page_title: Paul Bevilaqua
section_title: Invention of LiftFan
hierarchical_section_title: Paul Bevilaqua / Invention of LiftFan
caption_attribution_description: Turbofan of F-35B Turboréacteur du F-35
context_page_description: Paul Bevilaqua is an aeronautics engineer at Lockheed Martin in California. In 1990, he invented the lift fan for the Joint Strike Fighter F-35B along with fellow Skunk Works engineer Paul Shumpert.
context_section_description: 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.
  Bevilaqua was working for Lockheed Skunk Works in 1986, when DARPA and the similar British agency launched a program called ASTOVL and issued a 9-month contract to develop concepts for a stealthy supersonic STOVL plane, in accordance with USMC wishes, but without the usual strict technical requirements.
  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. A smaller engine with higher air flow was needed, but seemed impossible. 
  Inspired by the General Electric CJ805-23 aft-turbofan and the Rolls-Royce tandem-fan, an appropriate system seemed to be a dual thrust system with a lift vector at the front and a swivel nozzle at the back for the jet engine, counterbalancing each other.
  To leave no stone unturned, all kinds of options were investigated, some even bordering on the ludicrous (using a cannon for lift, transferring power with a laser beam) - Skunk Works employees are no strangers to cartoon antics.
  With one month left and no results, he took yet another look at the situation. Three elements were clear:
  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 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. "It took eight months of brainstorming to program the computer in my head, and ten seconds to come up with the idea."
  
  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. The transition between horizontal and vertical lift needs to be precisely controlled, and the two lift columns need to be carefully balanced, to maintain control of the aircraft.
  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 horizontally, or a turbine helicopter whose rotor is shrunk 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 where previous successful aircraft were limited to 1:1 at best.
  Paul is not a propulsion engineer, and got help from various Lockheed experts in propulsion, materials and other specialised fields to verify the theories of the concept, which was then patented in 1990-93.
  Both DARPA and the Marine Corps liked the concept, and from there it developed through various defense programs such as CALF and JAST into the Joint Strike Fighter Program and through to the X-35B and F-35B. Bevilaqua was a key figure in persuading 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 on board, the road was paved for the JSF concept of similar aircraft with different applications, in accordance with JAST Concept Exploration findings.
  The practical development and testing of the F135 engine and system was performed by Pratt & Whitney, Allison Engine Company, NASA, Rolls-Royce and others.
  One of the key factors in handing the $200B JSF contract to LM is said to be when the X-35B took off from 150feet of runway, went supersonic, and landed vertically in one flight on July 20, 2001 - a performance that only the X-35B had done, and only because of the LiftFan concept.
  The JSF team was awarded the Col
caption: The F135 engine with lift fan, roll posts, and rear vectoring nozzle, as designed for the F-35B, at the Paris Air Show, 2007
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