AMC1 27.959 Unusable fuel supply

• ED Decision 2023/001/R found in: CS-27 Amdt 10 - Small Rotorcraft (Feb 2023)

AMC1 27.959 Unusable fuel supply ED Decision 2023/001/R This AMC supplements FAA AC 27.959. This AMC provides clarification on the acceptability of analyses and ground testing which could be used as means of compliance if supported by actual flight test data. FAA AC 27-1B provides some guidance by focusing on a flight/test demonstration as being directly in line with the intent of the specification to validate ‘…any intended operations and flight manoeuvres…’, but also provides for acceptability of analyses and ground testing. In order to accept a demonstration by laboratory test with partial flight or ground test, the applicant should demonstrate the ability of the proposed substantiation method (bench testing, complemented by analysis and /or ground test) to cover the effects offered normally by the flight-testing environment. In case the full flight-testing environment cannot be accurately simulated, it is necessary to either: — revert to compliance demonstration based on flight test; or — apply some conservatism factors on the unusable fuel quantity value resulting from the laboratory testing to determine the final unusable fuel value. Any (steady or transitory) engine abnormal operation/malfunction has to be taken as an indication that the fuel in the tank is becoming unusable. [Amdt 27/10]