A320neo CFM LEAP-1A Engine Motoring Guide: Dry vs. Wet

Performing ground motoring checks on the Airbus A320neo’s CFM LEAP-1A engine requires a precise understanding of the operational distinctions between dry and wet procedures. A dry-motoring check rotates the powerplant core via the pneumatic starter without fuel or ignition to purge residual fuel, verify instrument operation, and ensure starter speed requirements are met. Conversely, a wet-motoring check introduces unignited fuel strictly through the pilot primary fuel manifolds to prime the system or perform localized leak inspections. Rigorous adherence to starter duty cycles, safety limits, and AMM-compliant circuit breaker configurations is mandatory to mitigate the risk of tailpipe fires and protect engine hardware during these ground operations.

1. Safety Warnings and Cautions

1.1 Safety Hazards for Dry and Wet Operations

• Thermal Hazard Warning: Be careful when you do work on the engine parts after engine shutdown. Use applicable thermal gloves. The engine parts and the engine oil can stay hot for 1 hour after shutdown and can burn you.
• Air Data Probe Hazards: Do not touch the probes during or immediately after this procedure. The probes will be hot and can burn you. Remove the protective covers from the probes before you do this procedure to prevent the probes and protective covers from becoming damaged or burned.
• Mechanical Fan Hazard: Do not try to stop the fan from turning by hand. This can cause injury to persons and damage to the equipment.
• Aircraft Movement Mitigation: Make sure that the landing-gear ground safety-locks and the wheel chocks are in position. Movement of the aircraft can be dangerous.
• Area Cleanliness Protocol: Make sure that all engine operating areas are as clean as possible. All ramps, taxiways, runways, and other operating areas must be very clean to prevent bad damage to the engine, aircraft, and persons in the area.
• Flight Control Travel Ranges: Make sure that the travel ranges of the flight control surfaces are clear. Movement of flight controls can cause injury to persons and/or damage to equipment.
• Cowling Limitations: Do not go above open cowling limitations when you do the tests. Natural winds and irregular forces from sudden gusts increase the dangerous area.
• Hydraulic Pump Protection: Make sure that there is no hydraulic ground power supply connected to the aircraft when you do this procedure. If a hydraulic ground power supply is connected, there is a risk of damage to the engine pumps.
• Fuel Pump Lubrication Caution: Do not operate the engine if the fuel inlet pressure is not positive. The fuel is necessary to lubricate the engine fuel pump and thus prevent damage.
• Leak Check Prohibition: Do not replace an idle leak check by a motoring test. You cannot detect potential oil leaks with a motoring test. If you do a motoring test instead of an idle leak check, you can cause an engine shutdown.

1.2 Wet-Motoring Specific Safety Mandates

• Hangar Explosion Warning: Do not do a wet motoring of the engine in a hangar or other closed area. A large quantity of very flammable fuel fumes comes out of the engine during this procedure and there is a high risk of fire. This test must be performed strictly outdoors.
• Pre-Test EGT Limitation: Before you do the wet-motoring check procedure, do a check of the Exhaust Gas Temperature (EGT) on the upper ECAM Display Unit (DU) and make sure that it is less than 100°C (212°F). This is to prevent the risk of fire in the engine tail pipe. If you do not obey this instruction, injury to persons and/or damage to equipment can occur.

2. Reasons for Dry vs. Wet Motoring

2.1 Dry-Motoring Check Objectives

It is necessary to do a dry-motoring check during inspection or after maintenance to make sure that:

• The engine turns freely and all instruments operate correctly.
• The operation of the starter obeys the speed requirements for correct starts.
• Remaining fuel that can collect in the combustion chamber or the lower section of the turbine casing is safely dried out.
• A leak check can be performed on Fuel System Line Replaceable Units (LRUs) located strictly upstream of the Fuel Metering Unit (FMV) High-Pressure Shutoff Valve (HPSOV).

2.2 Wet-Motoring Check Objectives

Wet-motoring is necessary for maintenance checks where you must turn the engine and have the fuel flow without ignition. This task provides minimal fuel flow and uses only the pilot primary/main fuel-manifolds with the pilot secondary manifold inactive to perform:

• A leak check of the fuel system.
• Alternative Fuel Leak Procedure: If necessary, do a wet motor procedure (menu mode) per AMM Chapter 73 with the pilot primary/main fuel-manifolds and the active pilot secondary manifolds, which increases the fuel flow and makes it easier to find fuel leaks.
• Priming of the engine fuel system after maintenance.

3. Starter Limits & Permitted Duty Cycles

The core speed engagement ceilings and starter duty cycles are identical for both motoring procedures:

• Core Speed Ceiling: Do not engage the starter when the core speed (N2) is above 63%.
• Permitted Starter Duty Cycles: Maintenance crews must obey one of the two following timing profiles:
  • Profile 1: Three motoring cycles one after the other. Each cycle has a duration of 2 minutes and there is a rest period of 60 seconds between each cycle. At the end of this rest period, a 15-minute cooling period occurs before a new start or motoring cycle.
  • Profile 2: Three motoring cycles one after the other. Each cycle has a duration of 5 minutes and there is a rest period of 5 minutes between each cycle. At the end of this rest period, a 15-minute cooling period occurs before a new start or motoring cycle.

4. Job Set-Up & System Configurations

4.1 Initial Aircraft Setup

1. Make sure landing-gear ground safety-locks and chocks are in position. For dry-motoring, put an adjustable 2-meter (6 ft) access platform in position if required.
2. Make sure that the engine inlet and exhaust covers are removed and that these areas are clear of unwanted objects. Look at the general condition of the fan spinner and fan blades, core exhaust nozzle, Low Pressure Turbine (LPT), and external surfaces of the cowls.
3. Do a visual check of the fan inlet, temperature sensors, and exhaust areas. Make sure that the engine inlet, inlet lip, fan, spinner, and fan exhaust duct are clear of ice or snow. Melt the ice or snow with hot air if the fan does not turn freely before an engine operation.
4. Do a check of the drain ports for fuel, oil, and hydraulic leaks per AMM Chapter 71. Make sure that the fuel drained from the engine does not cause a fire.
   • Sub-Zero Fuel Leak Note: At temperatures below -20°C (-4°F), minor fuel leaks from the drain may occur and should not be considered abnormal. A check for fuel leaks at the drain mast shall be performed only after the engine is fully stabilized at idle.
5. Verify flaps and slats are fully retracted per AMM Chapter 27.
6. Energize the aircraft electrical circuits from external power or the APU per AMM Chapter 24.
7. Do the EIS start procedure (upper ECAM DU and lower ECAM DU only) per AMM Chapter 31.
8. Supply the aircraft pneumatic system from the HP ground-power unit or the APU bleed per AMM Chapter 36.
9. On the lower ECAM DU, get the HYDRAULIC page. Make sure the pressure of the Green reservoir (for Engine 1) or Yellow reservoir (for Engine 2) is correct, and verify the reservoir fluid level is correct to lubricate the pumps.
10. On the HYD/FUEL panel 40VU, confirm the OFF legend of the ENG 1(2) PUMP pushbutton switch is off.
11. Do the operational test of the engine fire and overheat detection loop/squib per AMM Chapter 26. Obey local fire-fighting regulations.

4.2 Circuit Breaker Isolation Configuration

The system circuit breakers must be configured differently before the test to safely isolate the engine fuel or ignition systems depending on the task:

• For the Dry-Motoring Check Line-up: Open, safety, and tag the specific High-Pressure Fuel Shutoff Valve (HP FUEL SOV) circuit breakers on panel 49VU. This ensures no fuel can enter the engine. Make sure all engine ignition, EIU, and FADEC circuit breakers are closed as per AMM Chapter 71.
• For the Wet-Motoring Check Line-up: Make sure the FADEC and EIU circuit breakers are closed on panels 49VU and 121VU. Open, safety, and tag the specific Engine Ignition System (IGN SYS A and SYS B) circuit breakers on panels 49VU and 121VU to completely isolate the ignition path.

4.3 Cockpit Safety Controls

1. On the center pedestal ENG panel 115VU, ensure the ENG/MODE selector switch is in NORM, and verify the ENG/MASTER 1(2) control switch was in the OFF position not less than 5 minutes before you do this procedure. Put warning notices in position to tell persons not to operate these switches.
2. On the ENG section of maintenance panel 50VU, ensure the ON legend of the FADEC GND PWR/1(2) pushbutton switch is off, and place a warning notice not to energize the FADEC.
3. Access Note: It is only necessary to open the fan cowl door and the thrust reverser door when you do the leak check of the fuel system. For other maintenance tasks, you can do this procedure with the doors closed. If opened, ensure the thrust reverser system is deactivated for maintenance per AMM Chapter 78.

5. Step-by-Step Dry-Motoring Procedure

1. On the FUEL panel 40VU, push all the FUEL/PUMPS pushbutton switches inward (the OFF legends go off).
   • Vent Tank Leakage Caution: If the wing tanks are full, there is a risk of fuel leakage from the aircraft vent tank. Release center tank transfer switches (CTR TK LXFR and RXFR) via pushbuttons 5QL and 6QL to the OFF position (the OFF legend comes ON) and ensure the primary MODE SEL pushbutton 4QL is pushed inward (MAN legend goes off).
   • Preservation Task Exemption: If you do this procedure as part of an engine preservation task in which the aircraft main-fuel supply-hose to the engine is disconnected and replaced with the engine preservation kit, do not do this step and step 2.
2. Select the FUEL System Display (SD) page to make sure that the LP valve is open.
3. Make sure that the throttle control lever on the engine is in the idle stop position (zero on the graduated sector).
4. On the central pedestal ENG panel 115VU, set the ENG/MODE selector switch to CRANK.
   • System Response: On the lower ECAM DU, the ENGINE page comes into view.
5. Parameter Pre-check: Make sure that the available air pressure on the ECAM is between 25 psi (2 bar) and 55 psi (4 bar). Make sure that the quantity of oil in the oil tank of engine 1(2) is correct. If necessary, fill the oil tank per AMM Chapter 12.
6. On the overhead panel 22VU, push the respective ENG/MAN/START/1(2) pushbutton switch inward.
   • System Response: The ON legend of this switch comes ON. On the lower ECAM ENGINE page, the symbol for the starter valve moves to the open position.
   • Indications: Make sure that the engine turns and the oil pressure indication is positive. In cold weather conditions, important oil-pressure surges can occur due to viscosity.
7. While the engine does a motoring, do a visual check for leaks at the fuel and oil system tubes and manifolds. You can motor the engine as long as necessary within the strict starter limits.
8. To stop the test, release the overhead ENG/MAN/START/1(2) pushbutton switch. The internal ON legend goes off, and the symbol for the starter valve moves to the closed position. The engine motoring stops and the engine coast-down starts.
9. On the ENG panel 115VU, set the ENG/MODE selector switch to NORM. The ENGINE page goes out of view on the lower ECAM DU.
10. On the FUEL panel 40VU, release all the FUEL/PUMPS pushbutton switches (the OFF legends come ON).
11. On the ECAM control panel, select the ENGINE page to bring the ENGINE page back into view on the lower ECAM DU for post-test tracking.

6. Step-by-Step Wet-Motoring Procedure

1. On the overhead panel 115VU, ensure the ENG/MASTER 1(2) control switch is set to OFF before you start the fuel pumps.
2. On the overhead FUEL panel 40VU, push all the FUEL/PUMPS pushbutton switches inward (the OFF legends go off).
3. Make sure that the throttle control lever on the engine is in the idle stop position (zero on the graduated sector).
4. On the central pedestal ENG panel 115VU, set the ENG/MODE selector switch to CRANK.
   • System Response: On the lower ECAM DU, the ENGINE page comes into view.
5. Critical EGT Validation: On the upper ECAM DU, make sure that the Exhaust Gas Temperature (EGT) is less than 100°C (212°F). If the EGT is over 100°C, do not continue the wet-motoring check.
6. Pneumatic Check: Verify the available air pressure on the lower ECAM is between 25 psi (2 bar) and 55 psi (4 bar). Make sure that the quantity of oil in the oil tank is correct.
7. On the overhead panel 22VU, push the respective ENG/MAN/START/1(2) pushbutton switch inward.
   • System Response: The ON legend of this switch comes ON, and the symbol for the starter valve moves to the open position. Ensure the engine turns and the oil pressure indication is positive. (Important cold weather oil pressure surges can occur).
8. Fuel Command: When the core N2 speed is between 15% and 20%, set the ENG panel 115VU ENG/MASTER 1(2) control switch to ON.
   • System Response: On the upper ECAM DU, the fuel flow indication (FF) increases. On the lower ECAM DU, make sure that the oil pressure indication remains positive.
   • Time Limit Constraint: Do not operate the engine for more than 15 seconds with the ENG/MASTER 1(2) control switch set to the ON position.
9. Purge Cutoff: After a fuel mist spray is shown exiting the tailpipe, immediately set the ENG/MASTER 1(2) control switch back to OFF.
   • FADEC Behavior Note: The symbol for the starter valve can indicate that it is in the closed position for several seconds during the reset of the Electronic Engine Control (EEC). After the EEC reset, the starter valve is automatically opened again.
10. The Fuel-Clearing Run: Continue the dry-motoring of the engine for exactly 60 seconds. This will dry the raw fuel that remains in the combustor and prevent a tailpipe fire.
11. After 60 seconds has elapsed, release the overhead panel 22VU ENG/MAN START 1(2) pushbutton switch. The internal ON legend goes OFF, the starter valve symbol closes, engine motoring stops, and the engine coast-down starts.
12. On the ENG panel 115VU, set the ENG/MODE selector switch to NORM. The ENGINE page goes out of view on the lower ECAM DU.
13. On the HYD/FUEL panel 40VU, release all the FUEL/PUMPS pushbutton switches (the OFF legends come ON).

7. Motoring Sequence Dry vs. Wet

8. Post-Motoring Inspections & Close-Up

8.1 Acoustic Auditing & Visual Leak Inspections

• Coast-down Check: During engine coast-down, while the components continue to run, listen for unusual noise from these components. Gear noise and seal rubs are usual and normal noises.
• Core Roughness Check: Check the engine, fan frame, and turbine for unusual roughness.
• Oil Level Servicing: Check the oil level and service as necessary per AMM Chapter 12. If servicing is required, do servicing of the oil tank but fill the oil tank to the “MAX” mark minus 3 quarts (do not overfill).
• Dry-Motoring Leak Inspections: Meticulously check all fuel and oil lines, fittings, and upstream components for leaks per AMM Chapter 71. Inspect the fan inlet and turbine exhaust for abnormal conditions.
• Wet-Motoring Leak Inspections: Make a check of the fuel-nozzle manifold-shrouds for leaks. No leaks are permitted. Fuel on the shrouds is an indication of a leak in the system. Make an inspection of the lubrication system lines, fittings, and accessories for leaks per AMM Chapter 79.

8.2 Flight Warning Computer (FWC) Reset Protocol

• False ECAM Engine Alert: During the wet-motoring procedure, a false “ENGINE FAIL” ECAM warning message can come into view. If it does, ignore it during the test sequence.
• The Reset Process: If the ENGINE FAIL warning message came into view during the test, you must reset the two Flight Warning Computers (FWCs) after the run concludes:
  1. Locate and open the specific FWC supply circuit breakers on panels 49VU and 121VU as per the AMM close-up lineup.
  2. Close the circuit breakers to clear the false latched message from the flight deck display.

8.3 Final Close-Up Checklist

1. Remove all safety clips and tags, and close all opened engine ignition or fuel valve circuit breakers to return them to their operating configuration.
2. Stop the pneumatic supply to the aircraft by disconnecting the HP ground-power unit or stopping the APU per AMM Chapters 36 and 49.
3. Do the EIS stop procedure per AMM Chapter 31.
4. Make sure that the work area is clean and clear of tools and other items. Remove any access platforms used.
5. If the cowls were opened for leak checks, close the thrust-reverser cowl doors per AMM Chapter 78, do the reactivation of the thrust reverser after maintenance per AMM Chapter 78, and close the fan cowl doors per AMM Chapter 71. Remove all remaining warning notices.
6. Make sure that the air data probes are completely cold, and safely install the protective covers back onto the TAT, AOA, and pitot probes.
7. De-energize the aircraft electrical circuits per AMM Chapter 24.