TOWING AND TAXIING

民航

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TOWING AND TAXIING

民航

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.