Conformal fuel tank

File:USAF F-15E Strike Eagle, Iraq 2004.jpg

A McDonnell Douglas F-15E Strike Eagle fitted with conformal fuel tanks under the wing roots

File:F-15E CFT.jpg

Ground crew handling the CFT of an F-15E

Conformal fuel tanks (CFTs) are additional fuel tanks fitted closely to the profile of an aircraft that extend the endurance of the aircraft.

Advantages

CFTs have a reduced aerodynamic penalty compared to external drop tanks, and do not significantly increase an aircraft's radar cross-section. Another advantage CFTs provide is that they do not occupy ordnance hardpoints like drop tanks, allowing the aircraft to carry its full payload.

Disadvantages

Conformal fuel tanks have the disadvantage that, unlike drop tanks, they cannot be discarded in flight, because they are plumbed into the aircraft and so can only be removed on the ground. As a result, they will impose a slight drag-penalty and minor weight gain on the aircraft even when the tanks are empty, without any benefit. They can also impose slight g-load limits, although not always an absolute issue: the CFTs on the F-15E actually allow the same maneuverability without g-limitations.

Examples

Conformal fuel tanks

• F-15C Eagle/F-15E Strike Eagle/F-15EX Eagle II

F-15C entered service with CFT capability.<ref name="JOE1">Template:Cite web</ref> Initially known as FAST packs (Fuel And Sensor Tactical),<ref name="JOE1"/> each unit carried an additional Template:Convert of fuel,<ref>U.S. AIR FORCE "F-15E Strike Eagle" USAF military website, April 15, 2005.</ref> while retaining hardpoints for four AIM-7F Sparrow missiles or bombs, some on the FAST packs.<ref name="green">Green and Swanborough 1998, p. 371.</ref> They were first tested on the F-15B in 1974. All U.S. F-15Es, and Strike Eagle export variants such as the Israeli and Singapore models, are fitted with CFTs under the wing<ref name="lambert">Lambert 1993, p. 521.</ref> outside the engine intake and require modification to fly without them.<ref name="JOE2">Template:Cite web</ref> The FAST pack was originally intended to carry a navigational and targeting infrared sensor system (thus "Fuel And Sensor"); however, the F-15 simply began carrying LANTIRN pods for ground-attack missions instead.<ref name="JOE1"/>

File:Israeli F-16s at Red Flag2.jpg

Israeli F-16I Sufa, based on the F-16D Block 50/52+, with 2 attached CFTs on top of the aircraft near the wing root and 2 wing-mounted drop tanks.

• F-16C/D Block 50/52+, F-16E/F Block 60, F-16V Block 70/72 and F-16I Sufa

Export aircraft for Greece, Chile, Israel, Poland, Pakistan, Turkey, Singapore, Morocco, Egypt and the UAE are plumbed for carriage of two CFTs mounted atop the aircraft near the wing root. Together they hold Template:Convert or Template:Convert of fuel.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>

• Dassault Rafale

Two Template:Convert CFTs were first tested by Dassault in April 2001.<ref>Template:Cite web</ref> A static aircraft equipped with CFTs was seen in social media posts prior to the 2025 Paris Air Show.<ref>Template:Cite web</ref>

• Mikoyan MiG-29SMT – MiG-29S (Product 9.13)- Mikoyan MiG-35

One Template:Convert CFTs in a further enlarged spine.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>

• Eurofighter Typhoon

Wind tunnel tested by BAE, two CFTs with Template:Convert of capacity each.<ref>Template:Cite web</ref><ref>Cenciotti, David. "A Typhoon model fitted with conformal fuel tanks" The Aviationist, 22 April 2014.</ref>

• AIDC F-CK-1 Ching-kuo

The F-CK-1D prototype ("Brave Hawk") and the F-CK-1C single-seater prototype are equipped with the new CFTs. The prototype Indigenous Defence Fighter II “Goshawk” has over-wing CFTs.<ref>Cole, Michael. "Jet deals to keep state-owned firm busy" Taipei Times, 13 August 2011.</ref>

• Advanced Super Hornet

Conformal fuel tanks are mounted above the wings to replace the drag of underwing tanks. Combined, they carry Template:Cvt of extra fuel, while adding extra lift and expanding combat radius by Template:Convert with a small transonic acceleration penalty.<ref name="ainonline">Template:Cite web</ref><ref>Template:Cite magazine</ref>

• Chengdu J-10

Wind tunnel tested by Chengdu.<ref name="asian-defence">Template:Cite web</ref>

• WWII:
  • Supermarine Spitfire in the belly.
  • Messerschmitt Bf 109 in the belly.
  • Messerschmitt Bf 110D-1 in the belly – nicknamed Dackelbauch (dachshund's belly).

Distended internal tanks

Distended internal tanks are fuel tanks that either create a bulge in the fuselage, or are mounted flush with the fuselage.

• English Electric Lightning<ref>Template:Cite web</ref> Conformal ventral store was used for a small or large belly fuel tank which bulges out from the underbody.
• Gloster Javelin fitted with dual flush-mounted belly tanks with a capacity of Template:Convert. They were known as "bosom tanks" or "Sabrinas".<ref name="wingweb">Template:Cite web</ref><ref name="thunder-and-lightnings">Template:Cite web</ref>
• Gloster Meteor.<ref>Template:Cite web</ref>
• Shenyang J-6.
• Nanchang Q-5 "Fantan" weapons bay fuel tank extends below the fuselage profile.<ref>Template:Cite web</ref>

References

Notes

• Green, William and Gordon Swanborough. The Complete Book of Fighters. New York: Barnes & Noble Inc., 1988. Template:ISBN.
• Lambert, Mark, ed. Jane's All the World's Aircraft 1993–94. Alexandria, Virginia: Jane's Information Group Inc., 1993. Template:ISBN.