(2)
The no-back brake assembly consists of a brake disk that is pushed against a brake plate by flap airloads transferred through the drive system. The flaps are kept from retracting by rachet pawls which keep the brake plate from turning in the retract direction. During flap extension the pawls rachet freely and the brake plate rotates with the brake disk. During flap retraction the brake plate is locked in place and the brake disk rubs against it. This causes a large friction torque which the drive system must overcome.
(3)
Output from the flap transmissions drive ballscrew actuators which convert rotary motion to linear motion. The ballscrews are attached to the transmissions through universal joints which allow the ballscrews to change angle as the flaps are extended. Ballnuts on the ballscrews are attached through gimbals to flap carriages to drive the flaps.
H.
Flap Carriages (Fig. 12)
(1)
Each main flap is attached to two carriage roller assemblies which ride on flap tracks. The carriages are steel forgings to which roller bearings are attached. The rollers support the flap on the flap track and transfer the lift generated by the flaps to the wing structure. The carriage is moved along the flap track by the ballnut. Flap angle is determined by the shape of the flap tracks and the position of the carriage along the track.
I.
Aft Flaps
(1)
The aft flaps ride on tracks in the main flap and are actuated by bellcranks attached to the wings and pivoting at attachments on the main flaps. Both outboard flap bellcranks on each wing pivot on bearings on the flap carriages. On each inboard flap the outboard bellcrank pivots at the flap carriage while the inboard bellcrank is mounted to a special support fitting. The angle of the aft flap relative to the main flap is determined by programming tracks in the main flap.
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MAINTENANCE MANUAL
INBOARD FLAP DEPLOYMENT
Flap System Components
Figure 12
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757
MAINTENANCE MANUAL
J. Fairings (Fig. 12)
(1)
The flap tracks and the flap drive mechanisms are mounted below the wing surface so they are housed in aerodynamic fairings.
K.
Flap/Slat Electronic Unit (FSEU) (Fig. 13, Fig. 14)
(1)
Monitoring and control of the flap and slat drive systems is done electrically by the flap/slat electronics unit.
(2)
The FSEU consists of 3 interchangable modules; FSEU-1, FSEU-2 and FSEU-3. The 3 modules are physically and functionally identical but they perform different functions based upon where they are installed in the equipment rack.
Each FSEU module has a microprocessor programmed to perform all FSEU functions. When the module is installed in one of three locations in the equipment rack the wiring from the electrical connectors enables only a specific channel, defining the module's function.
(3)
FSEU-1 performs all primary flap and slat drive system protection, indication and automatic operation. Specifically, FSEU-1 provides:
(a)
Uncommanded motion detection and protection of the flaps during hydraulic operation.
(b)
Asymmetry detection and protection during hydraulic operation.
(c)
Flap load relief functions.
(d)
Autoslat controls.
(e)
Flaps up depressurization.
(f)
Slat position indication signals.
(g)
Signals to other aircraft systems.
(4)
FSEU-2 performs alternate flap and slat drive protection and annunciation. Specific functions are:
(a)
Uncommanded motion detection under alternate control.
(b)
Asymmetry detection under alternate control.
(c)
Autoslat control.
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