This post is one in a series on the development of the F-35. Click here for a Flash graphic with system cutaways. Click on Read More to read the entire post on that system and check out next week's special coverage of the program in the Dec 12 edition of AW&ST.
Mechanical unreliability caused significant delays from the outset of the F-35B flight-test program, requiring frequent replacement of seemingly pedestrian items such as cooling fans. One continuing source of reliability issues has been the actuator for the large lift-fan door.
Photos: Lockheed Martin
The actuator opens and closes the door, and also holds it at the 65deg fully open and 35deg mid position in flight. Early in the test program, the lift fan had to be removed every time the actuator malfunctioned, but a technique was developed to replace the faulty unit without removing the fan, reducing down time.
A lingering issue involves a locking mechanism inside the actuator that holds the door in the mid position. This can stick on the ground (there is an emergency opening capability in flight). A small design change invoving chamfering of pawls inside the actuator to prevent sticking is to be available early next year. Meanwhile, a study is under way on a simpler actuator that eliminates the complexity of the locking mechanism.
Back to F-35B Graphic or on to Doors (Pt.2)