NTSB Factual Report

On March 10, 2011, at 0856 eastern standard time, while climbing through approximately 28,000 feet near Haynesville, Maryland, a Cessna 560XL, N588QS, operated by NetJets Aviation, Inc., experienced stuck rudder controls. There was no damage to the airplane, and the two pilots and one passenger were not injured. Visual meteorological conditions prevailed. The airplane was operating on an instrument flight rules flight plan from Baltimore/Washington International Thurgood Marshall Airport (BWI), Baltimore, Maryland, to Lynden Pindling International Airport (MYNN), Nassau, The Bahamas. The personal flight was being operated under the provisions of 14 Code of Federal Regulations Part 91, Subpart K.

According to the company's director of aviation safety, the incident flight was the second of the day for the airplane, with the first being a positioning flight from Malcolm McKinnon Airport (SSI), Brunswick, Georgia to BWI. The airplane departed SSI at 0520, flew at an en route cruise altitude of 37,000 feet and landed at BWI at 0702. Other than encountering light to moderate rain upon arrival, the flight was uneventful with no anomalies noted with the airplane.

While the airplane was on the ground at BWI, there was occasionally moderate rain at a temperature of 9 degrees C.

The airplane departed the ramp at 0831 for MYNN with the copilot at the controls, flying from the right seat. During the departure, the airplane again encountered light to moderate rain.

As the airplane was climbing through approximately 28,000 feet, the copilot noted that the yaw damper was "not functioning properly." The copilot disconnected the autopilot and yaw damper, and as he exercised the flight controls, he found that the rudder was "frozen" in the neutral position. The crew continued the climb to 40,000 feet, and based on the captain's discussions with the company, then diverted to Myrtle Beach International Airport (MYR), Myrtle Beach, South Carolina. Descending through 13,000 feet, normal rudder operation returned, and the subsequent approach and landing were uneventful.

After the crew disembarked, they noticed water dripping from the belly of the airplane. Panel 321ABC was subsequently removed, and water and ice were found in the bottom of the compartment, through which, also ran the rudder and elevator control cables.

On December 1, 2010, another Cessna 560XL, N607QS, had landed without damage after the crew experienced rudder binding during the landing flare. According to the preliminary report for NTSB incident investigation CEN11IA087, a postflight examination of the inside of the tailcone stinger revealed an accumulation of ice that interfered with the rudder control cables and pulleys. It also noted that the airplane had previously been parked in light rain and subsequently departed in light to moderate rain before breaking out of clouds at 14,000 feet en route to a final altitude of 40,000 feet.

On December 13, 2010, another Cessna 560XL, N498AB, had landed without damage after the crew experienced rudder binding in flight. According to the preliminary report for NTSB incident investigation CEN11IA111, a postflight examination of the inside of the tailcone stinger revealed an accumulation of ice around the rudder control cables and pulleys. The report did not provide atmospheric conditions.

On January 21, 2011, Cessna issued Alert Service Letter [ASL]560XL-53-08, "Fuselage – Aft Canted Bulkhead Drain Installation," which stated, in part, that the tailcone stinger "may not drain water, and in turn, could allow ice to form around the rudder bias cable pulleys." The ASL provided instructions to inspect two 0.201 inch diameter drain holes in frames immediately forward and aft of access panel 321ABC and drill them if necessary, to seal an existing 0.201 inch diameter drain hole in the tailcone stinger, and to add a 0.75 inch diameter drain hole in the aft canted bulkhead.

According to the NetJets director of aviation safety, on March 7, 2011, another Cessna 560XL, N691QS, had landed in Canada without damage after the crew experienced rudder binding in flight after having parked in and taken off during rain. Ice was again found in the tailcone stinger that bound the rudder controls, but the ASL had not yet been incorporated into the airplane.

On March 15, 2011, the NTSB issued Safety Recommendation A-11-16, which recommended that the Federal Aviation Administration (FAA) issue an airworthiness directive to mandate that all Cessna 560XL operators comply with the ASL.

According to maintenance records, the ASL requirements were completed on N588QS on January 31, 2011.

Subsequent to the rudder binding of N588QS, Cessna, with FAA oversight, conducted further testing. According to an FAA response to the NTSB Safety Recommendation, flight testing occurred on another Cessna 560XL that had also incorporated the requirements of the ASL, and was modified with onboard video cameras, tufts to indicate ventilation, light sources, and tubing for the introduction of water to the stinger area during flight.

Flight tests revealed that even though the previously existing tailcone stinger drain hole had been sealed per the ASL, air was still coming through seams at the bottom of the stinger with enough force to splatter water onto the rudder cables and pulleys. Testing also revealed that air emanating from the new hole in the aft canted bulkhead also resulted in splattered water onto the rudder cables and pulleys, and that after large quantities of water were introduced, water would only drain forward through the hole.

As a result of the testing, Cessna issued Service Bulletin [SB]560XL-53-16, "Fuselage-Stinger Drain Installation" on October 4, 2011. The stated purpose of the SB was to reduce the amount of water entering the tailcone stinger and to improve drainage by installing a seal and an additional drain. The SB also noted that the ASL was to be completed prior to, or in conjunction with the SB.

The Cessna 560XL received FAA certification in April 1998; however, except for the events listed in this report, no previous documentation of rudder control binding due to internal tailcone stinger icing could be found in either the FAA Service Difficulty Report database or the NTSB accident database

NTSB Probable Cause

The manufacturer's inadequate design fix for previously known tailcone stinger water ingestion and retention.