Pilot’s Improper Installation Of The Control Stick Pushrod Assemblies, Which Resulted In Separation Of The Left Pushrod And A Total Loss Of Roll Control

Location: Auburn, Washington Accident Number: WPR24FA182
Date & Time: June 6, 2024, 12:00 Local Registration: N412JN
Aircraft: Vans Aircraft Inc RV-12 Aircraft Damage: Substantial
Defining Event: Flight control sys malf/fail Injuries: 1 Fatal
Flight Conducted Under: Part 91: General aviation - Personal

Analysis: While returning to the airport from a routine pleasure flight, the pilot of the experimental lightsport airplane reported a total flight control failure while maneuvering to land. Data from the onboard electronic flight instrument system and witness statements indicated that after turning from the crosswind to the downwind leg, the airplane entered an uncontrolled descending left turn consistent with a spin or spiral, culminating in a collision with a warehouse roof about 0.75 mile from the runway threshold.

Postaccident examination revealed that the left side (where the pilot was operating the airplane) control stick pushrod had become disconnected from the flaperon mixer bellcrank due to improper installation during construction. Both left and right pushrod rod-end eyebolt bearings had been installed in reverse orientation. The improper installation allowed the pushrod to gradually unscrew from its eyebolt, ultimately resulting in complete separation of the left pushrod. This condition rendered the primary roll control system on the pilot’s side ineffective.

The aircraft was equipped with an autopilot system featuring a “Level” mode capable of providing roll control independent of the cockpit control sticks. Prompt activation of this feature—or use of the rudder to counteract the developing roll—would likely have allowed the pilot to retain some degree of control. Similarly, the pilot would have been able to fully control the airplane if he had reached to his right and used the other control stick. However, given the sudden onset and rapid progression of the event, it is unlikely the pilot had sufficient time or situational awareness to identify and employ these options before the airplane entered an unusual attitude and became uncontrollable.

The pilot's autopsy identified heart disease, including severe coronary artery disease of a single coronary artery and mild thickening of the left cardiac ventricle. Although the pilot’s heart disease was associated with an increased risk of sudden impairment or incapacitation from a cardiac event, the circumstances of the accident were not consistent with a sudden medical event and it is unlikely that the pilot’s heart disease contributed to the accident. 

The improper assembly error was traced to the original construction of the airplane and was visible in build photographs taken in 2019. The oversight persisted through final inspection and three years of subsequent operation. The airplane kit manufacturer later issued a service bulletin addressing correct installation of the pushrods.

Probable Cause and Findings: The National Transportation Safety Board determines the probable cause(s) of this accident to be -- The pilot’s improper installation of the control stick pushrod assemblies, which resulted in separation of the left pushrod and a total loss of roll control during flight. Contributing to the accident was the failure to detect the installation error during the airplane’s construction, inspection, and subsequent maintenance.

FMI: www.ntsb.gov