What happened
NTSB summary, verbatimThe flight crew reported that the flight was uneventful until the nosewheel touched down, at which time, the airplane made an uncommanded left turn and then veered off the runway. Examination of the runway revealed a witness mark from the right nosewheel tire chine consistent with a left deflection of the nosewheel steering. Testing of the nosewheel steering system and its components did not reveal any anomalies that would have precluded normal operation. The pilot reported that he used a bracket to support his approach plate book and that, during the event, the book slid off of the bracket and onto his lap. He then tossed the book out of the way. He stated that, at some point, the book may have been in the area of the nosewheel tiller but that it was not on the tiller and that it was clear of the tiller before the airplane exited the runway. Although it is possible that the weight of a book engaged the tiller, it could not be determined if the tiller was engaged during the event.
Photographs
1the aircraft, and what the investigators foundProbable cause
the Board's determinationThe uncommanded left deflection of the airplane's nosewheel for reasons that could not be determined because postincident examination of the nosewheel steering system did not reveal any anomalies that would have precluded normal operation.
Occurrence sequence
2 stepsNTSB coding · CICTT taxonomy- 1 · Landing-landing rollLoss of control on grounddefining event
- 2 · Landing-flare/touchdownRunway excursion
Findings
2 causal · 0 contributing- CAUSENot determined › Not determined › (general) — Unknown/Not determined
- CAUSEAircraft › Aircraft oper/perf/capability › Performance/control parameters › Directional control — Not attained/maintained
Sequence of events
7 timed eventsfrom the FDR factual report · claude-fable-5-1 (in-session)- 00:08 EDTapproachp.2Descending through 1,700 ft pressure altitude on a magnetic heading of about 233 deg (runway 23)
- 00:08:45 EDTtouchdownp.2Air/ground switch to ground (touchdown), followed by symmetric spoiler and thrust reverser deployment; pilot brake pedal activity began
- 00:08:49 EDTlanding rollp.3Copilot's right brake pedal began to show activity
- 00:08:52 EDTlanding rollp.3Magnetic heading began to swing left as indicated airspeed fell below 100 kts
- 00:08:53 EDTlanding rollp.3Rudder reached its maximum deflection of 12.7 deg right (correcting the left swing)
- 00:08:55 EDTrunway excursionp.3Left and right ailerons at maximum deflection, 16.5 deg TED and 24.4 deg TEU (full right wheel)
- about 00:09:04 EDTstoppedp.3Aircraft came to rest on a magnetic heading of 199 deg (34 deg left of runway heading)
NTSB analysis
from the final reportThe flight crew reported that the flight was uneventful until the nosewheel touched down, at which time, the airplane made an uncommanded left turn and then veered off the runway. Examination of the runway revealed a witness mark from the right nosewheel tire chine consistent with a left deflection of the nosewheel steering. Testing of the nosewheel steering system and its components did not reveal any anomalies that would have precluded normal operation. The pilot reported that he used a bracket to support his approach plate book and that, during the event, the book slid off of the bracket and onto his lap. He then tossed the book out of the way. He stated that, at some point, the book may have been in the area of the nosewheel tiller but that it was not on the tiller and that it was clear of the tiller before the airplane exited the runway. Although it is possible that the weight of a book engaged the tiller, it could not be determined if the tiller was engaged during the event.