Cure for the aux inlet door hinge problem. Let's hope that the result isn't lift-fan door hinge problems! The additional load on the fully open door as speed increases must be substantial.
Hmmm, sideslip issues on a VTOL jet in the hover, how unexpected......
Ares:
Lockheed Sneaks Another F-35 Under the Wire
.........To achieve clearance for ship trails, the F-35B must complete 40 vertical landings in a range of conditions. The program has only done 10 since March 2010, seven of which count towards the total required. STOVL-mode testing was suspended in September, when premature wear on auxiliary-inlet door hinges was discovered. Vertical landings are expected to resume in January.
Auxiliary doors are aft of the lift-fan door (here open to 65deg)
Hinge wear has been traced to higher-than-predicted airloads on the auxiliary doors. Components have been redesigned, but the main fix is to change the operation of the large lift-fan door forward of the auxiliary-inlet doors. Flight tests have shown that, when the lift-fan door is fully open, loads on the auxiliary doors are reduced.
Originally, the lift-fan door was scheduled to open to 65deg below 120kt in semi-jet-borne flight, and to 35deg above that airspeed. Now the door will stay fully open to 165kt to reduce the loads on the auxiliary-inlet doors. Lockheed's JD McFarlan, who is now in change of the test program, says the change does not significantly impact short take-off performance.
Investigation of the hinge-wear problem also revealed a lot of variation of the loads on the auxiliary doors caused by aircraft sideslip, so McFarlan says the flight-control software has been adjusted to tailor the slideslip characteristics in semi-jet-borne flight.........