Small aircraft on approach experiences erroneous VOR indications.

Attributes
ACN	253802
Time
Date	199310
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : cma
State Reference	CA
Altitude	msl bound lower : 2100 msl bound upper : 2100
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	tracon : ntd tracon : avl
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Fixed Gear
Flight Phase	descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : cfi pilot : atp
Experience	flight time last 90 days : 16 flight time total : 5000 flight time type : 200
ASRS Report	253802
Person 2
Affiliation	Other
Function	controller : approach
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	other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other
Situations
Navigational Aid	Unspecified

Narrative:

I was vectored by mugu approach to intercept VOR 26 final approach course to cma. After interception I turned to inbound heading with centered needle and started descent to 2100 ft to cross acrat intersection. After scanning the instruments I saw the needed 'pegged' to the left, I put in a correction then the needle pegged to the right, all in about 10 seconds. As I crossed acrat intersection I tuned my second navigation radio to the VOR 26 final approach course. Then both needles began swinging from peg to peg in unison. As I was then in VFR conditions I could see the airport straight ahead and could confirm that the radios were receiving erroneous signals. I reported this to cma control tower. He warned the airplane behind me on the approach. The next airplane then informed the tower that it had experienced the same malfunction. Such errors are extremely critical at cma as there are mountains on both sides of the final approach course.

Original NASA ASRS Text

Title: SMA ON APCH EXPERIENCES ERRONEOUS VOR INDICATIONS.

Narrative: I WAS VECTORED BY MUGU APCH TO INTERCEPT VOR 26 FINAL APCH COURSE TO CMA. AFTER INTERCEPTION I TURNED TO INBOUND HDG WITH CTRED NEEDLE AND STARTED DSCNT TO 2100 FT TO CROSS ACRAT INTXN. AFTER SCANNING THE INSTS I SAW THE NEEDED 'PEGGED' TO THE L, I PUT IN A CORRECTION THEN THE NEEDLE PEGGED TO THE R, ALL IN ABOUT 10 SECONDS. AS I CROSSED ACRAT INTXN I TUNED MY SECOND NAV RADIO TO THE VOR 26 FINAL APCH COURSE. THEN BOTH NEEDLES BEGAN SWINGING FROM PEG TO PEG IN UNISON. AS I WAS THEN IN VFR CONDITIONS I COULD SEE THE ARPT STRAIGHT AHEAD AND COULD CONFIRM THAT THE RADIOS WERE RECEIVING ERRONEOUS SIGNALS. I RPTED THIS TO CMA CTL TWR. HE WARNED THE AIRPLANE BEHIND ME ON THE APCH. THE NEXT AIRPLANE THEN INFORMED THE TWR THAT IT HAD EXPERIENCED THE SAME MALFUNCTION. SUCH ERRORS ARE EXTREMELY CRITICAL AT CMA AS THERE ARE MOUNTAINS ON BOTH SIDES OF THE FINAL APCH COURSE.

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.