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An Experimental Investigation of the Effect of Propellers Used as Aerodynamic Brakes on Stability and ControlTests were made of a model representative of a single-engine tractor-type airplane for the purpose of determining the stability and control effects of a propeller used as an aerodynamic brake. The tests were made with single-and dual-rotation propellers to show the effect of type of propeller rotation, and with positive thrust to provide basic data with which to compare the effects of negative thrust. Four configurations of the model were used to give the effects of tilting the propeller thrust axis down 5 deg., raising the horizontal tail, and combining both tilt and raised tail. Results of the tests are reported herein. The effects of negative thrust were found to be significant. The longitudinal stability was increased because of the loss of wing lift and increase of the angle of attack of the tail. Directional stability and both longitudinal and directional control were decreased because of the reduced velocity at the tail. These effects are moderate for moderate braking but become pronounced with full-power braking, particularly at high values of lift coefficient. The effects of model configuration changes were small when compared with the over-all effects of negative-thrust operation; however, improved stability and control characteristics were exhibited by the model with the tilted thrust axis. Raising the horizontal tail improved the longitudinal characteristics, but was detrimental to directional characteristics. The use of dual-rotation propeller reduced the directional trim charges resulting from the braking operation. A prototype airplane was assumed and handling qualities were computed and analyzed for normal (positive thrust) and braking operation with full and partial power. The results of these analyses are presented for the longitudinal characteristics in steady and accelerated flight, and for the directional characteristics in high- and low-speed flight. It was found that by limiting the power output of the engine (assuming the constant-speed propeller will function in the range of blade angles required for negative thrust) the stability and control characteristics may be held within the limits required for safe operation. Braking with full power, particularly at low speeds, is dangerous, but braking with very small power output is satisfactory from the standpoint of control. The amount of braking produced with zero power output is equal to or better than that produced by conventional spoiler-type brakes.
Document ID
19930092530
Acquisition Source
Legacy CDMS
Document Type
Other - NACA Wartime Report
Authors
Hanson, Frederick H (National Advisory Committee for Aeronautics. Ames Aeronautical Lab. Moffett Field, CA, United States)
Date Acquired
September 6, 2013
Publication Date
July 1, 1945
Subject Category
Aircraft Stability And Control
Report/Patent Number
NACA-ARR-5C01
NACA-WR-A-19
Accession Number
93R21820
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
Keywords
AIRPLANES, MILITARY
PROPELLERS, TANDEM
PROPELLERS, CONTROLLABLE-PITCH - REVERSIBLE
STABILITY & CONTROL
PROPELLERS, TRACTOR
WIND TUNNEL TESTS - AAL (10' X 7')
RUDDERS - DEFLECTION
PROPELLERS - HAMILTON STANDARD CONSTANT-SPEED

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