AIR TRACTOR AT-502A, Секция обслуживания

Страница: 22 / 159

Air Tractor, Inc. Maintenance Page 3
AT-502A/502B/504 March 14, 2018
4. Camber is then measured by placing a protractor on the vertical axis of the wheel through the axle.
Camber should measure 1
o
to 2
o
.
5. Should the wheel fail to check within these limits, the axle bolts are removed and the tapered shims
rotated, deleted, or added to until the wheels check with these limits. With the aircraft hoisted and the
wheels barely touching the ground, toe-in should measure 3/8" and camber should measure 2 1/4".
BRAKES
The wheel brake units are Cleveland 30-98C. The brake unit consists of the wheel cylinder assembly
and the torque plate, which is attached to the gear leg with the four axle bolts. The torque plates are
interchangeable from right to left, but the cylinder assembly can be converted to a R/H or a L/H by moving
the bleed screw to the fluid entry port.
Brake fluid used is red Mil-H-5606A petroleum-base fluid which is used in most light aircraft. Do not
use automotive brake fluid as this will swell the O-rings.
The wheel units can be removed by using a 7/16" wrench to remove the six AN4 bolts attaching the
two halves of each brake assembly. The brake line may be left connected if only the linings are to be
changed. Linings are Cleveland p/n 66-59 and are attached with Cleveland p/n 105-2 rivets. There are 24
linings and 48 rivets per aircraft.
Each brake assembly has three pistons which are Cleveland p/n 92-33 and have an O-ring installed
which is a Cleveland p/n 101-50128. Each piston also incorporates a drag ring which holds the piston against
the backing plate of the lining so that excessive pedal travel is not required for positive brake action.
To remove the pistons in order to change O-rings, remove the brake line and apply air pressure at the
fluid entry port. The pistons are aluminum and should be checked for wear, or burrs that could cut the O-ring.
Check the bore in the housing at the same time. When installing new O-rings, soak them in brake fluid before
placing them on the pistons. Re-install the pistons with care, so that the O-ring is not damaged.
The brake disc is a Cleveland p/n 164-58 and is attached to the bolts that attach the two rim halves
together. The wheel must be removed from the aircraft per previous instructions, the tire deflated, and the
wheel disassembled in order to remove the brake disc. With the new brake disc in place, re-assemble wheel
and tire per previous instructions.
Brake Master Cylinders
The master cylinders are Cleveland p/n 10-23F. The upper end is bolted to an aluminum strap
connected to the rudder pedal. Both the strap and the pedal have bronze bushings that can be replaced
when worn. The bushings are oil-impregnated and do not require lubrication.
The lower end of the master cylinder is attached to a clevis with a check nut. If the rudder pedal
position (angle) should need changing for pilot comfort, the check nut can be loosened, and the round
plunger immediately above can be rotated with finger pressure in either direction to increase or decrease the
angle that the brake pedal makes with the cockpit floor. When desired angle is obtained, snug check nut.
To remove the master cylinder, loosen check nut and rotate plunger out of the clevis. Then remove the
bolt attaching the master cylinder to the aluminum strap and disconnect the two brake lines at the cylinder.
A repair kit is available for the master cylinder which is Cleveland p/n 199-09100. The cylinder may be
dis-assembled and repair parts installed per instructions furnished with kit. If the check nut at the bottom is
left in the original position, the pedal angle will be the same as before when the master cylinder is re-
installed. Be sure the clevis is free to swing with the master cylinder through the full range of rudder pedal
travel. If it does not, the two plates which attach the cylinder are too close together and require an additional
spacer washer.