Narrative:

It was very dark night conditions with dense fog. Aircraft preflight and boarding proceeded normally. System checks were performed normally. The aircraft was taxied with marshaller guidance from the parking area on the ramp. The captain proceeded to taxi slowly through dense fog following the usual route for runway 2 while I insured that all airport lighting was at maximum intensity using the no. 1 comm radio. When the aircraft was clear of the parking area and appeared to be heading along the correct route to the runway; I began tuning the no. 2 comm radio in preparation for requesting an IFR clearance from the FSS. When I looked back up; it appeared that we might have turned south prior to the parallel taxiway to runway 2/20 and that we were proceeding along the outer edge of the terminal apron and heading towards the general aviation ramp. While looking at the airport diagram and trying to determine where this might take us; I looked up and noticed through the fog a yellow airport arrow marker indicating runway 2 ahead. I felt that this indicated that we were proceeding along a route to runway 2. This proved to be an error as this route narrowed and abruptly stopped in a spot that may have been an unmarked helipad. Due to the low light and fog conditions we could not determine that we were going to dead end until it was too late to take further action. At this point the aircraft was stopped and we determined that we could neither proceed further or attempt to turn the aircraft around. Even though our airport diagrams were available; we both made an error in determining our exact location as we taxied. After it was determined that the aircraft could not be taxied further; operations was notified of the problem. Operations inquired as to our exact location on the ramp area. The captain suggested that it might be possible to position the aircraft for a tight nosewheel turn around if there was marshaller guidance. After starting the APU and shutting down the engines; the captain exited the aircraft to visually determine the distance the aircraft might require to make a turn. It was concluded by both flight crew and station personnel that there was an inadequate margin of error for this operation. It was therefore decided that a pushback was the only option. Station personnel were successful in locating both an available pushback tug and a trained operator to make the pushback. A pushback was accomplished and then after consulting with our dispatcher; we departed without further event. It is important to note that airports that become very familiar to flight crews during normal day to day operations can suddenly become very unfamiliar looking during times of low light and visibility. Also when operating at non-tower controlled airports where there are no specific taxi clearances issued; it is essential to actually brief the desired taxi route to the runway as part of the 'departure briefing.' it may seem overly obvious to some flight crews; but I have learned from this experience that it is quite possible to make an 'obvious' mistake during adverse conditions. Also; some improvements in airport signage that clearly indicate dead ends on ramps and taxiways could also be very helpful. Finally; managing workload is always very important. Taxi is the one time during a flight that one can come to a complete stop. If this had been done when it was first sensed that an error was possibly being made; then this situation may never have developed into problem that required outside assistance.

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Original NASA ASRS Text

Title: While taxiing for takeoff on a dark night at a non-towered airport in dense fog an air carrier flight crew made an incorrect turn and found themselves at a dead end. Ground crew assistance was required to extradite the aircraft from its dilemma.

Narrative: It was very dark night conditions with dense fog. Aircraft preflight and boarding proceeded normally. System checks were performed normally. The aircraft was taxied with marshaller guidance from the parking area on the ramp. The Captain proceeded to taxi slowly through dense fog following the usual route for Runway 2 while I insured that all airport lighting was at maximum intensity using the No. 1 COMM radio. When the aircraft was clear of the parking area and appeared to be heading along the correct route to the runway; I began tuning the No. 2 COMM radio in preparation for requesting an IFR clearance from the FSS. When I looked back up; it appeared that we might have turned south prior to the parallel taxiway to Runway 2/20 and that we were proceeding along the outer edge of the terminal apron and heading towards the general aviation ramp. While looking at the airport diagram and trying to determine where this might take us; I looked up and noticed through the fog a yellow airport arrow marker indicating Runway 2 ahead. I felt that this indicated that we were proceeding along a route to Runway 2. This proved to be an error as this route narrowed and abruptly stopped in a spot that may have been an unmarked helipad. Due to the low light and fog conditions we could not determine that we were going to dead end until it was too late to take further action. At this point the aircraft was stopped and we determined that we could neither proceed further or attempt to turn the aircraft around. Even though our airport diagrams were available; we both made an error in determining our exact location as we taxied. After it was determined that the aircraft could not be taxied further; Operations was notified of the problem. Operations inquired as to our exact location on the ramp area. The Captain suggested that it might be possible to position the aircraft for a tight nosewheel turn around if there was marshaller guidance. After starting the APU and shutting down the engines; the Captain exited the aircraft to visually determine the distance the aircraft might require to make a turn. It was concluded by both flight crew and station personnel that there was an inadequate margin of error for this operation. It was therefore decided that a pushback was the only option. Station personnel were successful in locating both an available pushback tug and a trained operator to make the pushback. A pushback was accomplished and then after consulting with our Dispatcher; we departed without further event. It is important to note that airports that become very familiar to flight crews during normal day to day operations can suddenly become very unfamiliar looking during times of low light and visibility. Also when operating at non-tower controlled airports where there are no specific taxi clearances issued; it is essential to actually brief the desired taxi route to the runway as part of the 'departure briefing.' It may seem overly obvious to some flight crews; but I have learned from this experience that it is quite possible to make an 'obvious' mistake during adverse conditions. Also; some improvements in airport signage that clearly indicate dead ends on ramps and taxiways could also be very helpful. Finally; managing workload is always very important. Taxi is the one time during a flight that one can come to a complete stop. If this had been done when it was first sensed that an error was possibly being made; then this situation may never have developed into problem that required outside assistance.

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.