Voor het eerst heeft een F-35 een hover uitgevoerd. Het vliegtuig zweeft dan als een helikopter boven de grond. De test werd uitgevoerd in Fort Worth, bij de F-35 fabriek. Voor de piloot is het een kwestie van 1 druk op de knop.
How it works:
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.
Ease in flight:
All of these components operate with ease allowing the pilot to focus on more important tasks. For the pilot, converting from conventional flight to STOVL mode is no more complicated than pushing the STOVL conversion button. This is the same button that pilots flying an F-35A or F-35C aircraft would push to lower the tail hook.
After the button is pressed, the transformation to STOVL mode begins, which includes the opening of all STOVL doors and the propulsion system preparing to engage the clutch. Once all doors are open, the clutch engages when sets of carbon plates press together to spin the LiftFan® up from a complete stop to engine speed. Once the speeds between the LiftFan® and engine are matched, a mechanical lock is engaged to remove the torque load from the clutch and permit operation to full lift fan power. After the lock engages, the propulsion system completes conversion to STOVL mode and responds to aircraft commands. The entire sequence takes approximately fifteen seconds.
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