Narrative:

The flight preparation was done orderly under no abnormal pressure and based on long time field experience. Briefing weather and notams performed in our hotel room; as always with the view to the tarmac and airfield. Temperature was plus 3 degrees celsius and visibility good for takeoff. Before takeoff time; arrived at FBO and received last update of weather and notams with the friction coefficient of 54 and forecast showed becoming 130 at 20g30 so we committed to go and avoid unnecessary delays. During refueling and outside check; we noticed the apron was slippery but no ice on the airplane and we were aware that another jet just made a takeoff. Asked the FBO to sand beside the aircraft door for the elderly passenger; who has difficulty in walking and being concerned not to fall on slippery surface.still nighttime dark; we requested startup and clearance to destination. The tower then informed us about the worse braking action on the runway and after consulting between us pilots; we decided to go. We were instructed for a departure on runway with a backtrack on the active; what gave us the welcomed opportunity to check on our own the braking condition; which we considered not too bad; partially covered with snow and ice patches centerline was not properly visible. At this time; we were not aware about other traffic and that a truck was sanding runway 13. Arriving to the end of the runway 19 there was a very slippery spot and light rain started and a new rain-shower was approaching the airport. We were concerned about ice accumulations so we switched; in take-off position; the anti-ice system on for wing/engine for preheat. For that; we had to add power N2 75% what was a very tricky undertaking on the slippery runway pad to avoid the airplane from sliding. During this operation; the non-flying pilot asked to confirm again for departure no negative answer; we believed we have been already cleared for takeoff combined with the clearance for backtrack. During lineup; we could not see any vehicle or airplane on the runway and were sure to have received the take-off clearance earlier. On takeoff; anti-ice off again to have maximum power available for better performance and shorter ground roll. Low temperature and at sea level; we could expect excellent acceleration. Only during rotation and climb out; we noticed a truck entering the runway from the right. During climb out tower informed us; that we did not have received a clearance for departure: we were concerned about this situation with a misunderstanding in communication.

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Original NASA ASRS Text

Title: Citation jet Captain reported observing a vehicle entering the runway while departing without a takeoff clearance.

Narrative: The flight preparation was done orderly under no abnormal pressure and based on long time field experience. Briefing Weather and Notams performed in our Hotel room; as always with the view to the tarmac and airfield. Temperature was plus 3 degrees Celsius and visibility good for Takeoff. Before takeoff time; arrived at FBO and received last update of weather and Notams with the friction coefficient of 54 and Forecast showed becoming 130 at 20G30 so we committed to go and avoid unnecessary delays. During refueling and outside check; we noticed the Apron was slippery but no ice on the airplane and we were aware that another Jet just made a takeoff. Asked the FBO to sand beside the aircraft door for the elderly passenger; who has difficulty in walking and being concerned not to fall on slippery surface.Still nighttime dark; we requested startup and clearance to destination. The tower then informed us about the worse braking action on the runway and after consulting between us pilots; we decided to go. We were instructed for a departure on runway with a backtrack on the active; what gave us the welcomed opportunity to check on our own the braking condition; which we considered not too bad; partially covered with snow and ice patches Centerline was not properly visible. At this time; we were not aware about other traffic and that a truck was sanding runway 13. Arriving to the end of the runway 19 there was a very slippery spot and light rain started and a new rain-shower was approaching the airport. We were concerned about ice accumulations so we switched; in take-off position; the anti-ice system on for WING/ENG for preheat. For that; we had to add power N2 75% what was a very tricky undertaking on the slippery runway pad to avoid the airplane from sliding. During this operation; the non-flying pilot asked to confirm again for departure no negative answer; we believed we have been already cleared for takeoff combined with the clearance for backtrack. During lineup; we could not see any vehicle or airplane on the runway and were sure to have received the take-off clearance earlier. On takeoff; anti-ice off again to have maximum power available for better performance and shorter ground roll. Low temperature and at sea level; we could expect excellent acceleration. Only during rotation and climb out; we noticed a truck entering the runway from the right. During climb out tower informed us; that we did not have received a clearance for departure: We were concerned about this situation with a misunderstanding in communication.

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.