Flap/Slat Depressurization Module
Figure 10
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(3)
The depressurization module contains a solenoid pilot valve, a shutoff valve, a landing gear priority valve, a flap/slat sequencing valve and a pressure switch.
(4)
Solenoid Pilot Valve and Shutoff Valve
(a)
The shutoff valve closes off hydraulic pressure to the flap/slat systems. The shutoff valve is actuated to the shutoff position by hydraulic pressure ported to the valve by the solenoid pilot valve.
(b)
The shutoff valve is normally spring-loaded open. When FSEU-1 commands depressurization the solenoid pilot valve opens, letting hydraulic pressure close the shutoff valve.
(c)
In the event of an electrical failure the shutoff valve remains open so that hydraulic control of the flaps and slats is available.
(d)
The solenoid pilot valve has two coils. FSEU-1 powers one coil to open the valve when the airplane is in cruise configuration or a failure exists in the flap/slat drive systems. The other coil is powered when either the flap or slat alternate drive system is armed.
(5)
The pressure switch provides information to the airplane maintenance system. If the hydraulic pressure remains high during a depressurized state, or low during a pressurized state, a FLAP ISLN VAL message is sent to the EICAS computer.
(6)
The landing gear priority valve gives flap and slat operation priority over landing gear operation. If pressure in the left hydraulic system drops below 1800 psi the priority valve closes, leaving a 3-gallon per minute orifice for the landing gear.
(7)
The flap/slat sequencing valve serves to reduce total flow to the flaps and slats when both systems are operating at the same time. The valve normally serves as a flow limiter to the flap system. When slat motion is commanded, flow to the flap system is reduced to allow adequate flow to the slat system. Total flow to the flaps and slats is limited to assure adequate flow to other hydraulic systems.
F.
Flap Torque Tubes (Fig. 11)
(1)
Output from the PDU is transmitted by a single torque tube system. The torque tubes are aluminum tubes connected with steel sleeve and spline couplings. Safety straps are installed to prevent damage to surrounding airplane systems in the event of a torque tube failure.
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TORQUE TUBESSEE A
PDU
TRANSMISSIONS
TORQUE TUBE COUPLING COUPLING SPLINES SUPPORT BEARING
SAFETY STRAP
A
TORQUE TUBE DETAILS
Trailing Edge Flap Torque Tubes
Figure 11
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(2)
Torque tubes attach to each other through intermediate support bearings. Torque tubes attach to gearboxes to change direction and to transmit power to flap actuation transmissions.
(3)
A lubrication point is provided at each spline coupling and support bearing.
G.
Flap Transmissions
(1)
Each trailing edge flap is driven by two transmission assemblies. Each transmission contains a 15-to-1 gear reduction, a no-back brake assembly and a torque limiter. The torque limiter is a ball ramp, disk brake device with a torque trip indicator. If the TE flap does not move freely, the torque brake stops the movement of the torque tubes. This protects the system from damage due to jamming. The trip indicator must be manually reset if it activates.
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