Torque Limiter
Brake Plates
Brake Shaft/
Sun Gear
Torque Limiter
Helical Spring
Actuator Output
Shaft/Spline
Actuator
Mounting Flange
Compound
Planetary
Gearset
Actuator Shaft
Seals
Slat Actuator Parameters
The following table defines the gearbox parameters for the various actuator configurations:
Slat Actuator Actuator Gear Ratio Panel Max Travel (deg) Rack & Pinion Gear Ratio
Inboard (#1 & #2) 155.52:1 20* 21.86:1
Midboard (Inboard) (#3, & #4) 155.52:1 25 17.50:1
Midboard (Outboard) (#5 & #6) 155.52:1 25 17.50:1
Outboard (#7 & #8) 155.52:1 25 17.50:1
*Note: 20° travel on Inboard Slat Actuator is limited due to engine cowl interference. Torque Limiter Settings
The torque limiter, under dynamic conditions, limits the maximum pass-through torque. Each actuator is tested to verify that the torque limiter setting is within the following range.
170 Series
Position (#1, #3 & #5) 427.6 Nm max
Position (#2, #4 & #6) 323.5 Nm max
Position (#7 & #8) 282.4 Nm max
190 Series
Position (#1, #3, #5, & #7) 427.6 Nm max
Figure 88: Slat Actuator Installation (Typical)
SLAT SKEW SENSOR GENERAL DESCRIPTION
Electronic skew sensors are located on the Slat system to prevent excessive panel skew in the event of an internal disconnect in one irreversible actuator while the other actuator on the same panel
continues to operate. Skew sensors are also used to annunciate dormant disconnect failures which allow the panel to continue normal operation. Two different types of skew sensors are utilized on the inboard slat panel and outboard slat panels.
-Slat Inboard Skew Sensor Description
Dual channel resolvers are used on the two driven end tracks for the inboard slat panels. The resolvers are driven by a spur gear that meshes with the pinion that drives the rack. The skew sensors are inter-connected such that differential movement between the two sensors on each end of the panel is monitored by the Slat/Flap ACEs. In the event that the differential movement detected by the skew sensors exceeds a predetermined acceptable limit the SF- ACEs will shut down the slat system and annunciate the fault.
The inboard skew sensor LRU in mounted to the slat rib opposite the slat actuators on tracks #1 and #3 using four screws. The skew sensor is provided with a spur gear that meshes with and is driven by the Slat pinion gear mounted on the actuator output shaft. The skew sensor housing and spur gear have timing marks for proper rigging of the sensors between the two tracks. The skew sensors have an integral electrical connector which mates with the aircraft wiring harness to interconnect the two sensors to the corresponding SF- ACE channels.
The inboard slat skew sensors consist of two dual channel resolver units with each unit mounted to the outboard rib of the driven tracks on each end of the inboard Slat panel. The primary coil of the resolvers on track #1 is excited by the SF-ACE slat channel 1. The
secondary coils of this resolver are electrically connected to the secondary coils of the resolver on track #3. The excitation coil of the resolver on track #3 (receiving resolver) is the skew sense output connected to the slat channel of SF-ACE 1. This interconnection forms one channel of skew sensing by providing an electrical signal to the SF-ACE 1 that is proportional to the differential motion between the two skew sensors on that panel. The remaining resolvers in both units are also electrically connected in the same manner and interfaced with the Slat channel SF-ACE 2 resulting in a dual channel architectecture for each inboard slat panel. Thus each of the two SF-ACEs independently implements skew sensing for each of the inboard Slat panels (left and right hand wings).
As the Slat is extended or retracted by the actuation system the actuator pinion gear simutaneously drives the Slat track attached to one end of the panel and also the spur gear attached to the skew sensor shaft. The difference in the instantaneous angular position of the two resolver shafts (and hence the slat panels) produces a proportional change in the sensed voltage of the reciever resolver. If the difference exceeds a predetermined threshold (either plus or minus), the SF-ACE will shutdown its channel of Slats and engage the PDU brakes.
SF-ACE 2 performs the same function on the same panels using the other channels of the resolvers. The dual channel approach allows for dispatch of the aircraft with a single slat channel active or a single skew sensor channel failure. Slat panel skew results in the Slat system being failed with “Slat Fail” annunciated.
Figure 91: Inboard Slat Skew Sensor Installation Slat Rack
Slat Pinion
Skew Sensor Gear/Timing Mark Inboard Skew Sensor-Slat Midboard/Outboard Disconnect (Skew) Sensor Description
The three midboard/outboard Slat panels utilize a reed switch located between panels 2-3 and 3-4 to provide skew detection and annunciation on each wing. The reed switch is mounted on one panel while the other panel contains a striker pin that provides adequate clearance to the switch under normal differential panel deflections. If the relative movement between panels exceeds the predetermined level, the striker pin will contact the reed switch and break a mechanical fuse that trips the switch.
The two reed switches on each wing are wired in series with the normally closed circuit connected to both SF-ACE slat channels. An open circuit in either wing will be detected by both SF-ACE channels and the Slat system will be shut down. A “Slat Fail” message will be annunciated.
Rigging of the slat midboard/outboard skew sensor is required to set the proper clearance between the skew sensor body and the striker pin during installation. The gap between the skew sensor arm and striker pin should be set using a feeler gauge, per aircraft documentation. The skew sensor mounting bolt provides an eccentric bushing to accommodate adjustment of the skew sensor gap. After adjustment of the skew sensor gap, the mounting bolt can
be tightened to maintain proper skew sensor position. Figure 92: Slat Outboard Skew Sensor Installation
POSITION SENSOR UNITS (PSUs) GENERAL DESCRIPTION The surface position sensor is called the Position Sensor Unit (PSU). The PSU provides surface position analog feedback to the SF-ACEs. Each PSU incorporates an anti-backlash reduction gear train for sensing, and two position resolvers. All hardware is internal to the PSU housings, which provide for mounting the PSU in the aircraft. Two connectors provide for attachment to the Slat/Flap electrical circuits.
The PSU for the Slats and the PSU for the Flaps are identical part numbers. The Flap PSU is mounted directly to the outboard end of flap actuator #4. The Slat PSU is mounted to a bracket on the outboard side of Slat rib #9. The Slat and Flap PSU uses an anti backlash gear train with 426.5:1 overall gear ratio (input shaft to resolver output). Anti-backlash features are employed to maintain a high degree of position accuracy.
The only load on the gear train is that from the two position resolvers and the effects of efficiency and tare in the gear train.
Two single channel brushless resolvers are mounted on the anti- backlash gear train housing. Each resolver has its own anti- backlash gear, and both resolvers mesh with the same output of the anti-backlash gear train. The resolvers are excited by their respective SF-ACE channel and provide an analog signal output to the SF-ACE for surface position feedback.
One of the two connectors on the PSU housing provides for the electrical connection of one position resolver to the right SF-ACE (to the SF-ACE Flap channel for Flaps PSU and to the SF-ACE Slat channel for the Slats PSU). The other connector provides for the connection of one position resolver to the left SF-ACE (to the SF- ACE Flap channel for Flaps PSU and to the SF-ACE Slat channel for the Slats PSU).