Narrative:

Msp has 2 parallel runways, 12L, 12R and 13R, 13L. The north runway 30R/12L uses the same frequency for ILS 12L and 30R. Presumably the tower switched procedures depending on wind to run approachs in the proper direction. Both approachs have an associated DME transmitter. There are separate morse code identifier, for each approach. In the saab 340 DME is identified by noting a higher pitch morse code every 30 seconds on the navigation audio. Localizer and VOR identification is made by noting the tower pitch morse code every 10 seconds. All the msp DME identifiers are the same as the localizer identifiers. This is a common configuration for many ILS approachs and I believe the standard when only one navigation frequency is used. On approach for runway 12L the identification is ipjl. The localizer identification's as described above and the DME also ids as described above. However, when tuning the ILS runway 30R, 2 separate DME identifiers can be heard at 30 second intervals and ipjl can be heard. Iinn can be heard also at 30 second intervals. The localizer for runway 30R ids correctly (iinn at 10 second intervals). I have pireded this NAVAID anomaly 3 times on over the last couple months, but it still occurs. Callback conversation with reporter revealed the following information: reporter advises that the anomaly appears associated only with the identification of the DME in use. The distance displays appear appropriate to the runway in use. A review of the approach plates indicate the DME localizer appears to be a single localizer, thus only the morse identify is altered while retaining appropriate distance display. In the case of this runway pair the only anomaly is when the runway 30R alternative is selected for the frequency.

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Original NASA ASRS Text

Title: RPTR ADVISES THE DME IDENT FOR THE MSP RWY 30R ILS APCH TRANSMITS BOTH THE APPROPRIATE MORSE CODE AS WELL AS THE DME ID FOR THE SAME FREQUENCY WHEN EMPLOYED FOR THE REVERSE APCH, THE ILS OR LOC RWY 12.

Narrative: MSP HAS 2 PARALLEL RWYS, 12L, 12R AND 13R, 13L. THE N RWY 30R/12L USES THE SAME FREQ FOR ILS 12L AND 30R. PRESUMABLY THE TWR SWITCHED PROCEDURES DEPENDING ON WIND TO RUN APCHS IN THE PROPER DIRECTION. BOTH APCHS HAVE AN ASSOCIATED DME TRANSMITTER. THERE ARE SEPARATE MORSE CODE IDENTIFIER, FOR EACH APCH. IN THE SAAB 340 DME IS IDENTIFIED BY NOTING A HIGHER PITCH MORSE CODE EVERY 30 SECONDS ON THE NAV AUDIO. LOC AND VOR IDENTIFICATION IS MADE BY NOTING THE TWR PITCH MORSE CODE EVERY 10 SECONDS. ALL THE MSP DME IDENTIFIERS ARE THE SAME AS THE LOC IDENTIFIERS. THIS IS A COMMON CONFIGURATION FOR MANY ILS APCHS AND I BELIEVE THE STANDARD WHEN ONLY ONE NAV FREQ IS USED. ON APCH FOR RWY 12L THE ID IS IPJL. THE LOC ID'S AS DESCRIBED ABOVE AND THE DME ALSO IDS AS DESCRIBED ABOVE. HOWEVER, WHEN TUNING THE ILS RWY 30R, 2 SEPARATE DME IDENTIFIERS CAN BE HEARD AT 30 SECOND INTERVALS AND IPJL CAN BE HEARD. IINN CAN BE HEARD ALSO AT 30 SECOND INTERVALS. THE LOC FOR RWY 30R IDS CORRECTLY (IINN AT 10 SECOND INTERVALS). I HAVE PIREDED THIS NAVAID ANOMALY 3 TIMES ON OVER THE LAST COUPLE MONTHS, BUT IT STILL OCCURS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR ADVISES THAT THE ANOMALY APPEARS ASSOCIATED ONLY WITH THE ID OF THE DME IN USE. THE DISTANCE DISPLAYS APPEAR APPROPRIATE TO THE RWY IN USE. A REVIEW OF THE APCH PLATES INDICATE THE DME LOC APPEARS TO BE A SINGLE LOC, THUS ONLY THE MORSE IDENT IS ALTERED WHILE RETAINING APPROPRIATE DISTANCE DISPLAY. IN THE CASE OF THIS RWY PAIR THE ONLY ANOMALY IS WHEN THE RWY 30R ALTERNATIVE IS SELECTED FOR THE FREQUENCY.

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.