JT8D Engine Maintenance Ground Run Procedure.

[Mr Meljoe Ferreira].

The following test provides necessary information to accomplish the tests required following repair or replacement of Engine and Airplane system components. Information is also provided for minimum ground check runs required to functionally test and troubleshoot airplane systems and components.

Because the extent of repair and replacement will vary with each engine, the type of the test required to ensure that satisfactory maintenance has been performed will vary also. To minimize ground running and to conserve fuel, this section provides ground test procedures which are related to the extent of repair or replacement. Prior to testing an engine after repair, see the repair reference table below, to determine the test required for any given engine repair:-

Unit Replacement or Repaired Minimum thrust required for Ground Run

Oil System:-

Ubing, Oil Tank, Filter Pressure and Scavenge Pumps, Accessory Gear Box seals [when neither gear box nor until Oil Temperature reaches 40 degC. Fuel system were removed]. Temperature Regulating Valve, Pressure Regulation valve - TEST A

Permissible to adjust Oil Pressure to 44-46 psi at Idle: 40degC Min oil temp recommended.

Accessory Gear Box:-

TEST C

Fuel System:-

Low Pressure Pump & Heater Filters, Fuel heater - low Pressure Tubing, Fuel pressure Diff switch - TEST A

High Pressure:-

Fuel control filter, Fuel pressurising & Dump valve filter. High pressure tubing, Tubing fuel nozzles, Fuel manifold, Fuel Oil cooler, Pressurising and Dump valve. - TEST C

NOTE:- Following pressurizing and dump valve repair or replacement, carefully inspect and after Test C f or fuel leakage at the end fittings of the transfer tubes between the P&D valve and fuel manifold inlet tube elbows [horns]. No leakage is permitted at the end fittings. On engines not having P & D valve drain port plugged. Fuel leakage at the P & D valve overboard drain must not exceed 300cc per hour measured during engine run only.

Fuel Control:-

TEST C

Hot Section:-

Combustion Chambers, Outlet duct nozzle, Guide vanes, Electrically actuated valves, Anti-icing valve fuel De-icing valve - TEST B

Visual check with Engines shut down. Observe valve position indicator on body of valve while actuating system on Aircraft.

Bleed Control system:-

Control valve tubing - TEST E

Ignition:-

Spark Igniters, Exciter unit, Leads Instrumentation. - Aural check. Perform start

Pt7 probes and tubing, EGT probes an harness. - Leak check system with Air, Check with portable Temperature Calibration Equipment.

Powerplant:-

System [Pretested and pretrimmed Engines]. Rig check thrust and start lever. Leak check. Applicable only when an engine is removed from using aircraft to facilitate airframe work / inspection and the engine is reinstalled in its original position. - TEST A

Airplane System components:-

Constant speed drive [CSD] - Motor Engine

Generator - TEST A

Engine Driven hydraulic pump - Motor Engine

Airplane system / component test:-

Engine Pressure Bleed Air compressor control system - Engine power as required. Not to exceed Test C maximum.

Constant speed drive - TEST A

Wing thermal Anti-icing system - TEST A

Bleed Air precooler system - Engine power as required

Airplane system troubleshooting:-

Engine bleed Air Compressor control system - Engine power as required not to exceed Test C maximum

Hydraulic System A - Motor Engine

For Engine start procedure follow routine ground run schedule.

CAUTION:- Before operation of Engine. Check that Engine Inlet, Exhaust and Run up areas are free of sand, gravel, loose objects, or equipment that could be drawn into the engine inlet or thrown aft by the exhaust blast.

TEST A - Ground check at Idle.

  1. Start Engine
  2. Operate Engine at Idle RPM for minimum of 5 minutes.
  3. Shut down engine
  4. Inspect Engine tubing, connections and components for fuel and/ or leaks.
  5. For Period of 20 minutes immediately following engine shutdown check for evidence of static oil leakage through No6 bearing carbon seals. Leakage appearing as an oil wetness but not puddling is acceptable. Any puddling that occurs within the 20 minutes period is unacceptable. If unacceptable, engine must be disassembled as necessary to determine cause and then repaired.

TEST B - Ground Check at Maximum Cruise.

  1. Determine part power trim target, Pt.7 and EPR for existing ambient temperature and true local barometric pressure. Refer to applicable trim table section.
  2. Start Engine.
  3. Advance thrust lever to part power trim target determined in step [1] above and maintain for minimum of 5 minutes. Ensure that Engine limits are not exceeded.
  4. Check Functional operation of repaired or replaced components and associated parts. Ensure that no air, fuel or oil leaks are present.
  5. If check of anti-ice system is required. Place anti-ice switch in open position. Proper operation of system will be indicated by an immediate drop in EPR.
  6. Place Antiice switch in close position. Check for increase in EPR.
  7. Retard thrust lever to IDLE and allow engine to cool for 5 minutes.
  8. Shut down engine.
  9. Inspect engine for evidence of fuel leakage at engine fuel pump and fuel control overboard drains. Leakage shall not exceed 60cc / hour during engine operation.
  10. Check for static oil leakage through No6 bearing seals. Leakage shall be measured for 20 minutes minimum period immediately following engine shutdown. Leakage appearing as an oil wetness but not puddling is acceptable. Oil puddling which occurs before expiration of 20 minutes is not acceptable. If unacceptable, engine shall be disassembled as necessary to determine cause and then repaired.

TEST C - Ground check at 3000 lb/hr Fuel flow.

  1. Start Engine
  2. Advance thrust lever as required to attain 3000 lb/hr fuel flow. Maintain for minimum of 5 minutes.
  3. Observe instrumentation and system components for proper operation.
  4. Retard thrust lever to Idle and allow engine to cool for 5 minutes.
  5. Shut down engine.
  6. Inspect engine for evidence of fuel and/ or oil leaks.

TEST D - Part Power Trim Check.

  1. Perform Engine power trim procedure. Refer to 71/09-200.Powerplant - Trim procedure.

TEST E - Ground check for bleed system operation.

  1. Start Engine
  2. Operate engine at Idle RPM. Check compressor bleed valve for proper operation. Refer to 71-09-100.Compressor Anti-surge bleed valve schedule.
  3. Shut down Engine.
  4. Inspect Engine for Evidence of Fuel and/or Oil leaks.

Before starting check that all precautions have been taken.

GROUND OPERATION:-

  1. Aircraft facing into the wind. MLG wheels chocked, All gear locks installed and struts inflated.
  2. Run up area clear of ladders, stands, rags and loose objects.
  3. Access panels and aircraft doors secure.
  4. Engine intakes for obstructions and secondary air door inlet recess for foreign objects.
  5. Check hydraulic brake accumulator.
  6. External Air source connected [If used].
  7. External electrical power connected [If used]. [Items 6 & 7 N/A if APU used].
  8. Check No.1,2 & APU Fire bottle pressure.[630psi at 70degF].
  9. All external covers removed.
  10. Ground Intercommunication check.
  11. Engine intake and exhaust efflux area clear of personnel.
  12. Ground fire bottle positioned.

COCKPIT:-

  1. External power check 'ON' [If used].
  2. Battery Switch 'ON'.
  3. CB's and Fuses checked and 'ON' [Power to be off while pulling or resetting CB's].
  4. Generators OFF.
  5. A/C Meter s/w - and Power or APU generator - 'Selected'
  6. Warning lights - press to test.
  7. Fluid level, sufficient fuel for run, Engine & hydraulic 'FULL'.
  8. Fuel crossfeed closed [unless required].
  9. Boost pumps warning lights checked [one tank at a time].
  10. Fuel Boost pumps 'ON'.
  11. Bleed Air Isolation valve 'OPEN'.
  12. Air conditioning packs 'OFF'.
  13. Equipment cooling blowers 'NORMAL'.
  14. Fuel heaters 'OFF'.
  15. Pneumatic Pressure Indicator 'CHECK' 40+/- 5 psig.
  16. No.1 'B' Hyd. System pump 'ON'.
  17. Hyd.Grd interconnect switch 'OPEN'.
  18. Hyd. 'A' system pumps switch 'ON'.
  19. Speed brake - down detent.
  20. Check brake pressure 3000 +/- 50 psi.
  21. With Rudder pedals 'NEUTRAL' Fully depress both brake pedals and lift parking brake lever, Release brake pedals. WARNING LIGHT ON.
  22. Reverse Thrust Forward and down.
  23. Thrust lever 'Idle'.
  24. Start lever 'cut-off'.
  25. Wing flap 'UP'.
  26. Undercarriage 'DOWN' Green lights 'ON'.
  27. Door warning lights checked.
  28. Anti-skid 'OFF'.
  29. Engine Anti-ice 'OFF'.
  30. Fire protection module check and test.
  31. Wing de-icer 'OFF'.
  32. Rotating beacon 'ON'.
  33. Pitot heat 'OFF'.
  34. Window heat 'OFF'.
  35. Visual check of Instruments.
  36. Ready to start APU [If to be used].
  37. Applicable engine bleed air switch 'ON'.
  38. Record data plate RPM [If required].

START AND IDLE:-

CAUTION:-

  1. When Engine is exposed to a Tail wind prior to starting. The N1 Rotor may windmill in reverse. Under these conditions. Ensure positively N1 rotation prior to introducing Fuel to the Engine.
  2. When possible The start lever should not be moved out of the cut-off position until 20% N2 is reached.
  3. Maximum starting EGT 420 degC on hotter than standard day and 350 degC cooler than standard day for P&W JT8D-9A Engines.
  4. Maximum starting EGT for P&W JT8D-15 is 550 degC and for JT8D-15A is 575 degC.

NOTE:- The use of Fast response EGT probes on this engine elements the need of Two ground starting EGT limits, as applicable to P&W JT8D-9A Engines.

  1. During Start if Fuel flow is found exceeding 550 kgs. It is an Indication of a Hot start and start lever must be moved to cut-off position.
  2. Whenever [a] The Engine fails to light within 20 seconds, [b] An indication on N1 RPM is not evident by 20% N2 RPM or [c] The EGT is climbing rapidly through 400degC, for JT8D-9A Engine. 550 degC for JT8D-15 and 575degC for JT8D-15A engines during start. Return lever to cut-off, continue to motor Engine for 10 to 15 seconds to remove fuel and vapour or evidence of fire from within the engine or until the EGT becomes normal after satisfactory clearing of the Engine. Override the start switch solenoid and return the switch to off. After Engine rotation ceases & before another start attempt. Determine & rectify the cause of unsatisfactory start.
  3. Normal starter duty cycle is 30 seconds On and 60 seconds Off, extended duty cycle of 60 seconds on at speeds upto 35-40% N2 and 60 seconds off may be repeated once ,then a 5 minute cooling period must be observed for motoring Engine. The cycle is 2 minutes on & 5 minutes off.
  4. Check that Engine Acceleration to Idle is satisfactory. Engine should reach Idle RPM within 2 minutes otherwise move start lever to cut off. Check that oil pressure warning light and CSD Low pressure light goes out.

    5. Before Engine start

    Record.

    Ambient Temperature___________________________________

    True Infield Barometric pressure in hg_____________________

    Computed Take off EPR_________________________________

    PROCEDURE:-

    Note:- Refer to B737 Maint Manual chapter 71 for operating limits.

    ENGINE

    1

    2

     

     

     

    RECORD

     

     

    CHECK

     

     

    CHECK

     

     

    RECORD

     

     

    RECORD

     

     

    RECORD MAX

     

     

    CHECK

     

     

 

  1. Select 'Grd' position on Engine to be started.
  2. Start Lever at Minimum 20% N2 advance the start lever to 'Idle'. Record N2 RPM at which N1 indicates.
  3. Light up within 20 seconds evidence by rise in EGT.
    4.
  4. Starter cut off 40% N2.Selector Switch returns to OFF automatically.
  5. Oil & CSD pressure warning lights out.
  6. Max Fuel flow Approx 400 kgs/hr.
  7. Max EGT Engine 420 degC with bleeds off & 480 degC bleeds on for P&W JT8D-9A,475 degC with bleeds off & 535 degC with bleeds for P&W JT8D-15 and 499 degc with bleeds off & 559 degc with bleeds On for P&W JT8D-15A Engines.
  8. Generator 'ON'. LOP lights out. Temperature in green band. Output 400 CPS 115 volts.
  9. Idle readings following initial start:-

ENGINE NUMBER

1

2

EPR

 

 

N1%

 

 

N2%

 

 

EGT

 

 

Fuel Flow Kg/hr

 

 

Oil Pressure [44 to 46 psi]

 

 

Oil Temperature. DegC.

[Max 120 degC for -9A & 130 degC for -15/15A]

 

 

Vibration level in MILS

FRONT

TURBINE

 

 

Check operation of Surge bleed valve as detailed in B737 manual chapter 71-00.

Record N1% RPM

Close

Open

CONDITION CHECKED [If required].

1.Record Data plate RPM of Engines as required.

No1 Engine_____________% N2 No2 Engine________________%N2.

Correction Factor for data plate RPM [Refer to B737MM Trim table chapter 71-09-22 to 71-09-227].

Corrected Data plate RPM.

No1 Engine_______________%N2 No2 Engine________________%N2.

Advance Throttle lever to 1.65 EPR and record data below:-

ENGINE NUMBER

1

2

N1% RPM

 

 

N2% RPM

 

 

EGT degC

 

 

Fuel Flow Kg/hr

 

 

Vibration level in MILS

FRONT

TURBINE

 

 

Advance Power lever to computed Take off EPR and record data [Engine bleed switches off] below:-

ENGINE NUMBER

1

2

N1% RPM [100.1% MAX.-JT8D-9A]

N1% RPM [102.4% MAX.-JT8D-15/15A]

 

 

N2% RPM [100.4% MAX.-JT8D-9A]

N2% RPM [100.4% MAX.-JT8D-15/15A]

 

 

EGT degC [590 DegC Max for P&W JT8D-9A]

EGT degC [620 DegC Max for P&W JT8D-15/15A]

 

 

FUEL FLOW Kg/hr

 

 

Oil Temp degC [Max 120 degC for P&W JT8D-9A & 130 degC for P&W JT8D-15/15A Engines}.

 

 

Oil Pressure degC [40 to 55 psi].

 

 

Vibration level in MILS

FRONT

TURBINE

 

 

Ensure RPM does not exceed N1 RPM MAX. Record if Anti-icing is 'ON' or 'OFF'.

Return Thrust lever to Idle, allow Engine to cool for 5 minutes before Shut down.

Generators 'OFF' ground power or APU power 'ON' Advance thrust lever to 75% N2 RPM for app 30 sec Return to Idle.

Check that Engine Decelerates freely. Turn off applicable booster observe that all indicators returns to Zero and warning lights 'ON'.

Check for static oil leakage through N06 bearing carbon seals for 20 minute period immediately following engine shutdown. Oil leakage appearing as an oily wetness but not puddling during this 20 minutes period is acceptable. Oil puddling which occurs before 20 minutes elapsed time is unacceptable and Engine must be disassembled as necessary to determine cause and then repaired.

On Completion of run, check engine and components for fuel , oil, air and hydraulic leaks.

If Engine controls are disturbed then carry out duplicate inspection on completion of rectification.

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