History Bulgarian Heinkel He-51B, with drop tank under fuselage A standard 300 liter capacity drop tank of the German WWII Luftwaffe A Bf 110 of 9./ ZG 26 with the rarely-used, fin-stabilized 900 liter drop tanks CFTs produce less drag and do not take up external hardpoints but some versions can only be removed on the ground. Some modern combat aircraft use conformal fuel tanks (CFTs) instead of or in addition to conventional external fuel tanks. Usually the fuel in the drop tanks is consumed first, and only when all the fuel in the drop tanks has been used, the fuel selector is switched to the airplane's internal tanks. The use of drop tanks also reduces the number of external hardpoints available for weapons, reduces the weapon-carrying capacity and increases the aircraft's radar signature. Drag in this sense varies with the square of the aircraft's speed. Some of the drop tank's fuel is used to overcome the added drag and weight of the tank. External fuel tanks will also increase the moment of inertia, thereby reducing roll rates for air maneuvers. The primary disadvantage with drop tanks is that they impose a drag penalty on the aircraft. External tanks are commonplace on modern military aircraft and occasionally found in civilian ones, although the latter are less likely to be discarded except in an emergency.ĭrop tank storage aboard USS Harry S. A drop tank is expendable and often capable of being jettisoned. In aviation, a drop tank ( external tank, wing tank or belly tank) is used to describe auxiliary fuel tanks externally carried by aircraft.

A 600 US gallons (2,300 L) Sargent Fletcher drop tank being moved across the flight deck of an aircraft carrier

Us air force drops tank