Design criteria for selection of aircraft electric power generation and distribution systems
STOL aircraft electric power variable frequency generation and high voltage DC distribution with secondary square wave AC distribution
Lee, C. H.↗
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Blown flap noise research
Noise measurement data on various types of blown flap configurations for STOL aircraft, discussing integration effects between jet and flap assembly
Dorsch, R. G.↗
Study of aircraft in intraurban transportation systems, volume 1
An analysis of an effective short range, high density computer transportation system for intraurban systems is presented. The seven county Detroit, Michigan, metropolitan area, was chosen as the scenario for the analysis. The study consisted of an analysis and forecast of the Detroit market through 1985, a parametric analysis of appropriate short haul aircraft concepts and associated ground systems, and a preliminary overall economic analysis of a simplified total system designed to evaluate the candidate vehicles and select the most promising VTOL and STOL aircraft. Data are also included on the impact of advanced technology on the system, the sensitivity of mission performance to changes in aircraft characteristics and system operations, and identification of key problem areas that may be improved by additional research. The approach, logic, and computer models used are adaptable to other intraurban or interurban areas.
Stout, E. G.↗
A study of the round jet/plane wall flow field
Impingement angles, between the axisymmetric jet axis and the plane wall, from zero to 15 degrees have been examined for nozzle heights of 0.75, 1.0, 1.5 and 2.0 diameters and for: (1) a fully developed pipe flow, and (2) a relatively uniform exit velocity condition. Velocity measurements have been used to define isotach contours and to determine mass, momentum and energy flux values for the near field (within five diameters) of the jet. Surface pressure measurements have been used to define surface pressure forces and jet centerline trajectories. The geometric and flow conditions examined and the interpretation of the results have been motivated by the externally blown flap STOL aircraft application.
Foss, J. F.↗
Externally-blown-flap noise
Noise data were obtained with a large externally blown flap model. A fan-jet engine exhaust was simulated by a 1/2-scale bypass nozzle supplied by pressurized air. The nozzle was pylon mounted on a wing section having a double-slotted flap for lift augmentation. Noise radiation patterns and spectra were obtained for nozzle exhaust velocities between 400 and 1150 ft/sec. The blown flap noise data are in good agreement with previous small model results extrapolated to test conditions by Strouhal scaling. The results indicate that blown flap noise must be suppressed to meet STOL aircraft noise goals.
Dorsch, R. G.↗
Mixer nozzle-externally blown flap noise tests
A summary is given of the noise suppression tests conducted for the STOL aircraft. The tests were made using a large scale mixer nozzle and externally blown flap model. Data were obtained over a range of nozzle exhaust velocities (172 to 284 m/sec) and flap angles. Comparisons were made between the results of the mixer nozzle and those obtained with a standard single convergent nozzle. The resulting conclusions show that a reduction in noise level did occur using the mixer nozzle system.
Goodykoontz, J. H.↗
Impact of subsonic aerodynamic considerations on a space shuttle booster configuration
Considerations of cruise-back efficiency and subsonic flying qualities are shown to have resulted in a configuration with an aft high wing of moderate aspect ratio and with vertical tails located at the wing tips. The need to protect the air breathing engines during ascent and reentry and the desire for a low trim penalty longitudinal control surface led to consideration of a jet-flap canard. The advantages of this application of STOL technology to a space system are examined and the results of both wind tunnel tests and flight simulations are discussed. Since the use of the jet-flap canard concept offers the potential for a minimum weight vehicle, a proposed technology development program is outlined in order that the full benefit of this concept may be realized.
Roensch, R. L.↗
Peak axial-velocity decay with multi-element rectangular and triangular nozzles
The aircraft noise created by the impingement of engine exhaust jet of STOL aircraft with externally blown flaps is discussed. It was determined that the jet-flap interaction noise can be lowered by reducing the impinging velocity of the jet. The reduction must occur at a specific distance from the flap to be effective. The peak axial-velocity decay obtained with rectangular and triangular single element mixer nozzles is presented. Equations are developed for estimating the peak axial velocity decay curves for a wide range of nozzle configurations.
Groesbeck, D. E.↗
Preliminary experiments on the noise generated by target-type thrust reverser models
Experiments are reported on the noise generated by model V-gutter and semicylindrical target-type reversers with circular nozzles. Nozzles were 5.24 and 7.78 cm in diameter. Nozzle pressure ratio ranged from 1.25 to 1.72. The spacing between reversers and nozzle, as well as the reverser orientation, was also varied. More noise was generated with reversers than with the nozzle alone. The measured maximum overall sound pressure level varied with the sixth power of the nozzle exit velocity. Noise levels were more uniform in regard to directivity with reversers than with the nozzle alone. It is concluded that thrust reversers, can be a significant noise problem, especially for STOL aircraft using thrust reversers during approach.
Gutierrez, O. A.↗
Design of a TF34 turbofan mixer for reduction of flap impingement noise
This portion of the TF-34 turbofan quiet engine studies has been devoted to the selection and design of a special mixer exhaust nozzle system to reduce the maximum 150 m (500 foot) sideline noise generated by the impingement of four engine exhausts on a STOL wing flap system to less than 92 PNdB. The design concept selected consists of a 12-lobe internal mixer and a 12-lobe external mixer mounted in series. The internal mixer reduces maximum exhaust velocities by mixing the fan and turbine streams. The external mixer is designed to reduce the velocity of the exhaust stream striking the wing flap surfaces. A ground test version of this concept has been designed to be installed and tested on an acoustically treated TF-34 engine nacelle, with flexibility to simulate a flight version of this concept which has also been defined. Estimated noise levels are 2 PNdB below the objective at approach and 2 PNdB above the objective at takeoff, with an uncertainty band of +3, -2 PNdB.
Chamay, A.↗
Acoustically treated ground test nacelle for the General Electric TF34 turbofan
A description is given of the ground test quiet nacelle for the TF34 engine. The suppression treatment consists of cylindrical splitters in the inlet and fan exhaust ducts plus duct wall treatment and core exhaust wall treatment. Aerodynamic design analysis of the inlet and exhaust ducts and overall engine performance with pressure losses from the acoustic treatment is included. The objectives of the test program are to obtain noise data for a heavily suppressed high bypass turbofan with various arrangements of exhaust systems and acoustic treatment, and to provide a basis for the power plants of the Quiet Experimental STOL Aircraft (Questol).
Edkins, D. P.↗
Revisions to V/STOL handling qualities criteria of AGARD report 408
A brief review of selected handling qualities criteria for V/STOL aircraft shows that although a clearer understanding of the requirements for controversial areas such as roll control power, vertical flight path control, and transition is in hand, considerably more research is needed to refine these criteria for operational IFR activity. Because many items interact to influence the pilots' overall impression of the aircraft's behaviour, additional work of a systematic nature must be done to clarify this aspect. A better definition of a gust model which includes discrete gust effects is needed to firm up criteria for both hover and STOL operation.
Anderson, S. B.↗
Operating systems in the air transportation environment.
Consideration of the problems facing air transport at present, and to be expected in the future. In the Northeast Corridor these problems involve community acceptance, airway and airport congestion and delays, passenger acceptance, noise reduction, and improvements in low-density short-haul economics. In the development of a superior short-haul operating system, terminal-configured vs cruise-configured vehicles are evaluated. CTOL, STOL, and VTOL aircraft of various types are discussed. In the field of noise abatement, it is shown that flight procedural techniques are capable of supplementing ?quiet engine' technology.
Cherry, G. W.↗
Automated aircraft scheduling methods in the near terminal area.
A general scheduling algorithm for aircraft from terminal area entry to touchdown is developed. The method has the following novel features: (1) many speed classes of aircraft are considered and speed variations within classes and along portions of the flight path are permitted; (2) multiple paths are considered which may merge or diverge - the analysis is not restricted to a single runway nor to departures only; (3) landings are scheduled along conflict free flight paths in minimum time. The algorithm is currently being incorporated in a fast-time simulation of a STOL air traffic system.
Tobias, L.↗
Externally-blown-flap noise.
Noise data were obtained with a large externally blown flap model. A fan-jet engine exhaust was simulated by a 1/2-scale bypass nozzle supplied by pressurized air. The nozzle was pylon mounted on a wing section having a double-slotted flap for lift augmentation. Noise radiation patterns and spectra were obtained for nozzle exhaust velocities between 400 and 1150 ft/sec. The blown flap noise data are in good agreement with previous small model results extrapolated to test conditions by Strouhal scaling. The results indicate that blown flap noise must be suppressed to meet STOL aircraft noise goals.
Dorsch, R. G.↗
S.T.O.L., V.T.O.L., and V./S.T.O.L. - Where do they fit in.
The problems and potential of V/STOL transportation are examined. A detailed review is given of the development, characteristics, and requirements of V/STOL, STOL, and VTOL systems. The problem of whether V/STOL is worth the effort is considered, and it is concluded that such aircraft have a role in meeting real transport requirements, and that their development should be pursued. Finally, a forecast of V/STOL economics is presented, and implementation problems are discussed.
Harper, C. W.↗
Some applications of buoyancy systems and parawings to replace conventional and proposed transportation systems.
An exploratory study has been conducted to assess the performance potential of buoyant airships and parawings in short-haul passenger transportation. Results show that such systems can be used effectively, from a performance standpoint, in a VTOL or STOL mode of operation. A supplementary assessment of potential applications of such vehicles is examined, with a brief look at economic factors and an examination of missions for which they might be effectively used.
Havill, C. D.↗
Maximum noise abatement trajectories.
Minimum noise annoyance trajectories for developing STOL operation procedures are obtained by modulating five control variables in two dimensions. The performance index is formulated such that it explicitly assigns the same relative importance to thrust as it does to distances between discrete listeners and the aircraft. However, using a steepest descent optimization program, results indicate that it is preferable to keep the thrusters at their maximum value to minimize the integrated annoyance rather than to reduce thrust which would lower the instantaneous annoyance. Thrust decreases below its bound only when the instantaneous noise at a listener is limited.
Zeldin, S.↗