Narrative:

I (aircraft X) was repositioning my EMS helicopter from a local hospital within the ZZZ class B surface area to the airport for fuel, under the terms of LOA. The controller in the tower cleared me to 'from present position fly south, cross runway 26R, remain clear of the departure end, traffic taxiing into position, then fly west between the runways, cleared to land.' I was flying southwest abeam midfield and I immediately turned south and crossed runway 26R at approximately midfield. I saw the B737 (aircraft Y) taxiing onto the runway at the departure end and I was south of the runway turning west to land at the west end when the controller came back and said remain east of the runway. At that point I believe she had intended for me to cross the approach end behind the aircraft taxiing into position but the clearance she gave me did not specify that. She asked me to call the tower when I landed, which I did. I talked to the tower boss. He said not to worry, she was a new controller and her clearance was not specific. I refueled and went on my way, nothing more said.

Related reports:

Google
 

Original NASA ASRS Text

Title: ATCT LCL CTLR ISSUES CTL INSTRUCTIONS TO B407, WHICH WHEN EXECUTED IS NOT WHAT THE CTLR WANTED. WHEN FLC REVIEW COMPLETED WITH TWR, SUPVR RECOGNIZES CTL INSTRUCTIONS WERE NOT SUFFICIENTLY CLR.

Narrative: I (ACFT X) WAS REPOSITIONING MY EMS HELI FROM A LCL HOSPITAL WITHIN THE ZZZ CLASS B SURFACE AREA TO THE ARPT FOR FUEL, UNDER THE TERMS OF LOA. THE CTLR IN THE TWR CLRED ME TO 'FROM PRESENT POS FLY S, CROSS RWY 26R, REMAIN CLR OF THE DEP END, TFC TAXIING INTO POS, THEN FLY W BTWN THE RWYS, CLRED TO LAND.' I WAS FLYING SW ABEAM MIDFIELD AND I IMMEDIATELY TURNED S AND CROSSED RWY 26R AT APPROX MIDFIELD. I SAW THE B737 (ACFT Y) TAXIING ONTO THE RWY AT THE DEP END AND I WAS S OF THE RWY TURNING W TO LAND AT THE W END WHEN THE CTLR CAME BACK AND SAID REMAIN E OF THE RWY. AT THAT POINT I BELIEVE SHE HAD INTENDED FOR ME TO CROSS THE APCH END BEHIND THE ACFT TAXIING INTO POS BUT THE CLRNC SHE GAVE ME DID NOT SPECIFY THAT. SHE ASKED ME TO CALL THE TWR WHEN I LANDED, WHICH I DID. I TALKED TO THE TWR BOSS. HE SAID NOT TO WORRY, SHE WAS A NEW CTLR AND HER CLRNC WAS NOT SPECIFIC. I REFUELED AND WENT ON MY WAY, NOTHING MORE SAID.

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.