AIR TRACTOR AT-502A, Maintenance Section

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Air Tractor, Inc. Maintenance Page 07
AT-502A/502B/504 March 14, 2018
Compressor Washes
Compressor washes are performed to remove dirt and deposits which hamper the efficiency of the
compressor. The quality of the Air Tractor induction system is so good that most engines require a
compressor wash only once a year. An inspection of your engine inlet is a good indicator of when to perform
a compressor wash. If the cone on the inside of your inlet is dirty, then the compressor is too. Anything going
into the compressor has to go by here. If the cone is clean, you can be sure the inside of your engine is in
pretty good shape. Don’t do a compressor wash just to be doing one.
Regardless of how many you do, there is only one way to accomplish the task with maximum results.
Remove the engine cowling and the air inlet cover over the engine inlet. Connect and start the battery
charger. Remove the P3 filter and leave the filter bowl off. If your engine does not have a P3 filter, remove
the compressor discharge line from the right hand side of the FCU. Remove the two gas generator case fuel
drain valves to allow the dirty water to escape rapidly. See Figure 103.
Figure 103
If you do not remove the valves, what happens inside your engine strongly resembles the bathtub after
the kids finish their bath. The rings left in the engine will do more harm than the washing does good.
After you get the engine ready, take a CLEAN open top 5 gallon bucket and mix 1 qt. of an approved
cleaning agent, (see Note *), 1 gallon of jet fuel, and 3 gallons of water. While motoring the engine, pour 1/2
of the contents into the engine inlet. Wait 15 minutes and pour the remaining mixture into the engine. Then at
20 minute intervals, pour in 2 to 3 gallons of clean water at a time until the water running out of the engine is
clean.
After the water stops dripping out of the engine, replace the fuel drain valves and safety them. Replace
the air inlet cover, P3 filter and engine cowling. When everything has been replaced, start the engine and run
for at least 15 minutes to dry the engine out. Never put the airplane up without running the engine until it is
dry.
Note *: B&B 3100 Cleaner: B&B Chemicals Co., P.O. Box 796, Miami, Florida 33166
Turco 4217 Cleaner: Turco Purex Industries Corp., 24700 South Main Street, Carson, California
90749