Pipistrel Alpha Trainer N119JP accident near Fort Collins, Colorado

Probable cause

A partial loss of engine power due to the failure of the throttle control cable, which resulted in the loss of control of the dual carburetor system. The cable failure was a result of improper soldering at the throttle cable input terminal on the splitter assembly, which led to the progressive separation of the cable strands.

NTSB analysis

The flight instructor reported that he and the pilot took off in the airplane to conduct a flight review and proceeded to the practice area. They conducted flight review maneuvers, emergency procedures, and the flight instructor demonstrated a power-on stall. The pilot took over the controls and when he added power, the engine did not respond. He manipulated the throttle several times, but the engine had reduced to idle power and would not change. The flight instructor initiated an emergency landing. The airplane descended to a nearby field and touched down. The nosewheel sank into a small ridge and the airplane flipped upside down and slid to a stop.

A postaccident examination of the throttle/choke splitter assembly revealed the single throttle cable, which runs to the cockpit, separated from the throttle/choke cable splitter assembly. A metallurgical examination revealed a lack of solder material where the input throttle cable connects to the terminal end of the splitter assembly. The lack of solder material left a void in the cable connection with the terminal fitting, which allowed the individual cable strands to fail in a progressive manner, until the cable eventually separated from the terminal fitting. A lack of solder was also noted at the output end of the throttle cable connection with the splitter assembly. The choke cable connections were normal.

The airplane maintenance manual indicates that the throttle and control cables need to be replaced every 5 years. In addition, the manual cautions that “all of the time limits…. must be considered when performing the 100 hour/annual inspection. Removal or overhaul of any these items must be entered into the aircraft technical logbook.” There is no logbook entry that explicitly states that the throttle and choke cables were replaced. Therefore, it could not be determined who produced the deficient solder joints or how long they had been in service.

Text from the NTSB. Open the NTSB docket for CEN21LA241 for the full record.