Weapon Bay Door comparison

I was checking out some photos of the F-35 and noticed that the weapons bay doors are different than those on the F-22. The F-22's doors sort of curl up and to the sides, while the F-35's open straight down and indeed the inside door serves as a missile rack for the AIM-120 (and the AIM-9 I suppose, once they get into that). What are the advantages of one design vs. the other? Is the Raptor's design more suited to supersonic weapons release?

One other question: I noticed this slit on the top right side of the fuselage. Looks kinda like a gun opening but I don't know if it is, does anyone know?

Thanks!

The gun is in the "long hump" on the pilot's left.

The opening on the right is likely a scoop for AC cooling.

As to the doors, it was likely a cost saving measure.

Those were the F-35 pics, now here are the F-22's.

P.S. Sorry about the multiple posts, my computer is slow as hell and freezes repeatedly, making it almost impossible to get any significant amount of data in a single post.

Hey SM,
I figured it probably wasn't the gun port cause exposing the barrel to the outside would increase RCS... LOL I was dumbfounded by that intake. Hadn't seen it before.

Tinito,
There is a fundamental difference in the F-35 and F-22 doors due to the 22 weapon bays being so close together, while the 35 bays are spread apart. The 22 bays are so close together there is no room for an inboard door hinged to the fuselage. So the inboard door is hinged to the outboard door. The AIM-120s are ejected straight down for launching, so the inboard door must be pulled completely out of the missile's ejection trajectory. To do that, the outboard door must rotate well beyond 90 degrees and curl up as you say.

The 35 doors only have to rotate approximately 90 degrees to provide a clear path for the weapons.

Why the geometric difference? My guess is that the 22 design results in reduced cross section area (lower drag) and the 35 design is mandated by the F-35B lift fan exhaust passing between the left and right weapon bays.

Those bays look like they could fit 2 AIM-120's and an AIM-9X in the inboard door easily. But anyways, at least those bays are positioned so the a/c can bomb straight and level. Take a look at these bays (and the bomb in them):



My question is: how did the X-32's designers plan to actually drop the bomb? Did the plane have to fly at a certain bank angle to drop?

There was a carriage that tilted into the airstream.

Look at the 50 second mark in this video.

http://www.youtube.com/watch?v=vdRPXJyoqIk

johnwill wrote:Why the geometric difference? My guess is that the 22 design results in reduced cross section area (lower drag) and the 35 design is mandated by the F-35B lift fan exhaust passing between the left and right weapon bays.

Not really. The lift fan exhaust is completely ahead of the bay doors. The reason the inner doors spay outwards. to avoid a Vee shaped area around the centerline hard point. In the F-35B and F-35C that is where the gun pod is.

Sorry, dwightlooi, I think you are wrong here. The last foot or so of the lift fan exhaust doors is between the weapon bay inboard doors according to the photos I've seen. Your point about the centerline hardpoint is accepted. You might want to reconsider the use of the word "spay".

But none of that matters to Tinito's original question.

It's tough to tell but is there a possibility of installing another missile station on the outboard door? It looks like it could fit, and you'd have 2xA2G and 4xA2A instead of just 2 + 2. Or will this make the opening for the 2,000 lb bombs too small?

It "looks" but it doesn't fit..

I am not sure the 2000lbs JDAM was such a good idea. The B-2s can carry a sh*t load of JDAMs if necessary and they can even be carried externally with RAM on them. That forced the bay to be about 5'' wider because the bomb with its little wings is about 22'' wide, while all the other weapons are no more than 16'' wide.

And it makes no sense to continue to carry missiles with no folded fins on those stealth aircraft.

So the bay could have been designed for 3 folded fins AIM-120Ds or 1 folded fins AIM-120Ds and 1 ~16'' a/g munition. narrower fuselage, less weight and drag.

At the same time the missile could have been stretched because 1) the missiles don't need to be staggered, 2) the bay is about 4.3m long. The pictures above actually show that the bay is quite long. So no need for a JDRADM, the stretched AMRAAM could do the same job.

An F-22 like folded door couldn't be used because the landing is right next to the door when it's open. On the F-22 the landing gear is behind the main bay.

and btw with a narrower bay the aircraft can still carry the 2000lb JDAM but with no missiles next to it.. The F-35s strike in package, so the other aircraft would be able to defend the ones that carry the JDAMs

Or they could design a longer bomb with a rectangular cross section really optimized for the F-35... it would weight maybe like 1500-1700lbs instead of 2000lbs doesn't make much difference.

And at the same time since the bay is much narrower, they can use a one panel design, and save more space because they don't need the second rotary door system, like on the F-22.

Tinito_16, technology has moved on and many new inexpensive manufacturing techniques have been developed since the design of the F-22A. On the F-22A to reduce the RCS problem between the fuselage and equipment bay doors, very fine tolerances were required to keep the gap to a minimum. On the F-35, the gaps are larger but have solutions such as having a fine wire (with a charge on it) that blocks the full return of the signal back to the radar that transmitted the signal. Other solutions include using wire mesh in the skin or layers of the F-35 with different voltages applied to each, all in an effort to keep the RCS very low but, at a far smaller cost than the F-22A.

Tinito_16 wrote:The F-22's doors sort of curl up and to the sides, while the F-35's open straight down and indeed the inside door serves as a missile rack for the AIM-120 (and the AIM-9 I suppose, once they get into that). What are the advantages of one design vs. the other?

Increased seeker FOV pre-launch? Might be useful at times