CS-E 340 Vibration Tests

• ED Decision 2007/015/R found in: CS-E Amdt 5 - Engines (Dec 2018)

CS-E 340 Vibration Tests ED Decision 2007/015/R (See [AMC E 340](#_DxCrossRefBm1371447699)) (a) Tests by approved methods must be made on an appropriate mounting to satisfy the Agency that no dangerous torsional or flexural vibration characteristic exists in the dynamic system throughout the operating range of crankshaft rotational speed and Engine power used in flight. In the absence of adequate evidence to the contrary, a maximum stress shown to be safe for continuous use must be regarded as the maximum safe stress. The range must include low power operation and must comprise crankshaft speeds from idling to the highest of the following: 110% of the desired Maximum Continuous speed, 105% of the desired maximum Take-off speed, or the maximum desired Over-speed. Observations must be made at increments of 50 crankshaft rpm throughout this range. Tests covering the range up to the desired maximum take-off speed rating must also be made with that cylinder not firing which is most critical from the point of view of vibration. (b) A representative flight Propeller must be used for these tests. In the case of a Fixed Pitch Propeller a ‘throttle’ curve must be run. In the case of a Variable Pitch Propeller the procedure must normally be the same, with the Propeller blade pitch set to a fixed value which will give maximum Engine power at maximum Engine rotational speed. If the results of the tests with a Variable Pitch Propeller show the existence of a serious critical vibration within the operating speed range, a more detailed investigation must be made at speeds within the critical range. (c) A harmonic analysis of the vibration records must be made by a method approved by the Agency, at each increment of Engine speed and the results plotted against Engine speed so that the predominant orders of vibration and their relative magnitudes are clearly shown throughout the operating speed range of the Engine. (d) In cases where torsional strain in the Propeller shaft has been measured by means of a torsional strain type of vibration pickup, the torque amplitude of the orders of vibration must be plotted about the mean torque curve for the Engine. In other cases where for practical reasons it is impossible to use the strain type of torsional vibration pickups, and a seismic type of instrument attached to the free end of the crankshaft is used, the angular displacement amplitudes of the various orders of vibration at the free end of the crankshaft must be plotted against Engine speed. (e) A tabulation based on the theoretical and test results obtained must be made detailing the following information relating to resonant conditions for the most serious criticals: Engine speed, order of vibration, frequency, maximum and minimum values of vibration stress in the crankshaft and Propeller shaft and the region at which they occur. Diagrams showing the displacement curves for the modes of vibration associated with these criticals should also be presented. (f) If excessive vibration is found to be present in the operating range of the Engine, suitable remedial measures must be taken prior to the endurance test of [CS-E 440](#_DxCrossRefBm1371447623). (g) If moderate vibration is found to exist, which is not sufficiently serious to warrant the introduction of modifications but needs proof of its effect on the Engine, a vibration penalty test must be substituted for those stages of the endurance test as are considered most suitable and must include sufficient duration under the most adverse vibration condition to establish the ability of the Engine to resist fatigue Failure. [Amdt. No.: E/1]