Anyone know much about the Mk12 Bang Seat?

[xffw45343tg]

Pretty much as the title says really.

I've found that aside from Martin-Baker's site and the line drawings that IV(AC) Plumb posted here on MB, there's pretty little in the public domain - and only about half a dozen different pictures that appear in all the Harrier books.

I'm interested if anyone has any pictures of the component parts (particularly of the back of the seat), parts lists, dimensional data etc.

Can you help?

Many thanks,

Kirk

[Julien]

No pics of the back, but some others here;

http://www.jetartaviation.co.uk/2012/10/raf-harrier-gr9-mk-12h-ejection-seat-now-avaialble/

Julien

[xffw45343tg]

Thanks Julien. I'd love to buy that seat but I suspect I'd be chucked out of the marital home!! Jet Art put a few other pics of it on the site a few months back; pretty much the best I've seen but fairly low res.

I believe that the Mk12 was originally designed to be a retro fit for the Mk10, so I suspect the mounting points, rake angle and beam dimensions are probably very similar. Any other ex "plumbers" out there?

Kirk

[pte1643]

I believe that the Mk12 was originally designed to be a retro fit for the Mk10, so I suspect the mounting points, rake angle and beam dimensions are probably very similar.

I've read somewhere, not that long ago, that the 12 is just a "pimped" up (better performance zero/zero wise IIRC) version of the 10, and as such can be used as a direct replacement. No "mods" to the airframe needed.

It was while looking into some replacement seats for a future (long into the future) Harrier build.

I don't think this actually answers your original question though.

[xffw45343tg]

Thanks mate - I'd read that too, though I'm sure there'd need to be a little customisation of pan shape, connection positions etc. All a bit arbitary though I suppose. Not going to happen to Tornados or Hawk T1s...

The seat questions keep coming:

One thing I haven't been able to figure out is the operation of the MOR. It seems to me that the general idea is that when the SAFE handle is up the lever is interlocked. With the seat live, then pulling the MOR would seem to depend on whether or not you are still in the aircraft. I *think* if you're flying through the air then it sets off Crtridge to fire the parachute deployment rocket (not drogue gun as in the Mk10) and releases the harness from the seat whereas if in the aircraft it just separates you from the seat? I'm not sure I've got this right because presumably if you want out of the seat in a hurry, you'd use the main QRB...

Another head scratcher is the little lever aft of the seat raise/lower switch. It's not shown on any of diagrams I've seen, but appears from the GR.7 onwards I reckon.

Finally, anyone know what happened to the Harrier Heritage Centre at Wittering? They had a training Mk12...

Many thanks in advance,

Kirk

[xffw45343tg]

(Re) Found a link for anyone looking for references: http://www.primeportal.net/hangar/luc_colin/harrier_gr7_walk_3.htm

[Phil]

Not 100% on the Mk12 MOR, but the MK10L MOR was interlocked to the seat pan firing handle - you couldn't pull it if you hadn't fired the seat.

[xffw45343tg]

That makes sense Phil - thanks for the reply.

I suppose MOR is only needed if you find youself descending and feel the need for a parachute canopy above you. On the ground if you want to climb out you'd go for the QRB. I've kind of worked out from looking at the SJU5 seat here that the MOR releases the harness at the occupant's hips, the negative G aft of the firing handle and the leg restraint lines as well as firing a cartridge to set off the parachute. I can't think of a circumstance where you'd want to do this on the ground.

Another thing I'm not clear about is how the PSP leaves the seat pan. I guess the occupant is attached to PSP and when separated from the seat just pulls it out - though I suppose the PSP must be mechanically attached to the pan at some point.

Cheers,

Kirk

PS/ Anyone wanting to acquire genuine Martin-Baker bits should type "MBEU" into ebay. Not me selling but highly recommended.

[Selwyn]

That makes sense Phil - thanks for the reply.

I suppose MOR is only needed if you find youself descending and feel the need for a parachute canopy above you. On the ground if you want to climb out you'd go for the QRB. I've kind of worked out from looking at the SJU5 seat here that the MOR releases the harness at the occupant's hips, the negative G aft of the firing handle and the leg restraint lines as well as firing a cartridge to set off the parachute. I can't think of a circumstance where you'd want to do this on the ground.

Another thing I'm not clear about is how the PSP leaves the seat pan. I guess the occupant is attached to PSP and when separated from the seat just pulls it out - though I suppose the PSP must be mechanically attached to the pan at some point.

Cheers,

Kirk

PS/ Anyone wanting to acquire genuine Martin-Baker bits should type "MBEU" into ebay. Not me selling but highly recommended.

A very simple description is:

On Ejection seats the PSP is attached to the pilots harness by two quick release(QR) boxes and a static line connection. there are also two "sticker straps" which clip into spring loaded clips on the seat pan to secure it in the pan.

on ejection the drogue chutes stabilise the seat. When this has happened the drogue line connection to the seat is released, at the same time the straps holding the pilot in the seat are released. the "pull" of the drogue chute is then transferred to the parachute pack. this secondary "pull" tips the pilot out of the seat complete with PSP (the sticker straps just pop out) and the parachute deploys, the seat falls away.

the pilot then releases the two QR connections to drop the PSP. He remains connected to it by the static line. So it will hit the ground or sea first . in water he releases his parachute and all he has to do is to reel in the static line to find the PSP and deploy the dingy. obviously on land and in the dark this static line ensures he is not seperated from his survival pack

Selwyn

[xffw45343tg]

Thanks Selwyn.

So would I be right in thinking that the sticker clip is the one shown in Steve (IV(AC) Plumb)'s post #58 first picture here (labeled above the EO handle)?

This seems much higher than the level at which the PSP shell sits - is there a short strap & buckle? I had it in my mind at first that the harness clipped in here but realise this must be much lower down in the pan if the mechanism that release it is closely connected to that cross shaft to which the MOR link connects.

Just thinking this through, the harness connects to the pan and the PSP connects to the harness so there's no chance of the PSP popping out in normal operation (e.g. Negative G) unless the harness is released. Is that right?

Cheers,

Kirk

[Phil]

That makes sense Phil - thanks for the reply.

I suppose MOR is only needed if you find youself descending and feel the need for a parachute canopy above you. On the ground if you want to climb out you'd go for the QRB. I've kind of worked out from looking at the SJU5 seat here that the MOR releases the harness at the occupant's hips, the negative G aft of the firing handle and the leg restraint lines as well as firing a cartridge to set off the parachute. I can't think of a circumstance where you'd want to do this on the ground.

,No you really wouldn't want to do this on the ground. As well as the actions you've noted, the MOR handle also unlocks the harness from the HPRU, basically unlocking you from the seat and deploying the parachute by unlocking the drogue shackle. It basically duplicates all the functions of the BTRU.

[xffw45343tg]

Cheers Phil. You set me off reading up further on the BTRU which is a little different on the Mk12 to that on the Mk10. Think I've understood the general principle though; don't fire the PDU & separate the occupant until you're down to a set pressure altitude.

I found a line drawing of the Mk.12 which labels that little lever on fwd end of the left outboard face of the pan as "Manual leg line and PEC release lever". I deduce from this that as the pilot straps in, the leg lines go through the rings in the garters, plug back into the seat and have the slack taken out(?). If they want to get out, they release the QRB but instead of squeezing on the lever on the back of the PEC to disconnect it, they pull back this lever to drop the leg line connection (presumably it will then just unthread as they stand) and pop the PEC - not forgetting to disconnect the static line to the PSP.

The only thing that bothers me about this is the connection that pops the PEC seems to be connected to the same mechanism as the Emergency Oxygen On/Off lever so I must have this wrong somewhere as that makes no sense; There's a lever that emerges from the top aft end of the PEC (seat part) right by the catch that connects to a pull rod running down the back edge of the pan , via a connection that I can't see properly to a link on tthe side of the pan to a bell crank to the EO handle. I'll bet the bit I've got wrong is the "connection I can't see properly".

It also strikes me as a particularly dumb thing to do for a pilot to separate themselves from the seat at high altitude as it would appear that they then also disconnect themself from an oxygen supply. Hypoxia blackout here we come.

Thanks again for the pointers guys.

Kirk

[Phil]

I'm not sure about the Mk12 leg line lever, on the Mk10L I'm sure it only released the leg lines and not the PEC as well, at least on the version I worked on, but PEC and O2 systems do tend to be the most common area of difference between various seat models. The leg lines run through snubbers and are at one end attached to the floor of the aircraft via shear pins. the other end is threaded through the garters and then pushed into the seat pan. As the seat leaves the aircraft the leg lines pull tight, then the pins shear.

As for the 'connection you can't see properly', is that the go-forward lever for locking the shoulder harness? (This is the green knob on the LH side of the seat pan)

[xffw45343tg]

As for the 'connection you can't see properly', is that the go-forward lever for locking the shoulder harness? (This is the green knob on the LH side of the seat pan)

No - though I found a side-on picture that sorts out some of the mystery. The connection from the top of the PEC goes to a crank that sits above the go-forward link and not to the link from the manual oxy lever (which seems to go further aft). This crank then connects via tortuous means to the MOR mechanism - implying that MOR=PEC release. Makes much more sense.

I reckon that the main ladder beams for the Mk12 are probably the same size as for the Mk10. Do you know their dimensions and/or the size of the gap between them?

Thanks once more for the continued assistance.

Kirk

[Phil]

No Sorry, I don't have access to any dimensions any more.

I do have a series of photos showing the step by step breakdown of the Mk10 main assemblies, including the main beams without the headbox or seat pan fitted:

[Phil]

Here's a link that will hopefully take you to the entire album:

http://s228.beta.photobucket.com/user/nzgunnie/library/Mk10

[xffw45343tg]

Very fantastic indeed!

[xffw45343tg]

Phil,

A question about the HPRU in your picture above: I spy a metal pipe that enters the base of the HPRU (which looks remarkably similar to the HPRU on the Mk12) on the left side of the seat. This appears to route to a black & yellow striped unit on the right side of the right ladder rail, level with the RRI.

What is that unit? Presumably it is supplying gas to retract the upper harness?

Another thing that looks very similar to the Mk.12 is the drogue shackle release arrangement which I think is entirely mechanical on the earlier Mk10s. Is it gas operated?

Cheers,

Kirk

[Phil]

The black and yellow unit is the balistic manifold. All the various gas lines from the seat pan (via the 'trombone assy') and the assemblies mounted on the beam run into it. My memory is a little rusty, but the line you are talking about looks like it is the HPRU firing line that takes the gas from the seat pan firing cartridge and fires the HPRU. The Trombone assy allows the seat pan to motor up and down, it is a telescoping pair of gas pipes that extend or retract as the seat pan motors up or down. The seat actuator assy is the metalic green piston attached to the lower surface of the HPRU at one end, and the lower seat pan slidy thingee at the bottom. Sorry can't recall the technical name for the sliding mounts for the seat pan!

The Drogue shackle release on the Mk10L above is gas operated. It takes the gas from the BTRU (or MOR) and retracts a piston, releasing the drogue shackle.

[xffw45343tg]

Yet again you come up trumps Phil. Thank you.

Bit by bit I feel like I'm beginning to understand how all the systems interact.

The NACES diagrams seem to refer to them as "Seat Pan Runner Guides" but "slidy thingees" gives a much better picture of their function!

Kirk

[xffw45343tg]

OK chaps, so here are the 1st snaps from my drawing. I'm only trying to get the major assemblies in place at first and then can go through systematically getting them more realistic:

I've got most of a real parachute box and this suggests that I'm not too far off in terms of position of the HPRU but have some work to do on the pitot assemblies. Fortunately (courtesy of Rays Tek) I have some real pitot tubes in the stash so this should be do-able.

Any feedback, suggestions or real dimensions would be most welcome. The one thing I'm really struggling with working out from reference pictures is how the various sub-assemblies on the sides of the ladder attach to it. At the moment the BTRU and PDU in particular just hang in space...

Cheers,

Kirk

Edited July 13, 2013 by Kirk

[Phil]

Shouldn't the GGRA have two secondary cartridge housings?

[xffw45343tg]

Thanks Phil - good spot! (Although unlike the Mk.10, the 12 does have only one somewhere roughly where I've positioned it. I suspect it is of larger diameter; not sure.)

It is missing much detail though - I still have to do the side rails, the attachment hoops and the mounting castings. I'm mustering up the enthusiasm to start the seat pan next. This will be quite a challenge as it's a pretty complex sub-assembly, more similar to a NACES than a Mk.10.

Kirk

[Phil]

From the MB website:

'Secondary cartridges fire in turn as seat rises'

Plural? Looks like it has two.

[kspriss]

This is a sorta on topic question, has anyone got a drawing of a seat hopefully with dimensions? I want to make a replica one for my pc chair but coming up short.

Cheers

Steve