One of the key technologies for developing air superiority in World War II was the fighter auxiliary ‘drop’ fuel tanks. They made deep penetration, fighter escorted, heavy bomber raids possible. Those raids forced Axis fighters to fight more numerous and increasingly better American fighters at a disadvantage, allowing the June 6th 1944 Normandy D-Day landings in Europe under Allied air superiority. For reasons having to do with both intra-service and inter-service politics, technical reasons, training and doctrine, plus plain good luck, MacArthur’s South West Pacific Area (SWPA) theater had such drop tanks in wide service on P-38 fighters during the Battle of the Bismarck Sea (2–4 March 1943), and on P-47’s during June-August 1943. Meanwhile, several months later and 1/2 a world away on the 14 Oct 1943, during the Schweinfurt–Regensburg mission over Southern Germany, the B-17’s of the 8th Air Force were unescorted because their P-38’s and P-47’s lacked drop tanks. This lack caused 20% of the attacking force — 60 B-17’s, and 600 airmen — to be lost.
Auxiliary ‘drop’ fuel tanks weren’t secret. They were common to most American fighters both Navy and Army in the early to mid 1930’s. Nor were they unknown around the world, as the Germans demonstrated in them in Spain early in 1939 (and forgot them for the Battle of Britain in 1940). They were also standard for the Imperial Japanese Navy (IJN) and were responsible — along with “long of lean” fuel control techniques — for the A6M3 Zero’s incredible range in 1941. Yet by the time of Schweinfurt–Regensburg mission, fighter “drop tanks” were unavailable for the 8th Air Force in England. The USAF did a lot to gloss this fact over in the post war narrative, but modern internet search engines will let you see the real facts from declassified documents hiding behind their self-serving unclassified institutional histories.
A 165 Gallon Lockheed Drop Tank in front of a P-38 Lightning Fighter
Development of the Long–Range Escort Fighter.
USAF Historical Study No. 136.
by Bernard Boylan,
USAF Historical Division, Research Studies Institute, Air University,
In February, 1939, Curtiss-Wright suggested to the Air Corps that it might be interested in testing a 52-gallon tank which could be mounted on the bomb rack of a P-36C. The company offered to build such a tank for experimental purposes and to provide the connection with the main tank. The Materiel Command accepted the offer in March, but in April OCAC (Note – Officer Commanding, Air Corps) questioned use of an external tank because of the fire hazard. The plea of Materiel command that the tank was only experimental was not overruled at first, but in May the Chief of the Air Corps directed that no tactical plane be equipped with a droppable fuel tank.l75
THE NEGLECT OF LONG–RANGE ESCORT DEVELOPMENT DURING THE INTERWAR YEARS (1918–1943)
Adding external fuel tanks to existing pursuit aircraft seemed like a logical solution to extending pursuit range. Making the tanks dropable in flight preserved maneuverability and performance when required for combat. Experiments with dropable fuel tanks had been conducted throughout the 1920’s and 1930’s. The greatest concern about drop tanks was the hazard of fire. In February 1939, Curtiss–Wright wanted to test a 52–gallon tank mounted on the bomb rack of a P–36C, but the “Chief of the Air Corps directed that no tactical plane be equipped with a dropable fuel tank” because of the potential for fires.18”
The Air Corps Chief of Staff in February 1939 was General Henry H. “Hap” Arnold. Arnold, like the rest of the US Army Air Force (USAAF) Heavy Bomber Clique saw longer range “Pursuit” as a threat to their mythic uber-bomber budget and more importantly the B-17’s potential to further Air Corps institutional independence, first as the US Army Air Force (B-17) and later as the US Air Force (B-29 plus A-bomb). During the mid-1930’s “Long of Lean” fuel control techniques for extending range were dropped from non-heavy bomber training courses. It took Charles Lindberg’s visit to the SWPA in 1944 to re-introduce the technique to USAAF Fighter pilots. Similar combat prohibitions for the use of internal ferry tanks on the medium bombers like the B-25 and B-26, that matched the range of B-17 heavy bombers in range of action and could still deliver bombs with external racks, were also put into place under Arnold.
While early versions of the P-38, P-39 and P-40 were proscribed from having auxiliary drop fuel tanks “because they might be used inappropriately”. These drop tanks were still offered to other customers by American aircraft manufacturers. The USN insisting their aircraft all have that capability. Point in fact the 165 gallon standard P-38 drop tank pictured above was developed for the Lockheed PV-1, called the Hudson by the British, which was the US Navy version of the Lockheed Ventura twin engine commercial transport. This is why successful drop tank designs were available when the USAAF Bomber Clique Generals finally discovered how desperately they were needed after the Schweinfurt–Regensburg mission.
The reason that MacArthur got the drop tanks first was a combination of luck meeting opportunity in the form of General George Kenney. Kenney was “the great innovator”. He was a technical trouble shooter for General Henry H. “Hap” Arnold, who was not a member of the Heavy Bomber Clique. Kenney was from the pre-war “Attack School”, which like the Heavy Bomber and Pursuit “schools” was established by Gen. Billy Mitchell after World War 1. Kenney did not hold the organizational prejudices of the Heavy Bomber Clique, had been heavily involved with the development of the P-38, and he took steps upon arrival in Australia in 1942 to extend the range of American fighters to match that of the drop tank using A6M3 Zero.
The following passages are from Kenney’s memoirs published in book form as “General Kenney Reports”
I know what he meant. He was right. We were not going to make hits until we could keep those bullets out of the bombardier’s cockpit. That new vitamin he wanted was fighter cover. We didn’t guess very well when we designed our fighters with insufficient range to do the job in the Pacific where distance was the main commodity. As soon as I could get those P-38s with their extra range and maybe add some more with droppable tanks hung under the wings, that kid and the rest of them would get their new vitamins.
Twenty-five P-38s, the first of the fifty promised me by General Arnold, arrived by boat at Brisbane. I sent word to Connell to come north from Melbourne, take charge of setting them up, and work twenty-four hours a day on the job. Also to give the Australian sheet-metal industry a contract to make about 10,000 150-gallon droppable gas tanks to hang under the wings so that we could extend the range.
I then went out to Eagle Farms, where the erection was to be done, and found that no droppable fuel tanks had come with the P-47s. Without the extra gas carried in these tanks, the P-47 did not have enough range to get into the war. I wired Arnold to send me some right away, by air if possible. About a week later we received two samples. Neither held enough fuel, they both required too many alterations to install, and they both were difficult to release in an emergency. We designed and built one of our own in two days. It tested satisfactorily from every angle and could be installed in a matter of minutes without making any changes in the airplane. I put the Ford Company of Australia to work making them. We had solved that problem but it would be another month before we could use the P-47s in combat.
This later DTIC paper adds the following information on the P-47 in the SWPA —
MacArthur’s Airman: General George C. Kenney and the Air War in the Southwest Pacific Theater in World War II
When the P-47s finally arrived in Australia they did not have droppable external fuel tanks to extend their range. Without those they could not fly far enough to accomplish any missions in the theater. According to Kenney, “this airplane must have extra gas to go anywhere.16 Although a drop tank had been developed in the United States, Kenney thought it “junk” and ordered a prototype 200 gallon tank constructed locally and then contracted with Ford of Australia for mass production. 17 Kenney also suggested that the radio equipment be moved from behind the pilot and the compartment then converted into a forty-gallon fuel tank. 18
It was the P-47, with British made drop tanks, during Operation Point Blank that made Normandy possible. The P-47C was designed to use a 200 gallon belly tank from the get go — the tank Kenney thought was junk — when it was ordered back in late ’41. The 75, 125, 150 and 165 gallon drop tanks for the USN were already standard issue. The P-38’s in England got its 165 gallon drop tanks in Feb 1944 letting P-38’s fly to Berlin and back…to no great effect due to 8th Air Force doctrinal problems.
And it was Lockheed P-38, Curtis-Wright P-40, Grumman F4F’s and Vought F4U’s with Navy and Australian made drop tanks that bled out the IJAAF and IJNAF units flying from Rabaul.
This was in spite of and not because of USAAF Bombardment clique leadership. To quote the Australian Airpower Expert Carlo Dr Carlo Kopp, Associate Fellow AIAA, Senior Member IEEE, PEng and Co-founder, Air Power Australia: http://www.ausairpower.net/
The heavy bombers did inflict the critical attrition on the production base and POL. But they did so only once they were properly supported by escorts. Air power performs best when operated as an integrated whole. The ideologues tend not to accept this. Yes the historical record is unambiguous.
(The sad story of the RAF fighter’s suffering from a lack of drop tanks through the first half of the war, when all American manufacturers could have supplied designs and fixtures, is too embarrassing to detail.)
While Kenney’s other acts of brilliance, like the improvised A-20s and B-25s with the 50 cal gun batteries in the nose, the parachute bomblets for airfield attacks, and skip bombing tactics are all clebrated in USAF institutional histories. It was the example of Kenney’s drop tanks in the SWPA, and the failure of the unescorted heavy bombers during Schweinfurt–Regensburg mission that finally resulted in the command and doctrinal changes to get drop tanks to USAAF fighters for Operation Point Blank, and the achievement of air superiority for D-Day at Normandy.
And now you know the truth behind another “MacArthur narrative.”