Use of the GPS Reciprocal Heading Method for Determining Pitot-Static Position Error in Helicopter Flight Testing

This thesis is an evaluation of using the Global Positioning System (GPS) reciprocal heading method to determine pitot-static position errors in helicopter flight testing. Determination of position error is a fundamental flight test task that must occur early in a test program, as all other results with regard to airspeed rely on the data. The test determines errors of the pitot-static system that cause inaccurate indication of airspeed to the pilot. The measured course, a currently approved method, provides a measure of the helicopter’s groundspeed by flying the helicopter over a known distance and converting elapsed time into the speed measurement. An aviation GPS computes a very accurate groundspeed in lieu of flying a measured course is the basis of this thesis. This report compares the two methods in terms of safety, reliability, accuracy of results, and cost. Flight tests were conducted using the GPS method and the measured course to obtain position error data for the OH-58A+ helicopter for comparison. The results of the comparison show the GPS reciprocal heading method to be, accurate, reliable, cost effective, and very safe to perform.