AMC2 27.307 Proof of structure
ED Decision 2023/001/R
FAIRING SUBSTANTIATION
This AMC supplements FAA AC 27-1B, § AC 27.307 and should be used in conjunction with that AC when demonstrating compliance with CS 27.307.
Further to CS 27.301, the specified loads must be distributed appropriately or conservatively and significant changes in the distribution of the loads, as a result of deflection, must be taken into account. FAA AC 27-1B, § AC 27.307 refers to the need for flight test measurement in the scope of the fatigue and damage tolerance demonstration. The methods used to determine load intensities and distribution should be validated by flight load measurements unless the methods used for determining those loading conditions are shown to be reliable.
Each fairing, when appropriate, should be constructed and supported so that it can resist any vibration, inertia, and air load to which it may be subjected in operation. The vibrations level, the inertia and air loads should be validated by appropriately instrumented flight measurements as recommended in FAA AC 27-1B, § AC 27.307.
For the fairings and the associated supporting structure, the loads can be shown unreliably predicted and require a measurement during flight tests.
The loads derived from flight testing should be compared with those obtained from analytical methods.
Note: AMC No.2 to CS 25.301(b) provides an acceptable means of demonstrating compliance with the provisions of CS-25 related to the validation, by flight measurements, of the methods used for determination of flight load intensities and distributions, for large aeroplanes.
The methodology presented in the CS-25 AMC material may be adapted to CS-27, to provide further guidance to this AMC.
[Amdt 27/10]
Small rotorcraft fairing structures must withstand operational vibration, inertia, and air loads. Compliance requires flight load measurements to validate load intensities and distribution, especially when analytical methods are unreliable. Flight test data should be compared with analytical predictions. Guidance from large aeroplane regulations may be adapted.
* Summary by Aviation.Bot - Always consult the original document for the most accurate information.
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