Guided missiles on Corsairs

Originally designed as a carrier-based gun dogfighter, the F4U Corsair, and it’s later attack variant, the AU-1, was used heavily as a ground attack plane during WWII, and almost exclusively in that role during the Korean War.

corsairprototype

(The first prototype Vought Corsair during WWII.)

A wide variety of weapons not originally envisioned were successfully used by the Corsair: air-to-ground rockets, napalm tanks, radar, depth charges, cluster munitions, and so on.

Easily the most unusual was something that could have never been envisioned by Vought’s engineers when they designed the plane; a guided missile.

F4U7SS-11

(French navy Corsair with SS.11 guided missiles aboard.)

the SS.11

At the end of WWII, Germany’s ballistic missile technology was primarily secured by the USA in operation “Paperclip”, however France managed to secure a great deal of information regarding the Third Reich’s ‘petite’ missile projects, namely the earliest SAMs like the Wasserfall, air-to-air missiles like X-4, and tactical battlefield missiles.

1946magazine

(Illustration from a 1946 French defense journal illustrating some tactical German missiles of WWII then being evaluated: the X-4 air-to-air missile, the Feuerlile surface-to-air missile, and the Enzian surface-to-air missile. For the Germans, all these had been too late to enter mass production. For postwar France, they were an intelligence gold mine.)

One such weapon was the Ruhrstahl X-7 ATGM (anti-tank guided missile), which the Wehrmacht had run under the code name Rotkäppchen (Red Riding Hood). Although it’s designers had been tinkering with ATGMs since the start of WWII, it wasn’t until late 1943 that it was (belatedly) given any importance. By the end of 1944 a working design was more or less ready but in any case, WWII in Europe ended a few months later.

The X-7 was 2’11” long and weighed around 19 lbs. Powered by a solid-fueled rocket, it was visually guided via a wire. It had a range of about 1,000 yards.

x7

After Germany’s collapse, Ruhrstahl workers insisted to the French that a small number of X-7s had made it to the front in 1945 and saw combat against the Soviets during the Oder offensive and the final battle in Berlin. Although they were keenly interested in the technology, these claims of actual usage were dismissed by the French, along with (later) most military historians. After the collapse of the USSR in 1991, it turned out that indeed a few of these missiles had seen use in 1945 and at least one IS heavy tank was destroyed by a X-7.

Throughout 1946 – 1947, the French debated the viability and future usefulness of a weapon of the X-7’s type. In 1948, a decision was made to utilize it’s basic concepts in a French-designed missile; #5203. Arsenal de l’Aéronautique (later part of Nord) developed a missile called the SS.10, which was put into production in 1954. Even while the final touches were being put on the SS.10’s design, work started on it’s replacement. The SS.11 entered service in 1956.

ss11ad

As an interesting historical sidenote, the designer of these missiles was Jean Bastien-Thiry, later more famous for his attempted assassination of Charles de Gaulle.

basic description

The 66 lbs solid-fueled SS.11 was 4′ long and had a finspan of 1’7½”. It was subsonic, with a flight speed of Mach 0.55 or roughly 427mph at sea level. It had a 15 lbs armor-piercing warhead, and a maximum range of 3 kilometers (3,281 yards) although the effective range was roughly about half that.

Ss11_01

(Much later in it’s career, the SS.11 was used by the US Army during the Vietnam War. It occupies AGM-22 in the American numbering system.)

The SS.11 was guided by wire, via the MCLOS (manual control / line-of-sight) method. By this, the firer (either on ground or in an aircraft) sighted the target, fired the SS.11, and used a reference flare on the missile’s tail to steer it in line with the target.

the Corsair in France

The French navy operated two versions of the famous WWII American fighter. A total of 94 of the F4U-7 were delivered in 1952-1953. These were new-build fighters with some tweaks specific to France’s requirements. They were also the last Corsairs ever built. Initial training on the Corsair was done by US Navy instructors at NAS Oceana, VA.

F4U7

(F4U-7 Corsair of the French navy in north Africa during the Algerian War.)

In 1954, these were joined by 25 of the AU-1 version, passed as surplus from the US Marine Corps. This model was designed from the start as a ground-attack plane, and had additional armor and weapons hardpoints. In turn it had a lower-performance engine and simplified gunsight, as by the 1950s it was considered unlikely to ever be used in an air superiority role.

The French navy flew Corsairs both off carrier decks and ashore during the Algerian war and Suez crisis.

ATGMs in the Algerian war

In Indochina and then in Algeria, the French military was the first to experience a problem that would plague the world’s best armies in the latter 20th century; an inability to leverage the advantages of very expensive, high-capability modern weapons against primitive guerilla forces.

Airpower during the Algerian war was critical to French planning but it was also expensive. Whatever aid had been given by the USA in acquiring Corsairs after WWII, their operating expenses were entirely French. Each mission took fuel, engine oil, ordnance, wear & tear on the planes, and the rations and pay of the pilots and ground crew.

1960tunisia

(French Corsairs in the Tunisian sector of the war.)

Due to the accuracy limitations of leftover WWII free-fall bombs and unguided rockets, it might take multiple planes several missions to destroy a target. If the target was a rag-tag platoon of guerillas with rusty bolt-action rifles, and it took double sorties by three or four Corsairs, destruction of the target would in the end be successful but was hard to quantify as a “victory” in the big picture.

France’s goal in mating a wire-guided missile with existing warplanes was that instead of the above situation, targets might be eliminated by one plane in one mission.

French tests

France first explored airborne use of the SS.11 in 1956. It was tested aboard one of France’s first post-WWII aircraft designs, the MD.311 Flamant, a version of the MD.312 Flamant transport which was used for training flight navigators and multi-engine pilots, and for testing aerial photography gear. A pylon was fitted to this non-combat aircraft just to see if the idea would even work. The missile fired off the Flamant with no problem.

as11Flamant

(SS.11 on a Flamant)

The next step was to adapt the weapon to an actual combat warplane, in this case the WWII-era Corsair. These tests started in 1956. The missile was fitted via an adapter rail and wire interface on the underwing hardpoints normally used for WWII-vintage HVAR Holy Moses unguided rockets. Because of the SS.11’s finspan, not all of the hardpoints could be adapted. On the AU-1 version, four adapters could be fitted, while the F4U-7 could only carry two SS.11s.

mount

(The adapters which fit on the Corsair’s rocket pylons were shaped like a sideways L.)

Internally, cabling was run from the wings to the cockpit. The weapon (only one could be in the air at a time) was controlled by a joystick on the righthand side of the Corsair’s cockpit.

Basic carriage tests all went well. The Corsair’s big propeller naturally produced a tremendous rearward air wash but this did not affect the SS.11’s performance at all. Flight trials were done ashore and aboard the aircraft carrier Arromanches (formerly the Royal Navy’s HMS Colossus of WWII). On the carrier, there were no problems with either catapulting off or recovering a Corsair with missiles aboard.

SS11Corsair

(French missile-carrying Corsair aboard the aircraft carrier Arromanches, herself a WWII ship.)

Actually firing a SS.11 from a Corsair was found to be much more tricky. The pilot basically had to “use two brains” at the same time, one obviously to fly the Corsair, and the other to acquire and steer the SS.11 onto it’s target.

This was not at all easy. The attack run started about ¾ – 1 mile from the target, at very low altitude, in a downwards slope. In this particular mission, the Corsair’s excellent speed was something of a hindrance. Using a typical 1,100 yards range; from the time the pilot fired the missile until it impacted, was only about 6 seconds. It took 1½ – 2 seconds for the pilot to mentally “find” the SS.11’s tracking flare and then get it lined up with the target. In the remaining three or four seconds, he had to stay focused on the missile and the target at the same time, and keep the missile lined up using his right hand on the joystick…….all the while keeping his left hand on the plane’s yoke to maintain control of his Corsair, which was on a different descent slope and at a much different airspeed than the departing missile. The Corsair went into stall around 80 – 85 kts so simply slowing down to build up more time was not really an option, and in any case, it’s heritage as a dogfighter meant it accumulated speed during a dive. The Corsair’s descent slope couldn’t be too gentle or the pilot would not be able to see the SS.11 past the plane’s nose, nor could it be too steep lest the plane hit the ground. Finally, since he was using his gunsight to view the target, the Corsair had to be kept on a nearly dead-on approach bearing throughout the whole attack.

The Corasir pilot had to quickly estimate the range to the target as his attack started. If he was wrong and it was too far away, the wire would run out and snap before the missile arrived. If it was too close, he would not have enough seconds to “find” the inflight SS.11 and begin steering it.

Another issue was the SS.11 itself. It had a HEAT warhead, which directed all the blast energy into a forwards narrow cone, as it was designed to rip through the armor of Soviet tanks. In use against open infantry, exposed light artillery, etc, this was not ideal. The islamic rebels the French were fighting had no tanks so it’s attributes were basically wasted.

End of project

Despite all these challenges, the French navy was satisfied with the results. One squadron, Flotille 15F, was selected as the first to transition.

However in the end, no Corsair ever fired a SS.11 in anger. Part of the decision was due to the challenges but more so, it was simple numbers. The French navy’s Corsairs were in great demand during the Algerian war, and as there were only 119 of them in the whole fleet, pulling fifteen or twenty at a time out of rotation to wire up the cockpits and train the pilots would have been a notable burden.

The idea did not fully fade away however. During the initial tests on the MD.311 Flamant navigator trainer, there were no problems, and since there were two MD.311 trainers already in French Algeria it was decided to simply try them. The Flamant was never intended for combat, but as there was zero air opposition and minimal anti-aircraft gun danger, they proved surprisingly effective with SS.11s.

FlamantDaniel-Bechennec

(Flamant firing a missile against rebels in Algeria) (artwork by Daniel Bechennec)

Ironically these lumbering transports were probably even more suitable than the Corsair. As a side-by-side, the pilot could fly the plane allowing the second crewman to fully concentrate on managing the missile from start to finish. Since the sight was now part of an add-on kit anyways, there was no need for the pilot to keep a constant direct bearing and the aircraft had a little leeway for left / right maneuvering with a missile in the air.

The next and most successful step was to adapt the SS.11 to one of France’s most successful Cold War aircraft, the SA-316 Alouette helicopter. This of course had the supreme advantage of being able to fully stop and hover during the attack.

as11

As an interesting sidenote, the Cold War-era SS.11 briefly intersected with WWII weaponry a second time. Aérospatiale proposed a beefed-up attack version of the Alouette called the SA-3164. Besides four SS.11 missiles, it would carry a MG-151 gun in the nose. This German 20mm weapon of WWII was carried by various Luftwaffe aircraft. In 1946, as France scrapped surviving Luftwaffe warplanes in it’s occupation zone of Germany, these guns were salvaged and stored. Some were issued to French troops in Indochina where they performed decently on river patrol boats. Others were mounted as pintle guns in French transport aircraft in Algeria. Since they were free anyways, it was proposed to fit them to a production version of the SA-3164, however the whole aircraft was eventually cancelled.

SA-3164

(SA-3164 with salvaged ex-Luftwaffe MG-151 fitted.)

The SS.11 tests are only a brief footnote in the Corsair’s long and legendary career however they show how flexible this WWII fighter could be.

 

 

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6 thoughts on “Guided missiles on Corsairs

    • From what I understand (and that’s not complete), the wire snaps when the missile hits due to the forward momentum of the aircraft. On the ground-fired version of the SS.11 there is a shear if that doesn’t happen. The wire itself is just a very thin copper filament, not an insulated wire like a home appliance’s power cord, etc. When the US Army was designing the TOW missile, one of the problems they had to overcome was making a wire that was strong enough not to snap in normal flight, but thin enough that the spool could contain the missile’s range in a reasonable sized spool.

      Liked by 1 person

  1. “The islamic rebels the French were fighting had no tanks so it’s attributes were basically wasted.”

    The Islamic rebels didn’t come until the 1990s in Algeria, many coming back from that mess that had become Afghanistan (vide Djafar al-Afghani), the FLN’s idealogical background was nationalist and socialist (in the sense of Arab socialism).

    Like

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