The flight instructor, who was in the rear seat of the Air Tractor AT-802, told investigators that during landing at the airport in Herington, Kansas, as they slowed to 35 to 40 mph, the tailwheel unlocked, and the airplane turned right.
The CFI applied full left rudder and attempted to apply the left toe brake, but the brake pedal was restricted from moving forward.
When left rudder and left brake were applied, the top of the pedal contacted the spray control lever pushrod and full brake could not be applied.
The airplane continued off the right side of the runway, hitting a ditch, which resulted in substantial damage to the wings.
Post-accident examination revealed that the front-seat rudder/brake pedals could move through their full range of motion without interference.
The rear-seat rudder/brake pedals were found in the forward adjustment position. With the rear pedals in the forward position, the left rear brake pedal range was restricted by the upper spray valve control pushrod, preventing the application of full left brake from the rear seat.
The upper spray valve push rod was installed in the airframe by Air Tractor during the original production of the airplane. Air Tractor reported that there were 94 other airplanes affected by this design installation.
As a result of this investigation, on Dec. 29, 2023, Air Tractor completed service letter (SL) 405, which was applicable to certain AT-802 airplanes with a spray valve control lever installed. The SL was issued due to the spray valve control valve pushrod’s interference with the left rear rudder pedal, which reduced controllability and could lead to an accident.
The interference was only possible when the left rear rudder pedal is in the forward adjustment position. This interference prevents simultaneous application of full left rudder and left brake when operated from the rear seat.
This control restriction could lead to a loss of control causing significant injury and aircraft damage. Placement of the rear rudder pedals in the rear adjustment position is a temporary solution that will allow full, simultaneous application of left rudder and left brake.
As result of this investigation, on April 25, 2024, the FAA issued special airworthiness information bulletin (SAIB) 2024-03, “Rudder Control System,” which recommended that all affected operators modify the rear cockpit rudder pedal adjustment in accordance with Air Tractor, Inc. Service Letter 405.
Probable Cause: The design of the spray valve control lever, which restricted the range of the left rear rudder and brake pedal and resulted in a loss of control during landing.
To download the final report. Click here. This will trigger a PDF download to your device.
This September 2023 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Wouldn’t a pre-takeoff “stop to stop” flight control travel check have caught this rudder pedal travel restriction? This little 5 second check before leaving the run up area or pushing the throttle forward may be a good addition to your efforts.