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Operational implications of some NACA/NASA rotary wing induced velocity studiesWind tunnel measurements show that the wake of a rotor, except at near-hovering speeds, is not like that of a propeller. The wake is more like that of a wing except that, because of the slow speeds, the wake velocities may be much greater. The helicopter can produce a wake hazard to following light aircraft that is disproportionately great compared to an equivalent fixed-wing aircraft. This hazard should be recognized by both pilots and airport controllers when operating in congested areas. Even simple momentum theory shows that, in autorotation and partial-power descent, the required power is a complex function of both airspeed and descent angle. The nonlinear characteristic, together with an almost total lack of usable instrumentation at low airspeeds, has led to numerous power-settling accidents. The same theory shows that there is a minimum forward speed at which a rotor can autorotate. Neglect of, or inadequate appraisal of this minimum speed has also led to numerous accidents. Ground effect and the problems it creates is discussed.
Document ID
19800011749
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Heyson, H. H. (NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 4, 2013
Publication Date
February 1, 1980
Subject Category
Aerodynamics
Report/Patent Number
NASA-TM-80232
Accession Number
80N20231
Funding Number(s)
PROJECT: RTOP 530-04-13-01
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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