Narrative:

An air carrier crew flying an exchange aircraft from another carrier and although it is the same type aircraft, the instruments and radios are considerably different in appearance and operation. It is an early morning departure with poor deteriorating WX at the destination. ATIS 500 ft overcast visibility 2 mi variable fog wind 080 at 8 KTS ILS 26/27. On downwind approach reported a wind of 090 at 12 KTS. We told approach that the tailwind was out of limits for landing on runway 26. Approach said standby and approximately two mins later they reported threshold wind of 070 at 7 KTS and cleared us to 2000 ft with vectors for approach. Aircraft was configured for approach with concern for a tailwind on final. We were given a vector to intercept the ILS maintain 2000 until intercepting ILS cleared for approach RVR 5000 change to tower frequency. A raw data ILS had been briefed but with RVR at 5000 I switched to approach mode on the hdi for the approach. At this time the V bars indicated above the GS so I started a descent to capture the V bars. When the first officer changed the radio frequency to the tower and came back to monitor the ILS prior to switching to tower frequency and announcing we are below the GS. Approach asked, check your altitude. At this point the first officer realized that he had not selected tower frequency so he selected and checked in with the tower and we were asked to check your altitude. At this point descent was stopped and a climb initiated until the GS was captured on raw data and the approach was completed to a normal landing. Contributing factors were unfamiliar radios and instruments in appearance and operation with the hdi approach mode giving opposite indications from normal in company aircraft when approach mode is selected. Concern with deteriorating WX with tailwind complications causing a lack of accurate x-chking of all instruments.

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Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION ON IAP ILS APCH.

Narrative: AN ACR CREW FLYING AN EXCHANGE ACFT FROM ANOTHER CARRIER AND ALTHOUGH IT IS THE SAME TYPE ACFT, THE INSTS AND RADIOS ARE CONSIDERABLY DIFFERENT IN APPEARANCE AND OP. IT IS AN EARLY MORNING DEP WITH POOR DETERIORATING WX AT THE DEST. ATIS 500 FT OVCST VISIBILITY 2 MI VARIABLE FOG WIND 080 AT 8 KTS ILS 26/27. ON DOWNWIND APCH RPTED A WIND OF 090 AT 12 KTS. WE TOLD APCH THAT THE TAILWIND WAS OUT OF LIMITS FOR LNDG ON RWY 26. APCH SAID STANDBY AND APPROX TWO MINS LATER THEY RPTED THRESHOLD WIND OF 070 AT 7 KTS AND CLRED US TO 2000 FT WITH VECTORS FOR APCH. ACFT WAS CONFIGURED FOR APCH WITH CONCERN FOR A TAILWIND ON FINAL. WE WERE GIVEN A VECTOR TO INTERCEPT THE ILS MAINTAIN 2000 UNTIL INTERCEPTING ILS CLRED FOR APCH RVR 5000 CHANGE TO TWR FREQ. A RAW DATA ILS HAD BEEN BRIEFED BUT WITH RVR AT 5000 I SWITCHED TO APCH MODE ON THE HDI FOR THE APCH. AT THIS TIME THE V BARS INDICATED ABOVE THE GS SO I STARTED A DSCNT TO CAPTURE THE V BARS. WHEN THE FO CHANGED THE RADIO FREQ TO THE TWR AND CAME BACK TO MONITOR THE ILS PRIOR TO SWITCHING TO TWR FREQ AND ANNOUNCING WE ARE BELOW THE GS. APCH ASKED, CHK YOUR ALT. AT THIS POINT THE FO REALIZED THAT HE HAD NOT SELECTED TWR FREQ SO HE SELECTED AND CHKED IN WITH THE TWR AND WE WERE ASKED TO CHK YOUR ALT. AT THIS POINT DSCNT WAS STOPPED AND A CLB INITIATED UNTIL THE GS WAS CAPTURED ON RAW DATA AND THE APCH WAS COMPLETED TO A NORMAL LNDG. CONTRIBUTING FACTORS WERE UNFAMILIAR RADIOS AND INSTS IN APPEARANCE AND OP WITH THE HDI APCH MODE GIVING OPPOSITE INDICATIONS FROM NORMAL IN COMPANY ACFT WHEN APCH MODE IS SELECTED. CONCERN WITH DETERIORATING WX WITH TAILWIND COMPLICATIONS CAUSING A LACK OF ACCURATE X-CHKING OF ALL INSTS.

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.