Sunday 27 March 2016

Light Tank M22: Steel Locust

Thanks to John Walther Christie, the USA was the leader in airborne tanks before WWII, but with one caveat: not a single one of his vehicles was actually accepted into service. However, Christie's experiments resulted in a very good understanding of what an airborne tank should be like. The idea of a tank with wings was quickly discarded in favour of a light tank that was attached under the fuselage of a heavy bomber or transport plane. This concept was used to make the Light Tank M22.

Christie's Last Chance

Christie received some funds to develop his airborne tank after a relative success in Britain. The tank was converted into the M1938 tank, which didn't have much luck with the American military either. Christie, experiencing major financial troubles, sold his company to William J. Bigley and his United States Convertible Systems Inc.

The situation changed in early 1941. The British, who were planning on mass purchases of American tanks, were interested in an airborne tank. The Americans immediately remembered Christie and his wonder-machines. In late 1941, the Christie M1936 airborne tank was tested at the Aberdeen proving grounds. During the trials, the vehicle broke down constantly, but showed impressive characteristics. The report referred to it as "Bigley-Christie".

Airborne Christie M1936 tank. In late April of 1941, the Americans performed trials of this vehicle and ordered a Christie tank as a result.

This is a good time to mention why the American army did not adopt any one of Christie's designs. The problem was that Christie designed tanks based on his own personal logic. Frequently, this logic contradicted what the customer ordered. For example, with airborne tanks, Christie considered the tank itself the most important thing. The army will figure out a delivery method.

In addition, not a single Christie tank past 1933 had a turret. His airborne vehicles had one calling: speed. The American army, on the other hand, was much better grounded. yes, speed was important, but they needed a tank, not a race car.

On May 22nd, 1941, specifications for the T9 Airborne Tank were developed. This vehicle would weigh 7.5 tons (sans crew), its length was 3.5 meters, width 2.13 meters, and height 1.68 meters. The armament, either a 37 or 57 mm gun, would be housed in a rotating turret and equipped with a gyroscopic stabilizer. The crew was 2-3 people. Remember the small dimensions of the vehicle and armament, which had to be in a turret.

The Christie M1942 Light Tank. The military received something completely different from what they asked for.

United States Convertible Systems Inc. began development of the new tank in July of 1941. A model was also built. Christie agreed to build the tank for $126,000, a very serious amount of money for the time. However, the proposed tank did not fit into the T9 specifications. The width was fine, but the length was 5.6 meters, more than 1.5 times than what was in the specification. The turret, or rather its absence, was also a problem.

Christie proposed another one of his visions in November of 1941. The Christie M1942 Light Tank also had no turret. Instead it had a casemate with a 37 mm gun. Five machineguns were placed in the hull. Christie ignored the fact that the rigid specifications came from the capabilities of the C-54 transport airplane that was currently in development, and soon he himself was ignored.

The story continues. In May of 1942, Christie proposed the same tank to the USSR. He was ready to travel there with his colleagues for the same price: $126,000. However, Major-General Lebedev put an end to the idea.

By the Book

In May of 1941, when the specifications for the T9 Airborne Tank were being developed, the Bureau of Ordnance decided to play it safe. In parallel with Christie, they tasked Marmon-Herrington Company Inc. and Pontiac with development of an airborne tank. Pontiac was likely a last resort, as the company had no experience in tank design. As for Marmon-Herrington, they had a respectable amount of tankettes, armoured cars, and light tanks, which were not only in production but already saw combat.

An alternative to the Christie tank: Light Tank T9 designed by Marmon-Herrington. A wooden model of the tank was presented in August 1941.

The full sized model of the Light Tank T9 was presented in August of 1941. Marmon-Herrington didn't reinvent the wheel and based their design on the CTLS light tank. Nearly the entire suspension, with the exception of the idlers, was borrowed from this tank. Externally, the tank was similar to the T7, which was currently being designed by the Rock Island Arsenal.

This similarity was not a coincidence, as the evolution of the tanks happened in a similar way. The tank received a riveted hull, traditional for American light tanks, with the exception that it was very low, due to the project's limitations. The plan was to install a cast two-man turret similar to the one on the Medium Tank M3 with a 37 mm gun and a coaxial Browning M1919 machinegun.

The vehicle was inspected by the Bureau of Ordnance, was well as representatives from the air force and Douglas company engineers. The latter were present for a good reason. As mentioned above, the C-54 transport airplane developed by Douglas was going to be the delivery method for this tank. In November, a full scale model was developed for Douglas to check the fit with the C-54. The tank was carried underneath the fuselage. The turret was demounted and carried inside the airplane. The turret was relatively light, and loading it into the plane was not particularly difficult.

Light Tank T9, Pontiac concept.

The competitor vehicle from Pontiac was presented in September of 1941. In general, the concept was the same as the Marmon-Herrington vehicle. The difference was in peculiarities of the hull and engine. The hull was going to be welded with the use of cast components. Two 6 cylinder 3.9 L 90 hp Pontiac automobile engines would power the tank. By comparison, the Marmon-Herrington tank would be equipped with a Lycoming O-435T  7 L opposite aircraft engine, which was just entering production in 1942.

The tanks were so similar that the cost was the main deciding factor. Marmon-Herrington's project was cheaper, which led to their victory.

An experimental prototype of the Light Tank T9, April 1942. The driver received a pair of machineguns so he wouldn't be bored.

Pontiac was not particularly disappointed, as an SPG was going to built on the chassis of their T9. This vehicle, the T42 GCM, evolved into the T49 GMC. From that point on, Buick, another division of General Motors, started working on that vehicle. The result was the T70 GMC, otherwise known as M18 Hellcat.

Necessary Lightness

The first experimental prototype of the Marmon-Herrington Light Tank T9 was finished by April of 1942. By then, a series of changes were made to the design compared to the initial project. First of all, the hull was fully welded. Only the upper front plate was bolted on to allow access to the transmission. Second, the Americans found only one coaxial machinegun insufficient. As a result, the tank received a pair of Browning M1919 machineguns in the hull. The driver would fire them, but the loader, sitting in the turret, would reload.

The tank was compact, but very reasonably laid out.

In April of that year, the tank was sent to Fort Benning where it underwent trials and fitting to a model of a C-54 fuselage. During trials, it was discovered that the suspension is insufficiently stiff. To resolve this problem, channel brackets were installed between the bogeys, and later special reinforcers developed by Marmon-Herrington engineer William A. Cost. Further trials demanded additional changes, which made the tank somewhat heavier. Due to the tank's low mass and powerful engine, it turned out to be fairly agile. Not as fast as Christie's tank, but the maximum speed of 56 kph was a very respectable figure.

On May 31st, 1942, in the middle of the trials, an unpleasant surprise arrived from the Americans. According to revised specifications, the mass of the tank had to be 7.1 tons, or 400 kg less than initially specified. Removing 400 kilograms was no easy task, especially since Marmon-Herrington engineers were already constrained by weight. Something important had to go.

The first thing to disappear was the pair of Brownings in the hull. Future loaders could breathe easier. The gyroscopic stabilizer and turret traverse motor followed. They were useful, of course, but not necessary. After that, the T9 continued trials, which ended only in January of 1943. Later, this vehicle was used by Marmon-Herrington as a display model.

Light Tank T9E1, Aberdeen Proving Grounds, December 1942. The altered hull is obvious in this photo.

Work on an improved T9 tank began in February of 1942. In April, a full sized model, indexed T9E1, was sent to Fort Benning to be fitted under the C-54 fuselage. As a result, the hull was radically changed. Once again, the influence of the T7, or rather the T7E2, was clearly visible. The upper front plate was composed of one piece, positioned at a sharp angle.

Other parts of the hull were changed, especially the rear. The driver received a separate cabin, which improved visibility. The turret design was also changed, and one large hatch was replaced with two small ones.

This is how the T9E1 was to be attached to the Douglas C-54 Skymaster.

The first experimental prototype of the T9E1 was produced in November of 1942, and intensive trials started that same month. The second vehicle was sent to England immediately after assembly. Both parties were satisfied with the result, and in April of 1943, the Light Tank T9E1 entered mass production. In total, Marmon-Herrington built 830 tanks of this type before February of 1944, the biggest success for the company in the field of tank building.

The T9E1 index was used in reference to the tank until September of 1944, when the vehicle was finally standardized as Light Tank M22. As for Britain, it was named "Locust" there. The tank was never called "M22 Locust", much like there was no "M4 Sherman". M4 Medium Tank was the American name, while the British called it Sherman I.

In 1944, an alternative appeared for transporting the Light Tank M22: the Fairchild C-82 Packet. The tank could fit inside of it whole.

Work on the T9E1 didn't end with mass production. In November of 1943, a program to install the T24E1 81 mm breech-loaded mortar into the turret started. In August of 1944, one tank was equipped with the weapon, indexed T9E2. However, no progress was made past some experiments.

Limited Viability

Most T9E1 tanks went into the American army, but these tanks were never used in combat. The army received the tanks coolly. The tanks were mostly developed for British needs, and looked quite weak by the middle of 1943. In addition, the M24 light tank, already in development by then, was also somewhat airborne, even though it had to be taken apart and transported in two C-82 airplanes.

Soviet foreign intelligence learned of the T9 and T9E1 in July of 1943. The tank interested the Soviet leadership with its high mobility. However, the T7E2 light tank, which later became the M7 medium tank, was deemed much more interesting.

GAL. 49 Hamilcar Mk.I glider, Britain's main airborne tank delivery system.

The British received 260 T9E1 tanks. Locusts in the British army were indexed T.15877 through T.159376. Judging by the numbers range, the order was initially for 500 tanks, but was later reduced. One of the reasons for this could have been mechanical problems that were revealed by trials. A second problem was the lack of obvious advantages over the domestic Tetrarch I.

Of course, unlike the British tanks, Locusts had HE shells in their arsenal. However, right as Locusts started making it into the army, the Tetrarch I gained HE shells for its 2-pdr (40 mm) gun. The British tank was faster, more comfortable, and the armour of both tanks could only protect it from small arms. Weighing the pros and cons, Locusts were left in reserve. Old but still competitive Tetrarchs flew into Normandy, and were only replaced with Locusts in fall of 1944 when the British adapted the Littlejohn adapter to American guns, which drastically increased the muzzle velocity and with it, penetration.

The Littlejohn Adapter was first designed for the 2-pdr gun. The Bovington Tank Museum retained a Littlejohn for the 37 mm gun installed in the Locust.

The Locust was used by the British in combat only one time. On March 24th, 1945, the Allied forces carried out Operation Varsity to cross the Rhine. The British 6th Airborne and American 17th Airborne divisions were the main forces in this operation. The British extensively used gliders during this operation, including heavy GAL.49 Hamilcar Mk.I for transporting tanks.

The operation began at 10:00. Main British forces were deployed north-east of Wesel. The strike group had 8 Locust tanks. The first never made it across the Rhine: after an AA gun hit the glider, is bottom fell out, the tank fell into the river, and the crew died. A second tank was lost during landing when its glider crashed into a local farm. One of the remaining tanks damaged its gun during landing, a second its machinegun, and the third broke its engine.

A Locust from the 6th Airborne Brigade.

Unlike Normandy, where the Tetrarch's main enemy was parachutes that tangled in their tracks, the Locusts had a warmer welcome. Minutes after landing, Lieutenant Kenward's tank ended up face to face with a Panther. Since the nose of the Hamilcar glider did not open, the tank had to ram its way through. The Lieutenant fired off a dozen shots with no visible effect. The Locust was knocked out by return fire, but two crewmen survived, including the commander. The tank with a damaged engine made a fine bunker, supporting its infantry with artillery fire. According to reports, the tank crew claimed about 100 dead Germans.

The remaining four tanks supported the British paratroopers. With their help, the 6th Airborne attacked German positions. The tanks kept fighting on the next day. On March 26th, the main forces crossed the Rhine, and the Locusts were replaced with the much better armed Cromwells. This was the end of the tank's service history with the British army.

In 1946, the Locust was deemed completely obsolete. They began to be written off. A small number made their way to Belgium. Many more were sent to Egypt, where they replaced the Light Tank Mk.VI. Compared to these vehicles, dropped by the British in 1941, the Locusts were quite modern. As of 1948, the Egyptian army had 50 Locust tanks that formerly belonged to Britain.

IDF soldiers inspect a knocked out Locust, December 1948.

During the Israeli War of Independence fought from 1947 to 1949, Locust tanks fought a lot more intensively. On May 14th, 1948, Israel declared its independence. On the next day, forces of neighbouring Arab countries entered Israel to erase it from the face of the Earth. The most well known episode in the service life of Egyptian Locusts was Operation Assaf (December 5-7th, 1948). The Egyptians attacked Sheih Noran (today, kibbutz Magen). A 57 mm anti-tank gun (also a former British weapon) knocked out 5 Locust tanks. The Egyptian attack failed. Another tank made it into Sheih Noran, but was knocked out by a British PIAT grenade launcher.

The Locust was used in battles for Al-Awja with similar success. Three tanks were captured by the IDF in working condition and remained in use until 1952. The Egyptians kept their tanks until the mid 1950s when they were finally deemed obsolete.

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