Narrative:

VFR/night time conditions. I just took the local control position; aircraft Y was on a visual approach to runway 16. Aircraft X was in the runway 16 run-up pad. Aircraft Y checks in; I clear aircraft Y to land runway 16. Shortly after aircraft X calls I'm at runway 16 ready to go. I instructed aircraft X to 'taxi up to and hold short runway 16' and aircraft X read back 'taxi up and hold short.' after reviewing the tapes aircraft X did leave out the 'runway 16' on the hold short read back. A few seconds after aircraft X says 'we are lining up and waiting'. I looked out the window to find aircraft X and I wasn't certain of the position of aircraft X with all the lights at the approach end. I asked the pilot of her position and determined that she was on the runway and I immediately send aircraft Y around who was just inside a half mile final. The pilot of aircraft X called the next morning. She explained that she was a student pilot and she misunderstood the instruction I gave her 'taxi up to and hold short runway 16' since she was already holding short of the runway. I gave the instruction to taxi up to and hold short of runway 16 because aircraft X appeared to be in the run-up pad.factors:1) misunderstanding of my instructions led to the event.2) I missed the runway 16 in the read back.3) still fairly new to the facility and I couldn't determine where aircraft X was.stick to simple instructions. 'Hold short of runway 16.'

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Original NASA ASRS Text

Title: PWK Local Controller reported of sending an aircraft around on final when a student pilot entered the runway when they were supposed to hold short.

Narrative: VFR/night time conditions. I just took the LC position; Aircraft Y was on a visual approach to runway 16. Aircraft X was in the runway 16 run-up pad. Aircraft Y checks in; I clear Aircraft Y to land runway 16. Shortly after Aircraft X calls I'm at runway 16 ready to go. I instructed Aircraft X to 'taxi up to and hold short runway 16' and Aircraft X read back 'taxi up and hold short.' After reviewing the tapes Aircraft X did leave out the 'runway 16' on the hold short read back. A few seconds after aircraft X says 'we are lining up and waiting'. I looked out the window to find Aircraft X and I wasn't certain of the position of Aircraft X with all the lights at the approach end. I asked the pilot of her position and determined that she was on the runway and I immediately send Aircraft Y around who was just inside a half mile final. The pilot of Aircraft X called the next morning. She explained that she was a student pilot and she misunderstood the instruction I gave her 'taxi up to and hold short runway 16' since she was already holding short of the runway. I gave the instruction to taxi up to and hold short of runway 16 because Aircraft X appeared to be in the run-up pad.Factors:1) Misunderstanding of my instructions led to the event.2) I missed the runway 16 in the read back.3) Still fairly new to the facility and I couldn't determine where Aircraft X was.Stick to simple instructions. 'Hold short of runway 16.'

Data retrieved from NASA's ASRS site 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.