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Paul Michael Bevilaqua
Born May 11, 1945 (1945-05-11) (age 64)
United States
Occupation Aeronautics engineer

Paul Bevilaqua is an aeronautics engineer at Lockheed Martin in California. In 1990, he invented[1] the lift fan for the Joint Strike Fighter F35B along with fellow Skunk Works engineer Paul Shumpert.


Life and career

Paul got a Doctorate in Aeronautics and Astronautics (subject: Turbulent wakes) at Purdue University in 1973.[2]
This seems to be concurrent with activities as an Air Force Lieutenant at Wright-Patterson Air Force Base, where he began professional work in 1971.[3]
At some point he became Deputy Director of the Energy Conversion Lab at WP-AFB, managed by jet inventor Hans von Ohain.
In 1975 Paul left the Air Force to be a Manager of Advanced Programs at Rockwell International's Navy Aircraft Plant.[3]
Ten years later, in 1985, he was appointed Chief Aeronautical Scientist at Lockheed, trying to come up with a new line of business.[3]

Hans von Ohain inspired Bevilaqua to think like an engineer rather than a mathematician[4][5] - "in school I learned how to move the pieces, and Hans taught me how to play chess"[6], although he said that about Purdue as well.[2]
Ohain also showed Paul "what those TS-diagrams actually mean".[3]

While at WP, Ohain[7], Bevilaqua and others investigated (see #List of Papers) and patented[8] various flow related concepts, some of them flow multipliers related to vertical take-off and landing.

Invention of LiftFan

(For the physical system, see Rolls-Royce LiftSystem)

Diagram of LiftSystem components and airflow
The F135 engine with lift fan, roll posts, and rear vectoring nozzle, as designed for the F-35B, at the Paris Air Show, 2007

In the 1980s, the United States Marine Corps wanted a Vertical/Short Takeoff and Landing (V/STOVL) aircraft with more speed and payload than the Harrier/AV-8B.[9][10][11]

Bevilaqua was working for Lockheed Skunk Works in 1986, when DARPA launched a program called ASTOVL and issued a 9-month contract to develop concepts[12] for a stealthy supersonic STOVL plane, in accordance with USMC wishes, but without the usual strict technical requirements.[3]

The challenge in combining supersonic flight and STOVL is that an engine powerful enough to lift an aircraft would be too wide to be supersonic, as shown by the Harrier.[3][5] A smaller engine with higher air flow was needed, but seemed impossible. Inspired by the Rolls-Royce tandem-fan, a lift vector at the front seemed appropriate to counterbalance the swivel nozzle of the jet engine at the back. In order to leave no stone unturned, all kinds of options were investigated, some even bordering on the ludicrous[2] (using a cannon for lift, transferring power with a laser beam) - Skunk Works employees are no strangers to cartoon antics.[13]

With one month left and no results, he took yet another look at the situation. Three elements were clear[5] :

  • a turbine is the best way of extracting power from a jet
  • a shaft is the best way of transferring that power forward
  • a fan is the best way of converting power to thrust or lift

but that was tried by many[14] and found insufficient - something more was needed.

Exploiting bypass air is the usual way of increasing thrust, but when air flow drops so does pressure, which increases engine speed at the risk of failure. This apparent flaw suddenly turned to a benefit when it dawned upon him that the extra engine power could be put to good use by turning a lift fan.[5] In other words; transforming some of the jet blast to vertical air flow by extracting energy from the hot jet blast with a turbine that turns a shaft driving a fan pointing down, thereby increasing impulse and thus lift, without increasing drag[2].

The system works similarly to a turbofan, with an extra bypass fan moved and tilted 90 degrees to move cool unburned air vertically instead of horisontally[12], or a turbine helicopter whose rotor is shrinked and encased. This effect is similar to the previous flow multiplier concepts investigated by Bevilaqua (see #List of Papers) and others (although methods are different), achieving a lift/thrust-ratio of 1.5:1[12] where previous aircraft were limited to 1:1 at best.

Paul is not[6] a propulsion engineer, and got help from various Lockheed experts in propulsion, materials and other specialised fields in order to verify the theories of the concept, which was then patented.[1]

Both DARPA and the Marine Corps liked the concept, and from there it developed through various defense programs such as CALF and JAST[11] into the Joint Strike Fighter Program and through to the X-35B and F35B. Bevilaqua was a key figure in persuading[10] the Air Force in 1992 that the concept aircraft could be useful as a conventional aircraft without the LiftFan. When the US Navy also came onboard, the road was paved for the JSF concept of similar aircraft with different applications.

The practical development of the F135 engine and system was performed by Pratt & Whitney, Rolls-Royce and others.

One of the key factors in handing the $200B[3] JSF contract to LM is said[15] to be when the X-35B took off from 150feet of runway, went supersonic, and landed vertically in one flight on July 20, 2001[16] - a performance that only the X-35B has done, and only because of the LiftFan.

The JSF team was awarded the Collier Trophy 2001[17][18] for the working system.

List of Papers

Paul M. Bevilaqua "Evaluation of Hypermixing for Thrust Augmenting Ejectors," Journal of Aircraft, Vol. 11, No. 6, June1974, pp. 348-354
Paul M. Bevilaqua, "Analytic Description of Hypermixing and Test of an Improved Nozzle," Journal of Aircraft, Vol. 13, No. 1, January 1976, pp. 43-48
Paul M. Bevilaqua, "Lifting Surface Theory for Thrust-Augmenting Ejectors," AIAA Journal, Vol. 16, No. 5, May 1978,pp. 475-581).
Paul M. Bevilaqua and Paul S. Lykoudis "Turbulence memory in self-preserving wakes", Journal of Fluid Mechanics, Volume 89, Issue 03, December 1978, pp 589-606
Paul M. Bevilaqua, Howard L. Toms Jr "A Comparison Test of the Hypermixing Nozzle."
Paul M. Bevilaqua, John D. Lee, "Development of a Nozzle to Improve the Turning of Supersonic Coanda Jets" (1980)
Paul M. Bevilaqua One-page Preview of "Joint Strike Fighter Dual-Cycle Propulsion System", Journal of Propulsion and Power, 2005, vol. 21, no5, pp. 778-783


  1. ^ a b "Propulsion system for a vertical and short takeoff and landing aircraft", United States Patent 5209428. PDF of original :
  2. ^ a b c d Purdue Awards, Purdue University website, retrieved December 2009
  3. ^ a b c d e f g The man with the fan, By Karen Auguston Field -- Design News, February 22, 2004. Retrieved January 2010
  4. ^ From napkin to first supersonic plane, By Jesus Diaz, Apr 22, 2008. Retrieved January 2010
  5. ^ a b c d Interview with Bevilaqua, retrieved from Engineering newspaper December 2009.
  6. ^ a b LM Video
  7. ^ "Jet pump or Thrust augmentor", United States Patent 3525474, 25august1970
  8. ^ List of patents by Paul M. Bevilaqua, retrieved December 2009
  9. ^ AV-8B Super Harrier: Separating myth from reality, by Major F. S. Durtcne, Marine Corps University Command and Staff College [1988]. Retrieved January 2010.
  10. ^ a b GovExec: The engine that could By George C. Wilson, National Journal, January 22, 2002. Retrieved January 2010
  11. ^ a b A history of the Joint Strike Fighter Program, Martin-Baker. Retrieved January 2010
  12. ^ a b c Going vertical – developing a short take-off, vertical landing system. Ingenia Online (PDF) August 2004. Retrieved: December 2009. Raw text:
  13. ^ How the Skunk Works® got its name, Lockheed-Martin website, retrieved January 2010.
  14. ^ V/STOL: The First Half-Century, by Michael J. Hirschberg, Vertiflite March/April 1997. Retrieved January 2010
  15. ^ PBS: Nova transcript "X-planes", retrieved January 2010.
  16. ^ From Supersonic to Hover: How the F-35 Flies By Chris Kjelgaard Senior Edito posted: 21 December 2007
  17. ^ Collier Trophy; list of winners. Retrieved January 2010
  18. ^ Propulsion System in Lockheed Martin Joint Strike Fighter wins Collier Trophy Lockheed Martin press release, February 28th, 2003. Retrieved: January 2010


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