Narrative:

A C525 called austin approach on frequency 119.0 requesting IFR clearance from gtu to pnc. The aircraft was airborne VFR about 8 mi north of gtu. I instructed the aircraft to maintain VFR and squawk the beacon code on his IFR flight plan. Austin approach controls north boundary is just north of gtu, so I had to coordinate with gray approach control to issue the IFR clearance in their airspace. After completing the 'point-out' to gray approach, I issued the clearance to the citation. While reading the clearance, the ARTS data tag went into 'coast' mode, and I was unable to see the mode C readout, although I knew the aircraft could not be much higher than 9000 ft or so, as I saw an altitude of 8000 ft shortly before. As the pilot read back the clearance, the ARTS data tag reacquired, and I could see the citation still had a good climb rate going, approaching 12000 ft. In the clearance I originally stated 12000 ft, and I am not sure what the pilot said during the readback, but it is a moot point. I restated 12000 ft as soon as the pilot finished reading back his clearance. It was too late, as I observed the mode C go to 12700 ft. This violates ZHU airspace. The aircraft descended to 12000 ft.

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Original NASA ASRS Text

Title: AUS CTLR EXPERIENCED OPDEV WITH ZHU WHILE TRYING TO ISSUE IFR CLRNC TO A C525 WHO OVERSHOT HIS ASSIGNED ALT.

Narrative: A C525 CALLED AUSTIN APCH ON FREQ 119.0 REQUESTING IFR CLRNC FROM GTU TO PNC. THE ACFT WAS AIRBORNE VFR ABOUT 8 MI N OF GTU. I INSTRUCTED THE ACFT TO MAINTAIN VFR AND SQUAWK THE BEACON CODE ON HIS IFR FLT PLAN. AUSTIN APCH CTLS N BOUNDARY IS JUST N OF GTU, SO I HAD TO COORDINATE WITH GRAY APCH CTL TO ISSUE THE IFR CLRNC IN THEIR AIRSPACE. AFTER COMPLETING THE 'POINT-OUT' TO GRAY APCH, I ISSUED THE CLRNC TO THE CITATION. WHILE READING THE CLRNC, THE ARTS DATA TAG WENT INTO 'COAST' MODE, AND I WAS UNABLE TO SEE THE MODE C READOUT, ALTHOUGH I KNEW THE ACFT COULD NOT BE MUCH HIGHER THAN 9000 FT OR SO, AS I SAW AN ALT OF 8000 FT SHORTLY BEFORE. AS THE PLT READ BACK THE CLRNC, THE ARTS DATA TAG REACQUIRED, AND I COULD SEE THE CITATION STILL HAD A GOOD CLB RATE GOING, APCHING 12000 FT. IN THE CLRNC I ORIGINALLY STATED 12000 FT, AND I AM NOT SURE WHAT THE PLT SAID DURING THE READBACK, BUT IT IS A MOOT POINT. I RESTATED 12000 FT AS SOON AS THE PLT FINISHED READING BACK HIS CLRNC. IT WAS TOO LATE, AS I OBSERVED THE MODE C GO TO 12700 FT. THIS VIOLATES ZHU AIRSPACE. THE ACFT DSNDED TO 12000 FT.

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.