Narrative:

Mlt was cleared by sfo ground control to taxi to the north pad (taxiway C between Q and right, depicted on the sfo diagram). We had just completed our hover checks, landed back on the pad, switched to tower to call for departure when a silver sfo safety passenger veh drove pas the pad (orange line). Neither ground nor tower advised us of the veh. The veh was driving on the taxiway. We held our position on the pad until the veh was past. After about 1 min, we called tower requesting departure (takeoff) clearance. Prior to pulling power, the silver veh and 3 other construction vehs came up from behind us and drove by our left side on the taxiway. No advisory from tower. We cancelled our takeoff request and called the air station on company frequency. The air station called the tower who stated that they did not control ground traffic in that area (they do control aircraft movements, including takeoff and lndgs to the pad). We often do test flts on that pad involving taxi turns, 360 degree hover turns, maximum control deflection in fore, aft, left and right. All of these take up the whole width of the taxiway. A veh coming up behind the mlt in any one of those instances would likely be hit. There are unimproved service roads (i.e., dirt roads) on either side at the taxiway.

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Original NASA ASRS Text

Title: ARPT SAFETY VEHICLE WITH 3 CONSTRUCTION VEHICLES PASSED WITHIN 50' OF MLT DEPARTING FROM THE DESIGNATED HELIPAD ON TXWY C BETWEEN TXWY R AND Q AT SFO.

Narrative: MLT WAS CLRED BY SFO GND CTL TO TAXI TO THE N PAD (TXWY C BTWN Q AND R, DEPICTED ON THE SFO DIAGRAM). WE HAD JUST COMPLETED OUR HOVER CHKS, LANDED BACK ON THE PAD, SWITCHED TO TWR TO CALL FOR DEP WHEN A SILVER SFO SAFETY PAX VEH DROVE PAS THE PAD (ORANGE LINE). NEITHER GND NOR TWR ADVISED US OF THE VEH. THE VEH WAS DRIVING ON THE TXWY. WE HELD OUR POS ON THE PAD UNTIL THE VEH WAS PAST. AFTER ABOUT 1 MIN, WE CALLED TWR REQUESTING DEP (TKOF) CLRNC. PRIOR TO PULLING PWR, THE SILVER VEH AND 3 OTHER CONSTRUCTION VEHS CAME UP FROM BEHIND US AND DROVE BY OUR LEFT SIDE ON THE TXWY. NO ADVISORY FROM TWR. WE CANCELLED OUR TKOF REQUEST AND CALLED THE AIR STATION ON COMPANY FREQ. THE AIR STATION CALLED THE TWR WHO STATED THAT THEY DID NOT CTL GND TFC IN THAT AREA (THEY DO CTL ACFT MOVEMENTS, INCLUDING TKOF AND LNDGS TO THE PAD). WE OFTEN DO TEST FLTS ON THAT PAD INVOLVING TAXI TURNS, 360 DEG HOVER TURNS, MAX CTL DEFLECTION IN FORE, AFT, LEFT AND RIGHT. ALL OF THESE TAKE UP THE WHOLE WIDTH OF THE TXWY. A VEH COMING UP BEHIND THE MLT IN ANY ONE OF THOSE INSTANCES WOULD LIKELY BE HIT. THERE ARE UNIMPROVED SERVICE ROADS (I.E., DIRT ROADS) ON EITHER SIDE AT THE TXWY.

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.