AMC E 20(f)  Power assurance data for engines with one or more OEI power ratings

ED Decision 2007/015/R

(1)     For Engines having one or more OEI ratings, the applicant should provide in the instructions for installation the necessary Engine data to support the installer in meeting the power availability specifications of CS-27.45(f) or CS-29.45(f).

These data should include the effects of those installation losses that can be defined at the Engine level. Such installation losses should include customer bleed, customer power extraction, and others as appropriate, up to and including the highest power rating.

(2)     The safety analysis of CS-E 510 should consider dormant Failures which could lead to non-availability of the OEI ratings and the results of this review should be part of the data required under CS-E 20(f).

(3)     The objective of the power availability procedures is to allow the installer to ensure that the Engine is capable of obtaining and sustaining the OEI ratings within the associated ratings operating limitations. The required Engine data are intended to be used for establishing a procedure for trending of individual Engine performance by the operator. These data should support maintenance procedures, intervals and standards applicable to the Engine, including sensors and indicating systems, to detect those latent or dormant conditions which are not detectable through the normal aircraft power assurance procedures (e.g., fuel control maximum flow capability, turbine section distress), or because the power assurance procedure will not include a topping check to the highest OEI rating power level.

The adequacy of these procedures, intervals and standards should be validated on the basis of the Engine and Engine systems Failure modes and effects analysis (FMEA) required under CS-E 510. The Engine database should include a thermodynamic model, the experience gained during development and certification testing, and the field experience gained with this Engine type or with engines of similar design, when applicable.

(4)     In order to satisfy the power availability specifications of CS-27/29.45(f) the data required under CS-E 20(f) should enable the installer to establish power assurance procedures in which the extrapolation of power assurance results can be achieved, from a lower power check level, up to the highest OEI rating power. The performance extrapolation may be accomplished by comparing the performance characteristics with the minimum acceptable Engine performance in a deteriorated state. The establishment of the minimum acceptable Engine performance characteristic depends on the existence of a reliable database. In a mature Engine programme, it is possible to use the new production Engine acceptance test data, Engine-to-Engine variation and also testing on engines prior to overhaul to determine the effects of deterioration. Thus, an up-to-date minimum Engine performance characteristic can be maintained.

For a completely new Engine design, or a remote derivative of an existing design, it may be somewhat difficult to establish the initial database. The experience from Engine development and certification tests should be used. This experience usually includes several thousand hours of running time to schedules which are expected to be more rigorous than normal commercial service. The information gathered from these tests could provide a sufficient database for the assessment of in-service engines, including the rate of deterioration. The testing of engines in production will eventually establish Engine-to-Engine variation, but an estimated worst variation should be assumed initially, based on the experience of engines of the same or similar design.

(5)     The applicant should also provide information on methods by which to assure that Engine limiter settings would not prevent the Engine from reaching the 30-Second or 2-Minute OEI power which would be automatically available in compliance with CS-E 50(f). These limiter settings may include Engine speed, measured gas temperature and fuel flow. Particular attention should be given to take-off conditions with a cold-soaked Engine.

[Amdt. No.: E/1]