Did someone mention flaps?
DESCRIPTION
The flaps are divided into three sections at the trailing edge of each wing and are operated by a hydraulically driven control unit in the fuselage, through bevel gearboxes and shafts to screw-jacks between and at each end of each flap section. Two transmission systems are provided to drive the flaps, a primary and a secondary system. In the event of a primary shaft failure, which is indicated by an amber warning lamp located in the centre instrument panel, the secondary system takes up the drive. Reserve hydraulic power is available from the AC pumps and in an emergency the DC pump will provide sufficient hydraulic power to obtain a 20° flap setting but will not then retract the flaps.
The control unit contains two hydraulic motors independently powered by No.1 and No.2 hydraulic systems. The motors are geared in parallel to a common output shaft which is connected to the primary and secondary transmission systems in both wings. The left side of the output shaft is connected to the left wing primary and right wing secondary transmission. The right side of the output shaft is connected to the right wing primary and left wing secondary transmissions.
The secondary transmission system is not normally carrying any load. Backlash is provided to permit the system to lag slightly behind the primary system but taking up the load outboard of a primary system failure. If one hydraulic system fails, the flaps can still be operated with a reduction of operating speed. If both hydraulic systems fail, a hydraulically operated mechanical brake within the flap control unit holds the flaps in the selected position.
A flap lever on the centre console controls the two hydraulic motors in the flap control unit. The lever is gated in the following positions UP, 6°, 13°, 20°, 26°, and 45°. A baulk at 20° requires a release of the lever and subsequent reselection when moving through this position. This prevents the inadvertent selection of more than 20 flap for take-off; it also aids the rapid selection 20 flap when overshooting. A flap position indicator which shows the position of the flaps is located on the centre instrument panel and is operated from a transmitter mounted on the starboard outboard No.4 screw-jack.
OPERATION
When the flap lever is moved to a selected position, the movement is transmitted by the cable circuit to rotate a pulley in the flap signalling mechanism. The pulley moves a cam which operates a lever connected to the flap control unit input shaft. Mechanism within the control unit operates valves controlling the operation of the hydraulic motors.
The primary drive shafting is connected to the input shaft of each screw-jack head through right-angle bevel gearing to drive the screw. As the screw rotates, the nut body moves along the screw and moves the attached flap carriages.
A hydraulic lock on each motor maintains the flaps at the selected position until a further flap selection is made.
TCF