Sts controller described an unauthorized runway entry; surmising the traffic information issued to a...

Narrative:

I was training on local control. Multiple aircraft were in right traffic to runway 14. Aircraft X called up from the run-up area of runway 14 ready for departure. I instructed him to hold short of runway 14 for landing traffic. Aircraft X read back the hold short instructions. After another aircraft landed; I planned to make a hole within which to launch aircraft X. I instructed aircraft Y on the downwind; next in sequence to land; to continue on the downwind and quoted him traffic; aircraft X; would be in position ahead of his arrival. At this time; aircraft X proceeded to cross the hold short bars to taxi up onto the runway. This was done without clearance from myself or my instructor for aircraft X to 'line up and wait.' I immediately noticed aircraft X moving into position; and issued the clearance for takeoff; as the previously landed traffic had already cleared the runway. No loss of separation occurred; and after takeoff roll; aircraft X was requested to contact the tower at his convenience. It is my belief that when aircraft X heard the 'traffic will be in position' quoted to aircraft Y on the downwind; the pilot mistook this as a clearance to 'line up and wait;' even though the words 'line up and wait' were never used in the traffic quote. Recommendation; the pilot of aircraft X needs to more clearly listen to what is being said; and to whom. Also; issuance of 'traffic in position' prior to actually telling the aircraft in question to 'line up and wait;' could have lead to the pilot's misunderstanding; and it maybe better to only issue such traffic calls after the 'line up and wait' clearance has been given.

Original NASA ASRS Text

Title: STS Controller described an unauthorized runway entry; surmising the traffic information issued to an aircraft on downwind may have been interpreted as a clearance onto the runway by the pilot in question.

Narrative: I was training on Local Control. Multiple aircraft were in right traffic to Runway 14. Aircraft X called up from the run-up area of Runway 14 ready for departure. I instructed him to hold short of Runway 14 for landing traffic. Aircraft X read back the hold short instructions. After another aircraft landed; I planned to make a hole within which to launch Aircraft X. I instructed Aircraft Y on the downwind; next in sequence to land; to continue on the downwind and quoted him traffic; Aircraft X; would be in position ahead of his arrival. At this time; Aircraft X proceeded to cross the hold short bars to taxi up onto the runway. This was done without clearance from myself or my instructor for Aircraft X to 'Line Up and Wait.' I immediately noticed Aircraft X moving into position; and issued the clearance for takeoff; as the previously landed traffic had already cleared the runway. No loss of separation occurred; and after takeoff roll; Aircraft X was requested to contact the tower at his convenience. It is my belief that when Aircraft X heard the 'traffic will be in position' quoted to Aircraft Y on the downwind; the pilot mistook this as a clearance to 'Line Up and Wait;' even though the words 'Line Up and Wait' were never used in the traffic quote. Recommendation; the pilot of Aircraft X needs to more clearly listen to what is being said; and to whom. Also; issuance of 'traffic in position' prior to actually telling the aircraft in question to 'Line Up and Wait;' could have lead to the pilot's misunderstanding; and it maybe better to only issue such traffic calls after the 'Line Up and Wait' clearance has been given.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	929560
Time
Date	201101
Local Time Of Day	1801-2400
Place
Locale Reference	STS.Tower
State Reference	CA
Aircraft 1
Make Model Name	Small Aircraft
Operating Under FAR Part	Part 91
Flight Phase	Taxi
Flight Plan	VFR
Aircraft 2
Make Model Name	Small Aircraft
Flight Phase	Final Approach
Person 1
Function	Local
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Deviation - Procedural Clearance Ground Incursion Runway

Sts controller described an unauthorized runway entry; surmising the traffic information issued to an aircraft on downwind may have been interpreted as a clearance onto the runway by the pilot in question.