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Conformal fuel tank

From Wikipedia, the free encyclopedia
A McDonnell Douglas F-15E Strike Eagle fitted with conformal fuel tanks under the wing roots.

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

Advantages

[edit]

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

[edit]

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 allow the same maneuverability without g-limitations.

Examples

[edit]

Aircraft in service with conformal fuel tanks

[edit]
F-15 family
Ground crew handling the CFT of an F-15E
Israeli F-16I Sufa, based on the F-16D Block 50/52+, with 2 CFT on the wing root.
Russia MiG-29 SMT with the spinal conformal fuel tank
Bf 110D with Dackelbauch tank
Supermarine Spitfire with a belly tank
From the F-15C Eagle[1], all the aircraft of the F-15 family were designed and built to receive the conformal fuel tanks. The aircraft in question are the F-15C Eagle, the F-15E Strike Eagle and the F-15EX Eagle II.
The tanks were nitially known as FAST packs (for "Fuel And Sensor Tactical").[1] The first tests took place on the F-15B in 1974.[2] Initially, the project intended to include navigational equipment and infrared targeting sensors on the FAST pack (thus "Fuel And Sensor"). But the sensor part of the concept was never implemented, instead specialised pods are being used by the F-15 family, such as the LANTIRN for ground-attack missions.[1][3]
Each aircraft carries two tanks, with each 2,840 L (750 US gal) of extra fuel for a total of 5,680 L (1,500 US gal).[4] Despite their presence, the F-15C kept the hardpoints on the side of the fuselage for 4 × AIM-7F Sparrow missiles or bombs, some of the hardpoints are on the side of the FAST packs.
Operators:
F-15 - Israel
IAI (Israel Aerospace Industries) developed their own conformal fuel tanks and they are used on the Israeli F-15 (A/B, C/D, E, EX).[12] These have been manufactured since 1984.[13][14]
F-16
The F-16C/D Block 50/52+, the F-16E/F Block 60 and the F-16V Block 70/72 were reinforced structurally to receive two CFT mounted atop the aircraft near the wing root. Each tank adds a capacity of 850 L (220 US gal) for a total of 1,700 L (450 US gal).[15][16][17] The first aircraft with CFT was a F-16E/F delivered to the UAE in 2004.[18]
The current operators include: Bahrain[19][20], Bulgaria[21], Egypt[22], Greece[18], Morocco[23], Oman[24], Pakistan[25], Poland[26], Taiwan[18], Turkey[27], Singapore[28], Slovakia[21], UAE[18]. Future operators: Peru (aircraft selected for procurement in 2026)[29].
F-16 - Israel
IAI (Israel Aerospace Industries) developed their own conformal fuel tanks and they are used on the Israeli F-16I Sufa. Each tank adds a capacity of 850 L (220 US gal) for a total of 1,700 L (450 US gal).[30]
Mikoyan MiG-29
The Mikoyan MiG-29 SMT is modified with an enlarged spine which is filled with an additional tank of 950 L (250 US gal).[31]
The countries that purchased this upgrade are Russia, Algeria and Yemen, but the Yemeni variant isn't equipped with the conformal fuel tank.[32]
Messerschmitt Bf 109
Some Bf 109 generation has a centerline belly tank.[33]
Messerschmitt Bf 110D-0
It was only used on the Messerschmitt Bf 110D-0 variant. It was nicknamed "Dackelbauch" (Dachshund belly). Its capacity was of 1,050 L (280 US gal).[34]
Supermarine Spitfire
It was known as a slipper drop tank. Multiple sizes existed:
  • 30 imp gal (140 L; 36 US gal)[35]
  • 45 imp gal (200 L; 54 US gal)[36]
  • 90 imp gal (410 L; 110 US gal)[37]
  • 170 imp gal (770 L; 200 US gal)[38]

Projects of aircraft with conformal fuel tanks

[edit]
AIDC F-CK-1 Ching-kuo
The F-CK-1C (single-seat), and the F-CK-1D Brave Hawk (2-seater), are both prototypes. They have two CFT that are atop the wings, near the wing root.[39]
Boeing F/A-18E/F Super Hornet
The US Navy planned to mount CFT on F/A-18 E/F Block III (and could have been retrofitted on Super Hornet E/F and Growler), but the plan was cancelled due to the practical considerations of space and maintenance at sea. Plus during some of the landing with the land-based arresting system (carrier landing simulator), the CFTs were heavily damaged due to the shock.[40]
The total capacity was 1,950 L (520 US gal).[41]
Chengdu J-10
Chengdu tested a design of CFT in a wind tunnel. They are located over the root of the wing.[42]
Dassault Rafale
Dassault developed and tested a Rafale equipped with two CFT in April 2001.[43] Each of the tank has a capacity of 1,150 L (300 US gal), for a total of 2,300 L (610 US gal). The tanks are located atop the fuselage, on each side of the spine.
Dassault exposed a Rafale equipped with CFT at the Paris Air Show 2025.[44]
Eurofighter Typhoon
BAE Systems tested in a wing tunnel a variant of the Eurofighter equipped with two CFT located atop of the fuselage on each side of the spine. They were designed to be retrofitted on every Eurofighter T2 and T3.[45][46]
Each of the tank has a capacity of 1,500 L (400 US gal), for a total of 3,000 L (790 US gal).
Saab Gripen
During the 2000s, Saab was assessing options to increase the range. One of the option was to add to CFT on the sides of the spine of the aircraft. The other that was later chsen was to develop the Gripen NG, which is today the Gripen E/F.[47]

Examples of distended internal tanks

[edit]
Gloster Meteor with a belly tank

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

English Electric Lightning
Conformal ventral store was used for a small or large belly fuel tank which bulges out from the underbody.[48]
Gloster Javelin
Fitted with dual flush-mounted belly tanks with a capacity of 1,100 L (290 US gal). They were known as "bosom tanks" or "Sabrinas".[49][50]
Gloster Meteor
Conformal ventral store was used for a large belly fuel tank which bulges out from the underbody.[51]
Shenyang J-6
An underbelly tank known as ‘Gondola’ fuel tanks, used by the Pakistani Air Force.[52][53][54]
Nanchang Q-5
The Q-5G is a Q-5E with a belly conformal tank.[55]
The Q-5L had the option of a belly tank.[55]

References

[edit]
Notes
  1. 1 2 3 Joe, Baugher (20 February 2000). "McDonnell F-15C Eagle". JoeBaugher.Com. Retrieved 2010-09-21.
  2. "McDonnell F-15C Eagle". Retrieved 2026-07-24.
  3. Green and Swanborough 1998, p. 371.
  4. U.S. AIR FORCE "F-15E Strike Eagle" USAF military website, April 15, 2005.
  5. Rogoway, Tyler (2018-02-05). "It's Back To The Future For U.S. F-15C Eagles And Conformal Fuel Tanks". TWZ. Retrieved 2026-07-24.
  6. Times, Bernard Gwertzman, Special To the New York (1981-03-07). "U.S. DECIDES TO SELL EQUIPMENT TO SAUDIS TO BOLSTER F-15 JETS". The New York Times. ISSN 0362-4331. Retrieved 2026-07-24.{{cite news}}: CS1 maint: multiple names: authors list (link)
  7. "The Carter administration wanted to sell Saudi Arabia offensive... - UPI Archives". UPI. Retrieved 2026-07-24.
  8. 1 2 3 4 Lambert 1993, p. 521.
  9. "F-15K Slam Eagle". 9 June 2020.
  10. "2010/04 - 21st Century Multi-Role Fighter". Republic of Singapore Air Force (RSAF). Retrieved 2026-07-24.
  11. 1 2 3 Hunter, Jamie (2023-01-27). "F-15E Strike Eagles Now Flying Without Conformal Fuel Tanks On Air Defense Missions". TWZ. Retrieved 2026-07-24.
  12. Rogoway, Tyler (2018-02-05). "It's Back To The Future For U.S. F-15C Eagles And Conformal Fuel Tanks". TWZ. Retrieved 2026-07-24.
  13. "Iai Builds F-15 Fuel Tanks". Jewish Telegraphic Agency. Retrieved 2026-07-24.
  14. "Israel Aircraft Industries Delivers 100th F-15 Conformal Fuel Tank to BOEING". www.globalsecurity.org. Retrieved 2026-07-24.
  15. "Lockheed Martin and U.S. Air Force Complete Flight-Testing of F-16 Conformal Fuel Tanks". 27 November 2002. Archived from the original on 16 August 2025. Retrieved 24 July 2026.
  16. "First phase of flight testing of the F-16 conformal fuel tanks completed". www.f-16.net.
  17. "L- M and USAF Complete Flight-Testing of F-16 Conformal Fuel Tanks". www.defense-aerospace.com.
  18. 1 2 3 4 "Why the First F-16 Fighter Built For a Modern Taiwan Strait War Carries Five External Fuel Tanks". 15 June 2026.
  19. Valpolini, Paolo (2019-10-29). "Assembly of first Bahraini F-16 Block 70 will start soon". EDR Magazine. Retrieved 2026-07-24.
  20. "Lockheed Martin and Royal Bahraini Air Force Celebrate Bahrain's First F-16 Block 70 Aircraft in Greenville, South Carolina". Media - Lockheed Martin. Retrieved 2026-07-24.
  21. 1 2 "Lockheed Martin Completes Production of Initial F‑16 Block 70 Fleets for Bulgaria and Slovakia". Media - Lockheed Martin. Retrieved 2026-07-24.
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  26. Trevithick, Joseph (2025-08-13). "Poland's F-16s Are About To Become Much More Potent". TWZ. Retrieved 2026-07-24.
  27. "F-16: Advancing the Future of Türkiye's Air Defense".
  28. Yeo, Mike (2023-09-08). "Singapore reveals upgraded F-16 jets can fire Python-5 missiles". Defense News. Retrieved 2026-07-24.
  29. "F-16 Peru". Lockheed Martin. Retrieved 2026-07-24.
  30. "Extended Range Solutions - Conformal Fuel Tanks". www.iai.co.il. Retrieved 2026-07-24.
  31. Cenciotti, David (2017-09-13). "Russia Has Deployed Its MiG-29SMT Multirole Combat Aircraft To Syria For The Very First Time". The Aviationist. Retrieved 2026-07-24.
  32. "MiG-29SMT Fulcrum Multirole Fighter Aircraft - Airforce Technology". Airforce Technology. Archived from the original on 2026-05-20. Retrieved 2026-07-24.
  33. https://www.warbirdphotographs.com/LCBW7/Me109G6-with-Prototype-Two-MG151-20mm-Cannons-In-Belly-Gun-Pack-But-Never-Put-Into-Production-271f.jpg
  34. "Messerschmitt Bf 110 D-0". 1000aircraftphotos.com. Retrieved 2026-07-24.
  35. Manchot (2018-06-27). "Drop it!". Heritage Flight Simulation. Retrieved 2026-07-24.
  36. "SPITBOMBER". Vintage Wings of Canada. Retrieved 2026-07-24.
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  38. "Prototype Spitfire VC BR202 170 gallon slipper fuel tank | World War Photos". www.worldwarphotos.info. Retrieved 2026-07-24.
  39. "Jet deals to keep state-owned firm busy - Taipei Times". www.taipeitimes.com. 2011-08-13. Retrieved 2026-07-24.
  40. Leone, Dario (2023-07-22). "Chief Petty Officer explains why the US Navy gave up plans to fit Conformal fuel tanks on its F/A-18 Super Hornet fleet". The Aviation Geek Club. Retrieved 2026-07-25.
  41. Centeno, Gabriel (2021-08-26). "US Navy Block III Super Hornet Fighters Will Not Have Conformal Fuel Tanks". Aeroflap. Retrieved 2026-07-25.
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  45. "BAE Systems begins new round of CFT trials for Typhoon". 23 April 2014. Archived from the original on 1 August 2014.
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  47. Poggio, Guilherme (2010-04-05). "Gripen com CFT". Poder Aéreo (in Brazilian Portuguese). Retrieved 2026-07-25.
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