07/31/2014. Remarks by Johan Visschedijk: "When, in 1940, the USN began an ambitious program to expand considerably the size of its carrier fleet, it could depend on having an adequate supply of fighter and dive-bomber aircraft to equip these new carriers. In the VF-class (fighters), the Navy was beginning to take delivery of its first monoplane, the Grumman F4F-3 Wildcat, while a successor to this aircraft, the Vought XF4U-1 Corsair which was to be capable of speed in excess of 400 mph (644 kmh), was just entering flight trials. In the VSB-class (scout bombers), the Douglas SBD-2 Dauntless was entering service and the prototype for a more advanced aircraft, the Curtiss XSB2C-1 Helldiver, had already been ordered on May 15, 1939.

All these aircraft were expected to have performance equal or superior to those of foreign naval aircraft and were a good match for the new carriers aboard which they were intended to operate. In the torpedo-bomber category (VT-class), the USN was not faring as well and could only depend on the obsolescent Douglas TBD-1 Devastator of which 129 had been delivered commencing in October 1937. From the pilot's standpoint the Devastator was a pleasant aircraft to fly but its performance was, in the light of the early events of WW II, wholly insufficient and the USN had an urgent requirement for a new series of torpedo-bombers.

Accordingly, on April 8, 1940, the Bureau of Aeronautics placed with the Grumman Aircraft Engineering Corporation a contract for the design and construction of two prototypes of a three-seat, carrier-based torpedo-bomber. In its instruction to the contractor, the Navy stressed the need to design an aircraft which would be easy to build and maintain and which could take considerable punishment under normal operating conditions as well as under combat conditions.

Time being the most critical factor in the design of this new torpedo-bomber for the US Navy, the Grumman engineering team led by William T. Schwendler elected to rely extensively on its experience with the development of the F4F-3 and to keep the aircraft's structure and systems as simple as possible. As work progressed, the XTBF-1 began to look as a large, fat-bellied aircraft bearing a strong family resemblance to the Wildcat. Like the single-seat Grumman monoplane fighter, the torpedo-bomber had mid-mounted wings folding alongside the fuselage sides.

Beneath the center section of the wings was installed an internal bomb-bay with hydraulically operated doors which could house either a 22 in (56 cm) torpedo or four 500 lb (227 kg) bombs whilst above the wings the crew of three (pilot, navigator/gunner, and radio-operator/gunner) sat in tandem beneath a large glazed greenhouse. Defensive armament consisted in a forward-firing 0.50 in (12.7 mm) machine gun mounted on the starboard side of the upper engine cowling and fired by the pilot, a flexible rear-firing 0.30 in (7.62 mm) Browning machine gun in a ventral step which was manned by the navigator and in a 0.50 in (12.7 mm) machine gun in a dorsal turret at the end of the large canopy.

With respect to this dorsal turret it is interesting to note that Grumman initially contemplated using a turret designed by Boulton Paul but that this turret of British design was rejected by the Grumman engineers for fear that it would be too prone to being put out of action following comparatively minor battle damages. Consequently, Grumman set out to design their own turret which was characterized by the mounting of the single 0.50 in (12.7 mm) machine gun offset to port and this turret proved extremely reliable in service. The engine selected to power the XTBF-1 was the 1,700 hp Wright R-2600-8 eighteen-cylinder two-row air-cooled radial driving a three-blade Curtiss Electric propeller. The aircraft was also fitted with a fully retractable landing gear and a retractable deck arrester hook.

Twenty-six months after having received the initial contract for two XTBF-1s, Grumman had completed the first prototype (BuNo. 2539) and this aircraft made its maiden flight on August 1, 1941, with Bob Hall at the controls. For the next three-and-a-half months the first XTBF-1 was utilized exclusively for manufacturer's trials which gave entire satisfaction with the exception of pointing out the need to improve directional stability. However, on November 28, 1941, this aircraft was lost when the two members of the test crew were forced to bail out following a fire in the bomb-bay.

Fortunately for the contractor and the USN little delays resulted from the loss of the first prototype as within three weeks of the crash the second XTBF-1 (BuNo. 2540) took to the air and three days later, on December 23, 1941, Grumman received an initial production contract for 286 TBF-1s. These production aircraft as well as the second XTBF-1 differed externally from the first prototype in having a large dorsal fin extending from a point slightly behind the dorsal turret to a point on the vertical fin level with the horizontal tail surfaces.

With the first production TBF-1 (BuNo. 00373) coming off its lines on January 3, 1942, and being handed over to the Navy on January 30, Grumman performed a remarkable industrial feat by launching the TBF-1 production at an amazing pace: by the end of May 1942, 85 TBF-1s had been delivered and during the following month a further sixty aircraft were accepted by the Navy. Eventually, including prototypes and experimental aircraft, the Grumman Aircraft Engineering Corporation built a total of 2,293 Avengers. Most of these Grumman-built aircraft were TBF-1s, the original production model, or TBF-1Cs, a version characterized by a revised forward-firing armament. Two experimental versions, the XTBF-2 and XTBF-3, primarily differing in the type of power plants used were also built and a multitude of variants based on the TBF-1 and the TBF-1C were realized and are identified below:

XTBF-1: Two prototypes powered by 1,700 hp Wright R-2600-8. Armament comprising a 0.50 in (12.7 mm) machine gun in the engine cowling, a 0.50 in (12.7 mm) machine gun in dorsal turret and a 0.30 in (7.62 mm) machine gun in ventral position. Second prototype had large dorsal fin to improve directional stability.
TBF-1: First major production model, 1,525 ordered; many modified as TBF-1D, TBF-1E, TBF-1J, etc. Basically identical to second XTBF-1.
TBF-1B: 402 TBF-1s delivered under lend-lease to the Royal Navy, initially named Tarpon, later Avenger Mk.I.
TBF-1C: Second and last major production model by Grumman. Differed mainly from TBF-1 in having engine-mounted machine gun replaced by one in each wing and featuring auxiliary ferry tank installed in ventral bomb-bay, raising maximum fuel capacity from 395 to 726 gal (1,495 to 2,748 l).
TBF-1CP: Photo-reconnaissance version of TBF-1C.
TBF-1D: Small number of TBF-1s or TBF-1Cs fitted with centimetric radar (wavelength smaller than 10 cm) installed in a radome on the starboard wing's leading edge.
TBF-1E: Small number of TBF-1s fitted with special electronics equipment.
TBF-1J: Small number of TBF-1s fitted with special equipment for operations under arctic conditions.
TBF-1L: TBF-1 fitted with a retractable searchlight in the bomb-bay to illuminate targets during night attacks by other aircraft.
TBF-1P: Photo-reconnaissance version of TBF-1.
XTBF-2: 21st production TBF-1 (BuNo. 0393) experimentally fitted with Wright XR-2600-10 engine, first flight May 1, 1942, not proceeded with.
XTBF-3: Two prototypes (BuNos. 24141, 24341) powered by 1,900 hp R-2600-20 radial, not placed into production by Grumman but served as prototype for Eastern-built TBM-3s.

To supplement production of the Avenger by Grumman and to free Grumman's facilities for the production of carrier-based fighters, the USN specified that the Eastern Aircraft Division of the General Motors Corporation place this torpedo-bomber aircraft in production in their Trenton, New Jersey plant. To cover this work a first contract was awarded to Eastern on March 23, 1942, and eventually, after Grumman suspended production of the Avenger in December 1943, the Eastern Aircraft Division became the sole manufacturers of Avengers. This company built a total of 7,546 Avengers in the following variants:

TBM-1, TBM-1C, TBM-1CP, TBM-1E, TBM-1J, TBM-1L and TBM-1P: 2,882 Eastern-built Avengers equivalent to the TBF-1 through TBF-1P variants built by Grumman. Wright R-2600-8 engine.
XTBM-3: Four prototypes (BuNos. 25175, 25521, 25700 and 45645) with R-2600-20 engine and similar to the two XTBF-3s.
TBM-3: Main production version fitted with armament similar to that installed on the TBF-1Cs and TBM-1Cs and powered by
R-2600-20 radials. TBM-3D: TBM-3 for night duty with centimetric radar in radome on leading edge of starboard wing.
TBM-3E: Last major production version by Eastern, characterized by a lighter but stronger airframe. Overall length increased by almost 1 ft (30 cm) and a centimetric radar was fitted in a radome beneath the starboard wing.
TBM-3H: Small number of TBM-3s fitted with special search radar.
TBM-3J: TBM-3s with special equipment for operations under arctic conditions.
TBM-3L: TBM-3s fitted with a retractable searchlight in the bomb-bay.
TBM-3N: Small number of post-war modified TBM-3s for night attack duty.
TBM-3P: Photo-reconnaissance version of TBM-3.
TBM-3Q: Small number of post-war modified TBM-3s fitted with electronic counter-measure gear in large ventral radome.
TBM-3R: Post-war modified TBM-3s to seven-seat carrier-on-board delivery transport aircraft.
TBM-3S and TBM-3S2: TBM-3s respectively TBM-3Es post-war modified to anti-submarine strike aircraft.
TBM-3U: Post-war modified TBM-3s for sundry utility duties including target-towing.
TBM-3W and TBM-3W2: TBM-3s respectively TBM-3Es post-war modified to anti-submarine search aircraft. APS-20 radar carried in large ventral radome, operated in pair with TBM-3S/TBM-3S2 as ASW hunter-killers.
XTBM-4: Three prototypes (BuNos. 97673 to 97675) basically similar to TBM-3Es but featured reinforced wing center section panels and improved wing folding mechanism. Quantity production as TBM-4 and Avenger Mk.IV cancelled following VJ-Day.

Besides the USA, WW II Avengers operators were the UK and New Zealand. Avengers were later also operated by Brazil, Cuba, France, Japan, the Netherlands and Uruguay."