Search results

This is the second of two companion papers presenting the results of research into a contra‐rotating propeller designed to drive a super manoeuvrable micro air vehicle (MAV) and is devoted to the experimental results. The first paper presented the design process and numerical analyses.

Most of experiments were conducted in the wind tunnel. Both contra‐rotating and conventional propellers were tested. The test procedures and equipment are described first. The attention is focused on the design of an aerodynamic balance used in the experiment. Then, the measurement error is discussed, followed by presentation of the wind tunnel results. Finally, an initial flight test of the MAV equipped with contra‐rotating propeller is briefly described.

Wind tunnel experiment results fall between theoretical results presented in the first part of the paper. The application of contra‐rotating propeller allowed to develop the propulsion system with zero torque. Moreover, the efficiency achieved appeared to be a few percent greater than that for a standard conventional propulsion system. The concept was finally proved during the first test flight of the new MAV.

The propeller was designed for a fixed wing aeroplane, not for helicopter rotor. Therefore, only conditions characteristic for fixed wing aeroplane flight are tested.

The designed contra‐rotating propeller can be used in fixed wing aeroplane if torque equal to zero is required.

Original design of the balance is described for the first time, as well as test procedures applied in this experiment. Most of wind tunnel test results are also new and never published before.

This is the first of two companion papers presenting the results of research into a contra‐rotating propeller designed to drive a super manoeuvrable micro air vehicle (MAV). The purpose of this first paper is to describe the design process and numerical analyses. The second paper is devoted to the experimental results verifying the computations.

Software based on the analytical formulas derived by Theodore Theodorsen was used in the design procedure. Three‐dimensional finite‐volume simulation, performed with the use of commercial software verified the results. Finally, two‐dimensional simulation was conducted to explore the effect of the propeller‐wing interaction. The meshes applied in these analyses are described.

Propeller geometry received as a result of the design procedure is presented. The computation results for different turbulence models applied are discussed. Time dependent characteristics of contra‐rotating propeller are presented as well as conclusions regarding propeller‐wing interaction.

Propeller was designed for a fixed wing aeroplane, not for helicopter rotor. Therefore, conditions characteristic for fixed wing aeroplane flight are analysed only. Reynolds numbers below 50000 are considered.

Designed contra‐rotating propeller can be used in fixed wing aeroplane if torque equal to zero is required. Software based on the formulas derived by T. Theodorsen can be used to design the propellers.

Software applied in the design procedure was originally developed by one of authors although it is based on the formulas derived by T. Theodorsen. Contra‐rotating propeller simulation results for different turbulence models are discussed for the first time. Moreover, unique time dependent characteristics of contra‐rotating propeller are presented.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Notes of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued

Early aircraft engines were usually bolted direct to the aircraft structure and no attempt was made to prevent the vibrations which they set up from being transmitted to the airframe. With increasing engine powers and the use of larger airscrews these vibrations eventually become of sufficient magnitude in some cases to cause annoyance to the occupants of the aircraft and also failure by fatigue of parts of the structure. Various attempts were made both to analyse the source of the vibrations with a view to eliminating them or reducing them to an acceptable magnitude. Where this was not possible attempts were made to isolate the disturbances from the airframe and its occupants. This paper presents the basic theory of vibration isolation and gives an account of the various sources of vibration met with in reciprocating, turbo‐propeller and pure‐jet installations. The loads acting on the engine during various conditions of flight are then examined as a knowledge of these is required in order to determine the strength of the supporting units. Various practical engine mounting configurations are then considered which will give vibration isolation together with adequate support of the engine under all conditions of flight. Some account is given of the properties of rubber and the design and testing of rubber vibration isolators, and some installation problems are examined. Finally, the complete programme of testing an installation both on the test‐bed and inflight to evaluate the degree of vibration isolation achieved is described, together with various criteria of acceptability both from a structural and physiological standpoint. A bibliography covering the various sections is included.

THE problem of designing an aircraft so that the pilot is able easily to regain and maintain control following the sudden failure of an engine has been for some years a serious one. It is thought that an elementary description of the aerodynamics of the problem and of the flight tests which are made to assess a particular aircraft may be of interest. The equally important problem of ensuring adequate performance after an engine failure is not discussed here.

THE development of aircraft penumatic equipment has progressed so satisfactorily in recent years that actuation of vital services by means of compressed air is becoming increasingly popular. In this brief review of developments to date an attempt will be made to show how the air which has been made available as a result of compressor improvements is utilized and by way of introduction it may be of interest to recall some of the bold experiments which were made in earlier years.

After briefly outlining the main features of the variable‐pitch propeller, this paper proceeds to describe the development of the piston‐engined hydraulically operated propeller as a brake, both in the air and on the ground. Examples are given of the magnitude of the braking effort of a propeller when windmilling under controlled conditions and when in reverse pitch under power. The advent of the gas turbine, originally intended as a means of jet propulsion, opened up a new field of application for the variable‐pitch propeller and this application with its attendant problems and their solution is discussed. Three types of gas‐turbine power plant, together with the appropriate propeller arrangements are reviewed. These arc: (I) the direct‐connected turbine; (2) the compound‐compressor turbine; and (3) the free‐propeller turbine.

ACCORDING to historical records the earliest known drawings for an aerial machine that can be classified under the heading of helicopter were made in the fifteenth century by the world renowned Italian scientist and artist Leonardo da Vinci (1452–1519). Probably the Chinese had been making their helicopter toy for some considerable time before da Vinci commenced his experiments. This toy consisted of two feathers, joined together by means of a cork or soft wood boss, to form a crude type of propeller which was pushed up a threaded stick so that upon leaving the stick the propeller rotated at high speed and continued to screw itself up in the air. When the speed of rotation decreased the propeller slowly windmilled down to the ground. A similar toy is still being sold today.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Memoranda of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued.