The flying services of the American military pioneered the use of fighter drop tanks, but there is no one place where you can go to get a historical ‘thumbnail sketch’ of their introduction and history of use. This blog post is my attempt to answer that need.
Drop tanks have been around over 90 years in American aviation, but their history prior to the 1942–1945 Combined Bomber Offensive is very obscure for a lot of reasons. The biggest historically American manufacturer of drop tanks Sargent Fletcher only reaches back to its 1940 founding. (It was bought by a British company in 1994.) So the recorded American aircraft drop tank history looks as follows:
The problem with the history above is that the first operational use of drop tanks pre-dated the founding of Sargent Fletcher by almost 18 years.
On March 5, 1923 the 1st Pursuit Group of the US Army Air Service flew their Boeing MB-3As Pursuit planes with 37 gallon centerline drop tanks and achieved a radius of action of 400 miles!
See article link and text:
With the MB-3As in place at Selfridge Field, Army Air Service engineers at McCook Field in Dayton, Ohio, began developing an external fuel tank that would expand the range of the new fighter. The tanks were delivered to Selfridge and on March 5, 1923, several MB-3As took off with the new 37-gallon tanks. The tank was suspended from the aircraft’s bomb rack along the centerline of the bottom of the fuselage. A releasing device was available to the pilot in the cockpit. The original tanks were designed to be jettisoned once empty, rather than to be kept aboard the aircraft and only jettisoned in an emergency situation, as are today’s tanks. With the added fuel from the tank, an MB-3A had a flying radius of about 400 miles, a marked improvement over previous pursuit-type aircraft.
As it turned out, new drop tanks weren’t the only thing that made the news at Selfridge Field on March 5, 1923. On that same day, pilots decided to use the frozen Lake St. Clair as a landing field, using other MB-3As that had been equipped with skis, rather than wheels. Both the new drop tanks and the frozen lake landings were reported upon in the Air Service Newsletter, the official publication of the Army Air Service.
The development of the drop tank stalled after those early tests as Selfridge, as the primary focus of the young Air Service (later Army Air Corps and then Army Air Force) was on the development of bomber aircraft, which could carry sufficient on-board fuel for most envisioned missions.
The fight between the “bombardment” and “pursuit” factions in the US Army Air Service lasted all through the 1930’s as mainly a Captain Claire Chennault versus the entire heavy bomber faction affair and it came to a head in 1933 when Chennault proved that “the bomber would always get through” was flat wrong.
The photo below is then Captain Claire Chennault’s 1933 Ft. Knox Air Defense Observer Network. It was so successful in catching bombardment formations that Chennault was black balled by the “Bomber Mafia” of two Air Chiefs of Staff as a threat to the B-17 development budget.
This institutional shunning lead to his retirement in 1937 and subsequent hiring as an air warfare consultant by the Nationalist Chinese government.
See my Chicagoboyz column here for that shunning story:
Two years later, in 1939, USAAF Chief of Staff General H.H. “Hap” Arnold banned drop tanks for “Pursuit” and “Attack” aviation as a “Safety Hazard” when Curtis-Wright offered a drop tank and wet wing fittings for it’s P-36 “Mohawk” fighter.
See this memo:
The only reason there was enough of a US Government drop tank market for Sargent Fletcher to be founded in 1940 was due to the US Navy’s SBD Dauntless Dive Bomber.
Barrett Tillman’s 2011 article here:
The Ten Most Pivotal Events in U.S. Naval Aviation
…makes clear that the development of biplane dive bombing followed by the 1929 fleet problem lead to the SBD requirement that required the use of drop tanks.
The SBD requirement meant meeting a pair of performance specifications. Specification #1 involved carrying a single centerline 1000-lb AP bomb and a couple of 100-lb bombs at short ranges for striking heavily armored targets.
Specification #2, the scout role, had the SBD carrying a centrline 500-lb bomb and a pair of drop tanks to search for the enemy fleet. In particular it was looking either for enemy scouting cruisers and carriers or the enemy battle line’s destroyer screen…for which the 500-lb bomb was just fine.
Buying drop tanks for this sort of extended range scouting was not just limited to the SBD. US Navy patrol bombers like the PV-1 Lockheed Ventura patrol bomber used drop tanks.
The Sargent Fletcher 150-gallon and 300 gallon drop tanks used on the P-38 Lightning fighter came from the PV-1 Ventura (the B-34 in USAAF service). Below is an example of the Sargent Fletcher 150 gallon tank used on P-38’s in the Solomon Island’s campaign in 1943.
See these articles on the PV-1 and PV-2:
Lockheed Ventura – Wikipedia
Lockheed Ventura / Harpoon Patrol / Light Bomber Bomber Aircraft – United States
Harpoon by Jack McKillop
From which pay particular attention to this passage:
PV-1: Initially, two 50 caliber (12.7 mm) machine guns in the upper decking of the nose; two 50 caliber machine guns in the Martin dorsal turret; and one 30 caliber (7.62 mm) machine gun in the ventral turret. The bomb bay accommodated one 2,000-pound (907.2 kg) or one 1,000-pound (453.6 kg) or six 500-pound (226.8 kg) bombs; or six 325-pound (147.4 kg) Mk. 17 depth charges; or one Mk. 13 torpedo. A pylon was located on each wing and this could accommodate two 150 US gallon (567.8 liter) drop tanks; or two 1,000-pound or two 500-pound bombs; or two 650-pound (294.8 kg) Mk. 29 or two 325- pound Mk. 17 depth charges. Armament later increased by the addition of three 50 caliber machine guns in a nose chin pod and the addition of launching rails for eight 5- inch (127 mm) High Velocity Attack Rockets (HVARs).
PV-2: Five 50 caliber (12.7 mm) machine guns in the nose, two in the upper nose decking and three in a chin pod; two 50 caliber machine guns in the Martin dorsal turret; and two 50 caliber machine guns in the ventral turret. The bomb bay accommodated four 1,000-pound (453.6 kg) bombs or a torpedo and underwing hardpoints accommodated eight 5-inch (12.7 cm) High Velocity Attack Rockets (HVAR) plus two 1,000-pound (453.6 kg) bombs, depth charges or fuel tanks.
PV-2D: As PV-2 except forward armament consisted of eight 50 caliber (12.7 mm) machine guns in the nose.
It can be truly said that it was the US Navy SBD drop tank specification that saved the USAAF Combined Bomber Offensive in the winter of 1943-1944.
William Emerson’s 1962 Harmon Memorial Lecture #4 makes clear it was the P-47D Thunderbolts using 150-gallon Sargent Fletcher drop tanks — produced at a rate of 20,000 a month starting in December 1943 — that made “Operation Pointblank” possible.
Operation POINTBLANK: A Tale of Bombers and Fighters, by William R. Emerson, 1962 Harmon Memorial Lecture #4
It was the Razorback P-47D’s that won air superiority over Germany in the winter of 1943–1944. While British produced paper drop tanks were of great assistance. It was primarily with the Sargent Fletcher 150-gallon drop tanks — that only the US Navy’s SBD and PV-1 made possible over the “Heavy Bomber Mafia” parochialism of USAAF Chief of Staff General H. H. “Hap” Arnold — with which those P-47D’s did the job.
After the success of drop tanks in Operation Pointblank, the American fighter drop tank was here to stay.