Incident Description
On March 10, 2011, at 0856 eastern standard time, a Cessna 560XL, registration N588QS, operated by NetJets Aviation, Inc., experienced stuck rudder controls while climbing through approximately 28,000 feet near Haynesville, Maryland. The aircraft was conducting a personal flight under 14 CFR Part 91, Subpart K, from Baltimore/Washington International Thurgood Marshall Airport (BWI) to Lynden Pindling International Airport (MYNN) in Nassau, The Bahamas, with two pilots and one passenger on board. No injuries to occupants or damage to the airplane were reported. Visual meteorological conditions prevailed, and the flight was operated under an instrument flight rules flight plan.
During the climb, the copilot observed that the yaw damper was not functioning properly. The autopilot and yaw damper were disconnected, and when the copilot exercised the flight controls, the rudder was found to be frozen in the neutral position. The crew continued climbing to 40,000 feet and, after consulting with the company, diverted to Myrtle Beach International Airport (MYR) in South Carolina. As the aircraft descended through 13,000 feet, normal rudder operation resumed, and the subsequent approach and landing were uneventful.
After disembarking, the crew noticed water dripping from the belly of the aircraft. Upon removing panel 321ABC, water and ice were discovered in the bottom of the compartment, through which the rudder and elevator control cables passed.
Previous Incidents
Similar rudder binding events had occurred on other Cessna 560XL aircraft prior to this incident. On December 1, 2010, N607QS experienced rudder binding during the landing flare, with postflight examination revealing ice in the tailcone stinger interfering with rudder control cables and pulleys. On December 13, 2010, N498AB also experienced rudder binding in flight, with ice found around the rudder control cables and pulleys in the tailcone stinger. On March 7, 2011, N691QS experienced rudder binding after parking in and taking off during rain, with ice again found in the tailcone stinger; the Alert Service Letter (ASL) had not yet been incorporated into that aircraft.
In response to these events, on January 21, 2011, Cessna issued Alert Service Letter (ASL) 560XL-53-08, which stated that the tailcone stinger may not drain water, potentially allowing ice to form around the rudder bias cable pulleys. The ASL provided instructions to inspect and drill drain holes, seal an existing hole, and add a new drain hole in the aft canted bulkhead.
Investigation and Corrective Actions
Maintenance records indicated that N588QS had the ASL requirements completed on January 31, 2011. Despite this, the March 10 incident occurred. On March 15, 2011, the NTSB issued Safety Recommendation A-11-16, recommending that the FAA issue an airworthiness directive mandating compliance with the ASL for all Cessna 560XL operators.
Subsequent to the incident, Cessna, with FAA oversight, conducted further testing on another Cessna 560XL that had also incorporated the ASL. The aircraft was modified with onboard video cameras, tufts to indicate ventilation, light sources, and tubing to introduce water into the stinger area during flight. Flight tests revealed that even with the ASL modifications, air still entered through seams at the bottom of the stinger, splattering water onto the rudder cables and pulleys. The new drain hole in the aft canted bulkhead also allowed air to splatter water. Large quantities of water only drained forward through the hole.
Based on these findings, on October 4, 2011, Cessna issued Service Bulletin (SB) 560XL-53-16, titled "Fuselage-Stinger Drain Installation," with the stated purpose of reducing water entry into the tailcone stinger and improving drainage by installing a seal and an additional drain. The SB noted that the ASL should be completed prior to or in conjunction with the SB. The Cessna 560XL had received FAA certification in April 1998, but no prior documentation of rudder control binding due to internal tailcone stinger icing was found in the FAA Service Difficulty Report database or the NTSB accident database, except for the incidents listed in this report.