off vertical.

Ken S, re the comment about Gemini ejections I think it was Tom Stafford who said that due the fact they had been saturated in O2 for some time if they had of ejected they would looked like firecrackers.

Only slightly related
I recall a T38 Talon (tandem seating) with an engine failure on takeoff where both occupants ejected at the same time and the ejector seats hit each other causing both to malfunction with the inevitable double fatal outcome.

When I had my rides in a Hunter T7 (Forward Air Controller course, Chivenor, 1963 or '64, can't remember) the pilot's briefing was succinct and clear; "If I tell you to eject, I'll be gone by the time your brain has registered it, so don't bother asking why, just pull one of the handles."

In that case, simultaneous ejection on parallel rails would probably not have been a problem.

Sad, sometimes bad stuff happens...

The F-4 had a sort of potential nasty where if the rear seater pulled the handle just before the front seater the rear seater would be going up the rails just as the front seat canopy ejected.... the rear seater would quite possibly "collect" the canopy with probably fatal results. As a result the SOP was if time was short the front seater would eject without warning, leaving the nav to eject PDQ..which in turn is why the nav got burns in the ejection I referred to early in the thread.

No doubt my memory is shot full of holes but I recall that the JP seats were divergent by a few degrees - not to a level that you would notice in the cockpit but with both guns extended the split was visable. The preferred technique though was for sequential ejections, which required a higher safe ejection speed on t/o (120kts?) when flown dual. I think.

ISTR that the in Gnat the seats were inclined towards each other and if fired together would meet 70 ft above the aircraft. Therefore the instructor need to go first

Interesting, never saw one with both guns extended...fortunately.

It has been a while but I don't recall any formal minimum speed limit for ejection whilst dual, other than the normal seat limit of 0/90.

With you on that, wiggy.

Somewhere from the back of my mind comes a thought that JP & Hunter 7/8 seats may have been "handed". Anyone remember? If so, it could be that the guns & rails were in matching pairs with an asymmetry on each that canted out the trajectory but had the seats mounted parallel in the cockpit. It's all many years ago and my ageing brain is unable to recall.

The other part of the vague recollection is that the seats may have had a second letter suffix that defined the side they were to be mounted? Anyone know?

Thanks for all the good information, the detail i'm not clear on is when there's a delay before the second seat fires.

The remaining crewmember is still seated in the cockpit when the adjacent seat launches if for only a brief time, surely the rocket efflux would affect him ?

Some responses state that a gun initially fires the seat before the rocket takes over however I thought this was only on much older seats and that newer models provide a far less violent ejection using a rocket.


Which takes me back to my original question !

Stilton, I think that on even the most modern seats the initial impetus is provided by a gun. Only when the seat has travelled X distance up the rails does the rocket fire.

Wasn't an issue on the F111...;)

Yes a gun or catapult does the initial work before the rockets (if fitted) do their thing. The seat rocket plume can still get very close to other occupants though, but this has to be seen in the context of the emergency itself, potentially rockets firing on the canopy (very close!) or an exploding charge on the transparency (bomb going off by your head). These are all violent events that your protective equipment has to cater for.