With a pilot and one passenger on board a Cessna P210N Centurion was operating a private flight (Part 91) between the cities of Hondo and Port Aransas (both in the state of Texas, USA). The take-off and initial part of the flight were uneventful as the aircraft cruised at 3200 ft AGL
The aircraft in its final position shortly after the forced landing (Source; www.kathrynsreport.com © Unknown)
Approximately 20 minutes into the flight, as the aircraft cruised along the pilot moved the throttle forward 1/8" and noticed a partial loss of engine power. As the aircraft was close to Pleasanton Municipal Airport (Texas, USA) the pilot changed heading towards that airport and started going through the applicable emergency checklists. During this time more engine power was lost, and although running smoothly, it appeared to be running at idle power. It quickly became apparent that they did not have enough altitude to make it to Pleasanton Municipal Aiport and an off-field forced landing would be inevitable. The necessary preparations were made for a forced landing on Highway 97 close to the airport. After observing road traffic on the Highway the pilot changed course and for a forced landing on the Pleasanton airport road. The pilot decided not to lower the landing gear until the last minute but stalled just before wanting to do so. Touchdown was just short of 1 mile from the runway, which runs almost parallel to Airport Road. During the landing, the aircraft struck a car and sustained major damage to the fuselage and both wings. Both occupants were injured in the landing. The National Transportation Safety Board (NTSB) was informed about the accident. An FAA inspector debriefed the pilot and performed an inspection of the wreckage. The FAA inspector found substantial damage to the ribs and spars of both wings and also to the firewall. Upon further examination of the engine and its related systems/controls it was found the following;
Ducting to the turbo was dislodged (this could have been caused by impact forces
The throttle linkage to the engine was disconnected, and not found at the accident side. (this linkage should have been connected to the engine with a bolt, washer, castellated nut and a cotter pin)
The aircraft had undergone an annual inspection in June 2016. On the 26th of September 2016, a starter adapter was replaced on the engine. To facilitate this replacement the throttle body and linkage would have had to be removed from the engine to gain access to the starter adapter. There were no other records of recent maintenance on the engine that would have disturbed the throttle linkage to the engine. NTSB investigators were not able to speak to the maintenance personnel involved in the maintenance.
Excerpt from the Cessna 210 Maintenance Manual, detailing the mixture and throttle controls (© Cessna)
The National Transportation Safety Board determined the probable cause(s) of this accident to be;
Maintenance personnel's improper installation of the throttle linkage attachment hardware, which resulted in a partial loss of engine power when the hardware separated in flight.
The NTSB investigation report which served as the source for this blog is available as .pdf file below, click on the file to open it;