Rotor Blade Motion in a Vertical Sharp‐edged Gust: A Study of the Dynamics of Helicopter Blade Flapping with a Method of Deriving Maximum Gust Deflexion Available to Purchase

Part I—Constant Chord Blades 1. Summary Rotor/fuselage clearance is the most fundamental design consideration when laying out a new project, and it is essential to estimate this accurately at a very early stage. When centrifugal force droop stops are fitted to a rotor, the design criterion is usually the effect of a sharp‐edged down gust impinging on the rotor when it is not generating thrust; for example, whilst running‐up on the deck of an aircraft carrier. In this paper the dynamics of blade flapping motion are developed and a method for rapidly obtaining maximum gust deflexion is presented in the form of a Data Sheet (FIG. 5). This enables the maximum deflexion in a gust to be determined with no calculation. The solution obtained is exact; hitherto the only attempts to calculate gust deflexion known to the writer have developed an approximate equation of motion for the blade, and offered the Particular Integral as a sufficiently accurate solution. It is shown in Part II of this paper that this can be very misleading, and undcr‐estimates the true deflexion. In preliminary project design, the blade inertia is, of course, unknown. It is shown that this is a function of the coning angle and CL, basic only, probably the two most fundamental design parameters.