AMC1 27.923 Rotor
drive system and control mechanism tests
ED Decision 2023/001/R
(a) Introduction
This AMC supplements FAA AC 27-1B, § AC 27.923 and should be used in conjunction with that AC when demonstrating compliance with CS 27.923.
(b) 30-minute power rating
(1) Explanation
The option to establish a 30-minute power rating for turbine engines for rotorcraft has been introduced in CS-E Amendment 5 (published on 14 December 2018) with the creation of CS-E 40(b)(4). Means to demonstrate compliance with this requirement are provided in the associated AMC E 40(b)(3) and (b)(4) 30-Second OEI, 2-Minute OEI and 30-minute Power Ratings.
In particular, AMC E40(b)(3) and (b)(4) mentions that ‘The 30-Minute Power rating may be set at any level between the Maximum Continuous up to and including the take-off rating, and may be used for multiple periods of up to 30 minutes each, at any time between the take-off and landing phases in any flight.’ In addition, CS-E 740(c)(2)(i) specifies additional running time for the endurance test for engines for rotorcraft for which approval with this rating is sought.
In comparison, the endurance test programme specified in CS 27.923 for rotorcraft rotor drive systems and control mechanisms:
— addresses the take-off power rating, which is ‘limited in use to a continuous period of not more than 5 minutes’ according to CS-Definitions, through the test runs specified in CS 27.923(b), and
— currently does not address the 30-minute power rating.
(2) Procedures
For applications including a 30-minute power rating, the applicant should consider that the approval of such rating should be supported by additional tests to be agreed with Agency, with the aim of determining that the rotor drive mechanism is safe considering the use of this specific power rating. In this context, the applicant may consider running additional test phases and/or extending the running time and/or increasing the minimum torque and speed conditions defined in CS 27.923 to include testing of this power rating.
[Amdt 27/10]
For small rotorcraft certification with a 30-minute power rating, EASA requires additional rotor drive system and control mechanism tests beyond standard requirements. These tests, agreed upon with the agency, ensure safety when utilizing this specific power rating, potentially involving extended run times or increased torque and speed conditions.
* Summary by Aviation.Bot - Always consult the original document for the most accurate information.
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