History of Flight
On March 26, 2014, about 1521 eastern daylight time, a Cessna 560XL airplane, N580QS, lost rudder authority when the rudder became bound during landing at Cherry Capital Airport (TVC), near Traverse City, Michigan. The airplane landed without further incident and was undamaged. The two pilots and two passengers were not injured. The flight was operated under 14 CFR Part 91K as a business flight. Day visual flight rules conditions prevailed, and the flight operated on an instrument flight rules flight plan. The flight originated from Sarasota/Bradenton International Airport (SRQ) about 1210 and was destined for TVC.
According to the operator, the incident crew picked up the airplane on March 25, 2014, at Dulles International Airport (IAD). The crew was assigned a revenue flight from IAD to Mobile Regional Airport (MOB). Prior to departing IAD, the airplane was de-iced with 34 gallons of Type I and 26 gallons of Type 4 deicing fluid. The IAD to MOB flight was conducted at FL 400, lasting 2 hours 35 minutes. That flight was uneventful with no rudder anomalies. While on the ground at MOB, weather reports indicated clear skies and no precipitation.
The crew repositioned the airplane from MOB to SRQ at FL 330 for 1 hour 11 minutes. The flight was uneventful with no rudder anomalies. The airplane remained overnight at SRQ, where weather reports indicated clear skies and no precipitation.
The next day, the crew initiated the incident flight from SRQ to TVC at FL 400 for 3 hours 17 minutes. The flight was uneventful until landing. The autopilot and yaw damper were turned off on final approach, and the flying pilot (right seat) noted the rudder pedals were hard or frozen during landing. He made an uneventful landing. Once safely on the runway, the non-flying pilot (left seat) confirmed the hard or frozen pedals. After slowing to a safe speed, the rudder pedals freed enough for taxi to the ramp without further issues. After parking, the rudder remained stiff and required more input than normal. Once powered down, the rudder pedals still exhibited the same stiffness.
Personnel Information
Left Seat Pilot: Held an FAA airline transport pilot certificate with airplane multiengine land rating and commercial privileges for single-engine land and sea. Held flight instructor certificates with single and multiengine and instrument airplane ratings. Held CE-500, BE-300, and CE-560XL type ratings. Held a first-class medical certificate with no limitations. According to the operator, he had accumulated 4,658 hours total flight time in the accident make and model, and 4,574 hours as PIC in that make and model. He logged 118 hours in the previous 90 days, 50 hours in the previous 30 days, and 7 hours in the previous 24 hours, all in the accident make and model.
Right Seat Pilot: Held an FAA airline transport pilot certificate with airplane multiengine land rating and commercial privileges for single-engine land airplanes. Held flight instructor certificates with single and multiengine and instrument airplane ratings. Held A-320, CL-65, and CE-560XL type ratings. Held a first-class medical certificate with a limitation for near vision corrective lenses. According to the operator, he had accumulated 2,796 hours total flight time in the accident make. He logged 74 hours in the previous 90 days, 34 hours in the previous 30 days, and 7 hours in the previous 24 hours, all in the accident make and model.
Aircraft Information
N580QS was a 2007 Cessna 560XL twin-engine, transport category, turbojet airplane, serial number 560-5741. It was equipped with two Pratt & Whitney Canada PW545B turbofan engines, each rated at 3,400 pounds of thrust. According to the operator, the airplane was configured for two flight crew and seven passengers. Maximum takeoff weight was 20,400 pounds; weight at time of incident was 15,487 pounds. The airplane was maintained on an approved aircraft inspection program; last inspection completed March 1, 2014, with 5,183 hours total time.
Dual flight controls include control wheel columns, adjustable rudder pedals, brakes, and mechanical nose wheel steering. Pushrod, bellcrank, sector, and cable systems actuate the rudder, elevator, and ailerons. The rudder control passes through the fuselage skin at FS 153.00 and LBL 6.580 as a torque tube, then transitions to a dual cable sector system with inboard and outboard cable sets. The overboard drain tube for the forward refreshment center passes through the fuselage skin at FS 176.5 and LBL 8.98. The drain tube has a valve and a heating element with foam insulation, connected to the pitot heat system. The refreshment drain tube valve is designed to be closed in-flight.
According to the manufacturer, clearance between the drain tube and the upper rudder cable is 0.389 inches, and between the lower cable and tube is 0.441 inches. The drain tube insulation (P/N S2958-7) has a wall thickness of 0.50 inches, which would indicate interference, but the insulation is held by clamps that compress it to provide clearance. The maintenance manual prescribed a 96-month inspection interval for the drain tube area but did not specify inspection of the drain tube or its heater.
Meteorological Information
At 1453, recorded weather at TVC: wind 210° at 5 knots; visibility 10 statute miles; sky condition few clouds at 4,200 feet, scattered clouds at 20,000 feet; temperature -2°C; dew point -13°C; altimeter 30.16 inches of mercury.
Tests and Research
On March 27, 2014, representatives from the FAA, the operator, and a fixed base operator examined the incident airplane. They confirmed compliance with service bulletins and inspected for moisture, frozen pulleys, and debris. All pulleys rotated freely. In the aft canted bulkhead, visible stains and moisture consistent with deicing fluid were observed. A gap in the stinger seal was noted. At FS 528.5, a witness mark consistent with a water line was observed. In the tailcone compartment, pooled fluid consistent with deice fluid was observed. Removal of belly panels revealed water.
On March 28, 2014, panels were removed to inspect cable runs forward of the wing. No significant moisture or debris was noted. The left-hand back rudder tube was slipped forward out of its adel clamp. Observations of the galley drain revealed water where the drain exits the pressure vessel. Water was exiting from the black foam wrap around the drain tube's heating element, and the foam showed deformation consistent with expansion of retained frozen water. Water poured into the galley drain exited from the black foam. Removal of the foam revealed an opening in the drain tube. With foam removed, the rudder cables were about 1/4 inch from the drain tube. Deposits consistent with black foam were on a rudder cable. Testing of the galley drain heating element revealed it was inoperative, and the drain tube valve was found open. Rudder cable tensions were within limits. A cold soak test of the rudder bellcrank area with dry ice showed no noticeable difference in rudder pedal stiffness.
Components including drain tube insulation and fluid samples were examined at Cessna. A limited laboratory test simulated ice bridging. With the drain insulation in contact with the cable and water introduced after cold soak, ice bridging occurred, requiring increased breakout force. Test results showed force increases at the rudder pedals ranging from 3.3 to 16.6 pounds above baseline. The drain insulation tore before ice yielded. The amount of water that exited through the opening during the incident flight could not be determined; the testing could not duplicate the exact icing scenario.
Additional Information
The operator subsequently checked their fleet of Cessna 560XL airplanes. Three other airplanes (N654QS, N698QS, N577QS) had deformed galley drain tube insulation. The operator reviewed usage rates: in 2012, the drain tube heater was replaced 12 times; in 2013, 13 times; and in 2014, 41 times. The drain tube assembly was replaced 12 times in 2012, 8 in 2013, and 18 in 2014. The failure of the galley drain heater is not annunciated to the crew or maintenance personnel.
A Cessna safety representative inquired about operational practices. The pilot's representative indicated that opening the ice bucket drain valve is not standard practice, but crews sometimes manipulate the hose to drain properly. The manual valve for the ice bucket is typically left open during flight; some crew close it if it whistles but reopen on ground. Neither pilot recalled hearing whistling during the flight. The push button valve for the drip tray is spring-loaded shut. The Cessna representative advised that if the galley drain valves were not opened, a split in the drain would not introduce water to form ice on the cables.
The operator recommended that the manufacturer modify the inspection program to include testing of the galley drain heater and mast, possibly with an indicator for heater failure. According to a Cessna representative, the manufacturer was designing a maintenance manual amendment including operational tests, scheduled for implementation in July 2015.