AIR TRACTOR AT-502A, Maintenance Section

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Maintenance Page 28 Air Tractor, Inc.
March 14, 2018 AT-502A/502B/504
FUSELAGE COCKPIT SKINS
The cockpit skins are riveted to the floor and to the support angles with MS20470AD4 rivets.
Attachments to the door frames are CR163-4-4 Cherry rivets. The cockpit skins may be removed by drilling
out the rivets where necessary and is not a difficult operation. The hopper should be removed in order to
remove the cockpit floor however.
FUSELAGE FRAME
The fuselage frame is of 4130N tubing and may be repaired in conventional ways. All fittings are also
of 4130N material. The repaired area should be sanded and burned paint should be removed to a point
where it can be feather-edged by sanding. A good etching solution would be a mixture of 1/2 fluid oz. of
concentrated phosphoric acid in one gallon of isopropanol (isopropyl alcohol). If relative humidity is extremely
low, add 1/4 cup of distilled water to the solution. Factory paint is Air Ag Yellow epoxy which does not require
a primer.
WINDSHIELD
For the plexiglass portion of the windshield be careful to always use a clean rag and plastic windshield cleaner
to prevent scratches. If a crack is found near one of the attaching screws, stop-drill with a no. 30 drill bit.
The safety glass center windshield can be cleaned with a soft rag and any good glass cleaner.
The windshield is sealed around the upper and lower edge under the metal flanges with PR1422-A1/2.
Then the entire perimeter of the windshield is sealed with PR1422 -
A2* (See “Fuel Tanks” for mixing
instructions).
To install new side plexiglass, drill .166 holes through the plexiglass to match the aluminum
attachments. Then remove the plexiglass and enlarge the holes in the plexiglass to 3/16" to prevent the
attach screws from over-stressing and cracking the plexiglass at any location.
*Alternate sealer is AC236A1/2TK6/5
CANOPY DOORS
The canopy doors seal against the door frame with p/n X202BT neoprene sponge. This material has a
PSA backing but it is best to apply 3-M 8001 adhesive to the door frame in order to get better adhesion. Be
careful not to stretch the neoprene sponge during installation or it will come loose.
The doors have a slight inward bow of 1/8" to allow for door deflection outward at high speeds. The low
pressure around the canopy causes the doors to bow outward. The door latch should provide a snug door fit,
and if it does not, and the weatherstrip is in good condition, bend the latch arm that rides on the plated striker
plate (p/n 10354-1 (L/H) or -2 (R/H).
The door glass is p/n 10211-2 and is attached with 1/16 x 1 1/4 felt with PSA backing (p/n F-7) around
the perimeter. The machine screws around the glass are AN526-632-8 and the nuts are AN365-632. Be
careful not to over-tighten the screws or the glass will crack.
SEAT
The seat is attached to the seat rails with two C4-13R-303 Faspins. Do not raise the seat above factory
installed position but a tall person may want to lower the seat some. This is done by lowering the seat to the
desired position and drilling the seat rails 15/64 and then reaming 1/4" for the Faspin installation. Make sure
the lowered position clears the push-rod from the control stick.