AIR TRACTOR AT-502A, Секция обслуживания

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Maintenance Page 24 Air Tractor, Inc.
March 14, 2018 AT-502A/502B/504
torqued (100 inch-pounds at the nut). We have seen elevator horns with badly elongated holes because the
elevators had been replaced in the field and the bolts were not fully torqued.
A repair for elongated holes in the horns has been to drill out the holes to 9/32", ream with a special
.3120 reamer (available at the factory if required), and installing a press-fit 4130N steel bushing. 3125 to
.3130 O.D. x .250 I.D. x .080 long. With the bushing in place, heli-arc weld the bushing to the horn in two
places with 1/8" long weld beads. Then sand, etch, and paint with Air Ag Yellow epoxy.
To replace the bearings, see the section on “Rudder” for instructions.
Elevator stops are at the elevator horn. The down stop has a p/n 70067-1 neoprene washer in
compression to absorb shocks and sometimes this washer splits and falls out so during 100 hour
inspections, check to see if this washer is in place. Also, if the control stick is pulled back sharply against the
up stop or if a wind gust blows the elevator up, the up stop bracket will bend and should be straightened if
found to be bent.
Elevator travel is 29
o
up, 16
o
down, +/-1
o
.
ELEVATOR CONTROLS
The aft elevator push-rod that connects to the elevator horns is p/n 70020-1 (AT-502A/502B) or 71783-
7 (504) and is adjustable on the forward end which has a Fafnir RE4M6 bearing installed. The aft end of the
push-rod has a NMB p/n ABT4 bearing same as the elevators and rudder and is pressed into place and
staked same as in other applications. If it is to be removed, see the “Rudder” section for removal instructions.
The aft elevator idler is p/n 70023-1 and attaches to the fuselage frame with a AN4-20A bolt. This idler
has two Torrington B 610 bearings installed, with a p/n 70055-1 spacer bushing and two AN960-416 washers
on each end to contain the Torrington bearings. During annual inspections, this idler should be removed, and
the bearings cleaned and packed with general purpose grease. Check for excessive wobble on the lower
end of the idler which would indicate worn bearings, or a worn spacer, or both. When the idler is re-installed
be sure to grease the bolt before installation and torque to 100 inch-pounds at the nut. After installation,
check the aft push rod to see that it will rotate slightly in either direction to indicate that the RE4M6 bearing is
positioned properly, and check the AN316-6 check nut at the bearing for snug.
Also remove the control lock and push the elevator through the full range of travel, checking the
clearance of the bolt through the elevator horns with the fuselage structure. Since two washers are installed
on this bolt, one may be under the bolt head, or both may be under the nut, depending upon which
arrangement gives the best clearance to the fuselage structure.
Check the position of the eyebolt in the aft idler that the tail wheel lock spring is attached to. The spring
is International Harvester p/n 54548-D and if the eyebolt is positioned correctly, the spring end will slide
easily through the eyebolt as the elevator is moved from full down to full up. A little grease at this point will
help.
The tail lock cable is p/n 71144-1 and attaches to an AN115-21 shackle and MS20392-2-21 clevis
pin at the lock pin lifting arms (p/n 40019-1) at the tail gear. At the forward end, the cable attaches to a p/n
71173-1 rod assembly using an AN3C6 bolt, AN960C10 washer, AN310C3 nut, and MS24665-151 cotter.
The rod assembly is supported by 40701-00 guides at the tail spring clamp and the fuselage frame. The
forward end of the rod assembly attaches to a p/n 71158-1 cable assembly using a MS21251-B5S barrel and
AN316-4 nut. The forward end of the cable assembly attaches to the 54548-D spring mentioned above.
Check for wear at the fairleads, and for general cable condition.