35d3-3-79-1_Operation.pdf

CHAPTER 4

OPERATION INSTRUCTIONS

4-1. THEORY OF OPERATION.

4-2. The aircraft engine lift trailer is made up of several major assemblies and systems: work platform assembly, winch clamp assembly, I-beam cradle, upper frame assem-bly, center section assembly, lower frame assembly, hydrau-lic system, electrical system, and weighing system. The following paragraphs give a brief description and function of those assemblies, their components, and systems (see Figure 4-1).

4-3. WORK PLATFORM ASSEMBLY.

4-4. Work platform assembly - the work platform assem-bly consists of ladder assemblies, ladder supports, jib crane, work platform assembly, storage boxes, lateral end work platform assemblies, powered work platform assembly, and longitudinal work platform assemblies.

4-5. Ladder assemblies and ladder supports - the lift trailer is equipped with two ladder assemblies. The ladder assem-blies are secured to the longitudinal work platform assem-blies with storage ladder brackets and ratcheted tie-downs.

Mounting locations are located on all four longitudinal work platforms allowing the ladder assemblies to be used on any of the four longitudinal work platforms. The ladder assem-blies must be stored on the forward (fwd) longitudinal platforms. The storage ladder brackets may be positioned out of the way by removing a quick release pin.

4-6. Jib crane - the jib crane can be mounted on the Left Hand (LH) forward longitudinal platform assembly and secured in place with pins. It is used for the removal and installation of the engine fan inlet cowl.

4-7. Work platform assembly - the work platform assem-blies are adjustable and are located on both of the forward longitudinal platforms. The height of the platform may be adjusted and is held in place with two pins. The work platform assemblies are to be used when performing main-tenance on the engine and must be in the stored position during roll transfer and raising and lowering of the cradle.

4-8. Storage box - two storage boxes are located on each of the aft longitudinal work platforms. One storage box houses the control pendants and the other storage box can house miscellaneous cables or tools.

4-9. Lateral end work platform assemblies - the lift trailer is equipped with two aft and two fwd lateral end work platform assemblies. The lateral end work platform assem-blies are designed to swing horizontally away from the lift trailer during roll transfer of the cradle-mounted engine and removal of the engine fan inlet cowl. Sliding lockbars are used to retain the platforms in the closed position.

4-10. Powered work platform assembly - the powered work platform assembly is hydraulically powered. The powered work platform assembly is located at the aft end of the lift trailer. The platform is lowered, to its lowest position, to allow for roll transfer of a cradle-mounted engine or the raised position to serve as a maintenance work area. There are two fold-out platforms on the powered work platform assembly which fold-out to provide a walking area during operations and maintenance. The powered work platform assembly is positioned using the control pendant.

The control pendant is equipped with a switch which allows the platform to be positioned in the UP or DOWN position.

This powered work platform assembly is only to be used as a maintenance work area, it will not raise or lower any personnel or equipment.

4-11. Longitudinal work platform assemblies - the four longitudinal work platform assemblies are attached to the upper frame of the lift trailer and fold up vertically for storage and transportation. The work platforms are secured in either the working position or the stowed position with pins. The work platforms are equipped with gas springs to reduce the effort required to position the platforms.

4-12. WINCH CLAMP ASSEMBLY.

4-13. Winch clamp assembly - the winch clamp assembly is mounted on either the fwd or aft lateral work platform assemblies. The winch clamp assembly is removed from its mounted position and installed on either the fwd or aft I-beam to facilitate roll transfer of support equipment between the lift trailer and the transport trailer. The winch clamp assembly provides pull and tension during the roll transfer procedure.

TO 35D3-3-79-1

4-1

Figure 4-1. Lift Trailer Major Assemblies and Systems

4-2 CHANGE 4

4-14. I-BEAM CRADLE.

4-15. I-beams - the four transfer I-beams are stowed in an upright position on the I-beam cradle. They are held in place on the longitudinal work platform assemblies with clamps which are removed by loosening knobs securing them in position. Pins secure the I-beams at the base. For prepara-tion for use, the clamps are removed first and the pins are removed releasing the I-beams which are then lowered to the horizontal position. The I-beams slide into position and are pinned securing them in the horizontal position ready for use and the four support jacks are lowered from the ends of the I-beams and adjusted to stabilize the I-beams prior to roll transfer procedures.

4-16. Support jacks - four support jacks are stowed on the fwd and aft ends of the I-beams and four support jacks are stowed on the frame assembly. The support jacks are held in position with quick release pins. The support jacks are used to stabilize the I-beams during transition of support equip-ment across the I-beams.

4-17. I-beam movement - I-beam movement provides alignment of a cradle or a cradle-mounted engine to the engine mount points. Roll, axial, and lateral movements have center position marks on the lift trailer. The vertical movement of the I-beams is controlled by the control pendant. To raise the I-beams, position the TRAILER FWD END and the TRAILER AFT END joysticks to the UP position. This will deploy the lift pads and begin vertical movement of the I-beams and work platforms. To lower the I-beams, position the TRAILER FWD END and TRAILER AFT END joysticks to the DOWN position. The vertical range of travel is approximately 54 inches I-beam height to a maximum of 148 inches I-beam height. There is one actuator which provides forward and aft movement of the positioning frame. This actuator is located in the centerline of the lift trailer.

4-18. Pitch - the pitch of the I-beams is controlled by the control pendants. Either the TRAILER FWD END or the TRAILER AFT END joysticks may be positioned UP or DOWN in order to obtain the desired I-beam pitch. The range of pitch motion is ± 5 degrees from the horizontal center or ± 10 degrees end to end.

4-19. Lateral movement - the lateral movement of the I-beams is controlled by two hydraulic motor driven screw actuators, one fwd and one aft. The lateral movement is controlled with the TRAILER FWD END and TRAILER AFT END joysticks on the control pendant. To move the I-beams laterally, simultaneously move the TRAILER FWD END and TRAILER AFT END joysticks to LH or RH position. The range of the lateral movement is ± 6 inches from the center line. There is a hydraulic pressure relief which is preset to limit the load on the I-beams to a maximum of 2,000 pounds to prevent overloading the engine pylon or the engine.

4-20. Yaw movement - the yaw movement of the I-beams is obtained by maneuvering the I-beam actuators using the control pendant. The yaw is controlled by operating the control pendant TRAILER FWD END joystick, TRAILER AFT END joystick, or both. The range of the yaw move-ment is ± 6 inches from the normal centerline of the engine.

There is a hydraulic pressure relief which is preset to limit the load of the I-beams to a maximum of 2,000 pounds to prevent overloading the engine pylon or the engine.

4-21. Axial movement - the axial movement of the I-beams is obtained by maneuvering the hydraulic motor driven screw actuator using the control pendant. The axial movement is controlled by operating the control pendant AXIAL/ROLL joystick to the FWD, AFT, Clockwise (CW) and Counter Clockwise (CCW) positions. The range of axial movement is ± 6 inches from the centerline until 57 to 148 inches above the ground is reached. There is a hydraulic pressure relief which is present to limit the load on the I-beams to a maximum of 2,000 pounds to prevent over-loading the engine pylon or the engine.

4-22. UPPER FRAME ASSEMBLY.

4-23. The upper frame assembly consists of four upper frame glide plates, actuators, and an upper frame.

4-24. Upper frame glide plates - the four upper frame glide plates provide the bearing interface between the upper frame assembly and the center section assembly rollers through the first half of the lift cycle. The upper frame glide plates are covered with a protective cover.

4-25. Actuators - there are three screw actuators attached to the positioning frame assembly. Two screw actuators are used to provide left and right lateral movement as well as yaw movement of the I-beams at both the fwd and aft ends.

The third screw actuator is attached to the positioning frame and I-beam cradle and provides forward and aft axial movement. There is also a hydraulically actuated cylinder assembly mounted to the positioning frame and I-beam cradle that provides for clockwise and counterclockwise roll movement of the I-beams. The powered work platform has two hydraulically actuated cylinder assemblies used specifi-cally for its operation.

4-26. Upper frame - the upper frame consists of longitu-

4-3 dinal beams, transverse beams, plates, gussets, and support ramp beams that are structurally welded together.

4-27. CENTER SECTION ASSEMBLY.

4-28. The center section assembly consists of the stabiliz-ing foot pad assemblies and transmission assembly.

c Ensure no foreign objects are under the four stabilizing foot pad assemblies. Failure to do so may result in damage to equipment.

4-29. Stabilizing foot pad assemblies - when being raised off of the ground the lift trailer is supported by four stabilizing foot pad assemblies located just inside the four wheels. The stabilizing foot pad assemblies are automati-cally deployed as vertical movement of the lift trailer begins. The stabilizing foot pad assemblies lift the lift trailer off the tires and fully support the lift trailer. The lift mechanism provides the vertical movement of the lift trailer. The lift mechanism consists of two electric motors, two chain drive transmissions and four lift screws. The lift mechanism is controlled by the control pendants TRAILER FWD END and TRAILER AFT END joysticks. The lift mechanism first deploys the stabilizing foot pad assemblies and then raises the upper platforms and rails. The center section is self-locking and does not require power when in the raised or lowered position. The lift mechanism has two speeds, slow and high. Slow speed travels 4 inches per minute and is used for close positioning of the engine to the pylon, or the cradle to the engine. High speed travels at 17 ± 3 inches per minute and is used for general raising and lowering.

4-30. Transmission assembly - the lift trailer center sec-tion contains two transmission assemblies that control movement of the lift mechanism. This movement is accom-plished by electric motors that drive the screws which extend and retract scissor-type lifting pylons. The transmis-sion assembly contains a series of chain driven sprockets, bearings and drive motor with a gear reduction that provides precision motion. In the event of a drive screw failure, the lifting mechanism is designed so that any three of the drive screws are capable of supporting the cradle mounted engine with a wind load on the wing of 6,000 pounds. This includes 1,200 pounds of live load consisting of maintenance per-sonnel and tools.

4-31. LOWER FRAME ASSEMBLY.

4-32. The lower frame assembly consists of the following:

running gear, steering, surge actuator, spindle and knuckle assembly, hub and drum assembly, rear axle steering, and winching and hoisting.

4-33. Running gear - the running gear provides the nec-essary components to move, steer and brake the lift trailer.

The running gear is divided into two major assemblies: the front axle assembly and rear axle assembly. The axle assemblies receive the weight of the lift trailer and distrib-utes it among the wheel and tire assemblies. The axle assemblies connect the running gear components through leaf springs to the frame assembly.

4-34. Steering - steering is provided on both ends of the lift trailer. Front axle steering uses a drawbar assembly containing a surge actuator, coil extension spring, shear pin, spring shackles and hinge pin. The drawbar may be re-moved from the lift trailer in order to minimize floor space.

The safety cable located on the surge actuator is attached to the towing vehicle and provides braking for the lift trailer in the event the drawbar is disconnected from the tow vehicle during transit. The shear pin is designed to shear when the lift trailer turn limit is exceeded during towing.

4-35. Surge actuator - the surge actuator is fully extended during normal towing. If the lift trailer begins to push the tow vehicle during deceleration, the momentum transmits a proportional compressive force to the surge actuator which, in turn, applies the lift trailer’s brakes. When backing, the lift trailer’s resistance to movement due to load, grade, or surface conditions often cause the activation of the surge actuator, resulting in momentary locking of the brakes.

Continued force by the tow vehicle causes diversion of fluid into the brake fluid reservoir allowing the master cylinder primary cup to move over the backup relief slot, dumping line pressure and releasing the brakes. The drawbar assem-bly attaches to the front center arm assembly. The front center arm assembly transfers the towing motion from the drawbar assembly to the lift trailer through the front axle assembly. The front center arm assembly also transmits turning/steering inputs to the spindle and knuckle assem-blies through the tie rod. The front center arm assembly has a bracket to connect the coil extension spring used on the drawbar assembly.

4-36. Spindle and knuckle assembly - two spindle and knuckle assemblies are attached to each axle assembly and provide the platform to attach the hand brake and cable assembly, brake assembly, hub and drum assembly and the wheel and tire assembly. The spindle and knuckle assembly receives inputs from the tie rods and makes the correspond-ing steering/turning correction. The lift trailer’s brakes are automatically activated by the surge actuator during towing operation or by the manually operated hand brake located at each wheel position.

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4-37. Hub and drum assembly - the hub and drum assemblies are located at each wheel position, and contain an inner and outer bearing to allow for lift trailer movement.

The hub and drum also contains the drum used in braking operation. The wheel and tire assembly enables the lift trailer to move, turn and stop. The tires are pneumatic and are suitable for both improved and unimproved surfaces.

4-38. Rear axle steering - the rear axle steering uses a rear steering bar that attaches to the rear center arm assembly.

The rear steering bar is stowed on the lift trailer frame assembly. Rear steering is used only for manual steering to satisfy close position requirements. Rear steering is disen-gaged during towing operations by pinning the locking strut assembly to the rear axle assembly. The end of the frame has a pintle hook installed to connect other support equipment or lift trailers for towing purposes. The rear axle compo-nents are similar in design and operation to the front axle components.

4-39. Winching and hoisting - two winching rings are provided on each end of the frame assembly for loading the lift trailer on a transport vehicle. The frame also has four permanently mounted hoisting rings that allow for move-ment by sling.

4-40. HYDRAULIC SYSTEM.

4-41. Hydraulic system - the hydraulic system contains a hydraulic system control unit, consisting of a motor, motor/pump adapter, pump, relief valve, reservoir, mani-fold, filters, solenoid control valves, and pressure reducer valves (see Figure 4-2).

4-42. Motor - the motor drives the pump through a coupler mounted within the motor/pump adapter.

4-43. Pump - the pump is mounted inside the reservoir and pulls fluid through a filter, that protects the pump from contaminates.

4-44. Relief valve - the relief valve is located on the manifold assembly and is preset at 2000 psi. This limits the maximum load on the I-beams thus protecting the engine pylon and engine from overload by the hydraulic system.

4-45. Reservoir and filter - The reservoir is vented to the atmosphere and contains a sight gauge mounted on the side of the tank to check fluid level. The filter assembly contains a side mounted rotary dial indicator with a bypass and cleanliness label.

4-46. Solenoid control valves - the solenoid control valves are double solenoid, three position, spring centered valves.

The manifold provides the interface for the solenoid control valves and pressure control valves with the tubing assem-blies.

4-47. Hydraulic cylinders and actuators - the hydraulic cylinders and actuators provide movement and positioning of the lift trailer. There are two lateral actuators that attach the upper frame assembly to the positioning frame assem-bly. The upper frame also contains a cylinder at one end attached to the I-beam cradle providing axial/roll. Another actuator is attached at the aft end to the upper frame and positioning frame assemblies providing forward and aft movement of the I-beam cradle. Two cylinders are attached to the powered platform and the positioning frame assembly providing it with up and down positions.

4-48. ELECTRICAL SYSTEM.

4-49. Electrical system - the electrical system consists of electrical power input to the electrical control unit contain-ing electro magnetic interference filtering and associated circuitry to control the forward and aft motors with associ-ated potentiometers, hydraulic electrical power, load cells with load cell amplifier and a main and remote pendant with pendant and auxiliary pendant junction box (see Figure 4-3).

4-50. Overload alarm - the lift trailer is equipped with an overload alarm which is located on the outside of the control pendant control storage box. When the preset load limit is exceeded, the overload alarm will sound. The operator will lose control at the control pendant, and the trailer will back down until the load is releived. To stop the trailer from backing down, the operator must press the EMERGENCY STOP button. To regain operator control, the RESET button must be pressed. When the RESET button is pressed and an overload condition still exists, the trailer will continue to back down until the load is releived. The RESET button must be pressed again for the operator to regain control.

4-51. The lift trailer is capable of being operated from any of the following power sources.

NOTE

Ensure that power sources are capable of supplying

10.0 KW.

1. Ground power, 208 VAC, 3 phase, 50/60 HZ.

2. Aircraft auxiliary power unit, 208 VAC, 3 phase, 400 HZ.

4-5

Figure 4-2. Hydraulic System Block Diagram

4-6 CHANGE 4

Figure 4-3. Electrical System Block Diagram

CHANGE 4 4-7

4-52. The following functions are controlled by compo-nents located inside the electrical control unit, load cell amplifier, and main or remote pendant controls. Refer to Chapter 6.

4-53. Heaters and thermal switches - the system will not operate unless the enclosure temperature is 45 degrees Fahrenheit (F) or greater. The heaters will turn on if the unit temperature drops below 45 degrees F and the heaters will turn off when the unit temperature exceeds 57 degrees F.

4-54. Relay board - the relay board performs three func-tions: It incorporates high current drivers for the hydraulic solenoid valves. The drivers receive a command from the Central Processing Unit (CPU) output. This signal activates the relay board input Light Emitting Diode (LED) associ-ated with that switch. The output of the relay board is then activated and it will provide power to the associated solenoid coil. The system also has a main power contactor which supplies power to the Semiconductor Controlled Rectifier (SCR) and hence to the motors (hydraulic and two lift motors). The contactor is activated by the CPU when a RESET push button is pressed on the control pendant, and deactivated when an EMERGENCY STOP push button is pressed. The emergency stop circuit has redundant paths for safety reasons. The emergency stop signal is passed through the CPU, as well as a redundant signal going directly to the emergency stop circuit located on the relay board. The circuit will shut off the contactor if either the CPU turns it off, or if the redundant circuit directly turns off the emer-gency stop circuit latch on the relay board. The CPU monitors the emergency stop circuit latch on the relay board and circuit output to prevent overload conditions. Flyback diodes are also provided across all inductive loads that are driven directly by the CPU. Two upper and two lower limit switches send a signal the relay board to shutdown the motors if the minimum and maximum software limits are exceeded.

4-55. Circuit breaker - the system has an ON/OFF circuit breaker located at the power in junction box.

4-56. Reversing relays - the two lift axes have current reversing relays in the armature circuit. These relays change states only when the current is zero, (i.e., the SCR control-ler), is Off, which maximizes the relay life.

4-57. Motor-solenoid valves - the wiring for the lift motors includes the armature compound field and thermal overload switch wiring. The hydraulic motor has armature wiring only. There are five four-way solenoid valves with ten coils total.

4-58. Modicon (CPU) - the Modicon CPU controls all logic of the system. There are seven channels of analog input. Two channels are for lift axes position feedback and four channels are for load cell weight data. There are digital inputs from the control pendant switches and the motor thermal switches. There are digital outputs to the SCR controller, control pendant display, motors, valves and relays. A seventh channel of analog input is used to verify operating voltage. An additional digital input is used for two positioning sensors. The Modicon CPU is equipped with a replaceable battery which maintains the operating system logic program in the internal RAM when power is turned off to the lift trailer. If the battery charge becomes low, a LED (bat low) will illuminate on the CPU front panel. The battery must be changed within 14 days or the battery will become completely disharged. If this occurs, the RAM memory will be lost or corrupted. The logic program stored on the Electrically Erasable Programmable Read Only Memory (EEPROM) must be uploaded to the RAM memory after the battery is replaced. The upper and lower limits must also be reset. The EEPROM card is installed into auxiliary memory socket on the CPU front panel.

4-59. Modicon CPU interfaces with the control pendant CCA, SCR motor controller board, and load cell amplifier board.

4-60. Control pendant - the main and remote control pendants are identical. Only one of the two remote control pendant jacks can be used at one time. The Liquid Crystal Display (LCD) displays total engine weight and the force of the wing. The LED array displays the center on the force. It represents the result of the force on the four load cells. Error codes are displayed on the control pendant. “E0001” thru “E0021” are operator related codes and “E0500” thru “E0525” are maintainer error codes. They are read by the CPU in six banks of four switch contacts. The control pendent switches are multiplexed.

4-61. SCR motor controller board - there are three SCR motor controller boards that supply power for the three VDC motors. The two lift SCR boards supply field excita-tion for running the motors at two speeds. The third SCR board supplies armature power for the hydraulic pump motor.

4-62. Load cell amplifier board - the load cell amplifier board multiplies the minute signals from the load cells by a factor of 100, allowing the CPU analog inputs to read the force or weight on the system. The amplifier also supplies 5 volts of excitation to all four load cells. The amplifier

4-8 contains four channels, one for each load cell. Four multi-turn potentiometers allow the channels to be zeroed inde-pendently.

4-63. WEIGHING SYSTEM.

4-64. Weighing system - the weighing system is used for measuring total load on the I-beams and platforms and can also be adjusted to measure loads applied to the aircraft engine pylon. The weight of the entire positioning frame assembly, including platforms and I-beams, has been zeroed out permanently and will never appear on the pendant display. The “absolute” displayed load on both control pendants will normally be some combined sum of cradle, engine, and personnel on the platforms.

4-65. LCD display - The two control pendants are equipped with LED display indicators which show the operator where the center of the applied load is during all stages of operation on the lift trailer. The indicator on the LCD display should show the load in the center, or very close to it, at all times during operations of the lift trailer.

The operator must be aware of the load location on the lift trailer at all times. If the LED display indicates the red dot in any of the outer perimeter locations the operator must stop operation of the lift trailer immediately and correct the loading situation. If the LED display is in one of the outer perimeter locations, the lift trailer is experiencing an uneven load condition which may result in damage to equipment, aircraft, or personnel.

4-66. LED display - When electrical power is applied to power supply PS1, a diagnostic check of internal circuitry, pendant cables, and machine wiring associated with the pendants is scanned for errors and faults. The red ″dot″ will scan with every LED activated one at a time from left to right across the LCD display. A numerical number will be displayed after approximately 20 seconds indicating the check is complete and no faults have been detected. The LED display on the control pendant also indicates, with a red ″dot″, where the center of gravity of the entire load on the lift trailer is located at all times. The red ″dot″ will move continuously within the LED display indicating load move-ment. The LED display is very sensitive therefore the red ″dot″ will move continuously within the LED display, for example, when personnel move about on the lift trailer the red ″dot″ will show that movement within the LED display.

Each ″dot″ represents approximately 500 torque of load.

During all operations of the lift trailer the red ″dot″ should be continuously monitored by the operator of the control pendant, the red ″dot″ should always be visible near the center of the LED display during all operations. If the LED display indicates the red ″dot″ in the outer perimeter locations of the display, the operator should stop all opera-tions and correct the loading conditions before continuing with any further operation. If the LED display indicates the red ″dot″ in one of the outer perimeter locations, the lift trailer will be experiencing an uneven loading condition. If the load is not corrected damage may result to the equip-ment, aircraft, or personnel. The top of the LED display indicates the FWD end of the lift trailer and the bottom of the LED display indicates the AFT end of the lift trailer.

Consequently, as viewed, LEFT is shown as the LEFT side of the lift trailer and RIGHT is shown as the RIGHT side of the lift trailer.

4-67. Load cell potentiometers and FWD/AFT potentiom-eters - There are four load cells on the lift trailer that sense the amount of load being applied to the lift trailer during operation. The combination of the absolute amounts of each load cell can be viewed in the LCD display. The amount visible in the LCD display is the value of the entire load that is being applied to the lift trailer. The load cells may be monitored for accuracy by entering the Built-In Test (BIT) mode. These load cell readings are depicted by a ″t″ in the left digit of the LCD display followed by 0001, 0002, 0003, or 0004. After releasing the BUILT IN TEST button on the control pendant the LCD display will read the mathematical number 4300 ± 50. This number does not indicate pounds (weight), it is a mathematical, calculated number. While in BIT operation mode, eight additional channels are available for use: ″t0005″ thru ″t0014″. Channels ″t0005″, ″t0006″, ″t0013″, and ″t0014″ are the only programmable BIT functions. Programming of these additional channels must only be used by maintainers in the event of a complete tear-down of the lift trailer. Channel ″t0005″ is used to program the forward limit for both the lower and the upper values and ″t0006″ is used to program the aft limit for both the lower and the upper values. Channels ″t0007″ thru ″t0012″ are read only BIT functions. Channel ″t0007″ is used to verify forward lower limit adjustments made in channel ″t0005″. Channel ″t0008″ is used to verify aft lower limit adjustments made in channel ″t0006″. Channel ″t0009″ is used to verify forward upper limit adjustments made in channel ″t0005″. Channel ″t0010″ is used to verify aft upper limit adjustments made in channel ″t0006″. The limits of travel should be 54 inches rail height and 8 to 10 inches from the ground for position of pads for the lower value. The upper value is 148 inches and the measurement should be taken from the ground to the top of the I-beam rail. Channel ″t0011″ is a self test to verify pendant switch operation. Channel ″t0012″ is a self test of pendant cables and pendant displays. No other action can be performed until this test is complete. Channels ″t0013″ and ″t0014″ are adjustable and used to display the setting of forward and aft off center limits respectively.

4-68. Load limiting - the weighing system is equipped with an adjustable load limiting function. The support

4-9 equipment, personnel and component weight must be ac-counted for when determining the preload setting. When the indicated load reaches a preset point, the lift drive motors automatically stop, an alarm is sounded and the direction of the motors is reversed until the excess load is relieved. The RESET button on the control pendant is pressed to continue operation of the lift trailer. The load limiting alarm is reset by pressing the RESET button on the control pendant. The load limit is based on the absolute load reading, not the pylon force. The load limit preset capabilities range from 15,000 to 20,000 pounds in increments of 500 pounds. The set point is accessed by depressing the LOAD LIMIT button on the control pendant. This display will increment in 500 pound steps when the LOAD LIMIT button is depressed and held. When setting the load limit, the set point scrolls to 20,000 pounds and then scrolls to 20,000 pounds and then scrolls to 15,000 pounds. When the appropriate value is reached, release the LOAD LIMIT button. After a few seconds, the weighing display will return to its regular function. The maximum upwards load under any condition is 20,000 pounds. The load limiting is based on the absolute weight.

4-69. Alarm functions - the lift trailer is equipped with an alarm system which is activated during several different scenarios. The alarm is equipped with four different sounds which are activated when the lift trailer enters any of the following conditions. Three of the sounds are operator alarms and one is a maintenance alarm, in maintenance box.

When the lift trailer reaches the 73 inch rail height all of the alarms will be armed. Condition one will occur when the control pendant LED display is indicating that the center of gravity has gone out of bounds. The LED display will indicate a red ″dot″ in the outer perimeter location of the display. An alarm (slow tone) will sound and error code ″E0002″ will display indicating that an 1800 pounds load differential has been reached. If the operator does not correct the problem and continues to go in a negative direction, a second alarm (rapid intermittent tone) will sound and error code ″E0003″ will be displayed indicating a 2500 pounds load differential and the trailer will stop. The lift trailer will automatically stop at this time, the operator must press RESET on the control pendant and redo the complete procedure. Condition two occurs when one of the four load cells reads a negative load differential of the other three of 415 pounds and error code ″E0004″ is displayed. If load limit is exceeded an alarm (steady tone) will be heard by the operator and error code ″E0001″ will be displayed.

The lift trailer will back itself down and correct the load back to the acceptable load rating. The operator will not be able to take any action at this time. The emergency stop button will stop the trailer and disable the pendant until the RESET button is pressed. The trailer will correct itself back to the original load limit, the operator must correct the situation adjusting the load or the same scenario will continue to occur sounding the alarm. If the operator has reached this point he needs to be aware that the trailer is overloaded and the situation must be corrected before continuing on with the procedure or damage may occur to the equipment, personnel, and/or the aircraft.

4-70. ALARM FUNCTION.

4-71. The following paragraph describes the function of the alarm system and maintenance cycle count for PT90-F- 507 configuration.

4-72. Alarm functions - the lift trailer is equipped with an alarm system which is activated during several different scenarios. The alarm is equipped with three different sounds which are activated when the lift trailer enters any of the following conditions. Two of the sounds are operator alarms and one is a maintenance alarm, in the maintenance box.

When the lift trailer reaches the 73 inch rail height all of the alarms will be armed. Condition one will occur when the control pendant LED display is indicating that the center of gravity has gone out of bounds. The LED display will indicate a red “dot’’ in the outer perimeter location of the display. An error code “E0002’’will display indicating that a 2200 pounds load differential has been reached. If the operator does not correct the problem and continues to go in a negative direction, the alarm (rapid intermittent tone) will sound and error code “E0003’’ will be displayed indicating a 2820 pounds load differential and the trailer will stop. The lift trailer will automatically stop at this time, the operator must press RESET on the control pendant and redo the complete procedure. Condition two occurs when one of the four load cells reads a negative load differential of the other three of 415 pounds and error code “E0004’’ is displayed. If load limit is exceeded an alarm (steady tone) will be heard by the operator and error code “E0001’’ will be displayed.

The lift trailer will back itself down and correct the load back to the acceptable load rating. The operator will not be able to take any action at this time. The emergency stop button will stop the trailer and disable the pendant until the RESET button is pressed. The trailer will correct itself back to the original load limit. The operator must correct the situation adjusting the load or the same scenario will continue to occur sounding the alarm. If the operator has reached this point he needs to be aware that the trailer is overloaded and the situation must be corrected before continuing on with the procedure or damage may occur to the equipment, personnel, and/or the aircraft.

4-73. FUNCTION.

4-74. The following paragraphs describes the function and operation of the lift trailer as a unit. An illustration showing the major assemblies, systems, and components of the lift trailer are also provided.

4-10

4-75. The lift trailer (see Figure 4-1) functions as a lifting device for support equipment used during maintenance, removal, and installation of the aircraft engines. The lift trailer consists of a work platform assembly, winch clamp assembly, I-beam cradle, upper frame assembly, center section assembly, lower frame assembly, hydraulic system, electrical system and weighing system. The lower frame provides for the interface attachment of the running gear.

The running gear provides both front and rear axle steering.

The center section assembly is attached to the lower frame and is equipped with a lift mechanism. The lift mechanism has two electric motors that drive two transmissions that power four lift screws. The center section has a scissor linkage on the aft end which extends on both sides of the lift trailer to the horizontal guide slots on the lower frame assembly. The camroller bearings which roll within the slots serve to stabilize the lift mechanisms. The lift screws actuate the scissors placing four stabilizing foot pad assem-blies onto the ground lifting the tires and supporting the lift trailer. The lower frame also contains four support ramps which are part of the lift mechanism through the first half of the lift cycle. The center section interfaces with the upper frame assembly and is attached to the upper frame assembly with pins and retaining rings. The upper frame contains two lateral actuators on one side which control lateral and yaw motions of the positioning frame and an axial actuator at one end. When the lift trailer is lowered from 56 inches to 54 inches the upper and lower centering position sensors must be aligned by the operator before the trailer can be lowered. The FWD and AFT sensors will lock indepen-dently in place when aligned. No error messages are displayed when the sensors are aligned and the trailer can be completely lowered. The bearing means allows the position-ing frame to move relative to the upper frame. It consists of a horizontal pad at each of the four corners of the upper frame on which ride sliding bearings which are mounted in the positioning frame. The positioning frame assembly has two forward and two aft I-beams that provide attachment from either end to the lift trailer for roll transfer. Four longitudinal platforms, forward and aft lateral platforms, two adjustable workstands, and a powered platform provide the working area to perform maintenance when working on the aircraft engine. Two access ladders provide access to the upper frame assembly.

4-76. Electrical system power on sequence begins with the main power circuit breaker located on the Power In Junction Box A4. When circuit breaker CB1 is closed, three phase power is applied through EMI Filter A2 to contactor A1K1, then applied to the control circuitry. Phase A provides power to heaters within the control box and AC power for the 24 V Power Supply PS1. This 24 VDC provides the main power for the lift trailer internal electron-ics. Phase A also provides power to the aft lift motor when contactor A1K1 is activated. Phase B provides power to the forward lift motor and to the hydraulic pump motor located in the hydraulic box. Internal temperature of the control system box is maintained 45° to 55° F by three thermal switches, A1S1, A1S2, and A1S3. When three phase power is applied and the temperature inside the control box is below 45° F, thermal switch A1S2 is open and power is not applied to 24 V Power Supply PS1, the internal control and logic circuitry of the trailer is off. Phase A power is applied to all heater coils to bring internal temperature up to an acceptable range inside the control box. When the tempera-ture reaches 45° F thermal switch A1S2 contacts close and Phase A power is applied to 24 V Power Supply PS1 which activates relay A1K2 taking power off heater coils HR1, HR2, HR6A, and HR7B by opening relay A1XK2 contacts between pins 1 and 9. The remaining heaters stay on until temperature reaches 55° F and thermal switch A1S1 re-moves power. Power to 24 V Power Supply PS1 will stay on until temperature within the control box drops below 45° F.

Thermal switch A1S3 is in series with relay A1XK2 and provides redundancy to remove power from main heater coils when temperature is greater than 55° F in case relay A1XK2 fails. When 24 VDC is applied to the internal circuitry, the CPU supplies a 24 VDC signal through Discrete Output Module (DOM) A1A23A3-16 to relay CCA A1A1-34. relay CCA A1A1 then generates a different 24 VDC signal to contactor A1K1 from CCAA1A1-33 (99).

Three phase power is applied to the rest of the circuitry when contactor A1K1 is energized. The contactor coil signal

(99) is fed back to the CPU via Discrete Input Module (DIM) A1A23A2-16 alerting the CPU that the contactor coil energizing signal is applied. If all the conditions are met, the lift trailer is powered up.

4-77. Operation of the lift trailer is controlled by either the main or remoter pendant controller. When the TRAILER FORWARD END switch is positioned to UP, a signal in form of a digital word (switch data), is sent to the CPU via the Pendant Junction Box, A7. Switch data output pins for all pendants are pins L, M, N, and P. Inside the Pendant Junction Box, the signal for the main pendant is routed through TB1 pins 9, 10, 11, and 12 while the signal for the remote pendant is TB1 pins 13, 14, 15, and 16. Switch data signals from the Auxiliary Pendant Junction Box A3 are parallel with remote pendant signals from the Primary Pendant Junction Box A7 as signals (75, 76, 77, 78, Figure 6-5) at the intrinsic barrier on pins A1A7-4, A1A6-4, A1A5-4, and A1A4-4. Switch data signals (71), (72), (73), and (74), from the main pendant are at the intrinsic barrier on pins A1A11-4, A1A10-4, A1A9-4, and A1A8-4. Inside of the barrier in the Electrical Control Unit, A1, the signal number are changed to 111 through 114 for the main and 115 through 118 for the other two pendants. All the switch signals are routed to A1A23A2 Discrete Input Module

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(DIM) on input pins 3 through 10, respectively. DIM’s convert 24 VDC discretes into digital inputs for the CPU which then interprets this data and sends appropriate com-mands to the lift trailer electronics to perform specific function. Information displayed on the pendant LED and LCD displays is controlled by the Discrete Output Module (DOM) A1A23A4, pins 3 through 10. The DOM sends out 24 VDC pulse signals on CPU command. These signals consist of four data lines-pin 3 (103, Figure 6-2, Sheet 2), pin 4 (104), pin 5 (105), and pin 6 (106), three address lines-pin 7 (107), pin 8 (108), pin 9 (109), and a strobe command-pin 10 (110). These signals are routed to intrinsic barrier slots A1A11-1, A1A10-1, A1A9-1, A1A8-1, A1A7-1, A1A6-1, A1A5-1, and A1A4-1, respectively. From output pins 3 of the barrier, the signals are renumbered as (63), (64), (65), (66), (67), (68), (69), and (70) respectively.

These signals go directly to the Auxiliary Junction Box A1A3 and TB1 pin 1 through pin 8 on the Primary Pendant Control Box A7. These output signals go to all three pendants, in parallel, on pendant pins C, D, E, F, G, H, J, and K. When commanded to raise the lift trailer forward section by the CPU from a pendant, the CPU sends a command from DOM A1A23A3-17 (94) to relay CCA A1A1-6. A signal is then generated out pin 5 (100) to the SCR Forward Motor Controller A1A22, pin 15. This signal is called the Forward Lift SCR Control Signal. Signals out of Forward Motor Controller A1A22 are mostly generated within the card itself. 220 VAC is applied to A1A22 pins 7 and 8 and a regulated ±10 VDC and a ±5 VDC is generated for use within the assembly. Also, lift motor 200 VDC field voltages (220 VAC, full wave rectified), signals (14, Sheet

1) and (15) are generated and sent to the lift motor from A1A22, pin 3 and 4. The 200 VDC SCR output voltages

(18) and (19) are applied to the Forward Lift Motor circuitry from A1A22 pins 5 and 6. To reverse lift motor direction, the CPU applies a 24 VDC signal from DOM A1A23A3 pin 20 to relay A1K3 so the current through the forward lift motor armature windings is reversed. The DOM signal is also routed to relay CCA A1A1 pin 10 which is used to control logic of the board. When the lift trailer is raised to its upper limit, Limit Switch S2 closes and applies ground to pin 4 of barrier component A1A12 pin 4 (133). The output of barrier A1A12 pin 2 (132, Sheet 6) goes to relay CCA A1A1, pin 15 turning off A1A22 SCR 200 VDC output on pins 5 and 6 thus removing current from the lift motor armature. Lift motor speed is changed by a pulsed 24 VDC signal from DOM A1A23A4, pin 14 (102, Figure 6-2, Sheet

2) routed simultaneously to both forward and aft motor controllers (A1A22, A1A21) on pin 9. The signal is con-trolled by the SPEED control switch (S52) on the pendants.

The forward lift motor armature is coupled to Forward Lift Position Potentiometer R1, sensing the height of the trailer.

The wiper of the pot is fed into Analog Input Module, A1A24A2, pin 3, (46) alerting the CPU of the exact trailer height. This is called the SOFT LIMIT and will stop the trailer from being raised or lowered beyond a preset limit.

When the pendant toggle switch for the forward end is placed in the DOWN position, DOM A1A23A3, pin 20 (97) applies a 24 VDC signal to phase reversal relay A1K3 coil, pin 2, reversing the polarity of the 200 VDC to the Forward Lift Motor armature, lowering the forward end of the trailer.

When the toggle switch is positioned UP all functions are the same except when the forward end reaches the down limit, FWD DOWN limit switch S1 is activated stopping the forward lift motor B1. Aft lift motor B2 is controlled identical to forward lift motor except for a change of pin assignments

4-78. When a command is received by the CPU to apply hydraulic pressure, DOM A1A23A3, pin 19 (96) applies a 24 VDC control signal to the Hydraulic Motor Controller A1A20 pin 15. The motor controller then applies a 200 VDC out pins 5 (22, Sheet 1) and 6 (23), through A1TB1 pins 16 and 17, to the Hydraulic Box A6 terminal block TB1, pins 2 and 3. The last two pins are connected to the hydraulic motor producing hydraulic pressure so the hy-draulic actuators can be activated. When the TRAILER FORWARD END toggle switch is positioned left, the CPU applies a 24 VDC signal from DOM A1A23A3, pin 5 (85, Sheet 2) to relay CCA A1A1 pin 19. Upon receipt of this signal, a 24 VDC drive signal is applied to actuator L1 via A1A1 pin 46 (55) to A6TB1-11 moving rails to the left.

When the rails move aft left to the limit, limit switch S8 opens and alerts the CPU to stop movement. 24 VDC (31) feeds through Intrinsic Barrier A1A31 pin 2 (input) and pin 4 (output) (156, Sheet 6) through normally closed limit switch S8 through the Intrinsic Barrier A1A29 pins 3 (159) and 1 (164) to Discrete Input Module A1A24A3 pin 9. This signal tells the CPU the rails are within normal operating range and when the left aft lateral limit is reached, the line opens and the CPU stops further movement. When the TRAILER FORWARD END toggle switch is positioned to the right, 24 VDC is applied to DOM A1A23A3 pin 6 (86, Sheet 2) to relay CCA A1A1 pin 20. A 24 VDC drive signal is applied to actuator L2 via A1A1 pin 47 (56) to A6TB1 pin 12 moving rails to the right. When right lateral movement limit is reached, limit switch S6 opens and the CPU stops rail movement the same as left limit switch S5. The TRAILER AFT END toggle switch controls actuators (L4, left) and (L3, right) in a similar method. Left and right limit switches, S7 and S8, for the aft end of the trailer work identical to the forward end except for a change of pin assignments. When the AXIAL/ROLL toggle switch is positioned to FWD, DOM A1A23A3 pin 10 (90) applies 24 VDC signal to relay CCA A1A1 pin 24 and out pin 51 (60) to A1TB1 pin 16 applying a 24 VDC drive signal to actuator L10 moving the rails forward along the longitudinal axis.

When the AXIAL/ROLL toggle switch is positioned to

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AFT, DOM A1A23A3 pin 9 (89) applies 24 VDC signal to relay CCA A1A1 pin 23 and out pin 50 (59) to A6TB1 pin 15 applying a 24 VDC drive signal to actuator L9 moving the rails aft along the longitudinal axis. The CPU is alerted when the aft limit switch S9 and aft left and right limit switches, S7 and S8, are opened. There is not a forward limit switch installed. When the AXIAL/ROLL toggle switch is positioned to CW, DOM A1A23A3 pin 3 (83) applies 24 VDC signal to relay CCA A1A1 pin 17 and out pin 44 (53) to A6TB1 pin 9 applying a 24 VDC drive signal to actuator L5 moving the rails clockwise. When the AXIAL/ROLL toggle switch is positioned to CCW, DOM A1A23A3 pin 4 (84) applies 24 VDC signal to relay CCA A1A1 pin 18 and out pin 45 (54) to A6TB1 pin 10 applying a 24 VDC drive signal to actuator L6 moving the rails counterclockwise. When the PLATFORM UP pushbutton is pressed, DOM A1A23A3 pin 15 (92) applies 24 VDC signal to relay CCAA1A1 pin 26 and out pin 53 (62) to A6TB1 pin 18 applying a 24 VDC drive signal to actuator L8 moving the platform up. When the PLATFORM DOWN pushbutton is pressed, DOM A1A23A3 pin 14 (91) applies 24 VDC signal to relay CCA A1A1 pin 25 and out pin 52 (61) to A6TB1 pin 17 applying a 24 VDC drive signal to actuator L7 moving the platform down. The forward and aft position sensors, A8S1 and A9S2, ensure the rails are centered before they can be safely lowered without damaging the lift trailer. Power supply PS1 provides 24 VDC from A1TB1 pin 6 (31) through A1A18 and A1A19 to A1A17 pin 1 to A1A26 pin 1 to forward A8 and aft A9 position sensors TB1 pin 1. When rails are not centered, the position sensors are open and 20 VDC is applied to the DIM A1A24A3 pins 4 and 3, respectively. This voltage comes from relay CCA A1A1 pins 2 and 3 and goes through the intrinsic barrier to position sensors TB1 pin 2 of A8 and A9. The CPU determines the rails are in normal operating position but not centered and cannot be lowered. When the rails are cen-tered, permanent magnets on the rails come in proximity with forward and aft position sensor S1 and S2.