Heatblur F-14 Tomcat

Wing-Sweep System

Wing-sweep schedule as function of Mach number and related flap interlocks.

The wing-sweep system controls the geometry of the F-14’s wings, allowing the wings to move from a 20° to a 68° position in the air. While on the deck an oversweep of 75° is also possible reducing the F-14’s wing span to 33 feet (about 10 meters).

The wings are moved by hydromechanical screwjack actuators which are interconnected mechanically, making sure they’re synchronized. As long as both main hydraulic systems are functioning the maximum wing-sweep change rate is about 15°/s. This can be affected negatively by negative g or large amounts of positive g.

In normal operation the CADC, Central Air Data Computer, controls the wing position as a function of current Mach via the wing-sweep program, this is known as the AUTO mode. The pilot can also select a wing position aft of the wing-sweep program manually or choose the BOMB mode that sets the wings to 55° or further aft depending on the program. Simply put, the CADC wing-sweep program determines the max forward position of the wings. All this is done electrically via two independent channels (for redundancy) to the wing-sweep actuators.

Currently commanded wing position, CADC program wing position and actual wing position can be seen on the wing-sweep indicator next to the ACM panel.

Emergency Mode

While the normal mode controls the wing-sweep electrically, to supplement this it’s also possible to control the wing-sweep mechanically via the emergency mode. This is done via the emergency wing-sweep handle on the right side of the throttle. That handle is connected mechanically to the hydraulic valves in the wing-sweep system, providing a physical back-up control.

Normally this handle is moved with the electronic wing-sweep program by a servo located beneath it, making sure it’s at the actual wing position. To disengage the electric system and enable the emergency mode the guard over the handle is opened and then the handle is extended for additional leverage. Then the handle can be forced out of the spider-detent normally connecting it to the electrical servo and then used to manually set the wing position.

In this mode the pilot has to make sure to follow the following schedule to avoid damage to the wings:

To return to the normal mode of operation, the handle should be pushed into the desired position and pressed down and the guard closed. The MASTER RESET button on the fuel management panel should then be depressed and the wing-sweep system set to the same position as the handle. The servo will then drive to the commanded position and re-engage the handle to the spider detent, resuming normal operation.

Oversweep

The emergency wing-sweep handle is also used to select the oversweep position of the wings. The oversweep is only used while on the ground to reduce the wing span to make it easier to spot the aircraft on the carrier deck. As the wing will sweep over the stabilizers on the tail the horizontal tail authority system is enabled to prevent the wings and stabilizers from damaging each other by restricting movement of the stabilizer.

To set the wings to oversweep the emergency wing-sweep handle should be moved to the 68° position and held in the extended position. This will deflate the wing-seal airbags and activate the horizontal tail authority system, indicated by the HZ TAIL AUTH caution light illuminating. When the HZ TAIL AUTH caution light goes out and the OVER flag on the wing-sweep indicator appears the oversweep interlocks are free and the handle can now be moved to the 75° position and stowed.

To move the wings out of oversweep the handle is pulled up and moved forwards of 68°. This will again illuminate the HZ TAIL AUTH caution light. When the wings have physically exited the oversweep the caution light and the OVER flag will turn off.

As with normal emergency mode operation the handle should now be set to the same position as the spider detent and the MASTER RESET button depressed.

Controls and Indicators

The controls for the wing-sweep system are on the right throttle (electrical) and to the right of the right throttle (mechanical). See the Throttle and the Throttle Quadrant.

The wing-sweep hat on the right throttle is normally set to AUTO enabling CADC control of the wings, this is the upper position. The down position sets the wing-sweep to the BOMB mode, 55° or aft.

The AFT and FWD (forward) positions enable manual movement aft of the CADC scheduled position.

The emergency wing-sweep handle on the throttle quadrant is used to control the mechanical emergency mode, see emergency mode above.

The wing-sweep indicator to the right of the ACM panel is used to indicate the current wing-sweep positions. The pointer on the left side shows the CADC scheduled wing position. The left tape shows the manually commanded position and the right tape shows the actual wing position.

The five windows on the right side show:

• OFF: System inoperable.
• AUTO: CADC controlling wing-sweep.
• MAN: Wings set manually with the control on the right throttle.
• EMER: Wings set with the emergency wing-sweep handle.
• OVER: Wings in oversweep.

The relevant warning and advisory lights are located on the Vertical Display Indicator (VDI) and the pilot Caution - Advisory Indicator.

The WING SWEEP advisory light on the right side of the VDI illuminates when both wing-sweep electrical channels are inoperable or the emergency mode is in use. If it illuminates without the emergency mode being used that mode should then be used as the electrical system might not work.

The WING SWEEP caution light on the pilot caution - advisory indicator illuminates when at least one electrical wing-sweep channel is inoperable.

Wing-Sweep System Test

The wing-sweep system can be tested on the ground in pre-flight without moving the wings using the Master Test Panel.

To conduct the test, set the wing-sweep mode to AUTO and push the MASTER RESET button. Set the MASTER TEST switch to WG SWP.

The CADC commanded position indicator on the wing-sweep indicator will now move to 44°. The WING SWEEP and FLAP light will illuminate on the pilot Caution - Advisory Indicator and the REDUCE SPEED warning light on the Vertical Display Indicator (VDI).

Note: The WING SWEEP advisory light will illuminate after 3 seconds into test, turn off and then illuminate again at 8 seconds.

When the CADC commanded position indicator moves forward to the 20° position the test is over and the above light will turn off. The MASTER TEST switch can now be set to OFF and the test is complete. The test will take about 25 seconds to complete.

Note: The RUDDER AUTH and/or MACH TRIM lights might illuminate and the control stick might move. This can be ignored.

Note 2: The WG SWP test on the Master Test panel is not implemented yet.