Narrative:

We had stopped the L1011 still facing south at the north end of taxiway 'D.' the so had gone back to check the wings for snow or ice. When he returned to the cockpit we were cleared into position on runway 36L. As we turned, just prior to entering the runway, the right main gear went off the taxiway and became stuck. Contributing factors: it was snowing and all txwys were covered with snow which left the centerline markings covered. The approach to this end of runway 36L is what I would call 'nonstandard.' instead of doing two 90 degree turns to get from taxiway 'D' onto runway 36L it requires approximately one 120 degree turn and then about a 60 degree turn onto the runway. I'd like to mention at this point that I had not been to runway 36L in probably several yrs and was not familiar with the 'nonstandard' turn on taxiway. In a high cockpit as on the L1011 the captain cannot see the taxiway to the immediate right of the airplane while turning to the right. The run-up pad to my left gave me plenty of room, but with no centerline markings visible, left no cues to where we were on the taxiway. I was completely surprised when the right main gear left the paved surface. Looking at the approach end of runway 36L even after we were stuck, it appeared we were right where we should be. The copilot said everything appeared fine to him, he was as surprised as I was. The aircraft behind us, even knowing we had a problem, was certain we were not off the taxiway. The passenger were deplaned onto buses and we left the aircraft. Our maintenance people assured me that the aircraft had not been damaged when the gear left the taxiway. (We were moving very slowly.) I believe the aircraft may have sustained what I hope was very minor damage during the recovery attempt. The airport operations manager told me that their taxiway was a 'trap' and they had aircraft doing what we did even in the summer. He also said that the airport had plans for construction on this taxiway to hopefully eliminate this problem. Callback conversation with reporter revealed the following information: reporter stated that the airport manager's plans for 'a solution' were expected to take place this coming summer. Supposedly a filling in of the 'dip' or bend area on the right side of the taxiway. Reporter could not give any advice as to any temporary solution to the problem. He said that other types of aircraft, other than the L1011, were doing this, even in the summer. The major problem with this taxiway design is that, even after turning and going off the taxiway, it still looked right. He further stated that after his observation of the aircraft's position after the event from the outside, right next to the right gear, it still 'looked right.' the airport taxi chart as depicted from the manufacturer is misleading. The taxiway curve or 'dip' is greater than what is shown. He said that a captain loses perspective as to where to turn because the 'odd' taxiway's design and its relationship to the end of the runway creates an optical illusion. You cannot turn where you think you should turn.

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Original NASA ASRS Text

Title: ARPT PROB TXWY DESIGN CONTRIBUTORY TO L1011 R GEAR GOING OFF THE SIDE OF TXWY IN A NIGHT OP.

Narrative: WE HAD STOPPED THE L1011 STILL FACING S AT THE N END OF TXWY 'D.' THE SO HAD GONE BACK TO CHK THE WINGS FOR SNOW OR ICE. WHEN HE RETURNED TO THE COCKPIT WE WERE CLRED INTO POS ON RWY 36L. AS WE TURNED, JUST PRIOR TO ENTERING THE RWY, THE R MAIN GEAR WENT OFF THE TXWY AND BECAME STUCK. CONTRIBUTING FACTORS: IT WAS SNOWING AND ALL TXWYS WERE COVERED WITH SNOW WHICH LEFT THE CTRLINE MARKINGS COVERED. THE APCH TO THIS END OF RWY 36L IS WHAT I WOULD CALL 'NONSTANDARD.' INSTEAD OF DOING TWO 90 DEG TURNS TO GET FROM TXWY 'D' ONTO RWY 36L IT REQUIRES APPROX ONE 120 DEG TURN AND THEN ABOUT A 60 DEG TURN ONTO THE RWY. I'D LIKE TO MENTION AT THIS POINT THAT I HAD NOT BEEN TO RWY 36L IN PROBABLY SEVERAL YRS AND WAS NOT FAMILIAR WITH THE 'NONSTANDARD' TURN ON TXWY. IN A HIGH COCKPIT AS ON THE L1011 THE CAPT CANNOT SEE THE TXWY TO THE IMMEDIATE R OF THE AIRPLANE WHILE TURNING TO THE R. THE RUN-UP PAD TO MY L GAVE ME PLENTY OF ROOM, BUT WITH NO CTRLINE MARKINGS VISIBLE, LEFT NO CUES TO WHERE WE WERE ON THE TXWY. I WAS COMPLETELY SURPRISED WHEN THE R MAIN GEAR LEFT THE PAVED SURFACE. LOOKING AT THE APCH END OF RWY 36L EVEN AFTER WE WERE STUCK, IT APPEARED WE WERE RIGHT WHERE WE SHOULD BE. THE COPLT SAID EVERYTHING APPEARED FINE TO HIM, HE WAS AS SURPRISED AS I WAS. THE ACFT BEHIND US, EVEN KNOWING WE HAD A PROB, WAS CERTAIN WE WERE NOT OFF THE TXWY. THE PAX WERE DEPLANED ONTO BUSES AND WE LEFT THE ACFT. OUR MAINT PEOPLE ASSURED ME THAT THE ACFT HAD NOT BEEN DAMAGED WHEN THE GEAR LEFT THE TXWY. (WE WERE MOVING VERY SLOWLY.) I BELIEVE THE ACFT MAY HAVE SUSTAINED WHAT I HOPE WAS VERY MINOR DAMAGE DURING THE RECOVERY ATTEMPT. THE ARPT OPS MGR TOLD ME THAT THEIR TXWY WAS A 'TRAP' AND THEY HAD ACFT DOING WHAT WE DID EVEN IN THE SUMMER. HE ALSO SAID THAT THE ARPT HAD PLANS FOR CONSTRUCTION ON THIS TXWY TO HOPEFULLY ELIMINATE THIS PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE ARPT MGR'S PLANS FOR 'A SOLUTION' WERE EXPECTED TO TAKE PLACE THIS COMING SUMMER. SUPPOSEDLY A FILLING IN OF THE 'DIP' OR BEND AREA ON THE R SIDE OF THE TXWY. RPTR COULD NOT GIVE ANY ADVICE AS TO ANY TEMPORARY SOLUTION TO THE PROB. HE SAID THAT OTHER TYPES OF ACFT, OTHER THAN THE L1011, WERE DOING THIS, EVEN IN THE SUMMER. THE MAJOR PROB WITH THIS TXWY DESIGN IS THAT, EVEN AFTER TURNING AND GOING OFF THE TXWY, IT STILL LOOKED RIGHT. HE FURTHER STATED THAT AFTER HIS OBSERVATION OF THE ACFT'S POS AFTER THE EVENT FROM THE OUTSIDE, RIGHT NEXT TO THE R GEAR, IT STILL 'LOOKED RIGHT.' THE ARPT TAXI CHART AS DEPICTED FROM THE MANUFACTURER IS MISLEADING. THE TXWY CURVE OR 'DIP' IS GREATER THAN WHAT IS SHOWN. HE SAID THAT A CAPT LOSES PERSPECTIVE AS TO WHERE TO TURN BECAUSE THE 'ODD' TXWY'S DESIGN AND ITS RELATIONSHIP TO THE END OF THE RWY CREATES AN OPTICAL ILLUSION. YOU CANNOT TURN WHERE YOU THINK YOU SHOULD TURN.

Data retrieved from NASA's ASRS site as of July 2007 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.