Hurricane, UT, USA
N6330N
Cessna T210
The pilot departed on a maintenance check flight with his mechanic to troubleshoot an oil temperature discrepancy. During takeoff, after the airplane lifted off the ground and transitioned into a climb, the engine began to lose power. The pilot was unable to maintain altitude, and the airplane descended to the ground. Postaccident examination revealed that the turbo waste gate was likely not functioning at the time of the accident. In addition, photographs taken moments after the accident showed that the throttle cable had detached from the arm of the throttle body metering unit and the bolt holes in both the rod end and throttle arm were intact. Further, maintenance records showed that the mechanic’s assistant (who was not a certificated mechanic) had removed and re-installed the throttle cable during the airplane's most recent inspection 1.5 flight hours prior to the accident. The assistant performed the removal by memory, and the reinstallation of the throttle assembly was likely not confirmed by the mechanic. The pilot was able to advance the throttle during takeoff, but the passenger observed mid-range fuel flow that was not consistent with takeoff power, which suggests that the throttle cable likely uncoupled from the throttle arm sometime during the takeoff sequence. As there were no anomalies with the airplane, the mechanic's improper installation of the throttle cable during recent inspection likely resulted in a detached throttle cable during takeoff, which resulted in a loss of engine power, subsequent descent, and impact with terrain.
On July 15, 2019, about 1430 mountain daylight time, a Cessna T210N, N6330N, was substantially damaged when it was involved in an accident near Hurricane, Utah. The pilot was not injured, and the passenger was seriously injured. The airplane was operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, his mechanic had recently serviced the airplane to troubleshoot a series of high oil temperature indications that had been reported to him by the pilot. Following the repair, the pilot continued to receive the indications, so the mechanic elected to accompany the pilot during a flight to observe. The pilot reported that he did not observe any anomalous indications during the ground roll, but once the airplane entered its initial climb, the engine lost power. The pilot was unable to maintain altitude and the airplane immediately descended to the ground. He did not deploy the landing gear because the airplane was at a low altitude. The airplane impacted the ground in an area of sage brush and dirt. In a subsequent statement, the pilot added that when he started to lose power, it felt like the manifold pressure was reduced, which he equated to a loss of the turbocharger. The passenger stated that he asked to accompany the pilot during a flight to observe the oil temperature gauge. During the airplane's ground roll, he noticed that the airplane took an unusually long time to lift off the runway surface and that fuel flow was about mid-range and not consistent with takeoff power. The airplane then lifted off the ground briefly before it settled back down on the runway surface. The airplane rotated again and was still unable to maintain altitude, so the pilot turned left as the airplane descended and impacted the ground. An on-scene examination of the airplane by the Federal Aviation Administration revealed substantial damage to the forward fuselage. Photographs taken by both a first responder and the pilot showed that the throttle cable rod end was disconnected from the throttle body valve arm (see figure 1). The first responder reported that he arrived within minutes of the accident and did not observe anyone tampering with the engine. Figure 1: Detached Throttle Cable at Accident Site According to the airplane parts catalogue, the throttle control cable rod end attaches to the throttle arm of the throttle body with an AN3-7 bolt, three AN960-10 washers, and a S1450-3-14-032 washer and is secured with an AN310-3 nut and MS24665-132 cotter pin (see figure 2). Photographs of the throttle assembly rod end and bolt hole taken after the accident showed that both were intact. Figure 2: Throttle Control Attachment from Parts Catalogue Review of the airplane's maintenance records revealed that the engine was inspected on July 9, 2019, following a report of an abnormally high oil temperature experienced by the accident pilot during a short flight. This took place about 1.5 hours following a recent 100-hour inspection and top engine overhaul that was performed 1 month prior by the same mechanic. A work order for the 100-hour inspection stated, "disassemble throttle cable…Pressure lubricate engine throttle cable, re-install throttle arm…", which took place on June 14, 2019. According to the certificated mechanic who performed the work, his assistant, who was not a certificated mechanic, removed and re-assembled the throttle cable on this day and did not use the illustrated parts catalogue at the time as he was familiar with the assembly. The mechanic who performed this service reported that he started to remove the mixture and propeller controls the morning after the accident. An examination of the airframe was performed by a certificated airframe and powerplant mechanic. He inspected the fuel system from the wing fuel tanks to the engine and did not observe any obstructions or anomalies in the fuel strainer, fuel selector, vent system, or fuel lines. Further, the throttle cable was not damaged nor was the throttle body arm except for an aft bend, consistent with impact with the engine firewall. The engine examination was performed by the engine manufacturer and the NTSB investigator-in-charge. The oil sump was partially crushed. The waste gate controller mounting bracket was fractured and the alternator bracket was broken. The engine was intact and, in a condition, to run without replacement of parts, except for the fuel manifold diaphragm and scat tubing, which were damaged. Initially, the engine reached 2,450 maximum continuous rpm, which was about 150 rpm below rated rpm. Several operational adjustments were made while troubleshooting the turbo charger, which included bypassing the turbo controller, including the replacement of a broken scat tube clamp, the tightening of loose exhaust and intake valve bolts, repair of a hole in the scat tube, and subsequent replacement of the scat tubing with induction hose. The engine started normally during several engine runs and achieved rated manifold pressure when the throttle was advanced to full power after the waste gate was replaced with a factory unit.
Maintenance personnel's improper installation of a throttle cable to the throttle body arm, which resulted in a throttle detachment during takeoff and subsequent loss of power. Contributing to the accident was the inadequate inspection of the throttle installation by the certified mechanic.
Source: NTSB Aviation Accident Database
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