PAUL LEWIS / WASHINGTON DC
STOVL version's new liftfan door configuration detailed as project approaches review
Lockheed Martin has revealed design refinements to the F-35 Joint Strike Fighter (JSF), including a completely new liftfan door configuration for the short take-off vertical landing (STOVL) version and improved thermal management, as the programme's preliminary design review (PDR) process nears completion.
PDR will conclude at the end of the month with a week-long review of the full Tier 1 JSF air system, after which build-to-print work packages will begin to be released for fabrication. Supplier-level PDRs are now complete and the programme is focused on a review of Tier 3 airframe, vehicle, mission, training, autonomic logistics information and support systems. This then cascades into a Tier 2 air vehicle, autonomic logistics and system engineering review.
The F-35 now incorporates several changes, the most visible of which is a single-piece cantilever inlet door to the STOVL aircraft's liftfan bay in place of the original side-hinged bi-fold hatch.
"Airflow over the doors and, in forward velocity in particular, air coming horizontally over the canopy being sucked down vertically, causes a disturbance over the fan and effects fatigue. The new door acts as an inlet," says Tom Burbage, Lockheed Martin JSF programme manager.
In STOVL mode with forward motion, such as a short take-off run, the rear-hinged door opens to 35° for lower drag and 65° in a full hover. Other surface changes include the addition of small air inlet scoops above the main inlet and dorsal body and more heat exchanges to improve cooling. The combination of a large single engine, internal sensors and electro-hydrostatic actuators, and the requirement for the first time to operate on a 49°C (120°F) day, has proven a thermal management challenge, says Burbage.
The need for more cooling and larger electrohydrostatic cabling in turn is presenting designers with a routeing challenge, particularly just aft of the inlets where the fuel tank sits above the two internal weapons bays creating a chock point. Running wiring through the fuel tank to avoid impinging on the weapons has necessitated an increase in the tankage area to avoid any loss of range.
Source: Flight International
