Before the flight in the experimental Thorp T-18, the pilot unbolted and rebolted the pilot’s seat from its middle position to the forward position.
He did not check to see if the flight control stick movement would be restricted in this new configuration.
During the takeoff roll, the plane would not rotate when he moved the flight control stick aft.
Not realizing the seat prevented the flight control stick movement to the full aft position, he adjusted the elevator trim and the plane subsequently lifted off, however, it would not climb.
He then aborted the takeoff, however the airplane did not have sufficient distance to stop. It departed the runway at San Rafael, California, and traversed through a field, hit trees, and came to rest inverted.
The airplane sustained substantial damage to the wings, rudder, and vertical stabilator.
The NTSB determined the probable cause as the pilot’s delayed decision to abort the takeoff. Contributing to the accident are an inadequate modification to the seat position, and the pilot’s failure to check flight controls for freedom and correct movement.
NTSB Identification: WPR15CA066
This December 2014 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.
The pilot’s real failure was skipping the standard pre-flight flight-control check. Ailerons moving up and down properly? Check. Elevator moving up and down…. uh oh. Better head back to the hangar…
Why would the manufacturer position forward seat bolts in a place where they would restrict the movement of the stick? I would think that this is their fault, not the pilots.
My guess is the person that moved the seat did not build the plane.
Recently I had a similar problem. I fly a Corby Starlet, a small wood plane, and I built a little wooden box to hold one of today’s tinny cameras, I glued the box to fuselage side wall making sure it did not interfere with any of the controls. Apparently when I secured it in place with a board the camera box moved a little. Once the glue dried I removed the board but failed to again check controls for free movement. In my sixty years of fly, old school, I pull the prop thru, do the preflight list, mount up and buckle in. Before I turn the fuel on I move the controls full deflection. NEVER have I found a problem until this day. The stick would not move full aft. I gave a tug aft, heard a crunch and had full aft on the stick. Found the elevator bellcrank just barely hit the bottom of the camera box. So folks it may seem like a useless motion to check those controls before you leave the barn but do it anyway!
Small changes can have big, unforeseen impacts. This pilot, unfortunately, did not approach the (to him) inconsequential relocation of the seat with a test pilot mentality. He didn’t think through the problem, then failed to test his assumptions BEFORE starting the engine. THIS was the root cause of the accident, not his delayed decision to abort the takeoff. An additional contributing factor was this pilot failed to fully understand the meaning of the required “Experimental” placard posted in his aircraft. Google defines “experimental” as “based on untested ideas or techniques and not yet established or finalized.” BINGO.
Some experimental aircraft exceed Google’s definitions. I remember just the other day talking to my brother Orville about the Internet. He had the interesting idea that anything found there is absolutely true. Especially that new thing called Wikipedia.