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Newbie Joined: Jul 21, 2008 Posts: 1 Status: Offline

Hello all,

why does the F-35 canopy open from the rear?

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I know I know...

So you can pull the seat without removing the canopy... (Like the F-16)

It is a maintenance cost saving measure. (At least one of the reasons)

Enthusiast Joined: Aug 09, 2008 Posts: 24 Status: Offline

I hope they don't have any problems with ejection.

StratoJet wrote:

I hope they don't have any problems with ejection.

The way the canopy opens is irrelevant as far as ejection on the F-35 is concerned. The F-35 netiher jettisons the canopy prior to ejection, nor does it have the ability to do so. There are detonator cords embedded in the canopy "glass", these blow to crack the canopy along the edges and down the center line. The seat simply punch through the cracked canopy.

Enthusiast Joined: Aug 09, 2008 Posts: 24 Status: Offline

Didn't know that. Thanks.

Enthusiast Joined: Nov 23, 2005 Posts: 64 Status: Offline

Actually that would be the last thing engineer would think about Wink

If you look carefully, you will notice, that canopy of the B model is shorter, because of the lift-fan that is positioned behind cockpit. Putting hinges and lifting system in front allows to make one system that will suit all three variants of the aircraft, without the need for designing, and producing one specially tailored for the F-35B aircraft.

Now add to this the fact that front of the canopy is naturally stronger and heavier - you need less force to lift it up from that end, and the whole frame don't need to be as strong as let's say the F-16 one. It all added up equals lower costs for both design, and production. Easier serviceability of the ejection seat is a byproduct... but it's countered by harder serviceability of MFDs and anything bellow the dash.

I thought the canopy explosive cords were only on the X-35... Anyone got a photo of them in the production model?

Enthusiast Joined: Nov 23, 2005 Posts: 64 Status: Offline

http://www.f-16.net/gallery_item207962.html

http://www.f-16.net/gallery_item209474.html

As you can see, it is quite different than Hawk, Harrier, or X-35 pattern. That det-cord will only slice canopy into two parts instead of making additional hole above the pilot and seat.

Thanks, I see now. Why was that particular system chosen for the F-35 but not the F-22?

Enthusiast Joined: Nov 23, 2005 Posts: 64 Status: Offline

No answer for that question. I would guess that with F-22 there was no pressure for making it is as light as possible, so they made a single peace canopy, that was known and was working very well on F-16. And a single peace is too thick, and heavy to be shattered with explosives, and there is no protection from wind blast... so it have to be jettisoned as whole.

Both designs have their pros and cons, and neither is ultimate.

Tinito_16 wrote:

Thanks, I see now. Why was that particular system chosen for the F-35 but not the F-22?

Because the F-22's archless canopy is a lot thicker. The F-35 went to a thinner canopy and added a composite arch support on the inside (the coated transparency is still one piece for stealth purposes). This allows the det-cord system to be used.

One of the reasons they went with this system is that it is lighter, but another is that it is faster than the traditional US practice of using a 2-step ejection system that first jettisons the canopy then firing the seat. Because of the necessity to wait for the canopy to tumble clear from the ejection path, the ejection seat has to wait a second or so before firing. This is a second or so which the pilot of a STOVL aircraft like the the F-35B doesn't have if there was a sudden loss of hover thrust.

Tinito_16 wrote:

Thanks, I see now. Why was that particular system chosen for the F-35 but not the F-22?

1. Speed of ejection in zero-zero conditions

2. Underwater ejection clearance

Enthusiast Joined: Nov 23, 2005 Posts: 64 Status: Offline

When considering full ejection sequence, than actually, the F-22 ejection system might work better underwater. The canopy, even though is heavy - got rocket motor that help it clear off the seat's way. Depends on how deep the aircraft is - this could help at least reposition the canopy so the seat would slide over it, and not try to go trough it like in the A-7 event.

In F-35, the outside pressure wont allow the parts of canopy to get clear of the seat, and it will have to go through them anyway. The impact may not be pleasant, and pushing through two parts of shredded plexiglas is not very safe either.

All those systems are made to work with at least equal pressure inside, and out of the cockpit - ideally with lower pressure outside. Under water, only safe moment for using the "rocket chair", would be when cockpit is fully flooded and equalized... but if aircraft is sinking that will happen only after hitting the bottom.

The deeper aircraft goes, the more useless both systems become - when considering full ejection. If pilot have choice to only blow the det-cord in canopy, and egress by himself - than the F-35 system would be better suited for over water work.

Sundowner wrote:

When considering full ejection sequence, than actually, the F-22 ejection system might work better underwater. The canopy, even though is heavy - got rocket motor that help it clear off the seat's way. Depends on how deep the aircraft is - this could help at least reposition the canopy so the seat would slide over it, and not try to go trough it like in the A-7 event.

In F-35, the outside pressure wont allow the parts of canopy to get clear of the seat, and it will have to go through them anyway. The impact may not be pleasant, and pushing through two parts of shredded plexiglas is not very safe either.

All those systems are made to work with at least equal pressure inside, and out of the cockpit - ideally with lower pressure outside. Under water, only safe moment for using the "rocket chair", would be when cockpit is fully flooded and equalized... but if aircraft is sinking that will happen only after hitting the bottom.

The deeper aircraft goes, the more useless both systems become - when considering full ejection. If pilot have choice to only blow the det-cord in canopy, and egress by himself - than the F-35 system would be better suited for over water work.

Ok is this opinion or something backed up by facts? As far as I know, there have been no sucessful underwater ejections without the use of det. cords.

BTW, one thing which I think should be noted is that the detonator cords in the plexiglass merely a nice to have feature to reduce the likelihood of injury during ejection. If they should fail, the seat will punch through the glass anyway and the pilot will be successfully removed from the cockpit to a parachute landing. This is true of systems where the canopy is jettisoned too. The seat can and WILL smash straight through the transparency if it has to.

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F-35 canopy - Why does it open from the rear