The development of airborne radar soon introduced a variety of aerial protrusions on Liberators modified for special missions. These included electronics designed for air to surface vessel search (ASV), electronic intelligence (ELINT), and electronic counter-measures (ECM). No American planes on the Pacific coast had ASV radar when the war began. British ASV sets used by Coastal Command were imported until American SCR-517s could be produced for anti-submarine patrols.
Dreadful Aleutian weather inspired the use of SCR-621 sets whose Yagi antennae cluttered the wings of the B-24D-7 model. The most widely used surface search radar was the APS-15 (H2X), first used with chin “Dumbo” radome in the nose of B-24Ds and then in a retractable radome in place of the belly turret. Most of them went to the 8th and 15th Air Force to lead “blind” bombing missions over heavy overcast. “Carpetbagger” B-24s of the 492nd BG were modified to drop agents and supplies into occupied Europe at night.
The first ELINT mission in the Pacific was flown to Kiska on March 6, 1943, by a B-24D-13 “Ferret” with an SCR-729. Liberators modified for ECM had APQ-9 jammers and chaff in the bomb bay, and added two operators to support the operations of conventional bombers. The 20th Air Force also used 35 B-24 and F-7 Ferrets to map radar sites protecting the Japanese homeland. Low-level night attacks on Japanese shipping were begun in September 1943 by the 394th Bomb Squadron, whose B-24Js had SCR-717 radar.
Several attempts to develop lighter nose and tail turrets were tried with limited success. A new hand-held tail gun mount had been specified for the B-24L, but only 186 B-24L-CO Liberators actually received them, the rest getting standard turrets. Armor steel and glass weight was reduced to 240 pounds, and side guns were enclosed, as on later J models. San Diego delivered 417 from July 1944 to January 1945 while Willow Run delivered 1,250 B-24L-FOs at the same time.
New light-weight power tail turrets appeared on 916 B-24M-COs, beginning in October 1944, and on 1,677 B-24M-FOs built by Ford from December 1944 to June 1945. Performance of models B-24G through M was essentially the same, depending on each aircraft’s load. In this book, data from the model specifications is offered as representative of typical loadings.
A single vertical tail was first tested on an early B-24D first flown with a Douglas B-23 fin on March 6, 1943. Then the XB-24K, a modified B-24D-40-CO was first flown September 9, 1943, with a high single tail fin, R-1830-65 engines, and Convair nose turret. Improvements in flight handling and field of fire for the rear guns was so great that the Eglin Field proving ground recommended on April 26, 1944, that all future B-24s be ordered with single tails.
An XB-24N-FO with the single tail, R-1830-75 Wasps and new Emerson nose and tail ball turrets ordered January 28, 1944, was first flown on November 5, but the end of the war in Europe curtailed production. Of 5,176 single-tailed Liberators ordered from Ford, only seven YB-24Ns were delivered in May-June 1945.
San Diego delivered the last B-24M-45-CO on May 31, and the last B-24M-30-FO came off the Ford line on June 29, 1945. Total Liberator production was 18,482, the largest of any American military airplane. Costs had dropped from $304,391 in 1942 to $215,516 per plane in 1945. They flew 312,743 sorties during the war, including 226,775 in the ETO. As with any aircraft built in large numbers, there were many variations, and only the most important can be given here. The C-87 was the 20-passenger transport version first accepted in September 1942. Since each C-87 meant one less bomber, the needs of the bomber and transport commands had to be balanced, and only 286 transports were delivered from Fort Worth. Five AT-22s were built from June to September 1943 to train flight engineers.
To support B-29s by flying fuel into their China-bases, 204 B-24s were converted to C-109 aerial tankers in 1944. A B-24D was converted to an XF-7 photographic aircraft with 11 cameras in January 1943, and was followed by 213 conversions of later aircraft to F-7, F-7A, and F-7B aircraft for use by Pacific reconnaissance units. Other rarely seen Liberators were the XB-24P, a B-24D modified in July 1945 to test Sperry fire control systems, and the XB-24Q, a B-24L testing the General Electric radar-controlled tail gun system in July 1946.
Nineteen Eighth Air Force groups used Liberators, but five of these were re-equipped with B-17Gs by September 1944. The Eighth Air Force in Britain favored the B-17 because it was easier to fly, had a higher ceiling, and seemed more resistant to enemy gunfire (see Table 5, page 243 for comparisons). Both heavy bombers had added much weight, but the smaller area of the B-24’s narrow wing handicapped it at high altitudes.
In most areas, because of their superior range, B-24s were preferred over the B-17. Fifteen Liberator groups worked with the Fifteenth Air Force in the Mediterranean and eleven groups operated against Japan, plus the single Aleutian-based 404th Squadron that made its first attack against the Kurils on July 18, 1943.
The longest daylight bombing raid by B-24 formations were the Thirteenth Air Force’s strikes against the Balikpapan oil center. The full fuel load of 3,590 gallons was needed to carry 2,500 pounds of bombs the 1,280-mile distance to the target. The 68,000-pound takeoff weight was far beyond that ever planned by the plane’s designers.
The story of the Navy’s use of the Liberator, and its development, the Privateer, will be told in a later chapter, but eight U-boats were sunk in the Atlantic by USAF anti-submarine squadrons in 1943. When the 13 U-boats sunk by the Navy and 68 by the RAF/RCAF are added, the Liberator became the most successful anti-submarine aircraft of the war.