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.