(This document supersedes and cancels AIR 12) 'Ground resonance' is a term which originated in the early days of autogiro development in this country. It is a somewhat ambiguous term as the conditions it describes usually occur at the ground but do not have any association with the common expression 'ground effect'. However, the troubles usually associated with 'ground resonance' do occur when the ship is on or near the ground.
This document is reissued for application to helicopters. It is primarily intended to apply to the engine or engines, but it shall also apply to fire protection of lines, tanks, combustion heaters, and auxiliary powerplants (APU). Post-crash fire protection is also discussed.
It is recommended that all helicopter engine development programs include an evaluation of engine starting requirements. The evaluation should include starting requirement effects on helicopter weight, cost, and mission effectiveness. The evaluation should be appropriate to the engine stage of development.
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”.)
The purpose of this Aerospace Recommended Practice (ARP) is to define a method of measuring those factors affecting installed power available for helicopter power plants. These factors are installation losses, accessory power extraction, and operational 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 determiantion and definition of engine installation losses.
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.
This Aerospace Information Report deals with protection of helicopter aircraft engines against erosion. Applicability is restricted to aircraft having a disc loading of less than 15 pounds per square foot.
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.