NTSB Identification: ERA13IA114
Nonscheduled 14 CFR Part 91 Subpart K: Fractional
Incident occurred Sunday, January 13, 2013 in Debary, FL
Probable Cause Approval Date: 12/02/2013
Aircraft: CESSNA 560XL, registration: N662QS
Injuries: 4 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
The flight departed uneventfully and was climbing to the pilots’ planned cruise flight level (FL) 380 (about 38,000 feet). As the airplane climbed through FL350 at a climb rate of 1,000 feet per minute (fpm) with the autopilot engaged, the airplane pitched nose-down and entered a 400-fpm descent. The pilots disconnected the autopilot, assumed manual control of the airplane, and leveled off at FL350. Both crewmembers noted that “excessive” force was required to change the pitch of the airplane and subsequently notified air traffic controllers of the situation. The pilots then requested a descent, during which they noted that trim and manual elevator control inputs resulted in an exaggerated pitch response from the airplane. However, the pilots stated that as they descended through FL180, it felt like something “broke loose,” and the elevator controls began to respond normally again. The pilots reengaged the autopilot and continued to the planned destination uneventfully.
Postincident examination of the airplane revealed that several of the fuselage tail area bilge drain holes were partially or totally obstructed by debris, allowing water to accumulate within the bilge and in areas adjacent to elevator control cables and pulleys. Several of the pulleys exhibited evidence of saturation with moisture, and two of the pulleys’ bearings had seized completely and displayed evidence that the control cable had subsequently worn their grooves. Additionally, examination showed that seals designed to limit the entry of moisture to the tail area had not been trimmed in accordance with the published installation procedure. It is likely that the accumulated moisture in the tail section froze as the airplane climbed to colder altitudes and resulted in the flight control stiffness. The ice subsequently melted as the airplane descended, and the pilots were able to regain control.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: An accumulation of debris in the airplane’s bilge drain holes that prevented accumulated moisture from properly draining; the accumulated moisture subsequently froze around the elevator control components, which resulted in the flight control stiffness. Contributing to the accident was maintenance personnel’s improper installation of seals in the airplane’s tailcone, which allowed water to enter the tailcone. Full narrative available
Index for Jan2013 | Index of months