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HELICOPTER TURBOSHAFT ENGINE IDLE POWER SCHEDULING

2018-08-09
WIP
AIR4121
The purpose of this AIR (Aerospace Information Report) is to provide aircraft and engine designers with a better understanding of helicopter turboshaft engine idle power characteristics and objectives to be considered in the design process. Idle is the lowest steady state power setting. At this setting, the engine typically does not produce enough power to obtain governed output shaft speed (i.e. the shaft speed is determined by the load imposed by the aircraft). In the aircraft, the engine is typically stabilized at this power setting after starting, prior to taxi and for some period of time after rotor shutdown for cool down prior to engine shutoff. Traditionally, the aircraft designer wants idle power scheduled as low as possible and of course, does not want any resulting aircraft operational difficulties such as overcoming the rotor brake. The engine designer, however, desires a higher scheduled power because of the reduced probability of engine operational problems.
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Substantiation of Power Available and Inlet Distortion Compliance for Rotorcraft Inlet Barrier Filter Installations

2017-03-20
WIP
ARP6912
This Aerospace Recommended Practice (ARP) identifies and defines methods of compliance to power available and inlet distortion requirements for rotorcraft with Inlet Barrier Filter (IBF) installations. The advisory material developed therein may be used as acceptable methods of compliance for determining power assurance, establishing power available, and for substantiating acceptable engine inlet distortion for IBF installations. It is agreed to treat dust, ice, salt water & snow as contaminants to IBF for the purpose of establishing power available and distortion. Flight in known icing will be addressed in ARP6901.
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The Effect of Installation Power Losses on the Overall Performance of a Helicopter

2005-06-07
CURRENT
AIR5642
The purpose of this SAE Aerospace Information Report (AIR) is to illustrate the effect of installation power losses on the performance of a helicopter. Installation power losses result from a variety of sources, some associated directly with the basic engine installation, and some coming from the installation of specific items of aircraft mission specific equipment. Close attention must be paid to the accurate measurement of these losses so that the correct aircraft performance is calculated. Installation power losses inevitably result in a reduction in the overall performance of the aircraft. In some cases, careful attention to detail will allow specific elements of the overall loss to be reduced with immediate benefit for the mission performance of the aircraft. When considering items of equipment that affect the engine, it is important to understand the effect these will have on overall aircraft performance to ensure that mission capability is not unduly compromised.
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Performance of Low Pressure Ratio Ejectors for Engine Nacelle Cooling

1999-03-01
CURRENT
AIR1191A
A general method for the preliminary design of a single, straight-sided, low subsonic ejector is presented. The method is based on the information presented in References 1, 2, 3, and 4, and utilizes analytical and empirical data for the sizing of the ejector mixing duct diameter and flow length. The low subsonic restriction applies because compressibility effects were not included in the development of the basic design equations. The equations are restricted to applications where Mach numbers within the ejector primary or secondary flow paths are equal to or less than 0.3.
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Oil Systems for Helicopter Powerplants

1998-11-01
CURRENT
AIR4281
Turbine engines installed in helicopters require a highly sophisticated oil system to fulfill two tasks: a Cooling/oil supply b Lubrication While lubrication is an engine internal procedure, cooling and oil supply require more or less design activity on the aircraft side of the engine/airframe interface for proper engine function, depending on the engine type. The necessity for engine cooling and oil supply provisions on the airframe can lead to interface problems because the helicopter manufacturer can influence engine related functions due to the design of corresponding oil system components. This SAE Aerospace Information Report (AIR) deals with integration of engine oil systems with the airframe and gives information for both helicopter and engine manufacturers for a better understanding of interface requirements.
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Defining and Measuring Factors Affecting Helicopter Turbine Engine Power Available

1998-09-01
CURRENT
ARP1702A
This SAE Aerospace Recommended Practice (ARP) identifies and defines a method of measuring those factors affecting installed power available for helicopter power plants. These factors are installation losses, accessory power extraction, and operation effects. Accurate determination of these factors is vital in the calculation of helicopter performance as described in the flight manual. It is intended that the methods herein prescribe and define each factor as well as an approach to measuring said factor. Only standard installations of turboshaft engines in helicopters are considered. Special arrangements leading to high installation losses, such as the fitting of an infrared suppressor may require individual techniques for the determination and definition of engine installation losses.
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Twin Engine Helicopter Power Requirements

1997-06-01
CURRENT
AIR1850A
This SAE Aerospace Information Report (AIR) defines the power spectrum during normal and emergency operations of a twin engine helicopter and thereby postulates suitable power plant rating structures. This document does not address the power requirements for single engine helicopters or those with more than two engines.
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Cockpit Information Required for Helicopter Turbine Engine Operation and Maintenance

1997-06-01
CURRENT
AIR1963A
This SAE Aerospace Information Report (AIR) identifies Propulsion Engineer’s recommendations for the instrumentation that is required for the safe operation and maintenance of turbine engines as installed in helicopters. It should be used as a guide for cockpit layout, as well as a reference for maintenance considerations throughout the propulsion area. Propulsion instruments should receive attention early in the design phase of the helicopter. Maintenance and diagnostics recorders are not considered within the scope of this document. (See ARP1587, “Aircraft Gas Turbine Engine Monitoring System Guide”.)
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Helicopter Power Assurance

1997-06-01
CURRENT
AIR4083A
This SAE Aerospace Information Report (AIR) defines helicopter turboshaft engine power assurance theory and methods. Several inflight power assurance example procedures are presented. These procedures vary from a very simple method used on some normal category civil helicopters, to the more complex methods involving trend monitoring and rolling average techniques. The latter method can be used by small operators but is generally better suited to the larger operator with computerized maintenance record capability.
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Helicopter Engine/Airframe Interface Document and Checklist

1997-06-01
CURRENT
ARP1507A
This SAE Aerospace Recommended Practice (ARP) provides a guide for the preparation of a Helicopter Engine/Airframe Interface Document and Checklist. This document and checklist is intended to provide complete relevant information on the characteristics, performance, and engine interfaces. Of most importance is the identification of the data and the location of data to assure that the engine manufacturer and the airframe manufacturer supply information that can be easily located by either manufacturer.
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Air Bleed Objective for Helicopter Turbine Engines

1997-05-01
CURRENT
AIR984C
This SAE Aerospace Information Report (AIR) defines the helicopter bleed air requirements which may be obtained through compressor extraction and is intended as a guide to engine designers.
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Helicopter Engine-Rotor System Compatibility

1997-05-01
CURRENT
ARP704A
This SAE Aerospace Recommended Practice (ARP) recommends a methodology to be used for the design, analysis and test evaluation of modern helicopter gas turbine propulsion system stability and transient response characteristics. This methodology utilizes the computational power of modern digital computers to more thoroughly analyze, simulate and bench-test the helicopter engine/rotor system speed control loop over the flight envelope. This up-front work results in significantly less effort expended during flight test and delivers a more effective system into service. The methodology presented herein is recommended for modern digital electronic propulsion control systems and also for traditional analog and hydromechanical systems.
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HELICOPTER TURBINE ENGINE WASH

1995-05-01
CURRENT
AIR4416
Engines subject to dust, industrial pollution, saltwater contamination or other chemically laden atmosphere (including pesticides and herbicides) lose performance due to deposits of contaminants on surfaces in the aidgas flow path. Engine wash and engine rinse procedures are utilized to restore turbine engine performance. These procedures are generated by the engine manufacturer and are included in the Engine Maintenance/Service Manuals. For most turbine engines these procedures are similar in concept and practice; however, application details, choice of solvents and many other service features can vary from engine manufacturer to engine manufacturer and may even vary within the range of engine models produced by any manufacturer.
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HELICOPTER POWERPLANT CORROSION PROTECTION

1993-05-01
CURRENT
AIR4495
This SAE Aerospace Information Report (AIR) describes the different aspects of corrosion on helicopter powerplants, on the components that are affected, and the subsequent consequences on the helicopter, engine durability, performance, and dependability. Guidelines that minimize corrosion during the design stage and during service operation are also discussed.
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EVALUATION OF HELICOPTER TURBINE ENGINE LINEAR VIBRATION ENVIRONMENT

1992-03-01
CURRENT
AIR1289A
This SAE Aerospace Information Report (AIR) outlines a recommended procedure for evaluation of the vibration environment to which the gas turbine engine powerplant is subjected in the helicopter installation. This analysis of engine vibration is normally demonstrated on a one-time basis upon initial certification, or after a major modification, of an engine/helicopter configuration. This AIR deals with linear vibration as measured on the basic case structure of the engine and not, for example, torsional vibration in drive shafting or vibration of a component within the engine such as a compressor or turbine airfoil. In summary, this AIR discusses the engine manufacturer’s "Installation Test Code" aspects of engine vibration and proposes an appropriate measurement method.
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HELICOPTER ENGINE MOUNTING

1991-05-23
CURRENT
AIR4172
This Aerospace Information Report (AIR) reviews the requirements to be satisfied by the engine mount systems and provides an outline of some suitable methods. Factors such as drive shaft alignment, engine expansion, mount crashworthiness, vibration isolation, and other effects on the installation are discussed.
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HELICOPTER ENGINE FOREIGN OBJECT DAMAGE

1989-11-30
CURRENT
AIR4096
The purpose of this SAE Aerospace Information Report is to disseminate qualitative information regarding foreign object damage (FOD) to gas turbine engines used to power helicopters and to discuss methods of preventing FOD. Although turbine-powered, fixed-wing aircraft are also subject to FOD, the unique ability of the helicopter to hover above, takeoff from, and land on unprepared areas creates a special need for a separate treatment of this subject as applied to rotary-winged aircraft.
Standard

ENGINE EXHAUST SYSTEM DESIGN CONSIDERATIONS FOR ROTORCRAFT

1989-10-01
CURRENT
ARP4056
Turbine engines installed in rotorcraft have an exhaust system that is designed and produced by the aircraft manufacturer. The primary function of the exhaust system is to direct hot exhaust gases away from the airframe. The exhaust system may consist of a tailpipe, which is attached to the engine, and an exhaust fairing, which is part of the rotorcraft. The engine manufacturer specifies a baseline "referee" tailpipe design, and guaranteed engine performance is based upon the use of the referee tailpipe and tailpipe exit diameter. The configuration used on the rotocraft may differ from the referee tailpipe, but it is intended to minimize additional losses attributed to the installation. This Aerospace Recommended Practice (ARP) describes the physical, functional, and performance interfaces to be considered in the design of the aircraft exhaust system.
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