Narrative:

We were cleared for takeoff from runway 9 by juliana ATC with instructions to turn right to a heading of 200 degrees and to maintain that heading until reaching 5000 ft, then continue the right turn on course to sju and climb to 10000 ft. We were established on a heading of 200 degrees and climbing through 1500 ft MSL when we fortunately sighted a twin otter directly in front of us, at our altitude. We made an evasive turn to 160 degrees and passed behind the twin otter (which was on a right downwind arrival to runway 9 at st martin). I believe the contributing factors to this incident are a very overloaded air traffic controller, the mountains obstructing our vision of the traffic, the apparent lack of operable transponder on the twin otter (our TCASII did not display the traffic, although it did display other traffic in the area), and the lack of radar in this very busy airspace. Juliana (st martin) ATC utilizes only 1 frequency for ATIS (WX), clearance delivery, engine start, ground control, tower, approach and departure control. It is needless to say there are many blocked communications, and the single controller is often overwhelmed. In the early afternoon there are typically 6-8 jets and 10-15 turboprops, and multiple cpr jets.

Google
 

Original NASA ASRS Text

Title: BE1900 HAS NMAC WITH TWIN OTTER IN THE TCA AT ST MARTIN, FO.

Narrative: WE WERE CLRED FOR TKOF FROM RWY 9 BY JULIANA ATC WITH INSTRUCTIONS TO TURN R TO A HDG OF 200 DEGS AND TO MAINTAIN THAT HDG UNTIL REACHING 5000 FT, THEN CONTINUE THE R TURN ON COURSE TO SJU AND CLB TO 10000 FT. WE WERE ESTABLISHED ON A HDG OF 200 DEGS AND CLBING THROUGH 1500 FT MSL WHEN WE FORTUNATELY SIGHTED A TWIN OTTER DIRECTLY IN FRONT OF US, AT OUR ALT. WE MADE AN EVASIVE TURN TO 160 DEGS AND PASSED BEHIND THE TWIN OTTER (WHICH WAS ON A R DOWNWIND ARR TO RWY 9 AT ST MARTIN). I BELIEVE THE CONTRIBUTING FACTORS TO THIS INCIDENT ARE A VERY OVERLOADED AIR TFC CTLR, THE MOUNTAINS OBSTRUCTING OUR VISION OF THE TFC, THE APPARENT LACK OF OPERABLE XPONDER ON THE TWIN OTTER (OUR TCASII DID NOT DISPLAY THE TFC, ALTHOUGH IT DID DISPLAY OTHER TFC IN THE AREA), AND THE LACK OF RADAR IN THIS VERY BUSY AIRSPACE. JULIANA (ST MARTIN) ATC UTILIZES ONLY 1 FREQ FOR ATIS (WX), CLRNC DELIVERY, ENG START, GND CTL, TWR, APCH AND DEP CTL. IT IS NEEDLESS TO SAY THERE ARE MANY BLOCKED COMS, AND THE SINGLE CTLR IS OFTEN OVERWHELMED. IN THE EARLY AFTERNOON THERE ARE TYPICALLY 6-8 JETS AND 10-15 TURBOPROPS, AND MULTIPLE CPR JETS.

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.