PLT OF AN SMA TWIN ENG ACFT HAD CONFLICT WITH ANOTHER ACFT WHILE ENTERING THE TFC PATTERN TO AN UNCTLED ARPT AND SUBSEQUENTLY EXPERIENCED DIFFICULTY IN EXTENDING THE LNDG GEAR.

Narrative

THE PIPER SENECA DEPARTED BOWING FIELD/KING COUNTY INTL ARPT (BFI) APPROVED FOR A 'VALLEY DEP' (ATTACHMENT A). THE INTENDED DEST WAS AUBURN MUNICIPAL ARPT (S50). BFI WX WAS VFR; CLR WITH 50 MI VISIBILITY. THE SENECA PLT REMAINED ON THE BFI TWR FREQ THROUGHOUT THE DEP PROC; UNTIL APPROX OVER THE KENT VFR CHKPOINT ON THE SEATTLE VFR TERMINAL AREA CHART (ATTACHMENT B). THE TWR FREQ WAS MONITORED THIS FAR S BECAUSE AN AERONAUTICAL CHART BULLETIN PUBLISHED IN THE MAR/94 EDITION OF THE NORTHWEST UNITED STATED ARPT FACILITY DIRECTORY EXTENDS THE SOUTHERN LIMIT OF THE BFI CLASS D AIRSPACE. OVER KENT; THE SENECA PLT CHANGED TO THE PUBLISHED AUBURN CTAF (UNCTLED ARPT) AND BEGAN MONITORING THE TFC PATTERN ACTIVITY. THE RWY IN USE AT AUBURN WAS RWY 34. THE SENECA PLT'S INTENT WAS TO CONTINUE ON A SOUTHERLY COURSE AND MAKE A DIRECT DOWNWIND ENTRY INTO THE AUBURN TFC PATTERN FOR RWY 34; AND TO RPT ENTERING DOWNWIND ABEAM THE CHARTED THEATERS. WHEN APCHING THE NORTHERN EDGE OF THE THEATERS; THE SENECA PLT OBSERVED A SINGLE-ENG AIRPLANE AT ABOUT 11 O'CLOCK; ROUGHLY 1000 FT AHEAD AND ABOUT 150 FT LOWER; NBOUND IN A L CLBING TURN. THE SENECA PLT IMMEDIATELY MADE A L CLBING TURN TO PREVENT A POSSIBLE COLLISION. THE L TURN WAS CONTINUED OVER THE THEATERS FOR 360 DEGS. UPON ROLLOUT ON A MAGNETIC HDG OF ABOUT 160; THE PLT MAINTAINED VISUAL CONTACT WITH THE SINGLE-ENG ACFT WHICH WAS THEN ESTABLISHED ON DOWNWIND; AND THE SENECA PLT RPTED ENTERING DOWNWIND ON THE CTAF. IMMEDIATELY FOLLOWING THIS RPT; THE SINGLE-ENG ACFT RPTED DOWNWIND. THE SENECA MADE ADDITIONAL RPTS TURNING ON BASE AND AGAIN ON FINAL. BOTH ACFT LANDED SAFELY. WHEN ON DOWNWIND; THE SENECA RPTED DOWNWIND ON THE CTAF AND MOVED THE LNDG GEAR SELECTOR SWITCH TO THE DOWN POS. ALL 3 WHEELS FAILED TO EXTEND; AND A RED 'WARNING GEAR UNSAFE' LIGHT REMAINED ILLUMINATED. THE PLT CHKED THE CIRCUIT BREAKERS AND CYCLED THE LNDG GEAR SWITCH. THE GEAR REMAINED IN THE UP POS WITH THE RED WARNING LIGHT ON. THE NOSEWHEEL WAS VISUALLY CONFIRMED TO BE IN THE UP POS USING THE VIEWING MIRROR ON THE L ENG NACELLE. BY THIS TIME THE SENECA HAD TURNED TO BASE LEG (L TFC). AT THIS POINT; THE PLT ELECTED TO ABORT THE APCH AND DEPART THE TFC PATTERN TO DO FURTHER INVESTIGATION OF THE PROB AND PERFORM THE EMER GEAR EXTENSION CHKLIST PROC. WHILE ENRTE TO LAKE TAPPS; THE LNDG GEAR EXTENDED TO THE DOWN AND LOCKED POS WITHOUT ANY ACTION FROM THE PLT. THE CTLED AIRSPACE CONFIGN BTWN BFI AND S50 (AUBURN) DOES NOT ALLOW MONITORING OF AND COMS ON THE AUBURN CTAF FOR 10 MI AS RECOMMENDED IN THE AIM (4-9C1). THE SENECA PLT CHANGED TO THE AUBURN CTAF APPROX 3-4 MI N OF THE ARPT; WHICH DID NOT ALLOW ADEQUATE TIME TO FULLY ASSESS THE TFC SIT. THE SINGLE-ENG ACFT DEPARTING AUBURN WAS NOT AWARE OF THE INBOUND SENECA BECAUSE THE SENECA DID NOT XMIT INTENTIONS ON THE CTAF PRIOR TO ENTERING DOWNWIND. A NON-STANDARD TFC PATTERN ENTRY WAS MADE BY THE SENECA. THE SEATTLE CLASS B AIRSPACE ON THE WESTERN SIDE OF AUBURN ARPT PRECLUDES MAKING A STANDARD 45 DEG ENTRY WHEN ARRIVING FROM THE N; ESPECIALLY IN HIGH PERFORMANCE ACFT WITH A WIDER TURNING RADIUS. A SHORT 45 ENTRY COULD HAVE BEEN ATTEMPTED BY MANEUVERING CLOSE TO THE EDGE OF THE CLASS B AIRSPACE; BUT THIS SIT IS POTENTIALLY MORE HAZARDOUS BECAUSE COLLISION AVOIDANCE MANEUVERING IN THIS AREA COULD RESULT IN AN INFRINGEMENT OF THE CLASS B AIRSPACE SURFACE AREA WHERE TRANSPORT CATEGORY ACFT MAY BE ON SHORT FINAL TO SEA. IN THIS CASE; A BETTER METHOD FOR THE SENECA TO ENTER THE FLOW OF TFC AT AUBURN WOULD BE TO FIRST OVERFLY THE ARPT WELL ABOVE TFC PATTERN ALT CIRCLING TO THE L; WHILE ASSESSING THE TFC IN THE PATTERN AND BROADCASTING INTENTIONS ON THE CTAF. HOWEVER; THIS METHOD HAS A DISADVANTAGE BECAUSE THIS AIRSPACE IS NEAR A PUBLISHED VFR FLYWAY ZONE. CIRCLING IN THE FLYWAY ZONE INCREASES THE RISK OF A COLLISION. THE TFC PATTERNS AT BOTH AUBURN AND CREST COULD BE MOVED TO THE E SIDE OF EACH ARPT. THIS WOULD PERMIT MORE STANDARD 45 DEG ENTRY LEGS WITHOUT HAVING TO APCH THE BOUNDARY OF CLASS B AIRSPACE. THE TFC PATTERN ALT AT AUBURN COULD BE RAISED FOR NOISE ABATEMENT IF THE PATTERN WERE ON THE E SIDE. ALLOWING ROOM FOR STANDARD TFC PATTERN ENTRY IMPROVES SAFETY AT UNCTLED ARPTS BECAUSE PLTS ON DOWNWIND TEND TO LOOK FOR INCOMING TFC ON THE 45 DEG ENTRY.