Giving RTK a Whirl — GPS Aces Flight Tests

GPS World, April, 2000 by Mark Hardesty, Greg Ashe

We usually conduct a height-velocity test at the conclusion of the test program because of the extreme hazards associated with the data-collection process. It is not uncommon to severely damage the airframe finding the end points of the envelope. Because of the risk to equipment and flight crew, it is imperative to provide cross checks for helicopter altitude above ground level. Wind shear between the helicopter and the landing zone can also dramatically affect the success of the sportier data points.

The Portable Test Range allows the pilot and ground crew to know the vehicle's exact altitude above ground level and to evaluate winds aloft for shear conditions, contributing greatly to the overall safety of the flight test exercise. We have damaged several aircraft conducting this test in the past, so we are all very happy to have the Portable Test Range as another cross check on wind conditions and truth source for altitude above the landing surface. If we perform this maneuver a few feet too low, we can damage the helicopter, regardless of how good our piloting skills may be -- something we all obviously would like to avoid.

THE REWARDS OF RTK

Many benefits have been reaped from the Portable Test Range, including significant time savings when conducting tests and the accuracy improvements demonstrated by the tests discussed in this article. The system's developer/programmer is also able to quickly refamiliarize himself with the program and make the necessary modifications to support new flight test programs, which has contributed to an unexpected increase in productivity. This has also greatly facilitated the continued implementation of the more-efficient testing techniques, including two new ones in the works, climbing and descending airspeed calibration and flight loads survey maneuver cueing.

The development and use of RTK DGPS as a truth source has contributed greatly to the success and safety of a variety of flight test programs. The accuracy of the position and velocity data provided by this technology have improved the fidelity of computer models used to design new products, speeding development and certification of new aircraft models. The Portable Test Range is helping flight test teams at The Boeing Company work smarter and faster, ensuring that they stay competitive in the ever-changing world of helicopter flight testing.

ACKNOWLEDGMENTS

The authors would like to thank the following individuals and organizations for their support in the development of the Portable Test Range: Francis Yuen and Tom Ford of NovAtel, Inc.; Ron Wilson Sr., Ron Wilson Jr., Jamie Wilson, and Ron Kostorowski of GLB Electronics; Neil Toso of NFT Ventures, Inc.; Gregg Fleming of the Volpe National Transportation Systems Center, U.S. DoT Research and Special Programs Administration; Bruce Conze of the Propulsion Department, FAA LAACO; Joe Flint of The Boeing Company-Mesa, Engineering Flight Test; Al Lehman and Ken Watterson of Allen Instruments, Scottsdale, Arizona; and Jay Zimmerman of GPS Neatly Done, Phoenix, Arizona.