Flight crew of large transport received a false signal from slc ILS positioning them over terrain in...

Attributes
ACN	120627
Time
Date	198908
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : slc
State Reference	UT
Altitude	msl bound lower : 9000 msl bound upper : 12000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : slc
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent : approach descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 4000 flight time type : 1000
ASRS Report	120627
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	121304
Events
Anomaly	other anomaly other other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other
Situations
Navigational Aid	Unspecified

Narrative:

On 310 degree vector to intercept ILS 34L slc localizer for approach at 9000'. ILS tuned/idented (no flags), captain intercepted. I noticed slc 159 degree right and slc LOM both indicated left of our position. Break in clouds allowed view of mountains ahead. Just as I brought all this to the captain's attention, approach called, giving immediate left turn 280 degrees, 11000' for terrain clearance. As we were already in turn left toward 159 degree right, an easy turn was completed and approach continued as normal when correct localizer signal appeared. Slc approach is investigating cause of a good, but false signal. We were second aircraft of the day with same problem. Callback conversation with reporter revealed the following: the timing did not seem right when the ILS was idented and the localizer came in too quickly. I went back to reident the ILS signal and was having trouble identing now. As I spoke to the captain, we received a vector. When captain spoke to supervisor in TRACON, he states they told him the ILS had been test flown a few days previous. I have no knowledge that this incident is being followed up on by slc approach control.

Original NASA ASRS Text

Title: FLT CREW OF LGT RECEIVED A FALSE SIGNAL FROM SLC ILS POSITIONING THEM OVER TERRAIN INSTEAD OF OVER THE VALLEY. CTLR INTERVENED WITH CORRECTING VECTOR.

Narrative: ON 310 DEG VECTOR TO INTERCEPT ILS 34L SLC LOC FOR APCH AT 9000'. ILS TUNED/IDENTED (NO FLAGS), CAPT INTERCEPTED. I NOTICED SLC 159 DEG R AND SLC LOM BOTH INDICATED LEFT OF OUR POS. BREAK IN CLOUDS ALLOWED VIEW OF MOUNTAINS AHEAD. JUST AS I BROUGHT ALL THIS TO THE CAPT'S ATTN, APCH CALLED, GIVING IMMEDIATE LEFT TURN 280 DEGS, 11000' FOR TERRAIN CLRNC. AS WE WERE ALREADY IN TURN LEFT TOWARD 159 DEG R, AN EASY TURN WAS COMPLETED AND APCH CONTINUED AS NORMAL WHEN CORRECT LOC SIGNAL APPEARED. SLC APCH IS INVESTIGATING CAUSE OF A GOOD, BUT FALSE SIGNAL. WE WERE SECOND ACFT OF THE DAY WITH SAME PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: THE TIMING DID NOT SEEM RIGHT WHEN THE ILS WAS IDENTED AND THE LOC CAME IN TOO QUICKLY. I WENT BACK TO REIDENT THE ILS SIGNAL AND WAS HAVING TROUBLE IDENTING NOW. AS I SPOKE TO THE CAPT, WE RECEIVED A VECTOR. WHEN CAPT SPOKE TO SUPVR IN TRACON, HE STATES THEY TOLD HIM THE ILS HAD BEEN TEST FLOWN A FEW DAYS PREVIOUS. I HAVE NO KNOWLEDGE THAT THIS INCIDENT IS BEING FOLLOWED UP ON BY SLC APCH CTL.

Data retrieved from NASA's ASRS site as of August 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.

Flight crew of large transport received a false signal from slc ILS positioning them over terrain instead of over the valley. Controller intervened with correcting vector.