EAA Sport Aviation - September 2011

limitations on the certificate prohibited aerobatic flight. By 1995 the airworthiness certificate had been updated to permit aerobatics after sufficient flight experience had been gained to demonstrate the airplane was controllable. The limitations at that time also required that aerobatic maneuvers performed must be recorded in the logbook.

The owner of the accident airplane purchased it in 2000, and the Acroduster had flown approximately 363 hours at that time. By the time of the most recent conditional inspection in 2008, the airplane had flown 838.2 hours.

BENT BELL CRANK

The NTSB found an Internet posting by a
person using the name of the accident pilot
in 2002 that said “practicing vertical torque
rolls. On the fifth one I had a monster, roll-
ing tail slide and a violent flop back toward
the ground. After which I noticed that the
stick was unusually stiff in roll and the air-
craft was now out of trim in roll. I
carefully returned to the airport and found
that with the stick centered, the [right]
aileron was in the proper position and the

The blocks are intended to prevent the high shock loads of the ailerons from traveling through the entire control system.

[left] aileron was deflected [approxi-mately] 3 inches up.” The Internet posting continued with a report that an inspection found that the left aileron bell crank inside the fuselage and an AN- 5 bolt that secured the bell crank were bent.

The NTSB found that new bell cranks were fabricated and installed, though the aircraft maintenance records did not show this. At some point wood aileron bell crank stop blocks were installed on the aft side of the main spar of both lower wings. The Acroduster has ailerons on each wing, but the stop blocks were only on the lower wing.

When the NTSB examined photos of the wreckage it found that the wood aileron stop blocks each had crush marks consistent with contact being made by the upper and lower portions of each aileron bell crank. The NTSB also noted scrape marks on a drag truss that it found were made by the outer aileron bell cranks on both lower wings. Another photograph showed that both inboard aileron bell cranks were bent slightly up.