Attitude controls for VTOL aircraft Patent
Development of attitude control system for vertical takeoff aircraft using reaction nozzles displaced from various axes of aircraft
Pauli, F. A.↗
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Automatic guidance for VTOL aircraft
Evaluation of automatic guidance modes and software for V/STOL aircraft flight control
Hoffman, W. C.↗
Performance of a modular combustor designed for a VTOL tip-turbine lift fan
Combustion efficiency and performance of swirl can modules under conditions simulating operation of 10,000 pound thrust lift engine for vertical takeoff
Marchionna, N. R.↗
Effect of the city center environment on VTOL terminal operations
Optimum flight paths for V/STOL aircraft operating in short haul transportation near city centers
De Maio, D. A.↗
Hovering and Transition Flight Tests of a 1/5-Scale Model of the Ryan X-13 VTOL Airplane
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Smith, C. C., Jr.↗
Acceptability of VTOL aircraft noise determined by absolute subjective testing
A program was conducted during which test subjects evaluated the simulated sounds of a helicopter, a tilt wing aircraft, and a 15 second, 90 PNdB (indoors) turbojet aircraft used as reference. Over 20,000 evaluations were made while the test subjects were engaged in work and leisure activities. The effects of level, exposure time, distance and aircraft design on subjective acceptability were evaluated. Some of the important conclusions are: (1) To be judged equal in annoyance to the reference jet sound, the helicopter and tilt wing sounds must be 4 to 5 PNdB lower when lasting 15 seconds in duration. (2) To be judged significantly more acceptable than the reference jet sound, the helicopter sound must be 10 PNdB lower when lasting 15 seconds in duration. (3) To be judged significantly more acceptable than the reference jet sound, the tilt wing sound must be 12 PNdB lower when lasting 15 seconds in duration. (4) The relative effect of changing the duration of a sound upon its subjectively rated annoyance diminishes with increasing duration. It varies from 2 PNdB per doubling of duration for intervals of 15 to 30 seconds, to 0.75 PNdB per doubling of duration for intervals of 120 to 240 seconds.
Sternfeld, H., Jr.↗
A VTOL translational rate control system study on a six degrees-of-freedom motion simulator
A linearized translational rate system for near hover flight was optimized on a large motion simulator under the constraints of no disturbances and limited control power. Both lateral and longitudinal modes were considered with the primary variables of investigation being control sensitivity and response stiffness and secondarily system damping. Yaw and height control characteristics were represented by an angular rate and acceleration system, respectively. General regions of desired sensitivity and stiffness for the longitudinal and lateral modes were determined under VFR conditions for both the rapid maneuver task and the station keeping/mild maneuver task.
Corliss, L. D.↗
Prediction and analysis of human performance in a VTOL hover task
An optimal control model is used to predict pilot performance in a series of longitudinal hovering tasks. Configurational changes are considered that alter significantly the system response to both control and disturbance inputs. Model predictions of mean-squared performance are compared with measurements obtained in an independent experimental study of the task. In addition, the optimal control model is used to predict describing functions that correspond to the loop closing pilot transfer functions frequently employed in classical multiloop manual control analyses.
Baron, S.↗
Effect of crossflow velocity on VTOL lift fan blade passing frequency noise generation
Analysis of noise measurements taken during tests of a remote lift fan wing installation, a V/STOL model transport with both lift and lift/cruise fans, and XV5B research aircraft flight tests has indicated a definite increase in pure tone sound pressure level due to crossflow over the face of the life fans. The fan-in-wing and V/STOL model transport tests were conducted in the NASA Ames 40 ft. by 80 ft. wing tunnel and the XV5B flight tests at Moffett Field. Increases up to 10 db were observed for the lift fan installation tested at crossflow to fan tip velocity ratios up to 0.25. Cruise fan noise levels were found to be unaffected by the external flow. The noise level increase was shown to be related to an increase in fan distortion levels.
Stimpert, D. L.↗
Effect of crossflow velocity on the generation of lift fan jet noise in VTOL aircraft
Analytical studies based on a turbulent mixing noise prediction technique indicate that jet noise power levels are increased when a jet is situated in a crossflow. V/STOL model transport acoustic test data obtained in the NASA Ames 40 ft. x 80 ft. wind tunnel confirmed this jet noise power level increase due to crossflow. Increases up to 6 db at a Strouhal number of 2.5 and crossflow velocity to jet velocity ratio of 0.58 were observed. The power level increases observed in the experimental data confirm the predicted power level increases.
Stimpert, D. L.↗
Synthesis of hover autopilots for rotary-wing VTOL aircraft
The practical situation is considered where imperfect information on only a few rotor and fuselage state variables is available. Filters are designed to estimate all the state variables from noisy measurements of fuselage pitch/roll angles and from noisy measurements of both fuselage and rotor pitch/roll angles. The mean square response of the vehicle to a very gusty, random wind is computed using various filter/controllers and is found to be quite satisfactory although, of course, not so good as when one has perfect information (idealized case). The second part of the report considers precision hover over a point on the ground. A vehicle model without rotor dynamics is used and feedback signals in position and integral of position error are added. The mean square response of the vehicle to a very gusty, random wind is computed, assuming perfect information feedback, and is found to be excellent. The integral error feedback gives zero position error for a steady wind, and smaller position error for a random wind.
Hall, W. E.↗
Preliminary design study of quiet integral fan lift engines for VTOL transport applications in the 1980s
Preliminary designs of three integral lift fan engines suitable for commercial certification in the 80's were completed. Emphasis was placed on low cost, simplicity, low noise, low emissions, minimum weight, and design features meeting all commercial standards for fire safety and containment.
Rabone, G. R.↗
Studies in tilt rotor VTOL aircraft aeroelasticity, volume 2
Two methods for natural mode vibration analysis are discussed. The first consists of a direct approach based on a finite element representation of the complete structure as an entity. The mass and stiffness matrices for the complete structure are assembled by properly combining the mass and stiffness matrices of the individual elements into which the structure has been divided. The second approach is that of component mode synthesis. This method is based on the concept of synthesizing the natural modes of the complete structure from modes of conveniently difined substructures, or components, into which the structure has been partitioned. In this way the expedient of reducing the system degrees of freedom, and thus the size of the eigenvalue problem, can be introduced by partial modal synthesis.
Kvaternik, R. G.↗
Conceptual study of four subsonic VTOL propulsion systems
Typical ejector wing, remote fan-in-wing, remote lift/cruise fan, and lift plus lift/cruise propulsion concepts are parametrically studied on the basis of airplane weights (gross, empty, and propulsion) for three types of airplanes, a Carrier-Onboard Delivery/Search and Rescue airplane for the U.S. Navy, a military utility transport, and a business jet. None of the four systems led to airplanes substantially lighter than the others, and therefore no best system is selected.
Strack, W. C.↗
Performance characteristics of a model VTOL lift fan in crossflow.
This paper presents a summary of principal results obtained from crossflow tests of a model 15-in.-diam lift fan installed in a wing in the NASA Lewis Research Center, 9 by 15 ft V/STOL Propulsion Wind Tunnel. Tests were run with and without exit louvers over a range of tunnel air speeds, fan speeds, and wing angle of attack. Fan thrust in crossflow was influenced by two principal factors: the effects of inflow distortion on blade-row performance, and changes in fan stage operating point brought about by changes in back pressure ratio. In this particular fan, flow separation on the inlet bellmouth did not appear to be a serious problem for crossflow operation.
Lieblein, S.↗
Effect of rotor design tip speed on aerodynamic performance of a model VTOL lift fan under static and crossflow conditions.
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Stockman, N. O.↗
Theoretical and experimental investigation of the performance of a fan-in-wing VTOL configuration
The incompressible-flow momentum theory is extended to the case of lifting fans. The resulting theory includes many of the known experimentally determined characteristics of fan-in-wing aircraft. These characteristics include the negligible effect of forward speed on fan thrust, the large momentum drag, and the generally inefficient performance throughout the transition speed range. Although mutual interference between the fans and the wing was totally neglected, the theory is confirmed by experimental results for the configuration tested. Examination of the results of an investigation of wall interference leads to the conclusion that the large fan-induced lift reported in many earlier investigations was largely the result of neglecting wall interference in the reduction of wind-tunnel data.
Heyson, H. H.↗
Flight investigation of manual and automatic VTOL decelerating instrument approaches and landings
A flight investigation was undertaken to study the problems associated with manual and automatic control of steep, decelerating instrument approaches and landings under simulated instrument conditions. The study was conducted with a research helicopter equipped with a three-cue flight-director indicator. The scope of the investigation included variations in the flight-director control laws, glide-path angle, deceleration profile, and control response characteristics. Investigation of the automatic-control problem resulted in the first automated approach and landing to a predetermined spot ever accomplished with a helicopter. Although well-controlled approaches and landings could be performed manually with the flight-director concept, pilot comments indicated the need for a better display which would more effectively integrate command and situation information.
Kelly, J. R.↗