1. FAA Tests An H-Field Antenna To Increase Loran-C Availability During P-Static Events R. Erikson, FAA WJ Hughes Technical Center and Dr. R. Lilley, Illgen Simulation Technologies Inc.

2. FAA/Illgen 11-6-032 Background Late 1980’s criticism: Precipitation static (P-static) said to deny Loran-C guidance just when you need it the most -- in instrument meterological conditions.

3. FAA/Illgen 11-6-033 Electrical Noise Generated in Flight Aircraft Charging –Electrons knocked free from particles of ice or water (triboelectric process) –MIL-STD-464 - charge based on Wetted frontal area Cloud & precipitation type Aircraft speed Aircraft Discharging or Equalization –Arcs Different elements of airframe are charged to different voltages Broadband noise, energetic

4. FAA/Illgen 11-6-034 Electrical Noise Generated in Flight - cont. Aircraft Discharging or Equalization –Streamers Low-current arcs form across dielectric surfaces ( windscreens, radomes) –Corona Packets of charge leaving the trailing edge Constant amplitude, rate variable Low current

5. FAA/Illgen 11-6-035 Solutions Add static dischargers Good aircraft maintenance Magnetic-loop (“h-field”) antenna

6. FAA/Illgen 11-6-036 Why Do We Expect H-field Antennas Will Increase Availability? Studies at Ohio University –Aircraft: DC-3, Piper Saratoga, Bonanza –Methods: Ground electrostatic calibration Flight –Equipment: Loran with e- and h-field antennas Wideband recordings Omega history and experience

7. FAA/Illgen 11-6-037 E-Field - H-Field Comparison 020406080100120 - 9 - 5 - 1 5 Time in minutes SNR (dB) Aircraft: Beechcraft V35A Loran Receivers: II Morrow Apollo 612A (TSO’d) E-field: II Morrow A-16 Whip (TSO’d) H-field: King Radio ADF (TSO’d) Severe P-Static (Snow) Secondary Y NorthEast U.S. (9960) Time 0 = 0734 EST on 20 March 2000 Flight from N39 W82 to N36 W83 Avionics Engineering Center Ohio University, Athens, OH 45701 E-Field H- Field E-Field

8. FAA/Illgen 11-6-038 Illgen/Ohio University Results V baseline V max SNR Time Difference V baseline - no charge on airplaneV max - maximum charging, 27 KV and 51 uA Time Difference from Seneca, N.Y. station tracked from Athens, Ohio Test performed by Illgen Simulation Technologies, Inc. with support of the Avionics Engineering Center, Ohio University. November 1998, using equipment provided by Locus (e-field) and Megapulse (h-field).

9. FAA/Illgen 11-6-039 Test performed by Illgen Simulation Technologies, Inc. with support of the Avionics Engineering Center, Ohio University. November 1998, using equipment provided by Locus (e-field) and Megapulse (h-field).

10. FAA/Illgen 11-6-0310 You want to do what ? Charge aircraft with 50,000 volt power supply Install polycarbonate tail boom (stinger) –with a cluster of airframe dischargers, operated "in reverse"

11. FAA/Illgen 11-6-0311 FAA Test Program - Overview Ground based artificial electrostatic charging –Controlled charge rate and quantity –Calibrate field mill and discharge currents –Measure Loran-C SNR performance Flight test naturally occurring charging –Measure aircraft potential, discharge currents, and Loran-C SNR performance with e- and h-field antennas Flight test with artificial charging –Measure aircraft potential, discharge currents, and Loran-C SNR performance

12. FAA/Illgen 11-6-0312 Equipment Suite SatMate 1020 (h-field and e-field antennas) Apollo Multi Chain Loran Sensor (MCLS -2010) Mission Instruments EF-1001 Field Mill High Voltage Power Supply (50kVa) Time Space Position Information (TSPI)

13. FAA/Illgen 11-6-0313 Work To Date Safety Plan (work in progress) Skin map of aircraft to determine loop antenna location Antennas, field mill, and equipment installed Hangar tests (on-air signals, simulator) Preliminary flight check-out

14. FAA/Illgen 11-6-0314 Ground Based Artificial Charging Variable HV Power Supply Tail tip discharge monitor 3 Ion flood fixtures with corona ball and ignition lead Ion collection fixtures Acrylic pads with leakage guard bands to isolate tires Current Metering Panel: uA Meter Array ------------ Rudder Rt Tail Lt Tail Lt Wing Rt Wing Rt Pad Lt Pad Nose Pad ---------- Total Current

15. FAA/Illgen 11-6-0315 Illgen/ Ohio University Tests

16. FAA/Illgen 11-6-0316 FAA N-50

17. FAA/Illgen 11-6-0317 Check-out N-50 Flight 10-22-03 Checkout of field mill data collection (Raw data. Rogue zeros are now gone!)

18. FAA/Illgen 11-6-0318 FAA N-50 Flight 10-22-03 Check out receivers data collection and observe airframe potential in cloud. Blue=SatMate e-field, Red=SatMate h-field, Black=Apollo e-field, legacy (hard-limited) Apollo: Outputs an SNR "number". A number in the 90s likely represents SNR of about +8 dB. (To be calibrated.)