TOWING AND TAXIING

民航发表于 2011-6-13 14:15:30

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民航发表于 2011-6-13 14:18:47

TOWING 1. General A. The airplane is normally towed or pushed by a tow bar attached to the nose gear. Maximum normal towing turning limits are indicated by painted stripes on the nose gear doors. B. The airplane is capable of being towed on firm and level terrain by the nose gear with one tire flat on each landing gear if starting loads are held to the minimum. For other abnormal towing loads, such as towing with two flat tires on one main gear, towing on soft terrain, towing up inclines greater than 5 degrees, the towing should be done from the main gears as the structural limitations of the nose gear may be exceeded. NOTE: With two flat tires on one main gear, effort should be made to replace one of the flat tires with a serviceable tire before towing to prevent excessive damage to the tires and wheels. C. Towing airplane with either or both engines removed presents no problem as long as the center of gravity remains forward of the aft center of gravity limits. Refer to par. 7 for center of gravity data. D. When it is necessary to tilt the airplane for tail clearance in hangars and storage areas, refer to 7-13-0, Tilt Airplane for Tail Clearance. 2. Equipment and Materials A. Standard tow tractor B. Tow Bar –C09002 (-1,-2,-5,-10,12 and –13) –9 is replaced by –58 and F72951-51. C. Eyebolt Assembly, Main Landing Gear Towing - F72719 D. Wire cable (3/4 inch) with end fittings to match F72719 and tow tractor (local fabrication) E. Steering depressurization valve lockout pin - F72735-13 3. Prepare for Towing Airplane A. Check airplane is within center of gravity towing limitations and for fuel imbalance. Refer to par. 7 for center of gravity data. B. Check that all landing gear ground lock pins are installed (Ref 32-00-01). NOTE: Towing or pushing with landing gear ground lock pins removed is optional. C. Tires and shock struts properly inflated (Ref Chapter 12). CAUTION: DO NOT TOW AIRPLANE WITH NOSE GEAR FULLY COLLAPSED OR EXTENDED MORE THAN 22 INCHES FROM BOTTOM OF INNER CYLINDER TO BOTTOM OF STEERING PLATE AS NOSE GEAR STRUT MAY BE DAMAGED INTERNALLY. D. Apply external electrical power or start and operate APU (Ref 24-41-0 or 49-11-0). NOTE: With external power applied or APU providing electrical power, parking brakes in parked position, and hydraulic system ground interconnect valve on (open), system B pump will pressurize both inboard and outboard brake accumulators A and B. If parking brakes are off, only outboard brake accumulator B will be charged and outboard brakes continuously pressurized.
E. Check that brake hydraulic pressure is normal, approximately 3000 psi. F. Check that antiskid switch is off. G. On airplanes without nose gear steering depressurization valve or if Lockout Pin is not installed. (1) Check that hydraulic system A is depressurized. NOTE: If hydraulic system A is pressurized, system pressure prevents steering actuator bypass valve from opening, preventing nose gear from being turned by the tow bar. (Do not confuse system A pressure with brake accumulator A which pressurizes only the inboard brakes.) (2) Remove external electrical power (Ref 24-22-0). The APU may be operated if the engines are not operating, or the engines are operating but no electrical power changes are made while towing. WARNING: ENSURE HYDRAULIC SYSTEM A IS COMPLETELY DEPRESSURIZED AND DO NOT MAKE ANY ELECTRICAL POWER CHANGES WITH TOW BAR CONNECTED. AN INTERRUPTION OF ELECTRICAL POWER COULD CAUSE MOMENTARY PRESSURIZATION OF ENGINE DRIVEN HYDRAULIC PUMPS WHICH COULD PRESSURIZE SYSTEM A AND CAUSE NOSE GEAR TO ALIGN WITH STEERING WHEEL POSITION. DAMAGE TO EQUIPMENT AND INJURY TO PERSONNEL COULD OCCUR. H. On airplanes with nose gear steering depressurization valve, depress button and install nose gear steering lockout pin in steering depressurization valve (Ref 32-00-01). CAUTION: TO AVOID DAMAGE TO STEERING COMPONENTS OR TOWING EQUIPMENT, THE DEPRESSURIZATION VALVE BUTTON MUST BE DEPRESSED AND HELD WHEN LOCKOUT PIN IS INSERTED. NOTE: Nose gear steering depressurizing lockout pin can be installed and removed without entering wheel well from aft of right nose wheel well door. I. Connect interphone system between control cabin, tow tractor operator and towing ground crew. J. Check that ramp area is cleared of all stands and equipment in the towing path. K. Connect tow bar to tow tractor and to airplane. L. Remove airplane static ground wires. M. Close the fan cowl panels, thrust reverser (Ref Chapter 71). CAUTION: MAKE SURE ALL ENGINE COWLS ARE CLOSED AND LATCHED BEFORE THE AIRPLANE IS TOWED. DAMAGE TO EQUIPMENT CAN OCCUR. N. To tow the airplane with the entry or lower cargo door open is optional.
4. Tow Airplane from Nose Gear A. Position wing, tail, tow tractor operator and ground crew so that all are in visual contact. B. Check that cockpit man, ground crew, and tow tractor operator are in intercom communication. C. Check that wheel chocks are removed. D. Check that hydraulic brakes are released. E. Tow airplane. Begin towing slowly and straight ahead before attempting to turn. CAUTION: MOVE AIRPLANE FORWARD BEFORE STARTING SHARP TURNS. AVOID SUDDEN STARTS AND STOPS. IF TOWING IS BEING DONE UNDER HIGH LOAD CONDITIONS, SUCH AS TOWING WITH BOTH TIRES FLAT ON ONE MAIN GEAR, TOWING ON SOFT TERRAIN, TOWING UP INCLINES GREATER THAN 5 DEGREES, OR SIMILAR CONDITIONS, REFER TO MAIN GEAR TOWING, PAR. 5, AS NOSE GEAR TOWING STRUCTURAL LIMITATIONS MAY BE EXCEEDED. F. Limit brake applications to minimum use within safety limitations. Fully charged accumulators are capable of approximately three brake applications. CAUTION: IF YOU USE A TOW BAR, YOU CAN CAUSE THE SHEAR PINS TO SHEAR IF YOU USE THE AIRPLANE BRAKES WHILE YOU TOW THE AIRPLANE. MOST TOWBARLESS TOW VEHICLES DO NOT HAVE A SHEAR PIN TO LIMIT THE LOADS IF AIRPLANE BRAKES ARE USED DURING TOWING. IF AIRPLANE BRAKES ARE USED WHILE TOWING WITH A TOWBARLESS TOW VEHICLE ATTACHED TO THE NOSE LANDING GEAR, PERFORM THE “HARD LANDING OR HIGH DRAG/SLIDE LOAD LANDING” INSPECTION FOR THE NOSE LANDING GEAR AREAS (REF 5-51-51).
G. Maximum normal turning angle is 78 degrees as indicated by red stripes on nose gear doors. If a greater turning angle is required, disconnect torsion links on nose gear. If an angle in excess of 90 degrees is required, disconnect nose gear taxi light wire. When disconnected, support lower torsion link against dragging to prevent damage to lubrication fittings. See Fig. 202 for turning dimensions. See Fig. 203 for wingtip turning radius for various turning angles. See Fig. 204 for ground turning techniques. H. Finish towing in a straight path for a minimum of 10 feet to relieve turning stresses remaining in tires and shock struts. I. At end of towing, position wheel chocks fore and aft of a main gear wheel on each main gear. J. Disconnect tow bar and remove nose gear steering nulling pin. 5. Tow Airplane under Abnormal Loads (Main Gear Towing) A. Preparation for towing and towing the airplane under abnormal loads is the same as towing airplane from the nose gear except for the following: (1) Eyebolt assemblies are installed in place of the jacking cone on each main gear and locally fabricated cables attach the gears to the tow tractors. The nose gear tow bar is not used. (2) Hydraulic system A is pressurized and airplane is steered during towing by the nose wheel steering system by directions from the ground crew. (3) The airplane motion is interrupted by application of airplane brakes. The number of applications is not limited as the hydraulic systems are operational. 6. Return Airplane to Normal A. Attach static ground wires. B. Disconnect and stow intercommunication set. C. If operating, shut down APU. D. If landing gear downlock pins were installed, remove them prior to taxi and takeoff. 7. Center of Gravity Calculations for Towing A. During all phases of ground handling and maintenance, the center of gravity (CG) of the airplane must be forward of the aft CG limit (Fig. 201). This CG limit provides a margin of safety to allow for grade, winds, and acceleration forces as noted. The configuration to be towed should be carefully checked to ensure that the CG is forward of the towing limit. If the aft towing limit is exceeded, the recommended procedure is to move the CG forward by adding ballast or fuel. The table in Fig. 201 gives the incremental CG shift for some of the items to be considered. A forward CG shift is (-) and an aft CG shift is (+). All data is for a level airplane.

bocome 发表于 2011-7-30 19:55:14

TOWING AND TAXIING

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TOWING AND TAXIING