Max power assurance run witnessing: what the MPA proves at redelivery

What an MPA run is

A ground run, on wing, at take-off power under controlled conditions, following the AMM's power assurance procedure. The crew or maintenance team records the parameters — EGT, N1, N2, fuel flow, oil pressure and temperature, vibration — corrected for ambient conditions and compared with the limits in the manual and, at a lease event, with the minimums in the lease.

What it proves

That the engine reaches its rated thrust with margin to spare. The EGT margin from the run is the number most leases care about, because it predicts how long the engine can stay on wing before a performance restoration.

Why a witness

The lease usually says the lessor's representative may attend. An independent witness confirms the procedure was followed, that the conditions were as recorded, that the data is complete and unedited, and that the result is compared with the right limits. When the numbers are later disputed, the witness's record settles it.

What is in the witness report

The date, aircraft and engine identity, ambient conditions, the procedure reference, the recorded parameters and their corrected values, the comparison with manual and lease limits, any deviations, and the witness's signature.