AIR TRACTOR AT-502A, Секция обслуживания

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Air Tractor, Inc. Maintenance Page 5
AT-502A/502B/504 March 14, 2018
the jam nut from the axle and remove the axle. Inspect the axle for wear at the bearing positions, as
insufficient greasing procedures will cause the bearing to turn on the axle and ruin both parts. Inspect the
AN6 bolt for wear and straightness, and slide the bolt through the fork to check the hole in the fork for wear.
There should be no wear in the fork holes since there is no movement between fork and bolt. If the tire is to
be removed, deflate and remove the bolts holding the wheel halves together. Since the rim halves were
sealed, the sealer may hold the parts together and tapping the rims with a wooden block may be necessary
to split the wheel. Don’t forget to remove the valve stem nut and push the stem until it is loose from the wheel
half. Clean all parts and re-assemble. Partial inflate the tube to keep from pinching it.
Tail wheel bearings are Timken L44643LA cone (the part with the rollers) and L44610 cup (the part
pressed into the wheel half). Hand pack the bearings with wheel bearing grease meeting MIL-PRF-81322
(such as Mobil grease 28) or Mobil SCH 100 grease, and install wheel on the axle. Install the 40034-1 jam
nut and 40051-1 tongue washer on the axle with the round shoulder inboard and tighten until all bearing
slack is removed but the wheel is free to turn. Inflate the tire to 50 psi. Grease the AN6C64A axle bolt and
install wheel and axle assembly on the fork. Torque the nut to 160 inch-pounds. Safety the jam nut against
the rotation of the wheel with MS20995C32 stainless safety wire.
Tail Wheel Fork
The tail wheel fork may be removed from the housing by removing the single AN4C26A stainless bolt
from the arm assembly that connects to the centering springs. With the fork removed, check for wear on the
spindle at the bronze bearing locations. Also check for condition of the steel bushing that the lock pin drops
into. This bushing is pressed into the steel plate at the bottom end of the spindle and staked in four places on
each side of the plate with a center punch. This holds the bushing in place since it has a beveled edge on
both sides. This bushing is p/n 40042-1. Excess wear on the fork spindle at the bronze bearing locations are
indication that grease is not reaching the proper area. To grease the bronze bearings properly, jack the tail
wheel clear of the ground and apply grease at the fitting on the housing, and rotate the fork until grease is
running out of the full perimeter of both upper and lower bronze bushings. Excessive wear in the spindle will
require a new fork assembly which is p/n 40095-1 and includes the steel lock pin bushing. The centering
springs are p/n 40044-1 and attach to a p/n 40035-1 bracket which wears on a p/n 40036-1 bushing. The
Bolt is a AN4C7A.
Tail Wheel Fork Housing
The housing is attached to the tail spring with two AN12H15A bolts, and MS20995C32 safety wire ties
the bolt heads together. These bolts have a tendency to loosen in service, particularly in the first 100 hours
of operation as paint between mating surfaces is compressed. At 100 hour intervals, the tail wheel should be
jacked clear of the ground, and with the locking pin in place give the tail wheel a vigorous tug from side to
side to check for movement between the housing and the spring. Torque the bolts to 2,800 inch-pounds. For
row-crop operation from smooth strips these bolts should be replaced at least every 2,000 hours and for rice
operation from rough strips should be changed every 1,000 hours or once a year. Be sure to grease the bolts
before installation with G.P. grease, and an added precaution would be to apply grease to the threads of the
housing to prevent the bolt from seizing.
A brass wear plate is attached at the lower plate of the fork housing assembly. This plate is attached
with counter-sunk machine screws and if worn to the point where the machine screw heads are flush, it
should be changed. The brass plate is p/n 40018-2. The large bronze bushings inside the housing are p/n
40023-1 (lower) and p/n 40024-1 (upper). These bushings are pressed into place and may be driven out with