CEN14IA172

The inoperative galley drain tube heater, which allowed water within the tube to freeze and led to its failure; the tube’s failure allowed water to drain onto the rudder cables and freeze and resulted in the rudder binding during landing.

The flight was conducted at flight level 400, and the entire flight was 3 hours 17 minutes long. During the landing at the destination airport, the flying pilot noted that the rudder pedals were hard or frozen; however, he was able to make an uneventful landing. The nonflying pilot then took the flight controls and confirmed the rudder pedal situation. Once slowed to a safe speed, the flight crew was able to break the rudder pedals free and to taxi the airplane to the ramp. After the airplane was parked and shut down, the rudder still felt stiff and required more input than normal to operate. Postaccident examinations confirmed compliance with an alert service letter and service bulletin related to control cable icing. Examinations also revealed witness mark consistent with a water line in the fuselage area, and a liquid consistent with pooled deice fluid, staining, and moisture was found in the tailcone compartment. Water was also found where the galley drain exits the pressure vessel and enters the fairing area. Water was observed draining from the black foam wrap around the drain tube's heating element, and the black foam exhibited deformation consistent with the expansion of frozen water. Removal of the foam revealed an opening in the drain tube. Testing of the galley drain heating element revealed that it was inoperative. Black foam deposits were observed on a rudder cable, but no rudder system anomalies were detected. Laboratory tests revealed that an opening in the drain tube caused the rudder cables to freeze to the drain mast, and some additional force above a baseline was needed to break the simulated rudder pedals free from a static position. At the time of the incident, the airplane's approved inspection program did not specify that the galley drain tube or heater should be inspected. Additionally, the failure of the galley drain heater is not annunciated to the flight crew nor to maintenance personnel. It is likely that the undetected failure of the galley drain tube heater allowed the water within the galley drain tube to freeze, which led to the tube's failure. Once the tube failed, water was allowed to drain from the tube onto the rudder cables; this water also froze due to the inoperative heater and caused the rudder to bind during landing.

TVC was located approximately two miles south of Traverse City, Michigan, and was owned and operated by the Grand Traverse and Leelanau County Northwestern Regional Airport Commission. TVC was a certificated airport under 14 CFR Part 139. TVC's field elevation was surveyed as 623.7 feet above mean sea level. The airport listed 124.2 megahertz as its common traffic advisory frequency and reported that it meets the fire and rescue requirements of aircraft rescue and firefighting index B. TVC had two runways: Runway 10/28 - 6,901 feet by 150 feet, asphalt and runway 18/36 - 5,378 feet by 150 feet, asphalt. Runway 28 was marked as a precision approach runway and had high intensity runway edge lights. A four-light, three-degree, precision approach path indicator serviced runway 28. Runway 28 obstruction remarks listed a 440 foot lighted tower, located 16,670 feet from the runway and 2,350 feet left of centerline, which indicated a 37:1 slope to clear that obstruction. On March 27, 2014, representatives from the FAA, the operator, and a fixed base operator examined the incident airplane and confirmed compliance with Alert Service Letter 53-08 and Service Bulletin 53-16. Beginning aft on the airplane and moving forward, they inspected for signs of moisture, frozen pulleys, and debris that might be blocking drain paths. All pulleys rotated freely. In the aft canted bulkhead, visible stains were observed on both bottom pulleys and cables, along with surrounding moisture and liquid consistent with deicing fluid. The airplane was last deiced on March 25, 2014 and the airplane accumulated 78.2 hours of flight time since the last bilge cleaning inspection conducted on March 1, 2014. A gap in the stinger seal was observed and the seal was deflected downward on one edge. At fuselage station 528.5 looking forward, a witness mark consistent with a water line was observed. The view looking rearward, at fuselage station 544.5, appeared clean. In the tailcone compartment, at fuselage station 479.5, looking forward, a liquid consistent with pooled deice fluid, moisture, and staining was observed to the left of the centerline. Removal of belly panel 313DC revealed it was holding water. Belly panel 313BC was removed and water was observed. On March 28, 2014, panels on the incident airplane were removed to inspect cable runs forward of the wing to the rudder pedals. No significant moisture or debris was noted. Observations did not reveal if the rudder cables rested on the bottom of the over wing passage tubes. The left-hand back rudder tube was slipped forward, out of its adel clamp. Manually running the autopilot revealed no resistance in cable movement. There was no moisture found near the rudder bias lines by their drain point and actuator. Observations of the galley drain revealed the presence of water where the galley drain exits the pressure vessel and enters the fairing area. Water was exiting from the black foam wrap around the drain tube's heating element and the black foam exhibited deformation consistent with expansion of retained, frozen water. Water poured into the galley drain exited from the black foam into the fairing area. Removal of the foam revealed an opening in the drain tube. With the foam removed, the rudder cables were about 1/4 inch from the galley drain tube. Deposits, consistent with the black foam, were observed on a rudder cable. Testing of the galley drain heating element revealed it was inoperative and its drain tube valve was found in the open position. The tension of the rudder bias cable, rudder servo cable, and rudder cables were tested and found to be within limits. The nose wheel was moved, full travel, without resistance from the nose wheel bearing. A test of the rudder bellcrank bearing was conducted by packing three pounds of dry ice around the bellcrank area and left to cold soak for one hour. After one hour, there was no noticeable difference in rudder pedal stiffness following that cold soak of the rudder bellcrank area. The rudder pedals were stiff when the control lock was engaged. The rudder pedals were stiff when the rudder was physically held in streamlined position. The right and left-hand lower rudder bias pulleys, a section of the forward galley drain tube insulation foam, part number S2958-7, and a sample of pooled fluid found in the tail cone forward of station 479.5 and left of centerline, were removed from the incident airplane and shipped to an FAA airplane certification office representative for an examination at Cessna. A NetJets representative was not able to attend the follow-on examination at Cessna, which was conducted under FAA supervision. According to the Cessna engineering report, a limited laboratory test was developed to attempt to simulate the incident conditions to determine if an opening in the drain tube could cause the rudder cables to freeze to the drain mast under various scenarios. A sample section of the incident drain tube insulation material was dimensioned and then submerged in water for 24 hours. The sample was then re-measured and no dimensional changes were found. No water was expelled when the sample was compressed. The insulation material was abraded and the test was repeated. No retained water or dimensional changes were found. A rudder cable icing test fixture was configured with a closed cable loop between two pulleys. A production galley drain tube with its drain insulation was mounted to the fixture adjacent to the cable in the approximate airplane orientation. The cable loop was constructed so that a spring scale could measure the pull force required to move the cable. The testing was conducted with the drain insulation in contact with cable resulting in an approximate .030 inch deflection of the insulation. The test article was cold soaked to -65 degrees F. External water was then introduced via spray bottle and simulated water drain line to determine the possible effects. After cold soak, a mist of water was introduced via spray bottle until drips were noted and allowed to soak for an additional 30 minutes, and then repeated, followed by another cold soak of approximately 1.5 hours. This test showed ice bridging between the cable and the drain tube insulation. The cable was then manually pulled and an increase in breakout force from the baseline force was observed. The breakout force is consistent with a 3.3 pound force increase at the rudder pedals. After another cold soak, a stream of water was introduced to the cable and drain tube contact interface by an external water line and by pouring water directly onto the cable. The application of water was then continued using a spray bottle, coating the setup until drips were noted for four more cycles. This test showed a greater ice build-up on the cable, with greater bridging between the cable and the drain tube insulation, as well as bridging between the cable and the test article structure. An increase in breakout force was observed, which would result in a 14.4 pound increase in force at the rudder pedals over the baseline force. The drain tube insulation was observed to tear before the ice yielded. Another test was repeated with the test setup reoriented so that the water would drain away from the structure before freezing the cable to the fixture. This test was conducted by spraying the cable contact interface with water after cold soak every five minutes for a total of nine applications. Observations revealed a greater ice build-up on the cable and a greater bridging between cable and insulation than during prior tests. An increase in breakout force was observed, which would result in 16.6 pound increase at rudder pedals over baseline. The drain insulation was torn before the ice yielded. The amount of water that exited through the opening in the failed drain tube during the incident flight could not be determined. The testing could not duplicate the exact incident icing scenario. All the icing te