A G1 captain reported an near midair collision while on approach to trm.

Attributes
ACN	467521
Time
Date	200003
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : trm.airport
State Reference	CA
Altitude	msl single value : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : corporate
Make Model Name	Gulfstream I (Large Turboprop)
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	descent : approach
Route In Use	approach : visual arrival : vfr
Flight Plan	IFR Combined VFR
Aircraft 2
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Fixed Gear
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : multi engine
Experience	flight time last 90 days : 150 flight time total : 10050 flight time type : 240
ASRS Report	467521
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Qualification	pilot : instrument pilot : multi engine pilot : commercial
Events
Anomaly	conflict : nmac non adherence : published procedure non adherence : required legal separation other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : insufficient time
Miss Distance	horizontal : 0 vertical : 25
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

The flight was conducting a visual approach after canceling IFR with psp approach. We passed overhead trm and entered left downwind for runway 35, still descending through 3000 ft. At the completion of the turn I saw a yellow agricultural looking plane very close to our left and coming straight at us. There was no time to react. The yellow aircraft passed overhead the cockpit -- close enough to hear his engine. After landing, I asked the lineman at the FBO about the aircraft and he said it was probably a glider towing aircraft operating out of trm using only a handheld VHF radio. We had called unicom for TA's, and made a position report on CTAF when passing overhead and also when turning downwind. The PF never saw the other aircraft.

Original NASA ASRS Text

Title: A G1 CAPT RPTED AN NMAC WHILE ON APCH TO TRM.

Narrative: THE FLT WAS CONDUCTING A VISUAL APCH AFTER CANCELING IFR WITH PSP APCH. WE PASSED OVERHEAD TRM AND ENTERED L DOWNWIND FOR RWY 35, STILL DSNDING THROUGH 3000 FT. AT THE COMPLETION OF THE TURN I SAW A YELLOW AGRICULTURAL LOOKING PLANE VERY CLOSE TO OUR L AND COMING STRAIGHT AT US. THERE WAS NO TIME TO REACT. THE YELLOW ACFT PASSED OVERHEAD THE COCKPIT -- CLOSE ENOUGH TO HEAR HIS ENG. AFTER LNDG, I ASKED THE LINEMAN AT THE FBO ABOUT THE ACFT AND HE SAID IT WAS PROBABLY A GLIDER TOWING ACFT OPERATING OUT OF TRM USING ONLY A HANDHELD VHF RADIO. WE HAD CALLED UNICOM FOR TA'S, AND MADE A POS RPT ON CTAF WHEN PASSING OVERHEAD AND ALSO WHEN TURNING DOWNWIND. THE PF NEVER SAW THE OTHER ACFT.

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.