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A wind-tunnel investigation of parameters affecting helicopter directional control at low speeds in ground effectAn investigation was conducted in the Langley full-scale tunnel to measure the performance of several helicopter tail-rotor/fin configurations with regard to directional control problems encountered at low speeds in ground effect. Tests were conducted at wind azimuths of 0 deg to 360 deg in increments of 30 deg and 60 deg and at wind speeds from 0 to 35 knots. The results indicate that at certain combinations of wind speed and wind azimuth, large increases in adverse fin force require correspondingly large increases in the tail-rotor thrust, collective pitch, and power required to maintain yaw trim. Changing the tail-rotor direction of rotation to top blade aft for either a pusher tail rotor (tail-rotor wake blowing away from fin) or a tractor tail rotor (tail-rotor wake blowing against fin) will alleviate this problem. For a pusher tail rotor at 180 deg wind azimuth, increases in the fin/tail-rotor gap were not found to have any significant influence on the overall vehicle directional control capability. Changing the tail rotor to a higher position was found to improve tail-rotor performance for a fin-off configuration at a wind azimuth of 180 deg. A V-tail configuration with a pusher tail rotor with top blade aft direction of rotation was found to be the best configuration with regard to overall directional control capability.
Document ID
19750003859
Acquisition Source
Legacy CDMS
Document Type
Other - NASA Technical Note (TN)
Authors
Yeager, W. T., Jr.
(NASA Langley Research Center Hampton, VA, United States)
Young, W. H., Jr.
(NASA Langley Research Center Hampton, VA, United States)
Mantay, W. R.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 3, 2013
Publication Date
November 1, 1974
Subject Category
Aircraft Design, Testing And Performance
Report/Patent Number
L-9325
NASA-TN-D-7694
Accession Number
75N11931
Funding Number(s)
PROJECT: RTOP 760-63-02-06
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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