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NASA-TN-D-6946
Lateral-directional aerodynamic characteristics of light, twin-engine, propeller-driven airplanes
Year: 1972
Abstract: Representative state-of-the-art analytical procedures and design data for predicting the lateral-directional static and dynamic stability and control characteristics of light, twin-engine, propeller-driven airplanes for propeller-off and power-on conditions are documented. Although the consideration of power effects is limited to twin-engine airplanes, the propeller-off considerations are applicable to single-engine airplanes as well.
The procedures are applied to a twin-engine, propeller-driven, semi-low-wing airplane in the clean configuration to determine the lateral and directional control derivatives as well as the static and dynamic stability derivatives as functions of angle of attack and power condition through the linear lift range of the airplane. Also determined are the spiral mode, roll mode, and Dutch roll characteristics for level-flight conditions over the speed range of the airplane. All calculations are documented.
Attempts to calculate the weathercock stability characteristics indicated a need to account for wing-body interference effects on the body contribution as a function of angle of attack and vertical position of the wing relative to the body. Vertical-tail-off windtunnel data of a single-engine version of the subject airplane are used to expand the design nomograph from which the body-plus -wing-body contribution to weathercock stability was determined in order to obtain the contribution for a semi-low-wing airplane as a function of angle of attack. Application of the expanded nomograph to the subject airplane resulted in improved correlation of calculated weathercock stability characteristics with wind-tunnel and flight data at low angles of attack. For additional improvement, in correlation, there is a need for design data to account for the effects of angle of attack on the sidewash acting on the vertical tail.
The correlation of the calculated effective dihedral with wind-tunnel data was excellent through the linear lift range for all power conditions considered, However, flightdetermined values were approximately 40 percent to 50 percent smaller than wind-tunnel values, Within the scope of this study, it was not possible to identify in-flight phenomena which altered the contribution of the wing or the wing-fuselage interference to the variation of rolling-moment coefficient with sideslip and which were not accounted for in the full-scale wind-tunnel tests of the airplane. The effect of the discrepancy on several response characteristics is noted at the end of this summary.
The calculated directional control derivatives correlated well with wind-tunnel and flight data throughout the linear lift range and all power conditions investigated.
The calculated rolling-moment lateral-control derivatives were approximately 10 percent lower than the values obtained from wind-tunnel or flight data. Wind-tunnel and flight data correlated well, The calculated yawing-moment lateral-control derivatives correlated reasonably well with wind-tunnel data; flight values were more adverse than either the wind-tunnel or the calculated values,
Calculated values of the variation of yawing- and rolling-moment coefficients with yaw rate correlated well with flight data, No dynamic wind-tunnel data were available for comparison,
The dynamic derivatives had a significant effect on the calculated Dutch roll frequency, The use of a simplified Dutch roll frequency equation, which included only the static derivatives, would have resulted in a difference of approximately 40 percent in the calculated roll subsidence root,
The calculated Dutch roll period was generally 10 percent lower than the flight values, The calculated Dutch roll damping ratio correlated well with flight data; the correlation was improved when the flight-determined effective dihedral was substituted for the calculated effective dihedral.
The calculated roll-to-sideslip amplitude ratio of the Dutch roll mode did not correlate well with flight data. When the flight values of the effective dihedral were substituted for the calculated values in the response equation, good correlation was obtained.
Calculated roll-rate response to aileron input correlated well with flight data, Substituting the flight values of the effective dihedral for the calculated values in the response equation improved the correlation.
The procedures are applied to a twin-engine, propeller-driven, semi-low-wing airplane in the clean configuration to determine the lateral and directional control derivatives as well as the static and dynamic stability derivatives as functions of angle of attack and power condition through the linear lift range of the airplane. Also determined are the spiral mode, roll mode, and Dutch roll characteristics for level-flight conditions over the speed range of the airplane. All calculations are documented.
Attempts to calculate the weathercock stability characteristics indicated a need to account for wing-body interference effects on the body contribution as a function of angle of attack and vertical position of the wing relative to the body. Vertical-tail-off windtunnel data of a single-engine version of the subject airplane are used to expand the design nomograph from which the body-plus -wing-body contribution to weathercock stability was determined in order to obtain the contribution for a semi-low-wing airplane as a function of angle of attack. Application of the expanded nomograph to the subject airplane resulted in improved correlation of calculated weathercock stability characteristics with wind-tunnel and flight data at low angles of attack. For additional improvement, in correlation, there is a need for design data to account for the effects of angle of attack on the sidewash acting on the vertical tail.
The correlation of the calculated effective dihedral with wind-tunnel data was excellent through the linear lift range for all power conditions considered, However, flightdetermined values were approximately 40 percent to 50 percent smaller than wind-tunnel values, Within the scope of this study, it was not possible to identify in-flight phenomena which altered the contribution of the wing or the wing-fuselage interference to the variation of rolling-moment coefficient with sideslip and which were not accounted for in the full-scale wind-tunnel tests of the airplane. The effect of the discrepancy on several response characteristics is noted at the end of this summary.
The calculated directional control derivatives correlated well with wind-tunnel and flight data throughout the linear lift range and all power conditions investigated.
The calculated rolling-moment lateral-control derivatives were approximately 10 percent lower than the values obtained from wind-tunnel or flight data. Wind-tunnel and flight data correlated well, The calculated yawing-moment lateral-control derivatives correlated reasonably well with wind-tunnel data; flight values were more adverse than either the wind-tunnel or the calculated values,
Calculated values of the variation of yawing- and rolling-moment coefficients with yaw rate correlated well with flight data, No dynamic wind-tunnel data were available for comparison,
The dynamic derivatives had a significant effect on the calculated Dutch roll frequency, The use of a simplified Dutch roll frequency equation, which included only the static derivatives, would have resulted in a difference of approximately 40 percent in the calculated roll subsidence root,
The calculated Dutch roll period was generally 10 percent lower than the flight values, The calculated Dutch roll damping ratio correlated well with flight data; the correlation was improved when the flight-determined effective dihedral was substituted for the calculated effective dihedral.
The calculated roll-to-sideslip amplitude ratio of the Dutch roll mode did not correlate well with flight data. When the flight values of the effective dihedral were substituted for the calculated values in the response equation, good correlation was obtained.
Calculated roll-rate response to aileron input correlated well with flight data, Substituting the flight values of the effective dihedral for the calculated values in the response equation improved the correlation.
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| contributor author | NASA - National Aeronautics and Space Administration (NASA) | |
| date accessioned | 2017-09-04T16:37:18Z | |
| date available | 2017-09-04T16:37:18Z | |
| date copyright | 01/01/1972 | |
| date issued | 1972 | |
| identifier other | BQYKAEAAAAAAAAAA.pdf | |
| identifier uri | https://yse.yabesh.ir/std/handle/yse/100802 | |
| description abstract | Representative state-of-the-art analytical procedures and design data for predicting the lateral-directional static and dynamic stability and control characteristics of light, twin-engine, propeller-driven airplanes for propeller-off and power-on conditions are documented. Although the consideration of power effects is limited to twin-engine airplanes, the propeller-off considerations are applicable to single-engine airplanes as well. The procedures are applied to a twin-engine, propeller-driven, semi-low-wing airplane in the clean configuration to determine the lateral and directional control derivatives as well as the static and dynamic stability derivatives as functions of angle of attack and power condition through the linear lift range of the airplane. Also determined are the spiral mode, roll mode, and Dutch roll characteristics for level-flight conditions over the speed range of the airplane. All calculations are documented. Attempts to calculate the weathercock stability characteristics indicated a need to account for wing-body interference effects on the body contribution as a function of angle of attack and vertical position of the wing relative to the body. Vertical-tail-off windtunnel data of a single-engine version of the subject airplane are used to expand the design nomograph from which the body-plus -wing-body contribution to weathercock stability was determined in order to obtain the contribution for a semi-low-wing airplane as a function of angle of attack. Application of the expanded nomograph to the subject airplane resulted in improved correlation of calculated weathercock stability characteristics with wind-tunnel and flight data at low angles of attack. For additional improvement, in correlation, there is a need for design data to account for the effects of angle of attack on the sidewash acting on the vertical tail. The correlation of the calculated effective dihedral with wind-tunnel data was excellent through the linear lift range for all power conditions considered, However, flightdetermined values were approximately 40 percent to 50 percent smaller than wind-tunnel values, Within the scope of this study, it was not possible to identify in-flight phenomena which altered the contribution of the wing or the wing-fuselage interference to the variation of rolling-moment coefficient with sideslip and which were not accounted for in the full-scale wind-tunnel tests of the airplane. The effect of the discrepancy on several response characteristics is noted at the end of this summary. The calculated directional control derivatives correlated well with wind-tunnel and flight data throughout the linear lift range and all power conditions investigated. The calculated rolling-moment lateral-control derivatives were approximately 10 percent lower than the values obtained from wind-tunnel or flight data. Wind-tunnel and flight data correlated well, The calculated yawing-moment lateral-control derivatives correlated reasonably well with wind-tunnel data; flight values were more adverse than either the wind-tunnel or the calculated values, Calculated values of the variation of yawing- and rolling-moment coefficients with yaw rate correlated well with flight data, No dynamic wind-tunnel data were available for comparison, The dynamic derivatives had a significant effect on the calculated Dutch roll frequency, The use of a simplified Dutch roll frequency equation, which included only the static derivatives, would have resulted in a difference of approximately 40 percent in the calculated roll subsidence root, The calculated Dutch roll period was generally 10 percent lower than the flight values, The calculated Dutch roll damping ratio correlated well with flight data; the correlation was improved when the flight-determined effective dihedral was substituted for the calculated effective dihedral. The calculated roll-to-sideslip amplitude ratio of the Dutch roll mode did not correlate well with flight data. When the flight values of the effective dihedral were substituted for the calculated values in the response equation, good correlation was obtained. Calculated roll-rate response to aileron input correlated well with flight data, Substituting the flight values of the effective dihedral for the calculated values in the response equation improved the correlation. | |
| language | English | |
| title | NASA-TN-D-6946 | num |
| title | Lateral-directional aerodynamic characteristics of light, twin-engine, propeller-driven airplanes | en |
| type | standard | |
| page | 294 | |
| status | Active | |
| tree | NASA - National Aeronautics and Space Administration (NASA):;1972 | |
| contenttype | fulltext |