How to Find the N1 Rotor Zero Index Mark on Airbus A320neo Family Engines (LEAP-1A)

ByAviationHunt Team Hours Updated on

Establishing the N1 rotor zero index is the mandatory baseline step before inspecting individual Low Pressure Compressor (LPC) and Low Pressure Turbine (LPT) blades. This procedure ensures a systematic inspection and prevents blades from being missed or double-counted.

Note: This guide is applicable for the Airbus A320neo family engine CFM LEAP-1A.

1. Identify Fan Blade No. 1

  • Look inside the engine inlet at the top area of the platform front shroud.
  • Locate the small, machined dimple stamped into the shroud structure.
  • The fan blade positioned immediately adjacent to this dimple is designated as Blade No. 1.

2. Mark the Reference Blade

  • Apply a temporary maintenance marking to Blade No. 1 so it remains easily identifiable during manual rotation.

CAUTION: Apply the temporary marking (LN9051 markers) only to the convex side of the metallic leading edge. Do not apply marking material to any other location on the fan blade, as improper chemical contact can cause material degradation or damage to specialized blade coatings.

3. Align with the T12 Sensor

  • Manually rotate the N1 rotor until Blade No. 1 points upward.
  • Align the marked leading edge of the blade precisely with the T12 sensor.
  • The T12 sensor serves as the physical “12 o’clock” reference point located inside the top of the inlet cowl.

Once Blade No. 1 is aligned with the T12 sensor, the N1 rotor is successfully zeroed, and the stage-by-stage blade inspection can safely begin.

AviationHunt Team

The AviationHunt team consists of active, dual-licensed Aircraft Maintenance Engineers with extensive line experience across Airbus and Boeing fleets. We share aviation insights, tarmac realities, technical notes, syllabus study guides, and safety practices to bridge the gap between the textbook and the hangar floor.