A C150 PLT APCHED CTAF MMV RWY 4 VFR NOT KNOWING THE DEFAULT CALM WIND RWY WAS RWY 22. PLT AVOIDED A GULFSTREAM DEPARTING OPPOSITE DIRECTION RWY 22.

Narrative

THE WX WAS UNUSUALLY CLR AND PLEASANT (SEVERE CLR). WINDS WERE LIGHT AND VARIABLE. ON A SHORT (34 NM) VFR FLT FROM VUO (PEARSON AIRFIELD; VANCOUVER; WA) TO MMV (MCMINNVILLE; OR); I MONITORED THE MMV ASOS AND LEARNED THAT THE WIND WAS 040 DEGS AT 3 KTS AND CHOSE RWY 4 FOR MY INTENDED LNDG. APCHING MMV AT ABOUT 15 MI OUT; I COULD SEE THE FIELD CLRLY. THERE WAS NO VISIBLE USE OF THE RWYS OR TXWYS. I MONITORED THE CTAF AND HEARD XMISSIONS FROM VUO (30+ NM AWAY) AND CVO (CORVALLIS; OR; 40+ NM AWAY); AS WELL AS FROM MMV (ALL 3 ARPTS USE THE SAME CTAF FREQ). SOME XMISSIONS WERE 'STEPPED ON;' SINCE THERE SEEMED TO BE MANY ACFT IN THE AREA; PROBABLY BECAUSE OF THE EXCELLENT WX. FROM MMV; I HEARD A HELI ANNOUNCE 'ILS APCH (GARBLED) FAR END OF RWY 22' AND ASSUMED THERE WOULD BE NO CONFLICT. I HEARD A SEPARATE 'STEPPED ON' XMISSION ABOUT AN ILS APCH (LOCATION AND RWY UNKNOWN) AND ASSUMED IT WAS THE HELI AGAIN. I ANNOUNCED MY INTENTIONS ON MMV CTAF ON 45 DEGS TO DOWNWIND; ON DOWNWIND; ON BASE; AND ON FINAL. DURING THAT TIME; I HEARD SOME GARBLED AND 'STEPPED ON' XMISSIONS (SOURCES UNKNOWN). THE HELI AT MMV XMITTED 'I HAVE YOU IN SIGHT; I'M RIGHT ABOVE YOU.' I ASSUMED THAT HE WAS ACKNOWLEDGING ME. WHILE ON SHORT FINAL (APPROX 200 FT AGL); I OBSERVED A GULFSTREAM TURBOPROP HEADED TOWARD ME ON RWY 22. IT DEPARTED MMV IN A STEEP CLBING TURN TO THE L. A GAR ON MY PART WAS UNWISE AT THAT POINT; AND I PROCEEDED TO LAND AND PARK IN THE TIE-DOWN AREA NEAR THE DEP END OF RWY 22. A MAN DROVE UP IN AN ARPT SVC CART AND ASKED IF HE COULD BE OF HELP. I TOLD HIM THAT I WAS ONLY STAYING ABOUT 5 MINS. HE THEN ADVISED ME THAT ON CALM-WIND DAYS; RWY 22 IS THE DEFAULT RWY AT MMV (NOTE: THERE WAS NO INDICATION OF THIS IN THE ARPT DIRECTORY WHEN I CHKED IT PRIOR TO COMMENCING MY FLT NOR WHEN I RECHKED IT AFTER RETURNING TO VUO. NEITHER IS THERE ANY INDICATION OF THIS IN THE AOPA 'MEMBERS COMMENTS' SECTION OF THEIR ON-LINE ARPT DIRECTORY). WHILE PARKED FOR ABOUT 10 MINS; THERE WAS ONE LCL TAXI AND DEP FROM MMV AND NO VISUAL EVIDENCE OF EITHER THE HELI OR THE GULFSTREAM. I RESTARTED; MONITORED MMV CTAF; AND HEARD NO XMISSIONS EXCEPT SOMEONE ON '5 MI FINAL TO MCMINNVILLE.' I ANNOUNCED MY INTENTIONS; AND DEPARTED MMV ON RWY 22. AS SOON AS I REACHED ABOUT 300 FT AGL; I BEGAN TO HEAR XMISSIONS FROM CVO AND VUO AGAIN; INCLUDING 'STEPPED ON' XMISSIONS. THE REMAINDER OF THE FLT WAS UNEVENTFUL. FACTORS AND CORRECTIVE ACTION: 1) THE UNUSUAL WX MAY HAVE CONTRIBUTED TO THE RECEPTION OF THE XMISSIONS OVER LONGER DISTANCES; 2) NEVERTHELESS; THE USE OF THE SAME CTAF FREQ AT MULTIPLE ARPTS WITHIN RECEPTION RANGE SHOULD BE CHANGED; TO AVOID 'STEPPED ON' XMISSIONS; 3) THE ARPT DIRECTORY SHOULD PUBLISH RWY 22 AS THE DEFAULT RWY FOR CALM-WIND CONDITIONS AT MMV; 4) ARRIVING PLTS SHOULD BROADCAST A BLIND REQUEST FOR RWY/TA'S; SUCH AS 'ANY MCMINNVILLE TFC; PLEASE ADVISE RWY IN USE' OR WORDS TO THAT EFFECT; RATHER THAN MAKING AN ASSUMPTION BASED ONLY ON AN AUTOMATED WX ANNOUNCEMENT; 5) PLTS SHOULD VERIFY BY EXCHANGED XMISSIONS THAT SOMEONE ANNOUNCING USE OF THE OPPOSITE END OF A RWY (EVEN JUST A HELI) IS IN FACT; NOT A CONFLICT; AND 6) TFC IN THE PATTERN SHOULD CLRLY ANNOUNCE A WARNING WHEN A POTENTIAL CONFLICT IS SUSPECTED; SUCH AS 'MCMINNVILLE TFC; BE ADVISED RWY 22 IS IN USE; DO NOT USE RWY 4' OR WORDS TO THAT EFFECT.