Hostname: page-component-cd9895bd7-dzt6s Total loading time: 0 Render date: 2024-12-26T04:47:20.980Z Has data issue: false hasContentIssue false
  • English
  • Français

Measuring the effect of helicopter rotors on GPS reception

Published online by Cambridge University Press:  03 February 2016

G. J. Brodin ,
J. A. Cooper  and
J. R. A. Stevens
G. J. Brodin
Affiliation:
Formerly of CAA Institute of Satellite Navigation, University of Leeds Leeds, UK
J. A. Cooper
Affiliation:
Formerly of CAA Institute of Satellite Navigation, University of Leeds Leeds, UK
J. R. A. Stevens
Affiliation:
Boston, Massachusetts, USA
Get access Rights & Permissions [Opens in a new window]

Abstract

This paper describes an experiment which was performed using an offshore transport helicopter to investigate the impact of the rotor blades upon Global Positioning System (GPS) reception.

The test aircraft was fitted with two separate GPS antennas which were positioned to isolate the effects caused by the main and tail rotors. Testing was undertaken with the aircraft on the ground and this allowed an assessment to be performed at different rotor speeds with accurate control over the relative geometry between the antenna, rotors and satellites.

Recorded data from a measurement system incorporating three dissimilar GPS receivers (including a technical standard order (TSO)-C129() compliant aviation unit and a custom research receiver) was analysed to identify the effect of the rotors at the correlator level and to determine the impacts upon ranging accuracy, the availability of ranging measurements, and the receivers’ signal level estimates.

Correlation data was used to demonstrate that the rotor blades were capable of generating both destructive and constructive interference effects, and the periodic nature of these oscillations was shown to correspond directly to the blade passing frequency. It was identified that signal degradation was not limited to satellite signal paths which intersected the rotor discs.

No evidence was found for any increase in code measurement error due to the rotor interference, but it was demonstrated that there could be a significant impact upon a receiver’s ability to maintain continuous tracking of the satellite signals. The overall effect of this availability problem for a given installation and type of operation will be dependent upon satellite geometry and other factors which are beyond the scope of this study.

The ability of a receiver to identify the presence of rotor interference was investigated by examining estimates of carrier-to-noise, and this revealed inconsistencies between the results from different receivers implying differences in the estimation algorithms employed. It was also identified that two alternative ‘textbook’ estimators do not give identical results in the presence of rotor interference and it is suggested that such data should therefore be interpreted with caution.

Type
Research Article
Information
The Aeronautical Journal , Volume 111 , Issue 1123 , September 2007 , pp. 561 - 570
Copyright
Copyright © Royal Aeronautical Society 2007 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1. Federal Aviation Administration, Airborne supplemental navigation equipment using the Global Positioning System (GPS), 1992, Technical Standard Order TSO-C129.Google Scholar
2. Federal Aviation Administration, Airborne supplemental navigation equipment using the Global Positioning System (GPS), 1996, Technical Standard Order TSO-C129a.Google Scholar
3. Civil Aviation Authority, UK policy for the airborne use of the United States Navstar Global Positioning System (GPS), November 2002, Aeronautical Information Circular 93/2002.Google Scholar
4. Howson, D.A., Johannessen, R. and Stevens, J.R.A.. GPS and DGPS for helicopter approaches to offshore platforms in the North Sea, September 1997, Proceedings of the 10th International Technical Meeting of the Satellite Division of the Institute of Navigation, Kansas City, MO.Google Scholar
5. Dodson, K.M. and Stevens, J.R.A.. A North Sea trial to investigate the use of differential GPS for instrument approaches to offshore platforms, September 1997, Proceedings of the 23rd European Rotorcraft Forum, Dresden, Germany.Google Scholar
6. Civil Aviation Authority, DGPS Guidance for helicopter approaches to offshore platforms, November 2000, CAA Paper 2000/5.Google Scholar
7. Civil Aviation Authority, DGPS guidance for helicopter approaches to offshore platforms – follow on studies, June 2003, CAA Paper 2003/2.Google Scholar
8. Federal Aviation Administration, Airworthiness approval of GPS navigation equipment for use as a VFR and IFR supplemental navigation system, May 1994, Advisory Circular 20–138.Google Scholar
9. Civil Aviation Authority, Effect of helicopter rotors on GPS reception, December 2003, CAA Paper 2003/7.Google Scholar
10. Sikorsky Aircraft Corporation, S76 composite materials manual, 1992, SA 4047-76-5.Google Scholar
11. Riley, S.. An integrated multichannel GPS/GLONASS receiver, September 1992, Proceedings of the fifth International Technical Meeting of the Satellite Division of the Institute of Navigation, Albuquerque, NM.Google Scholar
12. Department of Defense, Global positioning system standard positioning service performance standard, October 2001.Google Scholar
13. Van Dierendonck, A.J., GPS receivers, Global Positioning System: Theory and Applications, 1996, American Institute of Aeronautics and Astronautics.Google Scholar
14. Spilker, J.J., Digital Communications by Satellite, Prentice-Hall, 1977.Google Scholar
15. Civil Aviation Authority, September 2002, Final report on the helicopter operations monitoring programme (HOMP) trial, CAA Paper 2002/2.Google Scholar