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Standard

Instrumental Methods of Determining Surface Cleanliness

2017-09-20
CURRENT
ARP4252B
This Aerospace Recommended Practice is intended as a guide toward standard practices for the determination of surface cleanliness that are applicable to field operation. Some of these methods can also be used to determine quality assurance that a surface has been properly prepared and maintained. The instrumental methods are: Wettability, Surface Potential Difference (SPD), Ellipsometry, and Optically Stimulated Electron Emission (OSEE). Each instrument is described with respect to measurement techniques, limitations, and advantages and types of available instruments. Elementary theoretical principles and examples of the use of each instrument are also given.
Standard

Determination of Distance from Ground Observer to Aircraft for Acoustic Tests

2017-09-19
CURRENT
AIR902A
This document describes a practical system for a user to determine observer-to-aircraft distances. These observer-to-aircraft distances can be either closest point of approach (CPA) distances during field measurements or overhead distances during acoustic certification tests. The system uses a digital camera to record an image of the subject aircraft. A method of using commercial software to obtain the distance from such an image is presented. Potential issues which may affect accuracy are discussed.
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