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AIR TRACTOR AT-502A, Maintenance Section

The Air Tractor AT-502A user manual is available for free download on our website. This comprehensive manual includes a detailed Maintenance Section to help you keep your aircraft in top condition. Download your manual now from manualshive.com to ensure safe and efficient operation of your AT-502A.

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 AIR TRACTOR, INC. 

Olney, Texas 

 

AT-502A/502B/504 

 

TABLE OF CONTENTS 

 

MAINTENANCE SECTION 

 

 

Page No. 

 

ENGINE MAINTENANCE ................................................................................................................. 01 
 
 

Introduction .......................................................................................................................... 01 

 
 

Maintenance ......................................................................................................................... 01 

 
 

Cleaning Your Engine Exterior ............................................................................................. 01 

 
 

Fuel 

 ................................................................................................................................ 02 

 
 

Figure 101 Fuel Nozzles ...................................................................................................... 03 

 
 

Oil 

 ................................................................................................................................ 03 

 
 

Figure 102 Location of Oil Drain Plugs ................................................................................ 04 

 
 

Air Filters .............................................................................................................................. 05 

 
 

Miscellaneous ...................................................................................................................... 06 

 
 

Compressor Washes............................................................................................................ 07 

 
 

Figure 103 Gas Generator Case .......................................................................................... 07 

 
 

Troubleshooting ................................................................................................................... 08 

 
 

Starting Procedures ............................................................................................................. 08 

 
 

Ground Run Procedures ...................................................................................................... 09 

 
 

Routine Maintenance Inspection ........................................................................................ 010 

 
INTRODUCTION ................................................................................................................................. 1 
 
FUEL REQUIREMENTS ..................................................................................................................... 1 
 
OIL REQUIREMENTS ........................................................................................................................ 1 

Summary of Contents for AT-502A

Page 1: ...g Your Engine Exterior 01 Fuel 02 Figure 101 Fuel Nozzles 03 Oil 03 Figure 102 Location of Oil Drain Plugs 04 Air Filters 05 Miscellaneous 06 Compressor Washes 07 Figure 103 Gas Generator Case 07 Trou...

Page 2: ...EELS 2 Main Wheel Alignment 2 BRAKES 3 Brake Master Cylinders 3 Brake Bleeding 4 Parking Brake 4 TAIL WHEEL 4 Tail Wheel Fork 5 Tail Wheel Fork Housing 5 Tail Wheel Lock Pin and Housing 6 MAIN AND TAI...

Page 3: ...S AND FILTERS 14 AILERONS 14 FLAPS 15 AILERON AND FLAP RIGGING 16 AILERON AND FLAP BELLCRANKS AND SUPPORTS 16 FLAP ACTUATOR 17 Flap Actuator Troubleshooting 18 Flap Actuator Removal Instructions 19 Fl...

Page 4: ...TAB CONTROLS 26 TRIM LEVER 27 FUSELAGE REMOVABLE SKINS 27 FUSELAGE FIXED SKINS 27 FUSELAGE COCKPIT SKINS 28 FUSELAGE FRAME 28 WINDSHIELD 28 CANOPY DOORS 28 SEAT 28 ENGINE DRIVEN AIR CONDITIONER 29 Cau...

Page 5: ...CONTROLS 48 SPRAY LEVER CONTROLS 48 SPRAY PUMP 48 SPRAY PLUMBING 49 BOTTOM LOAD PLUMBING 49 SPRAY NOZZLES 49 STRIPPING AND RE PAINTING PARTS 50 Stripping and Repainting Aluminum Parts 50 Priming Alumi...

Page 6: ...oting Procedures 56 Lighting System Troubleshooting 58 Checking the Batteries 59 Oil Cooler Blower 60 Engine Instruments 60 Engine Overspeed Solenoid 60 Voltmeter 60 Boost Pump 60 Fuel Gauging 60 Wing...

Page 7: ...ICS 63 LIFE LIMITED ITEMS 63 PROPELLER MAINTENANCE 64 TIE DOWN INSTRUCTIONS 65 TOWING INSTRUCTIONS AND LIMITATIONS 66 DRAINING THE STATIC SYSTEM 67 LOW FUEL WARNING SYSTEM 67 Test Function 67 Correcti...

Page 8: ...tarts and flights MUST be kept for figuring cycle counts on the rotor components in your engine at each annual The cycles are figured using the number of starts and flights with a formula found in the...

Page 9: ...229 and 229A for more details on fuel filter inspection and maintenance The engine also has a disposable fuel filter on the high pressure pump located at the 3 o clock position on the accessory case...

Page 10: ...ng the transfer tubes clear the fuel nozzle may be removed from the engine The fuel supply lines will have to be disconnected from the lower nozzle When installing the fuel nozzles use anti seize or m...

Page 11: ...Maintenance Page 04 Air Tractor Inc March 14 2018 AT 502A 502B 504 LOCATION OF OIL DRAIN PLUGS 2 CHIP DETECTOR 7 OIL TANK DRAIN 10 ACCESSORY CASE DRAIN Figure 102...

Page 12: ...rely on the operating conditions When you replace these filters use the original equipment filters for replacement Cheaper aftermarket filters are not the same quality so they neither perform as well...

Page 13: ...e removed by loosening the nut on the retaining bolt After removing the band slide the starter out exposing the spline Get a good hold on the starter THE STARTER IS VERY HEAVY Grease the spline with a...

Page 14: ...move 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 resemble...

Page 15: ...bring the start lever to the RUN position Start counting 1001 1002 1003 etc your engine should ignite before you reach 1005 If it does not let off the start switch pull the start lever back to cut off...

Page 16: ...additional concrete 4 The airplane should be tied down at the tail using a polyester or nylon tow strap or lift strap looped around the tailwheel housing attach block and routed through the tailwheel...

Page 17: ...___ GREASE PROPELLER 200 Hour Intervals __________ REMOVE AND CLEAN OIL SCREEN __________ REMOVE AND CLEAN FUEL NOZZLES 300 hour intervals are OK if you are using Jet A and you are getting good report...

Page 18: ...RCIAL AIRCTRAFT PRODUCTS P N D 145 00 35 ACTUATOR AT 1500 HOURS __________ REPLACE THE RE4M6 BEARING ON THE AFT END OF THE FLAP PUSH RODS AT 2000 HOURS __________ OVERHAUL PROPELLER PER HARTZELL REQUI...

Page 19: ...This Page Intentionally Left Blank...

Page 20: ...50M 0 and should be stocked as a standard spares item After the jack pad is in place install the bolt and nut through the pad flanges with the bolt on the top side of the gear leg This is to keep the...

Page 21: ...he tire and tube apply enough air pressure in the tube to allow the tube to take shape and position itself properly in the tire before the two rim halves are assembled This will help prevent pinching...

Page 22: ...s 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 t...

Page 23: ...cockpit man pushes on the pedal and shouts Open to the man at the wheel cylinder who proceeds to open the bleed screw with a 1 4 open end wrench Brake fluid and air then rush through the bleed screw t...

Page 24: ...ate at the bottom end of the spindle and staked in four places on each side of the plate with a center punch This holds the bushing in place since it has a beveled edge on both sides This bushing is p...

Page 25: ...ing the Service Letter 171 lock pin bushing kit MAIN AND TAIL GEAR ATTACH BOLTS The bolts attaching the main and tail gear springs to the fuselage structure are among the most important structural com...

Page 26: ...formed heat treated and shot peened for fatigue resistance It is sandblasted and primed with Alumigrip 30 Y 94 primer and finished with Alumi grip 92 Y 444 yellow polyurethane paint The forward attac...

Page 27: ...destroy the old spring when it is replaced MAIN GEAR SPRING The main gear spring is p n 40086 1 and will fit on either side of the aircraft It is machined of E 4340 aircraft quality steel formed heat...

Page 28: ...ms that are in place Since each main gear leg is slightly different in thickness and since each clamp block is machined within a specific tolerance it is necessary to make a shim selection as describe...

Page 29: ...ing angles It should also be noted that there is no bolt through the attach angle and through the small leg of the lower spar cap This is to eliminate bolt fretting and make the joint more fatigue res...

Page 30: ...l If a new wing is to be installed contact the factory for wing installation instructions at the time the wing is ordered The hopper will have to be removed to remove or install the wings Torque value...

Page 31: ...o it is extremely important to stir the accelerator thoroughly in its container until an even consistency is obtained Once the accelerator is added to the base material the pot life is limited to two...

Page 32: ...on of a faulty sender remove the five screws attaching it to the tank top being careful not to damage the teflon washers under the head of each screw The fuel tank should be drained before the sender...

Page 33: ...on See Service Letter 229 for instructions on cleaning and inspecting the firewall mounted fuel screen p n 52351 1 AILERONS The ailerons are all metal and require very little maintenance The lead coun...

Page 34: ...ed through the full range of travel After being sure the bolt through the push rod and wing bellcrank has been torqued re install the inspection plate with the four screws The bearings in the aileron...

Page 35: ...ly p n 70014 2 that connects the flap torque tube to the 90 o bellcrank It should measure 6 65 from bearing hole to bearing hole 3 Check the length of the push rod assembly p n 70014 4 that connects t...

Page 36: ...for excessive wobble which would indicate a worn needle bearing spacer bushing or both The needle bearing should hand press fit into the bore of the bellcrank and the spacer bushing should be a loose...

Page 37: ...pulley next to the header tank so that the rudder interconnect cable will not be in the way and entering the fuselage from the R H side Remember that there is a washer under the pulley when it is re i...

Page 38: ...esired to change the actuator itself perform the following 1 Remove the two screws that hold the dust shield to the lower end of the assembly 2 Use open end wrench to remove down over ride stop from e...

Page 39: ...inspections the gap cover should be removed from the stabilizer and the bolt condition and torque checked At the same time inspect the fuselage fittings closely for cracks Torque is 100 inch pounds at...

Page 40: ...ge line to see that the hinges on both sides of the aircraft line up within 03 Adjust each strut length the same amount until the hinges are in line Then stand directly behind the aircraft on the exac...

Page 41: ...s it is very important to fully torque 100 inch pounds at the nut the three AN4 10A bolts that attach the rudder to the fin If the bolts are loose the bolts will turn on the fin hinge brackets and cau...

Page 42: ...2 bellcrank assemblies are interconnected with a 71952 3 pushrod assembly and four 71958 1 pushrod assemblies run forward to p n 70313 1 aluminum adjust channel The rudder pedal hanger assembly p n 71...

Page 43: ...960 416 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 excessiv...

Page 44: ...ward idler assembly with an AN4 13A bolt in each end The pushrod has Fafnir RE4H6 bearings in each end attached with 98296A999 roll pins If new bearings are ordered be sure to specify that they are to...

Page 45: ...m tab horn with an AN3 7A bolt and to the idler arm in the stabilizer with AN3 6 bolts AN310 3 nuts An960 10 washers MS24665 151 cotters Be sure the push rod is positioned with the bend on the fwd end...

Page 46: ...ch is made of a piece of 3 4 OD tubing and one end sharpened on a grinder At each Monadnock position the neoprene is marked and a 3 4 hole is punched The side skins are sheared to size but the Monadno...

Page 47: ...422 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 i...

Page 48: ...rculate 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 rot...

Page 49: ...compressor Liquid refrigerant can cause frostbite and or blindness D Ventilation Keep refrigerants and oils away from open flames Refrigerants can produce poisonous gasses in the presence of a flame W...

Page 50: ...uring air conditioning system repair cap all fittings as soon as opened and leave capped until just before they are reconnected If a repair is performed on an R134a compressor or system evacuate the s...

Page 51: ...compressor and system For total system required oil amount see section 2C System Requirements above b Remove the oil filler plug and charge the compressor with the amount of additional oil determined...

Page 52: ...in Check With clutch disengage the pulley should spin freely with no wobbling or roughness vibration b Air Gap Check Air gaps exceeding 0 051 1 3 mm can prevent engagement This often is noticed after...

Page 53: ...on of front housing O ring non repairable Oil around cylinder head gaskets service valves fittings repairable Oil around oil plug repairable Stripped threads non repairable Oil around crack in compres...

Page 54: ...place reinstall or tighten Drive pad shaft or bearing problem Inspect drive pad bearing and shaft condition b Unusual Noises Due to Compressor Suction pressure less than about 6 psig can cause unusual...

Page 55: ...sent remove the 3 or 6 bolts holding it in place and remove cover If auxiliary sheet metal pulley is present remove the screws holding it in place then remove pulley Insert pins of armature plate span...

Page 56: ...t Cover if applicable Shaft Key if applicable Shims d Rotor Pulley AssemblyRemoval Remove rotor snap ring Insert the lip of the jaws into the snap ring groove Place rotor pulley shaft protector Puller...

Page 57: ...A distinct change of sound can be heard when using the hammer to install the rotor Reinstall rotor retaining snap ring with external snap ring pliers If a bevel is present on the snap ring it should...

Page 58: ...rst removing the bolt and strap that hold the T head clamp in place The hose fittings can now be removed from the compressor s head without tools Separate the wrist lock connector in the wire that pow...

Page 59: ...reck a good compressor the photo to the right shows a small metal shaving lodged under the discharge valve The valve will open and close against the metal shaving resulting in a fatigue break of the v...

Page 60: ...erant recovery recycle machines which contain a flushing circulating pump to solvent clean using R134a A closed loop flushing machine in which the circulated flushing fluid is returned to a reservoir...

Page 61: ...nce Of Flushing Direction Back flush or flushing in the reverse direction to normal flow is the most effective The plate fin evaporators used on many front and rear evaporators have many small passage...

Page 62: ...ps oil will correct the problem Be sure to follow the manufacturer s recommendations for any maintenance on your evacuation pump Change the oil after use while the oil is still hot because contaminant...

Page 63: ...rigerant Excess oil can act as an insulator limiting heat transfer in the evaporator and condenser while too little oil can negatively affect durability b Oil Checking Is Not Required Under Normal Con...

Page 64: ...ponent the goal is to restore to the original factory oil amount Use the chart below as a guide for restoring oil quantities when replacing system components Component Typical Oil Amount Dual Cond Typ...

Page 65: ...rant returning from the evaporator provides cooling for the compressor Once the refrigerant charge is lost there is no refrigerant entering the compressor hence no compressor cooling Blockages in the...

Page 66: ...ppers The hopper brace and the hopper window is sealed on installation with Silicone sealer which is impervious to most chemicals The hopper is attached to the fuselage frame with AN6C24A 4 ea and AN6...

Page 67: ...ro calibrator installation is Air Tractor p n 80862 1 for AT 502A 502B p n 80862 29 for AT 504 SPRAY LEVER CONTROLS The spray lever assembly p n 80073 1 for AT 502A 502B Transland p n 21613 for AT 504...

Page 68: ...ort assemblies are p n 80383 1 and are attached with AN4C6A bolts D4 10T 303 Faspins are used to attach the support assemblies to the fuselage frame BOTTOM LOAD PLUMBING The bottom load valve is a Tra...

Page 69: ...roughly Rinse with cold water 8 Before the part is dry apply generous amounts of Alodine with a clean white rag The Alodine should act within two or three minutes and when rinsed off with cold water s...

Page 70: ...s are to be avoided 10 9 Cure time is 4 5 hours to tape at 120 o F or 6 8 hours to tape at 77 o F 10 10 Clean equipment using Ketone MEK solvent Do not allow material to cure inside spray equipment Pr...

Page 71: ...inum Parts Top cat is Desothane HS CA 8800 series or CA 8200 by PRC DeSoto Aerospace Coatings CA 8800 is to be used for high gloss top coat colors CA 8200 is to be used for matte or flat colors The to...

Page 72: ...everse of this procedure use the upper value 3 Tension type nuts are AN365 AN363 AN310 4 Shear type nuts are AN364 AN320 SizeofNut orBolt TensionTypeNuts TorqueValue inch pounds ShearT ypeNuts 1032 60...

Page 73: ...ns of ascertaining a faulty component is substitution with a known functioning component This is practical if the substituted part is a switch or light bulb or easily available part Do not use this me...

Page 74: ...such as overheating burned wires loose components and loose electrical connections Disconnect the Cannon plug and inspect it and all other electrical connections for corrosion Correct any of these pro...

Page 75: ...ect that S G field is shorted or GCU M to S G A wire shorted to ground GCU D S G D 0 If high check wire and connections GCU H LCR X2 0 If high check wire and connections LCR X2 S G E 50 If high suspec...

Page 76: ...GCU Probable Causes There is a discontinuity in the circuit feeding power to the GCU which includes the wiring the 15A C B Generator Switch and the Start Switch Fix Make sure that the 15A C B is not...

Page 77: ...arness for broken wires and corroded or bad connections To check for a short in the instrument light fixtures make sure the master switch is OFF and disconnect the 60302 114 transistor output wire fro...

Page 78: ...be more than one quarter inch above the split ring When a battery seems weak or will not hold a charge after charging replacing the battery may be necessary The charge capacity of individual cells ma...

Page 79: ...meter is shown in Drawing 60084 The Voltmeter shows the voltage on the airplane s electrical bus Voltmeter readings may be used to determine the condition of the battery and Starter Generator When the...

Page 80: ...will continue until the switch is released The purpose of the solenoid is to provide a sharp cut off of fluid when the switch is released This prevents the dribbling of fluid onto the windshield Wind...

Page 81: ...he lower switch panel These switches allow the landing lights to be stopped at any point in their extension or retraction to provide the best placement of lighting to suit the pilot The landing lights...

Page 82: ...the lower panel Wiring schematics specific to each avionics component may be obtained from manufacturer s data These schematics are found in the figures section of the manual LIFE LIMITED ITEMS FAA R...

Page 83: ...000 hours Large bolt Tail Spring NAS147 60 1 000 hours 500 hours Clamp bolts Tail Spring AN7 22A 600 hours 300 hours Forward bolt 2 bolts aft end AN12H15A 2 000 hours 1 000 hours Tail spring PROPELLE...

Page 84: ...EVER IDLE Propeller pitch settings are 15 0 reverse 8 2 low pitch at the 42 station This check should be made at 100 hour intervals as called out in the Inspection Section TIE DOWN INSTRUCTIONS To hel...

Page 85: ...t and an attachment to join to the towing lug or ball on a vehicle The three quarter inch steel bar is bent at 90 degrees with four inches of bar extending in one direction and three inches in the oth...

Page 86: ...warning light system as a means of determining the quantity of fuel remaining The wiring schematic is shown on drawing 60084 Test Function To test the warning light bulb turn on the master switch and...

Page 87: ...The proper maintenance of weight and balance records is important to ensure that the airplane is operated within the weight and center of gravity limits that are established in the Flight Manual The...

Page 88: ...of the tester to the end of the instrument lead Red that was connected to the Alumel terminal on the engine thermocouple block Connect the red clip to the lead Yellow that was connected to the Chromel...

Page 89: ...tached 12 For the calibration check the operator will need to take readings from the gauge inside of the cockpit as well as at the test set near the engine a Rotate the TEMP ADJ knob on the test set s...

Page 90: ...eries 500 C to 700 C 700 C to 800 C Beyond 800 C 800 C 1000 C 20 C 10 C 20 C 20 C 20 C PT6A 60 Series 500 C to 750 C 750 C to 850 C Beyond 850 C Varies 1000 C 30 C 10 C 30 C 30 C 30 C Sample Test Card...

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