AIR TRACTOR AT-502A, Maintenance Section

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Air Tractor, Inc. Maintenance Page 29
AT-502A/502B/504 March 14, 2018
The seat covers wear and need changing from time to time. The back cover is p/n 10541-1 and the
bottom cover is p/n 10540-1. If the crotch strap is installed through the bottom seat cover (used with AmSafe
Airbag System), use bottom cover p/n 10540-3. Tools are available from the factory to make seat cover
replacement easier.
The AmSafe Airbag system consists of a lap belt and crotch strap attached to the seat frame, a
shoulder harness with integrated airbags, two compressed gas inflators, and an electronics module and
cabling. All maintenance on the system must be performed by an AmSafe Authorized Service Center per
AmSafe Aviation Document Number E510500.
The maintenance requirements of the system include an annual inspection and functional test of the
system. The electronics module must be returned to AmSafe for refurbishment after a period of seven years
from month of manufacture and must be taken out of service after a period of 14 years from month of
manufacture. The inflators must be removed and replaced after a period of 10 years from the month of
manufacture.
Any time any component of the AmSafe Airbag system is disconnected or removed from the aircraft,
the system requires a functional test performed by an AmSafe Authorized Service Center.
ENGINE-DRIVEN AIR CONDITIONER
All Air Tractor aircraft use a gas-cycle air conditioning system for climate control. The air conditioning
system lets the pilot select ram air from outside, re-circulate cockpit air, or a mix of the two. The ram-air
control handle location is on the aft-cockpit wall on the RH side of the pilot.
The 53126-X compressor has five reciprocating pistons driven by a rotating wobble-plate. It uses
reed-type valves to control flow at the suction and pressure ports. Mechanical power to drive the compressor
comes from an engine accessory drive pad. Gears in the engine drive are a splined-quill shaft that turns a
small poly “V” groove pulley that drives the flywheel pulley with a serpentine belt. The flywheel pulley is
connected to the compressor shaft by an electromagnetic clutch.
The 53126-X compressor is factory-charged to the correct level with Sanden SP-15 oil. The initial oil
charge is 210 cc
. It is not necessary to check the compressor’s oil level as routine maintenance. The oil level
must be checked when a system component has been replaced or if you think there is an oil leak. All
refrigerant must be removed from the system (depressurized) before the oil is checked.
The air conditioner fans, blowers, and compressor clutch are powered by the aircraft bus. All control
switches for the air conditioning system are located on the Instrument Panel. The pilot can use the switches
to turn the system on or off and to control the cockpit-blower speed as HIGH, MED, or LOW.
A Freon Recycling Unit (FRU) that reclaims the R-134a refrigerant is recommended when refrigerant
is added or removed.
Servicing procedures for the air conditioner are generally the same as those for comparable
automotive units. Most servicing is accomplished by adding or removing Refrigerant R-134a at the servicing
ports. These ports are located beneath the upper right-hand side skin immediately aft of the cockpit.