Narrative:

Descent on the sfo 095 radial for the quiet bridge approach to san francisco. Copilot flying. Cleared to 6000. At approximately 6500', copilot tuned captain's navigation radio to sfo 28R ILS, as captain responded to approach control call of traffic. Traffic was not seen and captain noticed navigation radio tuned to ILS. Questioned copilot as to why, he responded, for the glide slope. Captain retuned his radio back to sfo VOR and noted altitude was 5800-5700, and called out deviation before aircraft stopped descent. Altitude went to 5600, started climb to 6000. At this point cleared to 5000, then cleared for visual approach. Contributing factors: 2-MAN airplane. Importance of pilot flying to do only that. Pilot flying stay with instruments and ask other pilot for information or radio changes. Captain was monitoring navigation on VOR and did not expect ILS, thereby interrupting his cockpit flow. Important to stay with phase of flight. Ie, navigating on VOR radial, descending to altitude for level flight. First things first. With DME on airport, no need for glide slope. That approach has recommended altitudes, then a prescribed transition to glide slope. By setting up glide slope before approach clearance, and hearing what you what to hear, you are setting yourself up for premature descent.

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Original NASA ASRS Text

Title: ACR MLG ALT DEVIATION OVERSHOT ON QUIET BRIDGE APCH TO SFO.

Narrative: DESCENT ON THE SFO 095 RADIAL FOR THE QUIET BRIDGE APCH TO SAN FRANCISCO. COPLT FLYING. CLRED TO 6000. AT APPROX 6500', COPLT TUNED CAPT'S NAV RADIO TO SFO 28R ILS, AS CAPT RESPONDED TO APCH CTL CALL OF TFC. TFC WAS NOT SEEN AND CAPT NOTICED NAV RADIO TUNED TO ILS. QUESTIONED COPLT AS TO WHY, HE RESPONDED, FOR THE GLIDE SLOPE. CAPT RETUNED HIS RADIO BACK TO SFO VOR AND NOTED ALT WAS 5800-5700, AND CALLED OUT DEVIATION BEFORE ACFT STOPPED DSCNT. ALT WENT TO 5600, STARTED CLIMB TO 6000. AT THIS POINT CLRED TO 5000, THEN CLRED FOR VISUAL APCH. CONTRIBUTING FACTORS: 2-MAN AIRPLANE. IMPORTANCE OF PLT FLYING TO DO ONLY THAT. PLT FLYING STAY WITH INSTRUMENTS AND ASK OTHER PLT FOR INFO OR RADIO CHANGES. CAPT WAS MONITORING NAVIGATION ON VOR AND DID NOT EXPECT ILS, THEREBY INTERRUPTING HIS COCKPIT FLOW. IMPORTANT TO STAY WITH PHASE OF FLT. IE, NAVIGATING ON VOR RADIAL, DESCENDING TO ALT FOR LEVEL FLT. FIRST THINGS FIRST. WITH DME ON ARPT, NO NEED FOR GLIDE SLOPE. THAT APCH HAS RECOMMENDED ALTS, THEN A PRESCRIBED TRANSITION TO GLIDE SLOPE. BY SETTING UP GLIDE SLOPE BEFORE APCH CLRNC, AND HEARING WHAT YOU WHAT TO HEAR, YOU ARE SETTING YOURSELF UP FOR PREMATURE DSCNT.

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.