A320neo LEAP-1A Engine Fuel, Oil, and Hydraulic Leakage Limits

For line maintenance teams, managing fluid leaks on the LEAP-1A engine is a daily balance between operational safety and fleet efficiency. Misinterpreting a harmless static weep can quickly lead to premature, costly component replacements, while overlooking an active system limit compromises dispatch reliability. This technical guide consolidates the engine’s fuel, oil, and hydraulic leakage tolerances into a direct, scannable reference, helping crews quickly differentiate between acceptable operational boundaries and immediate grounding triggers.

1. System Safety Fundamentals & Stabilization Logic

Before fluid leakage measurements are analyzed, specific aircraft configurations must be understood to ensure both personnel safety and data accuracy.

• FADEC Safe-State: The FADEC system must remain completely unenergized during visual inspections to prevent accidental component actuation or false fault generation.
• The 5-Minute Drainage Rule: Following an engine shutdown, the master control switch must remain off for not less than 5 minutes before evaluating static leaks. This window allows residual fluids in internal cavities and drain lines to completely settle, preventing false or exaggerated initial readings.

2. Fuel System Diagnostic Workflows

Fuel leakage analysis is divided into two distinct operational phases: static (engine off) and dynamic (engine running). This methodology isolates minor component weeping from active structural or seal failures.

Phase 1: The Static Fuel Leak Check

Conducted with the engine completely shut down at the aircraft drain mast assembly:

• If the fuel leakage rate is less than 180 ml/h (60 drops per minute or 3 cc per minute): The system is baseline serviceable. No immediate maintenance action is required.
• If the fuel leakage rate is more than 180 ml/h (60 drops per minute or 3 cc per minute): A dynamic leak check is required immediately to verify active operational limits.

Phase 2: The Dynamic Fuel Leak Check

Performed by starting the engine (AMM Chapter 71) and stabilizing it at minimum idle for 5 minutes to fully pressurize the fuel system components. Discharge is measured immediately at the drain mast:

• If the fuel leakage rate is less than 180 ml/h (60 drops per minute or 3 cc per minute): The system is fully serviceable. No further action is required.
• If the fuel leakage rate is more than 180 ml/h, but less than 270 ml/h (60 to 90 drops per minute or 3 to 4.5 cc per minute): The engine remains serviceable for dispatch. Corrective tracking actions must be planned and completed within a maximum window of 25 flight cycles without interfering with regular revenue service.
• If the fuel leakage rate is more than 270 ml/h (90 drops per minute or 4.5 cc per minute): The engine is unserviceable. Shut down the engine and initiate isolation troubleshooting (AMM Chapter 71) to identify the failing internal unit.

3. Component-Specific Fuel Leakage Limits

When an individual fuel component boundary is breached, maintenance tracking systems reference the Over Serviceable Limit Extension parameters found in AMM Chapter 72.

4. Lubrication System Boundaries & Testing Regimes

Oil leakage isolation depends heavily on the geographic point of accumulation. Different engine operating speeds are required to clear or confirm seal serviceability.

Operational Verification Windows

• Fan Drain Mast Accumulation: If oil is tracking from the Accessory Gearbox (AGB) rotating seal pads, a 70 percent N1 High-Power Leak Check must be conducted for a duration of 10 minutes (AMM Chapter 71).
• Core Drain Mast & C-Sump Accumulation: If oil originates from the A-sump drain tube, B-sump drain tube, or C-sump drain tube, an Idle Leak Check must be performed for a continuous duration of 10 minutes (AMM Chapter 71).

CFM does not recommend connecting a sealed collection bottle directly to the drain lines when evaluating the A, B, or C sump drain tubes. Doing so restricts the internal venting airflow balance, blocks natural drainage, and creates highly inaccurate fluid volume measurements.

Accessory Gearbox (AGB) Rotating Seal Pad Limits

Limits across all primary drive pads on the AGB are completely uniform. If any seal pad listed below meets or exceeds a leak rate of 20 ml/h (1 cc per 3 minutes or 7 drops per minute), the seal is unserviceable and must be replaced before the next flight (AMM Chapter 72):

• Fuel Pump Pad Rotating Seal
• Hand Cranking Pad Rotating Seal
• Integrated Drive Generator (IDG) Pad Rotating Seal
• Engine Driven Hydraulic Pump Pad Rotating Seal

5. The Oil Sump Continued in Service (CIS) Protocol

The standard maximum serviceable limit for individual engine A-sump, B-sump, and C-sump leakage is 60 ml/h (20 drops per minute). However, to prevent unnecessary operational groundings, a tracking protocol allows engines with elevated idle sump leaks up to 540 ml/h to continue operating in 150 flight cycle blocks, provided strict technical criteria are met.

The Four Mandatory CIS Release Criteria

To qualify for a 150-cycle tracking extension, the engine must satisfy all four parameters simultaneously:

1. The individual oil leak at the affected sump drain tube remains between 60 ml/h and 540 ml/h (20 to 180 drops per minute) at a stable engine IDLE.
2. The total cumulative oil leak combining discharge from the A, B, and C sumps plus all auxiliary drains tracks below 540 ml/h (180 drops per minute) at IDLE.
3. Total engine oil consumption remains strictly within standard operational limits (AMM Chapter 72).
4. A high-power verification run (engine operated at a minimum of 70 percent N1 for 10 minutes) confirms that no oil leak above 60 ml/h (20 drops per minute) is present at elevated power settings.

Mandatory Maintenance Oversight Within the CIS Window

When an engine is operating within a CIS window, the following technical evaluations must be performed and cleared before the 150-cycle limit expires:

• Consumption Monitoring: Verify oil consumption and active oil pressures are within nominal operating limits (AMM Chapter 72).
• Debris & Filter Screens: Complete a visual inspection of the main sumps, AGB, and transfer gearbox sump scavenge screen plugs for debris (AMM Chapter 79), and check the main oil filter cartridge element (AMM Chapter 79).
• Line Clearance: Clean and inspect the B-sump, C-sump, and auxiliary drain plumbing channels (AMM Chapter 71). (Note: The B-sump drain line is physically linked to both the B-sump and auxiliary lines).
• Carbon Coking Audit: Inspect the Center Vent Tube (CVT) inner walls for heavy carbon build-up (AMM Chapter 72).
• Eductor Air Valve Status: Physically inspect the eductor air valve pop-out window. If the indicator flag has tripped shut and the word OPEN is no longer readable on the mechanism, the oil eductor valve has failed and must be replaced immediately (AMM Chapter 79).

Re-Extension Protocols

An engine can be cleared for an additional block of 150 flight cycles if an intermediate leakage evaluation confirms it still meets all four baseline release criteria. This re-extension requires repeating the target plumbing line cleaning (AMM Chapter 71) and the CVT carbon coking inspection (AMM Chapter 72).

If even one of the four baseline tracking criteria is violated at any point during active operations or intermediate inspections, the CIS extension is instantly voided. The aircraft must be held from revenue service until engine technical engineering is consulted.

6. Hydraulic System Interface Rules

External cowl or core hydraulic line leak calculations and fluid volume ranges are managed outside the scope of the engine powerplant chapter.

When external hydraulic fluid staining or active leakage is observed at the main aircraft drain mast assembly, maintenance crews must immediately transition to AMM Chapter 29 (Check of the External Leaks of the Hydraulic Components) to identify component classifications, drop tolerances, and downstream deferral or repair timelines.

⚠️ Educational Use Only: This guide is designed strictly for educational and training purposes to build conceptual system knowledge. It does not replace, supersede, or modify the official Aircraft Maintenance Manual (AMM). Maintenance personnel must always consult the active, current AMM Chapter 71 and relevant system chapters when performing live aircraft diagnostics and clearing defects.