Narrative:

Approaching bur from the southeast, typical la basin hazy sky conditions prevailed. Approach control issued a descent and warned of impending GPWS and assured we were at MVA. The ridgeline was visible and, sure enough, the GPWS issued 'terrain, terrain,...etc' over the ridge, but continued the message 'terrain, terrain, terrain...' even as we passed the ridge. This very loud distracting message continued, and since we were in visual contact with the terrain but still level at an assigned altitude, after about 45 seconds we elected to disarm the GPWS system. Meanwhile, we were being vectored with speed restrictions just outside the OM for runway 8. Runway 8 at bur was visible and nearing vny the TCASII began calling 'traffic, traffic.' we were cleared for the approach and switched to tower frequency. TCASII continued calling 'traffic, traffic.' instead of holding the nose up to continue decelerating, we lowered the nose slightly to aid in the traffic search. Tower advised us that we were below GS. Never did spot the traffic and corrected back to GS and landed normally. After landing, tower relayed approach control's concern that we were low on GS near vny. This situation was confusing because of the ambiguous mixture of IMC and VMC procedures. We used VMC rules to ignore our GPWS then to search for VFR traffic called out by TCASII, while flying an instrument approach after a short turn to final. The 'bells and whistles' of GPWS and TCASII distracted us enough that, in this case, they were more of a hindrance than a help.

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Original NASA ASRS Text

Title: ALTDEV.

Narrative: APCHING BUR FROM THE SE, TYPICAL LA BASIN HAZY SKY CONDITIONS PREVAILED. APCH CTL ISSUED A DSCNT AND WARNED OF IMPENDING GPWS AND ASSURED WE WERE AT MVA. THE RIDGELINE WAS VISIBLE AND, SURE ENOUGH, THE GPWS ISSUED 'TERRAIN, TERRAIN,...ETC' OVER THE RIDGE, BUT CONTINUED THE MESSAGE 'TERRAIN, TERRAIN, TERRAIN...' EVEN AS WE PASSED THE RIDGE. THIS VERY LOUD DISTRACTING MESSAGE CONTINUED, AND SINCE WE WERE IN VISUAL CONTACT WITH THE TERRAIN BUT STILL LEVEL AT AN ASSIGNED ALT, AFTER ABOUT 45 SECONDS WE ELECTED TO DISARM THE GPWS SYS. MEANWHILE, WE WERE BEING VECTORED WITH SPD RESTRICTIONS JUST OUTSIDE THE OM FOR RWY 8. RWY 8 AT BUR WAS VISIBLE AND NEARING VNY THE TCASII BEGAN CALLING 'TFC, TFC.' WE WERE CLRED FOR THE APCH AND SWITCHED TO TWR FREQ. TCASII CONTINUED CALLING 'TFC, TFC.' INSTEAD OF HOLDING THE NOSE UP TO CONTINUE DECELERATING, WE LOWERED THE NOSE SLIGHTLY TO AID IN THE TFC SEARCH. TWR ADVISED US THAT WE WERE BELOW GS. NEVER DID SPOT THE TFC AND CORRECTED BACK TO GS AND LANDED NORMALLY. AFTER LNDG, TWR RELAYED APCH CTL'S CONCERN THAT WE WERE LOW ON GS NEAR VNY. THIS SITUATION WAS CONFUSING BECAUSE OF THE AMBIGUOUS MIXTURE OF IMC AND VMC PROCS. WE USED VMC RULES TO IGNORE OUR GPWS THEN TO SEARCH FOR VFR TFC CALLED OUT BY TCASII, WHILE FLYING AN INST APCH AFTER A SHORT TURN TO FINAL. THE 'BELLS AND WHISTLES' OF GPWS AND TCASII DISTRACTED US ENOUGH THAT, IN THIS CASE, THEY WERE MORE OF A HINDRANCE THAN A HELP.

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.