Helicopter Engine Research Articles

Development of an advanced vaneless inlet particle separator for helicopter engines

Design and development of an advanced integral engine particle separator are presented to meet the challenging operational requirements of helicopter engines of the future. The vaneless, low-weight, high-efficiency separator makes it possible to achieve new levels of engine reliability, durability, and life cycle costs. This paper presents the analytical methods developed, the design process, and the extensive experimental validation of the design.

IAC Mobile Helicopter Engine Test Facilities Feature Two Levels of Noise Supression

WITH ITS enormous versatility in performing reconnaisance, troop‐carrying and attack roles, the helicopter is essential to defence forces all over the world.

Contingency Power Concepts for Helicopter Turboshaft Engines

Twin helicopter engines are often sized by power requirement of safe mission completion after the failure of one of the two engines. This study was undertaken for NASA Lewis by General Electric Co. to evaluate the merits of special design features to provide a 2-1/2 minute Contingency Power rating, permitting an engine size reduction. The merits of water injection, cooling flow modulation, throttle push and an auxiliary power plant were evaluated using military life cycle cost (LCC) and commercial helicopter direct operating cost (DOC) merit factors in a rubber engine/rubber aircraft scenario.

Mechanical Engineering Aspects of Helicopter Design

The work of the early pioneers which led to the evolution of the current helicopter configurations is briefly reviewed. The major mechanical elements of the helicopter are then identified: the engine, transmission and blades analogous to the engine, transmission and wheels of a road vehicle. The paper then briefly reviews the design problems and the state of the art in helicopter engines, gearboxes, rotor blades and hubs, rotor controls and the important resonant and unstable conditions of the total system which must be avoided. Methods for ground testing the elements of the dynamic system are then presented. The paper concludes with a brief account of health and usage monitoring which will play an increasingly important part in improving reliability and reducing operating cost.

Advanced Concepts in Small Helicopter Engine Air-Cooled Turbine Design

Advanced Concepts in Small Helicopter Engine Air-Cooled Turbine Design

Measurement Techniques Used to Assess the Installed Power of a Helicopter Engine

Measurement Techniques Used to Assess the Installed Power of a Helicopter Engine

An advanced helicopter engine control system

The requirements of the first engine controllers were primarily to satisfy the needs of the engine and, almost as an afterthought, to consider interface with the aircraft and the pilot.The latter resulted in the overwhelming plethora of ‘essential’ ground test-sets and cockpit instruments that we see today. In a performance and integrity conscious world, beset with ever increasing costs and sometimes decreasing maintenance personnel skills, the engine controller can no longer be considered in isolation from the rest of the system that it serves. The obvious ability of a digital system to self-check and diagnose itself, its interface with the real world, and to make intelligent decisions based on those tests, has enhanced the case for digital engine control.

Particle Dynamics of Inlet Flowfields with Swirling Vanes

The particle trajectories are investigated for the inlet flowfield of a helicopter engine with swirling vanes and particle separator. The flowfield resulting from the swirling vanes is first computed on a hub-shroud midchannel stream surface. The trajectories of the solid particles are then determined in this flowfield, including particle impacts with the hub, tip, and vane surfaces. The particle rebounding velocity and direction after each impact is determined using empirical correlations derived from experiments conducted in a special tunnel. Different particle sizes are considered, and the resulting trajectories and separator effectiveness are presented.

Illustrated formats to teach procedures

Formats to teach procedures were developed to incorporate appropriate learning strategies. The formats contain a preponderance of graphics with supporting text and include a foldout, or paper mock-up, showing the face of the equipment. Exercises are provided for recalling individual steps and for chaining steps. These materials, called learning aids, were developed and field-tested on two pieces of complex equipment: tuning an oscilloscope probe and starting a helicopter engine. Results showed the learning aids reduce errors and produce quicker learning compared with narrative manuals commonly used to teach procedures.

Effects of Increased Jet Fuel Freeze Point on Cold Start Ability

In the interests of jet fuel availability, the Canadian commercial wide cut fuel specification has recently been relaxed by allowing an increase in the freeze point. An increased freeze point implies an increased lowtemperature viscosity and associated cold starting difficulties. To identify the amount of cold start degradation to be expected with such fuels, the Canadian Forces commissioned testing at the National Research Council of Canada to examine the cold start ability of an Allison T63-A-700 turboshaft helicopter engine using four fuels including typical in-service samples of kerosene Jet A-l and NATO wide cut F-40, as well as two intermediate wide cut fuels having freeze points corresponding to exact specification values. For the engine under test, the relaxed wide cut fuel produced a 20 °C degradation in cold start capability compared to the typical NATO F-40 fuel.

Helicopter engine technology — with particular reference to the Rolls-Royce Gem engine

Any aero engine designer works against a background of a list of general desirable features for all engines of:Low acquisition costsLow operating costsHigh reliabilityGood performance and fuel efficiencyEase of maintenanceIn the helicopter business however, the engine designer is faced with a real dilemma. On the one hand there is the desire to produce an engine which has as wide an application as possible, (i.e. turboshaft, turboprop, turbofan, APU, industrial power generator, marine traction etc) and this produces a basically low cost, high volume, production flow provided that the required changes in the engine configuration are kept to a minimum.

Comparison of predicted engine core noise with proposd FAA helicopter noise certification requirements

Calculated engine core noise levels, based on NASA-Lewis prediction procedures, for five representative helicopter engines are compared with measured total helicopter noise levels and proposed FAA helicopter noise certification requirements. Comparisons are made for level flyover and approach procedures. The measured noise levels are generally significantly greater than those predicted for the core noise levels, except for Sikorsky S-61 and S-64 helicopters. However, the predicted engine core noise levels are generally at or within 3 db of the proposed FAA noise rules. Consequently, helicopter engine core noise can be a significant contributor to the overall helicopter noise signature and, at this time, will provide a limiting floor to a further decrease in future noise regulations.

Noise Deafness in Helicopter Mechanics and Prevention

We performed air conduction audiometry tests at six different sounds ranging from 0.25KHz to 8KHz, on 245 helicopter mechanics who had no chronic tympanitis, and were grouped by age and length of time of employment.The noise level was tested at one meter away from the helicopter engine. The frequency was not tested. We used questionnaire material as the reference regarding findings of tinnitus.1) The hearing disturbance of over 20dB was 41.6% of the total number.2) Twenty-six percent of all workers complained of deafness and 23% of tinnitus, and 77% claimed that such occurred after employment at the Self Defense Force base.3) Seriousness of the hearing disturbances increased in direct proportion to the age and the number of years of employment.4) For both age and employment groupings, 4KHz and 8KHz resulted in a great number of disturbances and the number of those suffering from disturbances at 8KHz was the highest.5) The noise of the Reciprocator-engine helicopter at the highest measured 111-112 phones.6) The noise of the turbine engine helicopter at the highest was 107-110 phones.From the above findings we conclude that although individual differences in perception are evident, deafness as a result of noise occurs not only at 4KHz but also at 8KHz.

A new chip detector

For over a decade, electric chip detectors have been installed in virtually all helicopter transmissions and engines and in many propulsion and drive systems of military fixed‐wing aircraft. They contain a magnet which attracts the ferrous debris shed into the lube system by failing components and retains it for later visual inspection and failure verification. The debris particles which fall across the gap between two electrodes act like a switch and activate a chip warning light (see figure 1).

Roller bearing slip and skidding damage

Currently main shaft bearings are running at DN values in excess of two million. Within the next decade, it is reasonable to consider bearings operating at DN values of three million and higher. With slip being the primary parameter correlated to failure, it will become more troublesome at the higher DN values. Slip occurs in a cylindrical roller bearing when the radial load is inadequate to develop a frictional (tractional) drive force between rolling elements and rotating raceway to overcome drag forces. In order to predict the occurrence and magnitude of slip, an analytical method was developed to determine the cage speed through a series of force and torque balances. When excessive slip is predicted, there are several bearing designs that can be used to minimize it. However, the most successful has been to increase the applied load on the bearing with an out-of-round bearing which can have either a bilobe or trilobe. A main shaft bearing used in a particular helicopter engine had been a continued source of trouble. Although several bearing designs and materials were evaluated, the elliptical bearing was the most significant in reducing slip and skid damage.

A Test Plant for Helicopter Engines

This Note describes the design and construction of a “ Tilting Test Bed ” for helicopter engines for Alvis Ltd., for which some onerous requirements were laid down (Fig. 1). The most important of these were that:—(i)Readings of engine torque and b.h.p. must be given by a dynamometer, so as to provide accurate data.(ii)The engine, and therefore the complete test plant, must be capable of being tilted, while running, through 120°—from the horizontal to the vertical and 30° beyond.(iii)During the tilting process the engine throttle setting must remain unaffected and the readings of torque, b.h.p., fuel consumption, and so on, continue with unaltered accuracy.(iv)A powerful fan must be incorporated, for cooling certain types of engine not provided with selfcontained fan, and the air-blast must continue unchanged during tilting.

Research and Test Apparatus

A rig for the testing of helicopter engines has recently been completed at the works of Alvis Ltd., Coventry. The test plant was built by Heenan and Froude Ltd. of Worcester.

History of the Helicopter Engineering Division McDonnell Aircraft Corporation

History of the Helicopter Engineering Division McDonnell Aircraft Corporation

“Principles of Helicopter Engineering” by Jacob Shapiro (Temple Press Ltd, London, 1955)

“Principles of Helicopter Engineering” by Jacob Shapiro (Temple Press Ltd, London, 1955)

Helicopter Engineering. Raymond A. Young. The Ronald Press Co., New York. 1949. $10 net. 285 pp. Illustrated. Appendix. Index.

Helicopter Engineering. Raymond A. Young. The Ronald Press Co., New York. 1949. $10 net. 285 pp. Illustrated. Appendix. Index.