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Subject: Janes - UK F-35 to Carry ASRAAM on External Pylons
Softwar    3/5/2008 1:47:43 PM
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The UK has made a significant change to its weapons fit plans for the Lockheed Martin F-35 Lightning II Joint Strike Fighter (JSF).

The original UK intention was to clear four MBDA Advanced Short-Range Air-to-Air Missiles (ASRAAMs) for internal carriage but this has been revised to include two internal and two external weapons instead.

The configuration change was agreed with the JSF Program Office in the United States late last year and was shown in public for the first time during the Singapore Airshow in February. The external ASRAAM fit will be common across all three JSF variants and could therefore attract interest from other international customers, who will otherwise be tied to Raytheon's AIM-9X Sidewinder.

The new ASRAAM plan is a 'work swap' that does away with the requirement to clear the ASRAAM on the F-35's two internal air-to-ground weapon stations. The integration team now has the more straightforward task of providing underwing carriage on stations 1 and 11. The ASRAAM is a rail-launched missile and internal weapons must be carried on a trapeze that swings down clear of the F-35's weapon bay before they can be launched.

It has always been a credo of the JSF programme that external weapons carriage fundamentally compromises the aircraft's very low observable (VLO) design. Speaking at the Singapore Airshow, George Stanridge, Lockheed Martin's vice president of F-35 Business Development, noted that, in general, "if you see something hanging on the aircraft it means you are not a VLO airplane". A new 'stealthy' pylon has been developed for the external ASRAAM and MBDA notes that the finless missile already has a tiny radar cross-section.

Carrying the ASRAAM outside the weapons bay brings several advantages, primarily in allowing passive long-range - beyond-visual-range (BVR) - engagements cued by the missile's seeker or the F-35's infrared search and track sensor.

 
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jessmo_24       3/6/2008 4:56:29 AM
Wow the asraam is BVR?
 
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gf0012-aust       3/6/2008 6:16:27 AM

It has always been a credo of the JSF programme that external weapons carriage fundamentally compromises the aircraft's very low observable (VLO) design. Speaking at the Singapore Airshow, George Stanridge, Lockheed Martin's vice president of F-35 Business Development, noted that, in general, "if you see something hanging on the aircraft it means you are not a VLO airplane". A new 'stealthy' pylon has been developed for the external ASRAAM and MBDA notes that the finless missile already has a tiny radar cross-section.

This is a pretty poor articulation of doctrine.

JSF doctrine was always "first day of war".  ie "day one" (relatively speaking) is LO to kick in the doors, once suppression is accomplished then the platform can fight "dirty" and include external weaps.

The Clown Club and associated armchair fighter pilots will be making hay with this comment. (which will reinforce that they are clueless after all)
 
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Softwar       3/6/2008 8:57:20 AM

The Clown Club and associated armchair fighter pilots will be making hay with this comment. (which will reinforce that they are clueless after all)

Where is good old FS when you need him?  Cue the clown music please....
 
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Phaid       3/6/2008 9:16:56 AM
Wow the asraam is BVR?

It fits the definition.  The ASRAAM is the longest-ranged and fastest of the current crop of dogfight missiles (the others being IRIS-T, AIM-9X, Python V, and R-73), and it has an inertial navigation system and datalink so that it can be cued to a target and launched LOAL.

It is definitely not in the same class as a dedicated BVR missile like AMRAAM or MICA, but it can do beyond visual range shots.

This part of the article though is incorrect:

"Carrying the ASRAAM outside the weapons bay brings several advantages, primarily in allowing passive long-range - beyond-visual-range (BVR) - engagements cued by the missile's seeker or the F-35's infrared search and track sensor."

ASRAAM does not need to be carried externally to be capable of being cued by the IRST (or the radar, or Link 16).

As far as this carriage issue, I am not surprised.  ASRAAM and other IRMs are designed to fire right off the rail, unlike e.g. AMRAAM which drops away from the aircraft before the engine fires.  The internal air to air pylon swings out into the airstream with the bay door, so that isn't a problem.  On the other hand, the air to ground pylon is embedded deeply within the bay, and using an IRM there would require a complicated mechanical apparatus to lower the missile into the airstream before firing.

I'm not sure that this is some kind of huge crisis anyway.  Why would you arm a fighter only with four relatively short range IRMs?  The aircraft will have no problem carrying two ASRAAM and two AMRAAM at the same time, which makes a lot more sense as an air to air loadout.
 
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dwightlooi       3/6/2008 10:09:23 PM

As far as this carriage issue, I am not surprised.  ASRAAM and other IRMs are designed to fire right off the rail, unlike e.g. AMRAAM which drops away from the aircraft before the engine fires.  The internal air to air pylon swings out into the airstream with the bay door, so that isn't a problem.  On the other hand, the air to ground pylon is embedded deeply within the bay, and using an IRM there would require a complicated mechanical apparatus to lower the missile into the airstream before firing.
Actually, the internal air-to-air stations on bay doors are NOT rails. They are ejectors. The doors stations ejects the missile downwards and the motor fires after its release. The door stations cannot be fitted with rails because there is an insufficient clearance between the axis the missile is on and the bottom of the fuselage.

 
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dwightlooi       3/7/2008 12:17:08 AM
This is the door EJECTOR being fitted on the F-35-AA-1.


Notice that the fins on the AMRAAM won't even clear the ribs on the door. And even if they did, they'll be passing so close to the fuselage that any kind of movement on the part of the aircraft will see the fins hitting the fuselage.
 
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Phaid       3/7/2008 6:06:10 AM
Actually, the internal air-to-air stations on bay doors are NOT rails. They are ejectors. The doors stations ejects the missile downwards and the motor fires after its release. The door stations cannot be fitted with rails because there is an insufficient clearance between the axis the missile is on and the bottom of the fuselage.

"Actually", the AIM-132 ASRAAM cannot be ejector launched, so pictures of an AMRAAM ejector on the F-35 door are pretty irrelevant.  If it could, then the ASRAAM could be launched from the same (currently very hypothetical) ejector that (supposedly) will allow the AMRAAM to be carried on the air to ground station.
 
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dwightlooi       3/7/2008 11:30:42 AM


Actually, the internal air-to-air stations on bay doors are NOT rails.
They are ejectors. The doors stations ejects the missile downwards and
the motor fires after its release. The door stations cannot be fitted
with rails because there is an insufficient clearance between the axis
the missile is on and the bottom of the fuselage.

"Actually", the AIM-132 ASRAAM cannot be ejector launched, so pictures of an AMRAAM ejector on the F-35 door are pretty irrelevant.  If it could, then the ASRAAM could be launched from the same (currently very hypothetical) ejector that (supposedly) will allow the AMRAAM to be carried on the air to ground station.
Then you are in the same position as with the AIM-9X. The reason the AIM-9X is external ONLY is that the USAF doesn't see a priority in its internal carraige and DID NOT want to develop an AIM-9X variant for ejector launch or develop F-22 style extensible rails for any of the positions in the internal bays.
 
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Phaid       3/7/2008 11:57:07 AM
Then you are in the same position as with the AIM-9X. The reason the AIM-9X is external ONLY is that the USAF doesn't see a priority in its internal carraige and DID NOT want to develop an AIM-9X variant for ejector launch or develop F-22 style extensible rails for any of the positions in the internal bays.

Yup.  Which is why adapting ASRAAM for the air to air station on the door will entail an extensible rail - on the door that's a pretty simple thing to develop since the amount of extension required is very small, you don't need anything as big as the LAU-141/A that the F-22 uses in its side bays. 

A rail launch from inside the air to ground station would require a much longer extension requiring a more complex mechanism, which is why the requirement to carry them there was dropped.  This is why the article says "The ASRAAM is a rail-launched missile and internal weapons must be carried on a trapeze that swings down clear of the F-35's weapon bay before they can be launched."
 
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Mechanic       3/7/2008 12:06:13 PM
 AMRAAM which drops away from the aircraft before the engine fires.

While I know that Phaid knew this, I would like to add that the AMRAAM can also be faired from a rail launcher like LAU-127 or LAU-128 (which accept also AIM-9, IRIS-T or ASRAAM).
 
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Phaid       3/7/2008 12:22:41 PM
While I know that Phaid knew this, I would like to add that the AMRAAM can also be faired from a rail launcher like LAU-127 or LAU-128 (which accept also AIM-9, IRIS-T or ASRAAM).

Oh absolutely.  It's just that pneumatic ejectors are much simpler and lighter than articulated rails, and since the AMRAAM can use either one, it made sense to go with the ejector option to launch from bays.

I'll be curious to see what system they wind up using to launch AMRAAMs from the air to ground station in the F-35 bay.  You can't just hang the missile directly from an ejector pylon -- it would never get the velocity required to pierce the boundary layer -- so they will need something like the LAU-142A AVEL to carry an AMRAAM there.
 
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dwightlooi       3/7/2008 10:12:54 PM

While I know that
Phaid knew this, I would like to add that the AMRAAM can also be faired
from a rail launcher like LAU-127 or LAU-128 (which accept also AIM-9,
IRIS-T or ASRAAM).

Oh absolutely.  It's just that pneumatic ejectors are much simpler and lighter than articulated rails, and since the AMRAAM can use either one, it made sense to go with the ejector option to launch from bays.

I'll be curious to see what system they wind up using to launch AMRAAMs from the air to ground station in the F-35 bay.  You can't just hang the missile directly from an ejector pylon -- it would never get the velocity required to pierce the boundary layer -- so they will need something like the LAU-142A AVEL to carry an AMRAAM there.

Actually, so does the 2000, 1000, 500 lbs A2G stores. They all need pneumatic VELs. The SDB is a rack with four (4) VELs for four SDBs. Basically, you can't hang anything on any of the internal stations and just "drop" them.
 
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Mechanic       3/8/2008 3:37:16 AM

Actually, so does the 2000, 1000, 500 lbs A2G stores. They all need pneumatic VELs. The SDB is a rack with four (4) VELs for four SDBs. Basically, you can't hang anything on any of the internal stations and just "drop" them.

Why the ejectors have to be pneumatic? All current bomb racks use pyrotechnic ejectors, they don't just "drop" them. (That's why there are "s?)
 
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Phaid       3/8/2008 5:23:08 AM
Why the ejectors have to be pneumatic? All current bomb racks use pyrotechnic ejectors, they don't just "drop" them. (That's why there are "s?)

Safety and maintainability.  You don't really want explosives going off inside the airframe, and not using pyrotechnics cuts down on logistics and maintenance for the launcher.

The pneumatic ejectors like AVEL do a lot more than the conventional ejectors you see on bomb racks, though.  AVEL uses a hydraulic frame that shoves the missile downward before ejecting it.  It looks like this when extended:


But it folds basically flat when the bay doors are closed.

EDO, the company that developed AVEL, is also developing the pneumatic launcher for the F-35.
 
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Mechanic       3/8/2008 9:32:59 AM
Pneumatics are the future I agree, but I don't see why i couldn't be done with pyrotechnics. I really don't see any safety issues* and pyrotechnic solution would be lighter and cheaper. I would guess that F-111 and other older jets used pyrotechnics to eject ordnance from their bomb bays.  That worked at least in sub-sonic region.


*) Cartridges used are very insensitive and when they are removed for maintenance, there is absolutely no way to accidentally drop stores. Gunpowder used in cartridges doesn't explode, it burns to produce gas pressure for the pneumatic system. Very reliable, very simple.
 
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