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HELICOPTER EXTERNAL NOISE ESTIMATION

1989-05-01
HISTORICAL
AIR1989
This method estimates noise for both single and tandem main rotor helicopters except for approach where it applies to single rotor designs only. It does not apply to coaxial rotor designs. Application is limited to helicopters powered by turbo-shaft engines and does not apply to helicopters powered by reciprocating engine, tip jets or other types of power plants. It provides noise information using basic operating and geometric information available in the open literature. To keep the method simple, it generates A-weighted sound levels, precluding the necessity for spectral details. The method prescribes estimates for typical helicopter operations; certain maneuvers may produce noise levels different from those estimated. Estimates are given for the maximum sound levels at 4 ft (1.2 m) height above the ground. For aircraft in forward flight, the estimate is given for an aircraft at an altitude of 500 ft (152 m) on a path directly over the observer.
Standard

SELECTION AND APPLICATION OF RELAYS FOR PROPER PERFORMANCE

1989-04-28
HISTORICAL
ARP4005
This Aerospace Recommended Practice (ARP) provides information to guide the selection of electromechanical relays in both electrical and electronic circuits and their application in aerospace, ground, and shipboard systems to achieve proper performance.
Standard

DESCRIPTION OF ACTUATION SYSTEMS FOR AIRCRAFT WITH FLY-BY-WIRE FLIGHT CONTROL SYSTEMS

1989-04-28
HISTORICAL
AIR4253
This AIR provides a description of representative state-of-the-art, fly-by-wire (FBW) actuation systems used in flight control systems of manned aircraft. It presents the basic characteristics, hardware descriptions, redundancy concepts, functional schematics, and discussions of the servo controls, failure monitoring, and fault tolerance. All existing FBW actuation systems are not described herein; however, those most representing the latest designs are included. While this AIR is intended as a reference source of information for future aircraft actuation system designs, the exclusion or omission of any other appropriate actuation system or subsystem should not limit consideration of their use on future aircraft.
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