Grumman TBF/ TBM Avenger - Development and Overview

Introduction
Development
Production
Variants
Grumman
Eastern Aircraft Division, General Motors
Shared Sub-Variants
Post-war Variants
Service Record

Introduction

The Grumman TBF/ TBM Avenger was the US Navy's only front line torpedo bomber from the late summer of 1942 until the end of the Second World War, and was a sturdy robust aircraft that accounted for a large part of the Japanese fleet, as well as serving as the British Fleet Air Arm's main torpedo bomber in the later years of the war.

Development

In the mid 1930s the US Navy had adopted the Douglas TBD-1 Devastator as its main torpedo bomber. This had been a very advanced aircraft when it first flew in 1935, but like most aircraft of that period it was quickly outclassed, and by 1939 was both too slow and available in insufficient numbers.

In October 1939 the US Navy issued a design specification to the US aircraft industry. This called for a new torpedo bomber with a top speed of 300mph, a crew of three, an internal bomb bay capable of carrying a torpedo or three 500lb bombs, and a range of 3,000 miles without bombs, self-sealing fuel tanks and armour plating at vulnerable points.

Although several designs were submitted in response to these specifications, only Grumman and Chance-Vought received contracts to produce prototypes. Grumman was first, receiving a contract for two prototype XTBF-1s on 8 April 1940. The Chance-Vought contract, for a single XTBU-1, was issued on 22 April.

Grumman had no experience of building torpedo bombers, but they did have plenty of experience of designing and building carrier fighter aircraft. Since 1936 they had been working on the F4F Wildcat, their first monoplane fighter, and the main US Navy fighter aircraft for the first eighteen months after Pearl Harbor.

The new Grumman torpedo bomber had a clear family resemblance to the Wildcat (the resemblance was close enough to fool at least one Japanese fighter pilot, Saburo Sakai, who was blinded in one eye by fire from the stinger guns after attacking eight Avengers from below in the mistake belief that they were Wildcats). Both aircraft were chunky mid-winged monoplanes, powered by radial engines, and with a tapering oval fuselage. This shape allowed Grumman to give the TBF an internal bomb bay big enough to carry a 2,000lb torpedo or four 500lb bombs, one more than required by the specification.

Their custom-designed turret was controlled by two scaled-down industrial 'Amplidyne' electric motors, which helped solve the problem of how to install a powered turret on a single engined aircraft. The turret carried a single 0.50in machine gun. The prototype was also armed with a 0.30in gun in the engine cowling and a 0.30in gun in a 'stinger' position, in the rear of the radio operator's position.

The crew were normally carried in three separate locations. The pilot was at the front of the greenhouse canopy. A second seat was located behind him on the prototype and early production aircraft, but was often empty and was removed on later aircraft. The gunner was in the dorsal turret. The radio operator/ bomb aimer was in a compartment built into the rear fuselage. A window opened into the bomb bay and could be used for a Norden bomb sight, and the 0.30in tunnel gun was in the back of this compartment.

Grumman quickly produced a wooden mock-up of their design, including one wing with its folding mechanism. The Navy was confident enough to place an order for 286 aircraft in December 1940, well before the first prototype was ready for its maiden flight.

That maiden flight came on 7 August 1941. Early tests showed that the new aircraft missed both the speed and maximum range targets, reaching 271mph and with a range of 2,180 miles with an extra fuel tank in the bomb bay. The fall in speed was largely due to extra equipment ordered by the Navy, and so wasn't seen as a particular problem.

The first prototype was destroyed after a fire in the bomb bay on 28 November, but the second was ready to fly on 15 December 1941. In the aftermath of the Japanese attack on Pearl Harbor the new aircraft was named the Avenger, and the decision to place an order one year earlier paid off. On 23 December 1941 the Navy accepted the XTBF-1, and changed the order from one for 286 aircraft to an open ended order.

Production

The first production aircraft was handed over by Grumman on 30 January 1942. Five more followed in February, and in the first half of the year 145 aircraft were completed. By the end of 1942 Grumman had produced 646 aircraft and they averaged nearly 150 per month during 1943, for a total of 2,290 aircraft. These aircraft were produced as either the TBF-1 or TBF-1C with .50in wing guns replacing the .30in gun in the cowling.

Although these production figures were good, the Navy wanted far more Avengers than Grumman could produce, and at the same time wanted huge numbers of Grumman F6F Hellcats. The solution was to find a second source of Avengers. General Motors had stopped all car production after Pearl Harbor and was looking for military contracts. Although GM was expecting to produce aircraft parts, Grumman and the Navy asked them to build complete aircraft, both Avengers and Wildcat fighters. General Motor's five empty factories became the Eastern Aircraft Division. Three produced parts, one built the Wildcat as the FM-1 and the other built the FBM Avenger.

The production contract was signed on 23 March 1942, and the first Avenger was handed over in November, only eight months later. Production at Eastern sped up throughout 1943, and during 1944 and 1945 they were the only firm building the Avenger. In total Eastern built 550 TBM-1s, 2,332 TBM-1Cs, four XTMB-3s, 4,667 TBM-3s and TBM-3Es and three XTBM-4s, for a total of 7,545 aircraft, or just over three quarters of the total production of 9,838 Avengers.

Variants

Grumman

XTBF-1

Two prototypes, both making their maiden flights during 1941. Both were very similar to the TBF-1, although the first prototype was originally built without the long fin fillet between the turret and the tail, introduced after early tests to improve lateral stability.

TBF-1

The Grumman TBF-1 was essentially identical to the second prototype. 764 were produced.

TBF-1C

The TBF-1C saw the single .30in nose gun of the -1 was replaced with two .50in guns mounted just outside the fold in the wings. 1,525 were produced by Grumman, ending in December 1943.

XTBF-2

One prototype XTBF-2 was produced, powered by the Wright XR-2600-10 engine with 1,900hp.

XTBF-3

Two prototype XTBF-3s were produced by Grumman, powered by the 1,900hp Wright R-2600-20 engine. These were followed by four Eastern-built XTBM-3 prototypes and over 5,000 TBM-3s and -3Es.

Eastern Aircraft Division, General Motors

TBM-1

The TBM-1 was the TBF-1 as built by General Motor's Eastern Aircraft Division. It was identical to the TBF-1 other than some of the internal paint and the Bureau Numbers.

TBM-1C

The TBM-1C was the Eastern version of the TBF-1C with its two .50in wing guns.

TBM-3

The TBM-3 was powered by the 1,900hp Wright R-2600-20 engine, and with the -3E was the most numerous version of the aircraft.

TBM-3E

The TBM-3E was the final production version of the Avenger, and was lightened to improve performance. Enough weight was saved to bring the -3E back up to the speed of the original TBF-1, before weight began to be added.

XTBM-4

Three prototypes for an improved version of the Avenger, produced during 1944.

Shared Sub-Variants

TBF-1CP/ TBM-1CP

The -1CP was a photographic reconnaissance aircraft with a trimetrogen camera capable of taking panoramic pictures that stretched from horizon to horizon on a single shot.

TBF-1D/ TBM-1D

The TBF-1D/ TBM-1D was equipped with an ASD-1 radar set, with the parabolic dish antenna carried in a radome mounted on the leading edge of the starboard wing. It was produced for anti-submarine warfare and was used on escort carriers.

TBF-1E/ TBM-1E

The TBF-1E/ TBM-1E was a rare version equipped with extra radar equipment.

TBF-1J/ TBM-1J/ TBM-3J

The TBF-1J/ TBM-1J/ TBM-3J was modified for operations in the Arctic or severe bad weather, with de-icing shoes on each leading edge and extra heaters

TBF-1L/ TBM-1L/ TBM-3L

The TBF-1L/ TBM-1L/ TBM-3L carried a retractable searchlight in the bomb bay and was used for anti-submarine warfare and air-sea rescue.

TBF-1P/ TBM-1P/ TBM-3P

The -1P and -3P variants were photo-reconnaissance aircraft with the cameras carried in the bomb bay.

Post-war Variants

TBM-3N

The -3N was modified to operate at night, with a dedicated radar operation in a modified rear cockpit and no turret.

TBM-3Q

The -3Q was a radar counter measures aircraft, carrying radar jamming equipment in a nacelle below the bomb bay.

TBM-3R

The -3R was a seven-seat transport designed for Carrier On-board Delivery (COD) to carry supplies, personnel and nuclear bomb components onto aircraft carriers in emergencies.

TBM-3S

The -3S was an anti-submarine version normally used as the killer element in a hunter-killer team with the -3W.

TBM-3U

The -3U was a utility version used as a target tug and general squadron hack.

TBM-3W

The -3W was designed during the Second World War to as an airborne early warning aircraft, but didn't enter service until 1946. It was then used as part of a hunter-killer team operating as the hunter alongside the -3S.

Service Record

United States

The Avenger's combat debut was a costly one, and came during the Battle of Midway. VT-8 had been the first squadron to receive the new aircraft, but they didn't arrive until the squadron's carrier, USS Hornet, was at sea crossing the Pacific. The first six aircraft flew to Pearl Harbor in an attempt to catch up with her, but missed her again. Instead they flew on to Midway Island, arriving just in time to take part in the battle. On 4 June all six aircraft took off to attack the Japanese fleet, but only one badly damaged Avenger managed to return to Midway, and no successful torpedo attacks had been made.

Midway also saw the majority of TBD Devastator's lost, again without achieving any successes. This forced the US Navy to rush the Avenger into frontline service, and by the end of August it was the only torpedo bomber in service with the fleet. From then until the end of the war the Avenger took part in every major US Naval action in the Pacific, although armed with bombs, depth bombs or rockets far more often than with torpedoes.  Avengers took part in the carrier battles around Guadalcanal, the Battle of the Philippine Sea and the Battle of Leyte Gulf, as well as supporting most of the amphibious landings as the Allies advanced across the Central Pacific.

The Avenger played a major role on US escort carriers in the Atlantic, playing a part in the sinking of 30 U-boats, mostly during the crucial year of 1943. They also achieved six victories over Japanese fleet destroyers.

United Kingdom

The Fleet Air Arm received 921 Avengers, calling them the Tarpon until the start of 1944 when the American name was adopted to avoid confusion. Somewhat surprisingly the first British squadron to take the Avenger into combat, No. 832, did it from an American carrier, the USS Saratoga, during operations in the middle Solomon Islands during June and July 1943. The squadron was allocated to HMS Victorious, which operated alongside the Saratoga during these operations, helping to make up for a temporary shortage of fleet carriers in the US Navy.

The Avenger played a limited role in the battle of Atlantic and the Arctic convoys, but it was involved in a series of attacks in Norwegian waters, including Operation Goodwood I to IV, the August 1944 attacks on the Tirpitz.

The Fleet Air Arm used most of its Avengers in the Far East, where they served on the escort carriers of the East Indies Fleet, but their main successes came with the British Pacific Fleet, operating alongside the Americans in the Pacific. During 1945 Fleet Air Arm Avengers were used to attack Sakashima Gunto and Formosa during the invasion of Okinawa, before taking part in the final series of attacks on the Japanese Home Islands.

The Avenger I, II and III were rapidly phased out of service at the end of the Second World War, but the aircraft returned in the 1950s as the Avenger AS Mk.4, an anti-submarine warfare aircraft carrying a large search radar in a radome below the forward part of the bomb bay. This aircraft remained in service until the early 1960s.

New Zealand

New Zealand received sixty three Avengers. They were used to equip Nos.30 and 31 Squadrons, and saw combat in the Solomon Islands during 1944 before being disbanded.

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How to cite this article: Rickard, J (20 August 2010), Grumman TBF/ TBM Avenger - Development and Overview , http://www.historyofwar.org/articles/weapons_grumman_TBF_TBM_Avenger.html

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