What makes the F-35B hover?

F-35B Lightning II hovering at RIAT

The F-35B is the fifth generation of the Lightning II and is the most advanced aircraft ever built for the UK with them due to enter service with the Royal Navy and RAF from 2018. The jet has the ability to statically hover and land vertically.

The F-35B STOVL operation is made possible through the Rolls-Royce patented shaft-driven LiftFan® propulsion system and an engine that can swivel 90 degrees when in short takeoff/vertical landing mode. Rolls-Royce is subcontracted to Pratt & Whitney on the F135 engine to provide the Lift System for the Lightning II. The Rolls-Royce LiftSystem® is the first to enable Short Take Off and Vertical Landing (STOVL) operations for supersonic-capable aircraft.

There are two primary components that provide the vertical lift necessary for hover — the LiftFan® and 3-Bearing Swivel Module (3BSM). The LiftFan® is mounted horizontally right behind the cockpit. As the aircraft transitions to hover mode, two doors open on top of the aircraft and the two counter-rotating fans blow about 20,000 pounds of unheated air straight down, producing almost half of the downward thrust needed for a pure hover mode.

The majority of the remaining vertical thrust is provided by the 3BSM at the rear of the aircraft. With the ability to swivel ninety-five degrees downward in just two and half seconds, the 3BSM can direct up to 18,000 pounds of heated thrust from the engine exhaust.

For stabilization and control, there are also two roll posts under the wings that provide approximately 10 percent (up to 2,000 pounds each) of the downward thrust drawn from engine air flow. Most importantly, the two roll posts are used to control aircraft attitude, or its orientation in relation to the earth, in the roll axis. The exhaust areas of the two roll posts can be varied independently. The posts, therefore, control roll by expelling different amounts of thrust between the two sides of the aircraft.

There is one other component that is built into the airframe — the vane box. It is essentially the base of the LiftFan® with moveable vanes that can control the thrust by directing the downward flow. This vane box enables the F-35B to move slightly forward or backward when it is in STOVL mode.

DE&S are proud to procure these amazing jets and work closely with our Armed Forces to ensure the latest technology is used to protect them when on duty.

Credit: https://www.f35.com/

RAF F-35B Lightning II
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