A-4 Skyhawk 105 millimetre gun

[Jason Dykstra (Wyvern)]

Hello everybody,

I was scrolling through the internet recently and I found an interesting project of an A-4 Skyhawk armed with a 105 millimetre howitzer. I don't know what it is with me and small planes with large guns this week. From what I've found this seems to be a legitimate program. Was this ever flight tested and why would such a large gun be mounted? What were the benefits? Why was a gun like this chosen rather than having it armed with smaller, faster firing guns or rockets? Were there any other American projects which mounted such large guns to such small aircraft?

Thanks in advance,


Wyvern

 

[riggerrob]

I suspect that back-to-back howitzers were installed to minimize recoil .... sort of like a recoil-less rifle.
A simple 105 mm howitzer would rip bomb rack off the belly of the Skyhawk!
They were probably testing how muzzle blast might damage the nose of the airplane.

 

[TomS]

It's mounted so far away from the fuselage that I question whether it was actually meant to be armament for the aircraft. Possibly this is a test rig to apply intense blast overpressure to the airframe to see how it would hold up to such events (e.g., the pressure wave from a nearby nuclear explosion)?

 

[Foo Fighter]

It looks a little similar to German ww2 projects, I don't have the link to hand but on this forum.

 

[DWG]

Fairly certain this was being discussed in another thread on here back before Christmas.

 

[Jason Dykstra (Wyvern)]

Yes, but it was about aircraft armament, rather then the actual project.

 

[TomS]

Yes, but it was about aircraft armament, rather then the actual project.

THis post, I think.

https://www.secretprojects.co.uk/threads/north-american-rockwell-ov-10-bronco.10958/#post-316645

Says it was actually a 106mm recoilless rifle (which had an real bore of 105mm) and it was static fired from an A-4. Could be the aft-pointing tube was to get the back-blast away from the airframe.

 

[Jason Dykstra (Wyvern)]

What would have been the benefits of mounting such a weapon on an aircraft?

 

[edwest4]

Aircraft rockets were unguided and most missed. Putting a gun like this on an aircraft meant that it could be fired in a similar way to a machine-gun. Is the range of this gun known? What about the payload/ROF? If the range was adequate, it could attack large aircraft from a safe distance and such a weapon could bring one down with one shot. The Germans did experiment with large cannons on aircraft during the war. The primary concern was possible structural damage from the barrel exit blast.

 

[yasotay]

We should combine this with the post of the DH Mosquito with a 90mm gun.

 

[Jason Dykstra (Wyvern)]

It looks a little similar to German ww2 projects, I don't have the link to hand but on this forum.

Do you mean the multiple times they fitted 50mm and 75mm guns to aircraft and that one time they fitted a 356mm gun to a Dornier DO 217 and a Junkers JU 288?

 

[Foo Fighter]

Just so.

 

[riggerrob]

106 mm recoil-less rifle had a rate of fire of 1 round per flight.
Hah!
Hah!
The loader had to climb outside, open the breech, etc.

106 mm recoil less rifle as fitted with a .50 calibre spotting rifle with a small
Magazine. Ammo for .50 Battalion Anti-Tank was distinct from Browning .50 calibre heavy machine gun. .50 AT ammo had the same trajectory as 106 mm rounds. A small cloud burst from the .50 spotting round on impact. Spotting ammo was light and easy to carry. It also allowed them to fire their single 106 mm round accurately before fleeing the cloud of back blast attracting bullets from angry enemy.


If they wanted to use 106 mm RR for air-to-ground tank-busting they would need to invent a completely new receiver that could fire multiple shots. 5-round revolver?

 

[Antonio]

Wyvern,

please find the Ju288 with the 280 mm gun here

https://www.secretprojects.co.uk/threads/mosquito-with-a-32-pounder.33413/#post-5669

 

[Foo Fighter]

.50 as a ranging method makes sense and is cheap. We used it exclusively when I was training as a gunner in 1976.

 

[riggerrob]

.50 BAT spotting rifles pre-date modern laser range-finders.

 

[Grey Havoc]

.50 BAT spotting rifles pre-date modern laser range-finders.

And they continued to be useful for situations where laser range-finders couldn't be used.

 

[iverson]

106 mm recoil-less rifle had a rate of fire of 1 round per flight.
Hah!
Hah!
The loader had to climb outside, open the breech, etc.

106 mm recoil less rifle as fitted with a .50 calibre spotting rifle with a small
Magazine. Ammo for .50 Battalion Anti-Tank was distinct from Browning .50 calibre heavy machine gun. .50 AT ammo had the same trajectory as 106 mm rounds. A small cloud burst from the .50 spotting round on impact. Spotting ammo was light and easy to carry. It also allowed them to fire their single 106 mm round accurately before fleeing the cloud of back blast attracting bullets from angry enemy.

If they wanted to use 106 mm RR for air-to-ground tank-busting they would need to invent a completely new receiver that could fire multiple shots. 5-round revolver?

Actually, modified M-40 106-mm recoilless rifles were tested on a Cavalier Mustang and proposed for use on the OV-10 and, if memory serves, the Piper Enforcer derivative of the Cavalier.

Two test guns were mounted on the Cavalier's wingtips, which I think causes some problems with vibration and accuracy, but apparently worked well enough for Piper to propose up to six on the underwing racks of the Enforcer.

The OV-10 was to use version of the gun that incorporated an autoloader. See https://www.ov10squadron.com/flying-the-bronco-2/

"Our favorite, essentially “ideal” ground weapon for our airplane was the 106mm recoilless rifle. This weapon was a lot more accurate that the equivalent aerial weapon, the five inch rocket, and a single round only weighed 40lbs as opposed to about 100lbs for a rocket. The problem was that the 106 was a single shot weapon and we wanted more shots. … On one visit I happened to mention something about the desirability of an automatic recoilless rifle. They immediately showed me two working prototypes and introduced me to Dr. Musser who had patented the first recoilless rifles during WWII. This put the recoilless rifle back in the concept more strongly than ever. We even took one of the prototypes to Camp Pendleton where the Marines demonstrated it to a group of scientists from China Lake. It worked beautifully and was very impressive. Dr Musser indicated that with a modest change to the nozzle, the weapon could be made suitable for operations from a twin boom aircraft like the one we proposed."

 

[Jason Dykstra (Wyvern)]

Was there to be some sort of auto-loading system on the A-4? Also, how would the airframe cope with the blast? Would there have to have been some sort of dampener?

 

[riggerrob]

The idea originated when US Army Major Charlie Carpenter strapped 2 of the newly-introduced bazookas to his light-weight Piper L-4 Grasshopper (aka. Piper Cub) spotter plane during the summer of 1944. He later bolted a total of 6 bazookas to his wing struts. Bazookas were especially deadly against the thinly-armoured roofs of tanks.
Colonel Carpenter survived WW2 and was credited with destroying 17 German tanks.
This never became official US Army policy. As late as the Viet Nam War, Cessna Bird Dog and Raven spotter planes were only armed with radios and smoke rockets. Spotter pilots were reminded that their primary mission was calling in “heavy iron” fighter bombers to destroy VC and NVA ground forces.
Both German and VC troops understood this mission and generally avoided firing at spotter planes for fear that their AAA fire would attract artillery or bombers.

 

[edwest4]

Just like the Germans attached panzerfausts to the wings of the Bf 108.

 

[riggerrob]

Close dear edwest,
Late in WW2, a handful of Bucker 181 Bestman trainers were armed with up to 4 Panzerfaust anti-tank rocket launchers. They harassed advancing Soviet soldiers, but did little damage.
To your credit Messerschmitt 108 and Bu 181 look similar from a distance. Up close you see that Me 108 has 4 seats while Bu 181 has only 2 seats.

 

[edwest4]

Thank you for the correction. Note to self: always check references.

 

[TomS]

Was there to be some sort of auto-loading system on the A-4? Also, how would the airframe cope with the blast? Would there have to have been some sort of dampener?

I doubt they ever got that far. This was very preliminary feasibility assessment work.

 

[Jason Dykstra (Wyvern)]

Would the Cavalier Mustang have had to fire its recoilless rifles at the same time? Also, was there a way to reload them? Was it meant to be a modification to existing Cavalier Mustangs? Was it ever meant to enter service or was it just used for experimental purposes only?

 

[iverson]

Would the Cavalier Mustang have had to fire its recoilless rifles at the same time? Also, was there a way to reload them? Was it meant to be a modification to existing Cavalier Mustangs? Was it ever meant to enter service or was it just used for experimental purposes only?

As one of the photos shows, being recoilless, the guns could be fired one at a time. They could be reloaded on the ground, but not in flight.

I don't think that Cavalier had anything to do with the experiment. The Army simply used one of the Cavalier chase planes left over from the AH-56 project.

Piper proposed the recoilless rifles for operational use on the Enforcer, mainly to give it an antitank capability. Company lobbyists got Congress to mandate tests of the Enforcer against the A-10 and, I believe, the A-7. The Air Force was anything but amused (after all, it didn't really want the A-10).

 

[Temistocle]

Actually, modified M-40 106-mm recoilless rifles were tested on a Cavalier Mustang and proposed for use on the OV-10 and, if memory serves, the Piper Enforcer derivative of the Cavalier.

Hi, I write here about the 106-mm armed Enforcer (I let the administrators to split this in another thread, if needed).
I found this image here (page 96); it is a hearing in front of a US Congress Subcommittee, in part to consider the Enforcer as an alternative to the A-10:

Enforcer Aircraft: Hearing Before the Subcommittee on Research and Development of the Committee on Armed Services, United States Senate, Ninety-fourth Congress, First Session, July 29, 30, 1975



The texts says the Enforcer could be armed with 3 x 106 mm recoilless gun on each wing as tank buster instead of A-10... a very big punch, if real .
On page 86 there is a sketch of the proposed Enforcer version; due to the dimension of the three tubes at the wingtip, the guns seem like a series of bazooka, instead of a real recoilless gun; a similar armament was used in WW2 by P-47 and A-20, but they were rocket launchers.



At page 130-131 there are some details about the 106 mm recoilless gun, that was designed by David Lindsay himself (the owner of the Cavalier Aircraft). The debate is always about Enforcer vs. A-10 (and its 30 mm gun that is "still a question mark to many"). I tried to find the patent of Mr. Lindsay about the recoilless gun, but without success.




******************************************

In the following document (three years later) there are some other info about the 106 mm armed Enforcer:

Hearing on the Enforcer aircraft before the Research and Development Subcommittee of the Committee on Armed Services, House of Representatives, Ninety-fifth Congress, second session, June 22, 1978.

Page 84:


Page 89:



********************

BTW, on page 24 there is a scale model of the Enforcer armed with a GAU-8 gunpod; the previous document stated that the Enforcer can carry two of these gunpods.




*******************

BTW 2, as an extra from the first document (pages 64-65), this is a detailed two views of the Enforcer; enjoy!.

 

[Jason Dykstra (Wyvern)]

Interesting.

 

[Grey Havoc]

BTW, on page 24 there is a scale model of the Enforcer armed with a GAU-8 gunpod; the previous document stated that the Enforcer can carry two of these gunpods.

[Blinks] [Rubs eyes] [Blinks] [Raises eyebrows]

 

[TomS]

So, assuming this is the GPU-5, each one is just under 2000 pounds loaded. So yeah, technically it could carry two of them. Shudder to think about the recoil though.

The rest of the comparisons to the A-10 are so disingenuous as to be painful. The practical warload for the A-10 was a fraction of its theoretical capacity, while the Enforcer would be struggling to get airborne with the comparable loads.

 

[riggerrob]

So was the much-modified Cavalier/Piper Enforcer primarily privately funded need?
During its development and sales pitches, many listeners questioned the logic of updating a WW 2 vintage airframe when a wide variety of jet-powered, ground attack airplanes had already been proved in Viet Nam??????

 

[RanulfC]

So was the much-modified Cavalier/Piper Enforcer primarily privately funded need?
During its development and sales pitches, many listeners questioned the logic of updating a WW 2 vintage airframe when a wide variety of jet-powered, ground attack airplanes had already been proved in Viet Nam??????

It was "supposedly" all about costs as while the Air Force didn't want the A-10 they wanted 'something' because the new build up money still had some political strings attached to find 'justificaitons' for spending and there was both internal and external (political) pressure to field a dedicated ground attack bird. The Air Force had shot itself in the foot by complaining about the A7 as a ground attack aircraft but had hoped to simply buy more F-15s and barring that maybe some more F-16s. Instead the got the choice of the A-9 or A-10 and even AFTER that there was still political and internal pressure to find a 'cheaper' alternative which is how you got things like the Cavalier/Enforcer.

Randy

 

[iverson]

So, assuming this is the GPU-5, each one is just under 2000 pounds loaded. So yeah, technically it could carry two of them. Shudder to think about the recoil though.

The rest of the comparisons to the A-10 are so disingenuous as to be painful. The practical warload for the A-10 was a fraction of its theoretical capacity, while the Enforcer would be struggling to get airborne with the comparable loads.

Indeed. I doubt it would be possible to fire the GPU-5 pods individually/asymmetrically.

I'm going from memory, but I seem to remember reading that there were also vibration/accuracy problems with the GPU-5 pods themselves.

Plus, it turned out the Cavalier-reinforced wings weren't stiff enough to support the tip tanks alone in service use, with the result that they weren't used on the Cavalier airplanes used in South America.

 

[iverson]

So was the much-modified Cavalier/Piper Enforcer primarily privately funded need?
During its development and sales pitches, many listeners questioned the logic of updating a WW 2 vintage airframe when a wide variety of jet-powered, ground attack airplanes had already been proved in Viet Nam??????

It was "supposedly" all about costs as while the Air Force didn't want the A-10 they wanted 'something' because the new build up money still had some political strings attached to find 'justificaitons' for spending and there was both internal and external (political) pressure to field a dedicated ground attack bird. The Air Force had shot itself in the foot by complaining about the A7 as a ground attack aircraft but had hoped to simply buy more F-15s and barring that maybe some more F-16s. Instead the got the choice of the A-9 or A-10 and even AFTER that there was still political and internal pressure to find a 'cheaper' alternative which is how you got things like the Cavalier/Enforcer.

Randy

True. It was also (really?) about poor timing on the part of the suppliers and changes in the A-X requirement. The Vietnam War ended in the middle of the A-X program and changed its character. What was originally imagined as a turboprop T-28/A-1/A-26 replacement for third-world, counterinsurgency use mutated into an antitank airplane for stemming an imagined Red blitzkrieg in the Fulda Gap. By then, the backers of the Enforcer had invested heavily in an airplane tailored closely to the counterinsurgency requirement. They lacked the resources required for a new antitank design. So they hung recoilless rifles, gunpods, and Mavericks on their airplane, beefed up the armor as much as they could with composite materials, and deployed their lobbyists and state Congressional delegations.

We should probably be grateful to the Enforcer, though. If nothing else, it showed the fast-jet faction in USAF leadership that continued anti-A-10 politicking could get them something rather worse.

 

[iverson]

So was the much-modified Cavalier/Piper Enforcer primarily privately funded need?
During its development and sales pitches, many listeners questioned the logic of updating a WW 2 vintage airframe when a wide variety of jet-powered, ground attack airplanes had already been proved in Viet Nam??????

As I wrote a moment ago, the Enforcer addressed a Vietnam-era notion of what a counterinsurgency (COIN) aircraft should be. Such aircraft were not primarily close-support airplanes or fighter-bombers, per se. COIN airplanes were expected to patrol, keep militants' heads down, and support troops in contact only ocasionally. The US COIN people were heavily influenced by French experience in Indochina and Algeria. The French found propeller-driven types to be more effective than fast jets, because they could loiter over besieged outposts and take their time identifying small bands of insurgents on the ground. The workhorses of the French colonial campaigns were thus the T-6, the T-28, the AD4, and the B-26--the same, WW2-era/WW2-inspired aircraft that became the preferred COIN types in the USAF.

When it came time to replace aging, piston-engined aircraft, propeller turbines in remanufactured, proven WW2 airframes seemed like the obvious choice. Hence the T-28E, the Cavalier Dart-Mustang III, and the Enforcer.

Unfortunately for the companies involved, in the interim, structural updates for overloaded WW2 airframes turned out to be less cheap and more short-lived than than anticipated (wing cracks in re-sparred B-26s/A-26s, etc.). Worse, relatively cheap, new-production COIN types appeared in the OV-10 and A-37. Both had twin-engined reliability, ejection seats for the COIN-preferred, two-man crew, better cockpit visibility, and all the weapons capability needed. The OV-10 even had a modest transport capability.

Post-Vietnam, even the A-37 and OV-10 held little attraction for the services, other than for limited use as observation/FAC types. The Enforcer was thus effectively obsolete long before it tried to compete with the A-10. But its developers had sunk so much of their limited capital into the project that they couldn't/wouldn't eat the loss without a fight.

 

[Jason Dykstra (Wyvern)]

In Robert E.Bradley's "Convair Advanced Designs II", a design called the A-8 was tendred to a requirement to replace the USAF's ageing types (i.e. A-1/A-26/T-28). It was to be powered by a turboprop and had an overall look similar to that of the A-1 Skyraider. The program eventually merged into the A-X requirement and the design was subsequently abandoned in favour of jet powered types such as the YA-9 and the (Y)A-10.