In 1943 the Navy issued a requirement for a new series of carrier-based attack aircraft, looking to combine the heretofore separate missions of scout/dive bomber and torpedo bomber. The venerable Dauntless had been replaced by the problematic Curtis Helldiver and the TBF/M Avenger had assumed the torpedo and bomber missions. Drawing on lessons learned to date from CV-ops in the Pacific and anticipating increased demands on striking power from the carriers, the Navy’s proposal called for “Bomber Torpedo,” or “BT” proposals.
The BT was to be single seat, a reflection of increasing speed from increasingly powerful engines, with emphasis on load-carrying ability and overall performance. Unlike the Avenger, stores would be carried externally which would not only improve ease of arming on busy and tight flight decks, but expand the range and amount of ordnance to be carried. Several manufacturers were assigned development, but two principals emerged – Douglas with the (designed by Ed Heinemann) and the Martin XBTM-1. The Martin entry utilized the experimental Pratt & Whitney XR-4360 radial which generated close to 3,000 hp.
The Navy awarded Martin a contract for two prototypes in Jan 44 for what was to be known as the AM-1 “Mauler.” First flight was in August and subsequently, the Navy increased that order to 750 in anticipation of the invasion of Japan.
Like so many other aircraft of that period, the Mauler suffered developmental problems, pressing the envelope as it was in combining conventional designs with experimental/developmental equipment. The size of the engine and aircraft was such that it was difficult to fly, especially in the CV-environment. This mandated the development of a complicated hydraulic boost system (which all of us who’ve flown and maintained *know* never leak…) and off-setting of the engine mount by 2-degrees to account for the massive torque of the R-4360. Additional work was required on the prop spinner, wing and tail. Eventually, a re-designed AM-1 entered the fleet in 1947, but in reduced numbers as production was substantially cut following the end of the war. It was also facing the AD-1 Skyraider which grew from the ABT2D following an extensive Heinemann re-design effort (he hated the original Navy mandated-design).
Joining the fleet in 1948, the AM-1, at first labeled “Able Mabel”, quickly made a name for itself –and it was less than complimentary. The “Awful Monster” still had troubles in the CV-environment with an unfortunate tendency to violently vibrate in the tail section following a trap. Of course, this was less than desirable for a carrier-based aircraft and in spite of a tailhook redesign to resolve this issue, more time was lost in terms of fleet acceptance and in growing competition from the AD-1. By all accounts, the Mauler lost points to the Skyraider in the air and on the deck. One maintainer allowed as how it took three days just to change the 56 spark plugs – one day each to remove the cowl and complicated ducts and replace them and another day just to swap out the plugs. The complicated wheel retraction system frequently failed, leading at one point to 6 belly landings in 4 months at NAS Jax. Then too, there remained the ever-present pool of hydraulic fluid underneath the aircraft.
Aviators came to despise the AM-1 and loved the AD-1, especially in dive bombing with its big barn door dive brakes, one comparing it to hanging from a maneuverable parasol in a dive whichsignificantly improved bombing accuracy. The AM-1 was a big, heavy aircraft and in spite of the larger engine, could barely get airborne in a deck run with 28 knots of wind over the deck and no load. The AD-1, on the other hand, could take a 3,000 lb load on a 330 ft deck run under similar conditions.
Finally, the Mauler was a real bear to land and had an unfortunate tendency to act like it was on springs if all three wheels didn’t hit the deck at the same time. During the 1949 deployment of VA-44 on Midway, at one point an AM bounced completely over the barrier and into the parked aircraft in front of it. Fortunately no one was injured. Clearly, the Mauler was not destined for fame as a frontline, CV-based attack aircraft and the Navy was rapidly reaching that conclusion.
Not to be deterred, in 1949 Martin test pilot Pat Tibbs flew a Mauler with an incredible payload of 10,648 lbs (3 x 2200 lb torpedoes, 12 x 500lb bombs and 800 rounds of 20mm ammo) which set a single engine record. It probably also set a single engine record for a take-off run too and undoubtedly a pig to fly, not unlike this configuration…
By 1950 the Mauler was removed from Fleet service and passed to the Reserves which used them until 1953. Eighteen were converted to electronic counter-measures aircraft, but this too was short lived as the Skyraider proved more capable at this and other mods for Fleet missions. Today a small handful still exists and maybe found at the National Museum of Naval Aviation in Pensacola and the former NAS Tillamook in western Oregon.
Next week: What do you get when you mix fiberglass, aluminum sheets, balsa wood and a jet engine? Well, it didn’t set the world afire… ‘Til then keep ‘em flying!
Footnote: There remains some controversy surrounding the AM-1 and its engine configuration with some claiming it actually flew with the smaller Wright 3350. According to the model specifications for all those produced at this website, the AM-1 was exclusively powered by the R-4360. There may have been subsequent field mods to use the Wright engine instead.