In 1942 the Allied powers faced the most serious challenge to their control of the seas encountered in the Second World War: the menace of the U-boat. Fast, well armed, and long-ranged, Hitler's submarines attacked shipping throughout the North Atlantic, often within sight of America's coastal towns and cities.
Lockheed A-29, the type of aircraft flown by the crew that made the first successful Army Air Forces attack on a German submarine in the American Theater . German U-boat U-701 was destroyed on 7 July 1942 while running on the surface off Cape Hatteras by a Hudson of the 396th Bombardment Squadron (Medium), United States Army Air Forces (USAAF) [Via]
Eventually, the combination of intelligence, land and sea based air power, and surface vessel operations from both North American and British bases ended this threat, making possible the Allied build-up for the invasion of Europe in 1944. Flying radar-equipped long-range patrol planes, Army Air Forces (AAF) airmen demonstrated the value of land-based air power against naval threats.
# North American B-25 Mitchell
In anti-shipping operations, the AAF had urgent need for hard-hitting aircraft, and North American responded with the B-25G. In this series the transparent nose and bombardier/navigator position was changed for a shorter, hatched nose with two fixed .50 in (12.7 mm) machine guns and a 75 mm (2.95 in) M4 cannon, one of the largest weapons fitted to an aircraft. The shorter nose placed the cannon breech behind the pilot where it could be manually loaded and serviced by the navigator; his crew station was moved to just behind the pilot. The navigator signalled the pilot when the gun was ready and the pilot fired the weapon using a button on his control wheel [photo Via]
The AAF medium and long-range bombers, including the twin engine Douglas B-18 Bolos and North American B-25 Mitchells and the four-engine Boeing B-17 Flying Fortresses and Consolidated Vultee B-24 Liberators, were potentially capable of an antisubmarine role. These carried bombs rather than depth charges and lacked radar or other special submarine detection equipment. Also, like the Navy, the AAF had many demands for the few aircraft on hand. The shortage of aircraft equipped for antisubmarine war continued into mid-1943, with fighters and light bombers often used as antisubmarine aircraft
# Douglas B-18 Bolo
122 B-18As were modified for anti-submarine warfare. The bombardier was replaced by a search radar with a large radome. The Plexiglas nose was replaced with a bulbous radome for to house an SCR.517 radar. Magnetic anomaly detection (MAD) equipment was sometimes housed in a tail boom. Some had "retro" bomb racks, with a propelling charge that slowed the depth charges down to zero airspeed, so that they fell vertical. B-18Bs are credited with two U-boat kills—U-654 on August 22, 1942 and U-512 on October 2, 1942. These aircraft, designated B-18B, were used in the Caribbean on anti-submarine patrol [photo Via]
Initially, the AAF leadership considered the AAF's role in antisubmarine war to be temporary, and the major thrust of its efforts remained strategic bombing. Thus the AAF somewhat reluctantly began flying antisubmarine missions in a two-front naval war waged off both the East and West Coasts of the United States.
# Consolidated Vultee B-24 Liberator
Possibly the best all-round sub hunter aircraft of the war was the Consolidated B-24 Liberator. The Liberators made a significant contribution to Allied victory in the Battle of the Atlantic against German U-boats. Aircraft had the ability to undertake surprise air attacks against surfaced submarines. Carrying up to 2,500 gallons of fuel, the modified B–24 had an impressive range—about three hours of patrol time after flying a thousand miles from its base. A mission could last sixteen hours, although the average was ten to twelve hours. The Liberator flew day and night, except in bad weather. The heart of the anti submarine B–24’s capabilities was its microwave radar equipment, known as Airborne Surface Vessel Detection ten millimeter (ASV–10) radar. The modified B–24 carried six 500-pound depth bombs; four 20-mm, forward-firing cannons; and six .50-caliber machine guns. In the fall of 1943, several B–24s were fitted with a chin turret housing four more machine guns for increased forward firepower. Depth bombs had shallow fuse settings, and when dropped on a submerged submarine, their blunt shape caused them to sink slowly and explode at a depth of about twenty five feet [photo Via]
As part of the overall Allied antisubmarine effort, the Army Air Forces significantly affected the outcome of the campaign. In terms of the force available, the AAF increased its antisubmarine force from a few obsolete observation aircraft, medium bombers, and B-17s, all without radar, to 187 operational B-24s, 80 B-25s, 12 B-17s, and 7 Lockheed B-34 Venturas, most equipped with microwave radar and other detection equipment. These 286 aircraft were assigned to the Antisubmarine Command when, on August 24, 1943, the AAF withdrew from antisubmarine operations in the American Theater. In this theater, AAF aircraft flew over 135,000 operational combat hours on antisubmarine patrols. Altogether, the Army Air Forces participated in ninety-six attacks on German submarines between December 7, 1941 and August 24, 1943.