SD3-60 AIRCRAFT MAINTENANCE MANUAL & RETRACTION - DESCRIPTION & OPERATION

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Clara Hamilton
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1 AMM EXTENSION & RETRACTION - DESCRIPTION & OPERATION 1. Description A. General The landing gear is extended and retracted by the operation of a hydraulic actuator at each of the main and nose gear units. The nose gear bay doors are mechanically linked to the gear and thus open and close automatically during extension and retraction. The gear is secured at extremes of travel by uplocks and downlocks, which operationally, are mechanically engaged and hydraulically released. The uplocks are internal features of the actuators and the downlocks are incorporated on the respective gear shock absorbers. Hydraulic power for normal operation of the landing gear is provided by main system pressure. A reserve pressure supply for emergency lowering is stored in an accumulator which is charged via an integral non-return valve when the main system is 'on load'. Position indication of the respective gear units is provided by warning lights, together with aural warning of conditions under which the gear should be selected down but is retracted. Refer to , pb1. B. Electrics Electrical power for gear control is taken from the 28V dc right essential services busbar via 5 amp C/B No. 188 on distribution panel 2D. C. Controls A selector lever unit, mounted on panel 1P provides for normal operation of the landing gear. The lever moves in a slot between gated UP and DOWN positions and is employed to energise the appropriate of two solenoids mounted on the landing gear selector valve. The valve will then direct main system pressure into the actuator up or down lines according to selection and will vent the unpressurised lines to the reservoir. The control lever assembly incorporates an inhibiting solenoid, which when de-energised by weight switches mounted at the main gear beam pivot points (left and right) will prevent an UP selection being made when the aircraft is resting on its wheels. NOTE: The inhibiting solenoid can be mechanically overridden by the selector lever to permit 'on ground' retraction in operational circumstances where it is vital to reduce ground speed as quickly as possible. Page 1

2 SD3-60 AIRCRAFT MAINTENANCE MANUAL Landing Gear - Schematic Figure 1 Page 2

3 A LANDING GEAR DOWN - EMERGENCY control lever on the flight compartment roof console is used for emergency lowering of the landing gear. The lever is cable connected to (a) the emergency accumulator release lever and (b) to an operating lever on a three-way manual selector. The manual selector is employed to by-pass the electrically-operated selector when returning fluid from the up lines to the reservoir during emergency extension. NOTE: By-passing of the electrically-operated selector caters for the contingency whereby a normal DOWN selection was unsuccessful as a result of the gear selector failing to changeover. D. Hydraulic details 2. Operation The landing gear normal and emergency down lines are respectively routed from the landing gear selector and the emergency accumulator to opposing sides of a shuttle valve on each actuator. The up lines are taken through the three-way manual selector to the up connection on each actuator. A restrictor, fitted downstream of each branch line to the respective gear downlocks ensures consistent release of the downlocks before actuator movement takes place when an UP selection is made. Each of the main gear up lines additionally incorporates a downlock sequencing unit (fitted upstream of the associated downlock). The unit is employed to restrict return flow when a DOWN selection is made, thus ensuring that the downlock remains hydraulically retracted until full down movement is achieved. NOTE: The units afford full flow (via bypass passages fitted with check valves) when an UP selection is made. A nose downlock sequencing unit is also fitted in the nose gear up line (upstream of the downlock), the principle of operation being identical to that of the main downlock sequencing units. On aircraft Ser. Nos SH3651 and up those prior Ser. Nos on which Serv. Bull. SD is incorporated, a restrictor in the landing gear down lines vents main system pressure to the reservoir approximately 15 seconds after both engines are shutdown (or when a power rig is stopped during servicing). Refer to Figure 1. A. Retraction (normal) With the landing gear down and locked, wheels clear of ground (weight switches released) and electrical and hydraulic power available, movement of the gear selector switch from DOWN to UP will respectively energise and de-energise the landing gear selector valves 'up' and 'down' solenoids. The valve ports will then changeover to admit main system pressure to the gear up lines (via the three-way selector). Page 3

4 SD3-60 AIRCRAFT MAINTENANCE MANUAL With the up lines pressurised, the downlocks will then retract against their engagement springs and when released, pressure acting on the respective annular and full areas of the nose and main actuators will cause the landing gear to retract. NOTE: Fluid in the 'down' side of each actuator will be vented to reservoir via the electricallyoperated selector. When full travel is reached, the uplocks within each actuator engage to lock the gear in the retracted position. B. Retraction (emergency) With the wheels on ground (weight switches depressed) and selector lever inhibiting solenoid effective, the lever lock may be overridden in operational circumstances where it is vital to reduce ground speed as quickly as possible. This entails turning the selector lever knob clockwise through approximately 60 deg. before moving to the UP position. NOTE: The sequence of oprations thereafter is identical to those for normal retraction. C. Extension (normal) With electrical and hydraulic power available and the landing gear up and locked, movement of the selector switch from UP to DOWN will respectively energise and de-energise the landing gear selector valves 'down' and 'up' solenoids. The valve ports will then changeover to admit main system pressure to the gear normal down lines. With the down lines pressurised, the uplocks within each actuator will release and pressure acting on the respective full and annular areas of the nose and main gear actuators will cause the gear to extend (fluid in the 'up' side of each actuator will be vented to reservoir via the electrically-operated selector). When full travel is reached, the downlocks fitted on the respective gear shock absorbers mechanically engage to lock the gear in the down position. D. Extension (emergency) With the landing gear up and locked and the EMERGENCY LANDING GEAR gauge on panel 7P showing available pressure of 3000 psi. gear down may be selected by pulling the LANDING GEAR DOWN - EMERGENCY control lever on the flight compartment roof console. Operation of the lever simultaneously results in (a) release of pressure from the emergency accumulator to the gear emergency down lines and (b) changeover of the three-way manual selector. With the emergency down lines pressurised, the uplocks within each actuator will release and pressure acting on the respective full and annular areas of the nose and main gear actuators will cause the gear to extend. Fluid in the 'up' side of each actuator will vent to reservoir via the three-way selector. Page 4

5 When full travel is reached, the downlocks engage to lock the gear in the down position. NOTE: When the gear is extended under emergency pressure, the accumulator will fully discharge to the reservoir via a restrictor (approximately one minute after all three units have extended and locked down). This ensures that when pressure is restored to the normal down lines, the shuttle valves on the actuators will return to their normal positions. Page 5

6 AMM EXTENSION AND RETRACTION - MAINTENANCE PRACTICES 1. Servicing A. Restoration drill (post-operation of emergency down controls). NOTE: The following drill must be carried out subsequent to (a) operational or test functioning of the landing gear emergency down controls or (b) following inflation check of the landing gear emergency accumulator. Special tools and equipment:- Hydraulic power rig : T (1) Check that normal gear selector lever is in the DOWN position. CAUTION: WHEN PERFORMING OPERATION (2) BELOW - DO NOT TWIST HANDLE. (2) Using a suitable implement eg. a thin screwdriver, reset the LANDING GEAR DOWN - EMERGENCY control lever in the roof console to its normal retracted position. This entails pulling down on the forward edge of the circular lock plate (sited immediately above the spring on the handle assembly) whilst returning the handle to the fully up position. NOTE: Paragraphs (3) and (4) refer to Pre and Post Mod 7551 respectively:- (3) Remove panel 720AT (for location, Refer to , pb1.) and check that the undercarriage selector valve operating lever has returned to its NORMAL position. This entails checking that the centre of levers clevis pin is no more than 0.80 inches from the inboard side of the bulk wall (upper profile rib at 57.0V) to which the selector is mounted. Refer to Figure 201. (4) Visually inspect that the undercarriage selector valve operating lever is properly aligned with the NORMAL quadrant identified on the perspex portion of panel 720AT. Refer to , pb1. (5) Perform the following at the hydraulic servicing panel:- (a) Connect hydraulic power rig to the GROUND TEST (PRESSURE and RETURN) connectors. (b) Open the L/G EMERGENCY accumulator valve and operate rig until ACCUMULATOR pressure gauge reads psi. Stop rig. NOTE: Step (6) is applicable only to those aircraft Serial Nos prior to SH3651 which have not had Service Bulletin SD incorporated. (6) Off-load main system pressure (repeatedly operate wheelbrakes until SYSTEM pressure gauge on panel 7P reads ero). Page 201

7 SD3-60 AIRCRAFT MAINTENANCE MANUAL (7) After a period of ten minutes, check that the pressure shown on the ACCUMULATOR pressure gauge on the servicing panel has held at psi., indicating that the emergency landing gear accumulators integral selector valve has correctly been reset closed (para. (2)). (8) Close the L/G EMERGENCY accumulator valve, evacuate the ACCUMULATOR pressure gauge and close the charging connection. (9) Disconnect rig. B. Prime and bleed the landing gear system Special tools and equipment:- Hydraulic hand pump rig : T With the landing gear down and aircraft raised on jacks, proceed as follows:- (1) Disconnect the nose and main gear actuators at opposite ends to structural anchorages. Position and secure the units such that extension and retraction of the piston rods can cause no damage. (2) Check that hydraulic CONTENTS gauge (panel 7P) reads within GREEN sector. (3) With reference to the hydraulic servicing panel, inflate the reservoir with nitrogen (alternatively dry air) to a nominal pressure of 15 psi. NOTE: This will ensure follow movement of the reservoir piston during priming and bleeding operations. (4) Connect hand pump rig to the GROUND TEST (PRESSURE and RETURN) connectors on the servicing panel. (5) Slightly slacken the normal down LGD line connection at the shuttle valve on each actuator. Operate the hand pump and tighten connections when fluid is delivered. (6) Continue operating hand pump to fill the down side of each actuator (noted by build up of pressure). (7) Select landing gear UP. (8) Slightly slacken connections at downlocks and operate hand pump until air-free fluid is delivered. Tighten connections. (9) Slightly slacken the up line LGU connection on each actuator. Operate hand pump until fluid flows from connections. Tighten connections and continue pumping until actuators have moved through full travel. (10) Select landing gear DOWN. Page 202

8 (11) Repeat (5), (6), (7), (8) and (9) as necessary until fluid delivered at slackened connections is air-free. NOTE: Finish with the actuators in the gear down position and tighten all connections. (12) Slacken the emergency down line LGDE connections on the actuator shuttle valves. CAUTION: WHEN PERFORMING OPERATION (13) BELOW - DO NOT TWIST HANDLE. (13) Pull the LANDING GEAR DOWN - EMERGENCY control lever (roof console) to the emergency position. (14) Operate the hand pump until air-free fluid flows from connections. Tighten connections. (15) Return the emergency control lever to its normal position. (16) Reconnect the actuators to respective gear units. (17) Disconnect hand pump rig. (18) Top up reservoir. Refer to , pb301. NOTE: The reservoir should be re-bled following the next complete day of operation. (19) Function test the landing gear as detailed in para 2.B. 2. Adjustment/Test A. Rig the emergency controls Refer to Figure 201. Special tools and equipment:- Rigging pins M-1-P : E-H-1 : T T NOTE: After final adjustment of turnbuckles, fit locking clips. Refer to , pb1. (1) Disconnect the accumulator operating push rod SD from the pivot lever (detail B) and insert rigging pin E-H-1 where shown. (2) Hold and maintain operating lever on accumulator against its closed stop, adjust the push rod to suit and reconnect to pivot lever. (3) With the LANDING GEAR DOWN - EMERGENCY CONTROL LEVER (detail A) in its normal 'up' position, insert rigging pin M-1-P where shown. Page 203

9 SD3-60 AIRCRAFT MAINTENANCE MANUAL (4) Arrange control cables in a slack condition as shown on main view. (5) Adjust the forward turnbuckle such that cable slack is taken up and that the rigging pin at detail B can be removed and inserted freely. Refit rigging pin. (6) Place selector operating lever (detail C) in its normal position and adjust the aft turnbuckle such that cable slack is taken up without movement of the selector lever. (7) Check that both rigging pins can now be removed without further system movement occurring. B. Test landing gear operation Special tools and equipment:- Hydraulic power rig : T (1) Raise the aircraft sufficiently to provide adequate clearance for retraction and extension of the landing gear. (2) Open C/B No.38 on distribution panel 1D to isolate landing gear position warning horn circuit. (3) Check that C/B No. 187 and 188 on distribution panel 2D are closed. (4) Provide electrical power. Refer to , pb301. (5) Disconnect control linkage to right nose wheel bay door. (6) Connect hydraulic power rig to the GROUND TEST (PRESSURE and RETURN) connectors on the hydraulic servicing panel. (7) Start rig, adjust flow rate to 2.0 ± 0.5 gal/min. and raise SYSTEM pressure (panel 7P) to psi. (8) Select landing gear UP and check that:- (a) the time for complete retraction i.e. from 'locked down' to 'locked up' is secs for both main and nose gears. NOTE: Retraction times are to be recorded (measured from gear up selection until red gear in transit light extinguishes). Attention must be paid to the times recorded. Slow times, or times approaching the upper limit may be an indication of bearing stiffness/deterioration of the aft pintle pin inner bush. If such conditions exist, the inner rib bush should be inspected. Refer to , pb201. (b) the following indications are provided by the position warning lights on panel 1P:- 1 gear DOWN and locked - three greens Page 204

10 2 gear in transit - three reds 3 gear UP and locked - all lights extinguished (c) there is a clearance of 0.75 in. (min) between the wheel and the roof of the nose wheel bay. NOTE: Adjust if clearance is insufficient. Refer to , pb201. (9) Check nose gear door profile meets the following requirements:- (a) Forward and aft edges of doors are flush with the associated fixed fairings within ± 0.03 in. (b) Both doors adjacent edges are flush within in. (10) Stop the rig. Off-load main system pressure (operate flaps) and check that the landing gear remains up and locked by applying a load to each wheel in turn. (11) Start rig and again raise SYSTEM pressure to psi. (12) Select landing gear DOWN and check that:- (a) the time for complete extension from 'locked up' to 'locked down' is: ±.4 secs - nose gear ±.4 secs - main gear (b) that the warning lights provide correct indication before, during and at completion of extension. (c) downlocks remain retracted until full extension is achieved. NOTE: Retraction times are to be recorded (measured from gear up selection until red gear in transit light extinguishes). Attention must be paid to the times recorded. Slow times, or times approaching the upper limit may be an indication of bearing stiffness/deterioration of the aft pintle pin inner bush. If such conditions exist, the inner rib bush should be inspected. Refer to , pb201. (13) Visually check that the downlocks are engaged. (14) Repeat operations (7), (8), (11) and (12) to complete 5 cycles of operation. (15) Select landing gear UP. Page 205

11 SD3-60 AIRCRAFT MAINTENANCE MANUAL CAUTION: WHEN PERFORMING OPERATION (16) BELOW - DO NOT TWIST HANDLE. (16) Pull the LANDING GEAR DOWN - EMERGENCY control lever in the roof console and check that the gear moves to the down and locked positions (three GREENS). (17) Effect restoration drill (para 1.A.). (18) Close C/B No.38 (Panel 1D). C. Check landing gear bearing clearances. A check on summated bearing wear throughout the main/nose gear linkages is made by determining the degree of axle free play in three axes. NOTE: Where movement in excess of the worn limit/s tabled below is detected, report findings to Bombardier Aerospace, Belfast. Max owable Axle Free-Play FORE & AFT (HORIZ. PLANE) SIDE TO SIDE (HORIZ. PLANE) UP AND DOWN (VERT. PLANE) New (in.) Nose Gear Worn (in.) New (in.) Main Gear Worn (in.) Page 206

12 Emergency Down Controls Rigging Figure 201 Page 207

SD3-60 AIRCRAFT MAINTENANCE MANUAL - DESCRIPTION & OPERATION

SD3-60 AIRCRAFT MAINTENANCE MANUAL z PAMM 54.0.0.0STEERING - DESCRIPTION & OPERATION 1. Description The nosewheel is operationally steerable through a radius of 55 degrees on either side of the aircraft