An atx pilot (PA31 piper navajo) reports that the use of ILS frequency 108 pt 9 created a loss of hi...

Attributes
ACN	408257
Time
Date	199807
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : sfb
State Reference	FL
Altitude	msl bound lower : 10000 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zjx
Operator	common carrier : air taxi
Make Model Name	PA-31 Navajo Chieftan/Mojave/Navajo T1020
Operating Under FAR Part	Part 135
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	pilot : atp
Experience	flight time last 90 days : 300 flight time total : 20000 flight time type : 300
ASRS Report	408257
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : overcame equipment problem other
Consequence	Other
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other

Narrative:

I have noticed that on about 50% of my arrs into the sanford airport (sfb), my GPS loses its satellites and ceases to provide information. On this particular day, WX at sfb looked rough, so I tuned in the ILS 9 localizer frequency 108.9 during cruise about 80 mi out to plan the approach. Within 2 mins, I noticed that my garmin 195 map had lost its satellites and failed to provide steering data. I changed the frequency in the NAVAID window to a different frequency and within 2 mins the GPS returned to normal. I repeated the test several times with the same result -- the ILS frequency of 108.9 somehow interferes with the GPS. In flight today, I asked a company flight if he had ever had any GPS problems in the sfb area. He had on numerous occasions. I told him of my discovery and he tried it inbound to sfb. His GPS was a trimble but the result was the same: tuning 108.9 shut down the GPS data. I now know that the problem has nothing to do with location, but only occurs when 108.9 is tuned. Thought you'd be interested. The times I had lost data approaching the sfb airport were not random but happened only when wind/WX caused me to tune 108.9. Callback conversation with reporter revealed the following information: the reporter stated that his aircraft was a PA-31 piper navajo. He was supplementing his navigation capability with the GPS which was his own and was mounted on the yoke with the antenna laying on the glare shield. The unit was not certified for IFR, for VFR only. He now feels that had he placed the antenna behind him, away from the radio consoles, that the use of 108.9 ILS frequency would not have interfered with the GPS signal. A friend of his used a trimble GPS, type number unknown, and experienced the same anomaly as he had with the use of 108.9 ILS frequency. The reporter also speculated that it might not happen with every aircraft but would depend upon the type and the wiring of the aircraft. He thought that this event was so unique that the GPS manufacturers should know about it for issuance in their information bulletins.

Original NASA ASRS Text

Title: AN ATX PLT (PA31 PIPER NAVAJO) RPTS THAT THE USE OF ILS FREQ 108 PT 9 CREATED A LOSS OF HIS GARMIN 195 GPS SIGNAL. THIS WAS CHKED SEVERAL TIMES FOR REPEATS OF THE INITIAL EVENT.

Narrative: I HAVE NOTICED THAT ON ABOUT 50% OF MY ARRS INTO THE SANFORD ARPT (SFB), MY GPS LOSES ITS SATELLITES AND CEASES TO PROVIDE INFO. ON THIS PARTICULAR DAY, WX AT SFB LOOKED ROUGH, SO I TUNED IN THE ILS 9 LOC FREQ 108.9 DURING CRUISE ABOUT 80 MI OUT TO PLAN THE APCH. WITHIN 2 MINS, I NOTICED THAT MY GARMIN 195 MAP HAD LOST ITS SATELLITES AND FAILED TO PROVIDE STEERING DATA. I CHANGED THE FREQ IN THE NAVAID WINDOW TO A DIFFERENT FREQ AND WITHIN 2 MINS THE GPS RETURNED TO NORMAL. I REPEATED THE TEST SEVERAL TIMES WITH THE SAME RESULT -- THE ILS FREQ OF 108.9 SOMEHOW INTERFERES WITH THE GPS. IN FLT TODAY, I ASKED A COMPANY FLT IF HE HAD EVER HAD ANY GPS PROBS IN THE SFB AREA. HE HAD ON NUMEROUS OCCASIONS. I TOLD HIM OF MY DISCOVERY AND HE TRIED IT INBOUND TO SFB. HIS GPS WAS A TRIMBLE BUT THE RESULT WAS THE SAME: TUNING 108.9 SHUT DOWN THE GPS DATA. I NOW KNOW THAT THE PROB HAS NOTHING TO DO WITH LOCATION, BUT ONLY OCCURS WHEN 108.9 IS TUNED. THOUGHT YOU'D BE INTERESTED. THE TIMES I HAD LOST DATA APCHING THE SFB ARPT WERE NOT RANDOM BUT HAPPENED ONLY WHEN WIND/WX CAUSED ME TO TUNE 108.9. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT HIS ACFT WAS A PA-31 PIPER NAVAJO. HE WAS SUPPLEMENTING HIS NAV CAPABILITY WITH THE GPS WHICH WAS HIS OWN AND WAS MOUNTED ON THE YOKE WITH THE ANTENNA LAYING ON THE GLARE SHIELD. THE UNIT WAS NOT CERTIFIED FOR IFR, FOR VFR ONLY. HE NOW FEELS THAT HAD HE PLACED THE ANTENNA BEHIND HIM, AWAY FROM THE RADIO CONSOLES, THAT THE USE OF 108.9 ILS FREQ WOULD NOT HAVE INTERFERED WITH THE GPS SIGNAL. A FRIEND OF HIS USED A TRIMBLE GPS, TYPE NUMBER UNKNOWN, AND EXPERIENCED THE SAME ANOMALY AS HE HAD WITH THE USE OF 108.9 ILS FREQ. THE RPTR ALSO SPECULATED THAT IT MIGHT NOT HAPPEN WITH EVERY ACFT BUT WOULD DEPEND UPON THE TYPE AND THE WIRING OF THE ACFT. HE THOUGHT THAT THIS EVENT WAS SO UNIQUE THAT THE GPS MANUFACTURERS SHOULD KNOW ABOUT IT FOR ISSUANCE IN THEIR INFO BULLETINS.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

An atx pilot (PA31 piper navajo) reports that the use of ILS frequency 108 pt 9 created a loss of his garmin 195 GPS signal. This was checked several times for repeats of the initial event.