Pilot seat displacement causes loss of control during takeoff in Cirrus SR22

Casualties unknown • FORMIGA, MG, BR

A Cirrus SR22 veered off the runway and entered a cornfield after the pilot's seat slid backward, disconnecting the pilot from the rudder pedals.

What happened

On December 20, 2009, a Cirrus SR2HM (registration PR-NAT) was performing a ferry flight from Fazenda Capão Seco, in Formiga, Minas Gerais, to São Paulo. The aircraft was occupied by a pilot and one passenger. During the takeoff roll, the aircraft veered left from the runway and exited the paved surface, coming to a stop in a nearby cornfield. The impact resulted in substantial damage to the aircraft, though both occupants were unharmed.

The investigation

CENIPA investigators examined the aircraft's seat mechanism and the pilot's pre-flight procedures. The investigation established that the pilot's seat was mounted on tracks set at a 12-degree positive pitch angle. While the aircraft's maintenance, documentation, and the pilot's qualifications were all in order, investigators found that the seat had moved backward along its rails during the takeoff acceleration. This movement caused the pilot to lose physical contact with the rudder pedals, leading to the loss of directional control.

Testing with a similar aircraft revealed that the rounded shape of the locking pins, designed to facilitate easier insertion into the tracks, could also allow the pins to slip out of the holes if they were not fully seated. The investigation noted that the pilot's checklist only required adjusting the seats securely, rather than explicitly verifying the locking pins' engagement. Furthermore, the pilot may have experienced a "false lock," where the locking lever appeared fully depressed, creating the illusion of a secure connection while the pins were actually only partially inserted.

Findings

  • The pilot seat displacement was the primary factor in the loss of control.
  • The 12-degree upward pitch of the seat tracks, combined with the acceleration forces during takeoff, facilitated the backward movement of the seat.
  • The pilot lost contact with the rudder pedals due to the seat sliding away from the controls.
  • The locking pins were not fully engaged in the tracks, a condition that was not detected during pre-flight checks.
  • The aircraft's checklist and manual provided instructions that could lead to a false perception of the seat being properly locked.

Probable cause

The pilot's seat slid backward along its tracks during the takeoff roll due to insufficient engagement of the locking pins, causing the pilot to lose access to the rudder pedals and resulting in the loss of directional control.

Frequently asked questions

What happened in the 2009-12-20 aircraft accident near FORMIGA, MG, BR?

A Cirrus SR22 veered off the runway and entered a cornfield after the pilot's seat slid backward, disconnecting the pilot from the rudder pedals.

What aircraft was involved and where did it happen?

The accident on 2009-12-20 involved a aircraft, registration PRNAT, at FORMIGA, MG, BR.

What was the probable cause of the accident?

The pilot's seat slid backward along its tracks during the takeoff roll due to insufficient engagement of the locking pins, causing the pilot to lose access to the rudder pedals and resulting in the loss of directional control.

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