Same ILS frequency for runway 30 and 12. Different identification.

Attributes
ACN	82993
Time
Date	198802
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sjc
State Reference	CA
Altitude	msl bound lower : 3000 msl bound upper : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Retractable Gear
Flight Phase	cruise other
Flight Plan	None
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : cfi pilot : commercial pilot : instrument
Experience	flight time last 90 days : 30 flight time total : 1300 flight time type : 3
ASRS Report	82993
Person 2
Function	instruction : instructor
Qualification	pilot : instrument pilot : cfi
Events
Anomaly	other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other

Narrative:

Isjc - 110.9, runway 30. Islv - 110.9, runway 12. Identification's are so close, it's very easy to get a back course west/O realizing it. Accident waiting to happen. Charts give no indication of possible confusion. Callback conversation with reporter revealed the following: was having problems identifying the ILS, last digits were garbled. Became confused as to indication on his CDI since he assumed 30 ILS was transmitting when in fact 12 was in use. Would like to see frequency changed. Explained probably interference problems and the shortage of available frequency. Suggested he contact the FAA hotline or flight inspection field office. Advised to be very careful of the information he is seeing when the identify is not clear.

Original NASA ASRS Text

Title: SAME ILS FREQ FOR RWY 30 AND 12. DIFFERENT IDENTIFICATION.

Narrative: ISJC - 110.9, RWY 30. ISLV - 110.9, RWY 12. ID'S ARE SO CLOSE, IT'S VERY EASY TO GET A BACK COURSE W/O REALIZING IT. ACCIDENT WAITING TO HAPPEN. CHARTS GIVE NO INDICATION OF POSSIBLE CONFUSION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: WAS HAVING PROBS IDENTIFYING THE ILS, LAST DIGITS WERE GARBLED. BECAME CONFUSED AS TO INDICATION ON HIS CDI SINCE HE ASSUMED 30 ILS WAS XMITTING WHEN IN FACT 12 WAS IN USE. WOULD LIKE TO SEE FREQ CHANGED. EXPLAINED PROBABLY INTERFERENCE PROBS AND THE SHORTAGE OF AVAILABLE FREQ. SUGGESTED HE CONTACT THE FAA HOTLINE OR FLT INSPECTION FIELD OFFICE. ADVISED TO BE VERY CAREFUL OF THE INFO HE IS SEEING WHEN THE IDENT IS NOT CLEAR.

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.