Air carrier flight crew reported difficulty taxiing to the de-ice pad at SGU; citing lack of charting and poor lighting as contributing.
Synopsis
Air carrier flight crew reported difficulty taxiing to the de-ice pad at SGU; citing lack of charting and poor lighting as contributing.
Narrative
Pre-dawn pushback at Spot 1 in SGU; south-most spot on terminal ramp. First flight of the day and frost present so 2-engine taxi planned to de-ice pad south of terminal ramp. Before closing Main Cabin Door (MCD); pushback crew visited flight deck at least once to ensure we knew where to taxi for de-ice; to which both Captain and FO confirmed visually gesturing to airplane right/south and the visible/lit de-ice pad. Preflight briefing did not include discussion of left-hand turn advised by Jepp company charts from Spot 1.After pushback; salute from pushback crew received as we waited to start engines until XA:00 flight exited de-ice pad. Started engines and performed Taxi Check. FO made CTAF taxi announcement. CA said clear left; coming right." FO responded "clear right." Just after the airplane had turned about 90 degrees and CA began relaxing tiller pressure; we perceived what was the nose gear leaving the tarmac and then crunching along the firm gravel. CA immediately applied brakes; stopped the airplane; and set the parking brake. Main landing gear remained on tarmac.We called Operations for assistance. We considered if it made any sense to power the nose back to tarmac (and decided not). Operations arrived on scene and connected communications/headset. Operations reported they would ask Airport Operations if they could assist. Operations then reported they were willing and able to push the airplane back so that the nose gear would be back on the tarmac. We performed the After Landing Check; then shut down the engines; then performed the Shutdown Check. We considered leaving the airplane in present position (and decided not primarily to avoid deplaning and providing a bad public photo opportunity with the airplane off the ramp).Before pushback from the gravel Operations reported the nosewheel angle was too steep to push and requested we straighten the nosewheel. With the ground crew clear CA attempted to turn the nosewheel left with reportedly little success. Nevertheless the Operations crew was able and proceeded to pushback the airplane (nose gear steering off). After a few feet of pushback Operations again asked if we could straighten the nose gear. This time; with ground crew clear CA was able to move the nose gear. Operations then continued the pushback (again; nose gear steering off) such that the nose gear was back on tarmac. However; during the pushback Operations also reported the tow bar shear pin was probably broken.After the plane was fully back on tarmac; Operations suggested we start the engines and taxi back to Spot 1. However; as the airplane had now been reported with mechanical irregularities that could prevent safe taxiing; we opted to not operate the airplane. When we asked; Operations reported they did not have anyone qualified to tow the airplane in. After confirming the plan with Operations; we made arrangements to deplane passengers on the ramp. Operations brought the passenger ramp out and arranged cones along with a few agents to ensure passengers were appropriately handled.CA wrote up the mechanical irregularity. CA called Dispatch; then Maintenance Control. All three flight crew remained on the airplane waiting for Maintenance. After Maintenance arrived he reported it would take some time to work through details with Company. Just as that work was completed and Maintenance was informing us a taxi test under maintenance supervision would clear the mechanical irregularity; Maintenance Control called CA and advised us not to operate the airplane. Maintenance Control called back a few minutes later and told us to remain with someone from Operations and to make plans to move to a private location in the terminal to await drug testing. Eventually Operations took us off the airplane where we waited for drug testing. After drug testing was complete; we took a scheduled deadhead to ZZZ.Cause: CA mental model was to taxi across what appeared to be tarmac but was actually very flat (unlit) gravel. CA was unaware of lack of consistent tarmac all the way to de-ice pad. Lack of lighting contributed; though terminal and de-ice pad are lit. Airport/Taxi Chart did not depict de-ice pad and thus the need to navigate all the way to A to go "out and then in" from ramp to de-ice pad. In other words; CA was planning to make an approximately 135-degree turn instead of a 180-degree turn (or left turn). It was a visual illusion for the CA; coupled with omission of recognizing and discussing the Company Charts' note regarding the recommendation to turnout to the left. Additionally; this turnout to the left would need to be toward an airplane parked in Spot 2 immediately to the left. The right turnout was accomplished to avoid the airplane in Spot 2.Suggestions: De-ice pad is not depicted on Airport/Taxi Chart. If it were; it would be obvious of the need to taxi to A taxiway to get to the de-ice pad; which would provide additional impetus to navigate to A as opposed to directly (across gravel) to de-ice pad.CA could walk around airplane at outstations at night to get better situational awareness of surrounding areas before taxiing.CA could make "clear left; coming right" callout with a pause before and/or after to ensure FO is not responding by habit but taking time to process what the Captain is preparing to do.Always brief everything pertinent in the Company Charts."
Second reporter narrative
During the preflight brief; the Captain and I discussed the need for de-ice services and the taxi route that needed to be taken to reach the de-ice truck. Although I thoroughly briefed the taxi; as well as the rest of the standard brief items; I did not brief the 10-7 chart; which is a usual part of the briefing and includes the correct left turn instruction for the gate. It was still dark out as we pushed off the gate; and I noticed there were no identifying ground features for at least a few hundred feet off to the right; near the de-ice truck. It just looked like unlit pavement. We started our engines normally; ran our checklists; and began the taxi. The Captain announced he was going to taxi by making a right turn toward the direction of the de-ice truck.I looked off to the right of the aircraft and noted that there was nothing to block our path if we made the right turn. I saw a post further off in the distance and assumed it was an identifying mark for the end of the ramp. We had plenty of room between the aircraft and the post to make the turn and stay on the ramp.The Captain called clear left" and I responded "clear right." The Captain then maneuvered the aircraft to the right to begin the taxi. As the turn commenced I continued to look at the post and judge the spacing between the aircraft and the post. All indications showed that we had plenty of room throughout the turn. As the aircraft continued the turn I spun my head further right to check behind the aircraft for further clearance. As the nose of the aircraft came around and started to light up the ground; I saw that the end of the ramp was not located where the post was; but was actually right in front of us. The end of the ramp backed up into a large field of gravel. However; this could not be seen from the cockpit before we initiated the turn due to the lack of discernable ground features in the dark.At the same moment I noticed what was wrong; the nose wheel on the aircraft contacted the gravel and the Captain immediately came to a stop. After taking a moment to inspect our surroundings and gain clarity on what had just happened; we called the Airport Operations over the radio; told them the situation; and asked to be pushed back onto the ramp.Airport Operations came over with the towbar and tug and told us the nose wheel was turned hard right but did not note any damage. They hooked up the towbar and pushed us a few feet back; at which point they said the shear pin on their towbar had broken and requested we straighten the nose before continuing the push. After they disconnected the Captain managed to straighten the nose wheel without applying any power to the aircraft. The ramp workers hooked back up to the plane and successfully pushed us back onto the ramp. The Ramp asked us to power forward into the "gate" (hardstand) but the Captain said he was not willing to taxi the aircraft with the unknown condition of the nose gear; and I agreed with his assessment; so we left the engines powered down. Once we were back on the ramp; the Captain made calls to Maintenance; the manager on duty; and Dispatch; to inform all parties of the situation.Maintenance told us to deplane before any inspection was to be done. We had the Ramp bring the hardstand to the plane and deplaned the passengers. Maintenance came out to the plane roughly 30 minutes later and inspected the situation including the nose gear; the towbar; and the gravel area that we made contact with. He informed us that everything looked OK and all that was left was to do a simple Taxi Check. At that point; the Captain was on the phone with Company administrators; who informed him that we are being relieved from duty and we are not to power up the aircraft.Cause: The cause of this event relates to the lack of identifying ground features on the edge of the ramp during night operations. There were no lights or signage to indicate that the ramp did not go any further. A second cause is inadequate review of the 10-7 charts on FliteDeck Pro during the preflight brief. A third cause was an aircraft parked to the left of us. This congestion was used to make the decision to proceed with a right-hand turn.Suggestions: My suggestions for avoiding this event would be: Encourage all pilots to be diligent when reviewing 10-7 forms on FliteDeck Pro.Add reflective signs or some form of lighting that is visible from the cockpit denoting the edge of the ramp area.Encourage ramp personnel to stay near the aircraft during taxi out and marshal aircraft the correct direction to safely turn away from this hazard."
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.