Does anyone know how to calculate how much downwards force a helicopter would exert on the roof of a house if it hovered over it at 700ft?
That is very true. Usually something along these lines would be calculated via fluid dynamics package or simply measured in the field. There are so many things that could have an effect on the outcome.Momentum theory is very good to calculate the induced velocity at rotor dics as well as at distance very below the rotor. Unforturnately, it does not have any information for determining the induced velocity at these points which are between the rotor dics and infinte distance, for example at 3 or 4 radiaus below the rotor.