What happened
On April 17, 2009, an EMB 721C, registration PT-EOO, was performing a flight from Estância Santa Rita (SJCY) to the Hotel Baiazinha (SWWF) airfield in Cáceres, Mato Grosso. The flight, carrying the pilot and three passengers, proceeded normally until the landing phase on the grass runway of the private airfield.
Upon touchdown on runway 18, the right landing gear retracted. This caused the aircraft to lose directional control and veer toward the right side of the runway. As the aircraft entered a 180-degree ground loop, the left main landing gear and the nose gear also retracted. The impact of the left main gear caused a puncture near the root of the left wing. The aircraft sustained further light damage to the propeller, ailerons, and flaps, eventually coming to a stop approximately 100 meters from the initial touchdown point.
All four occupants (the pilot and three passengers) were uninjured.
The investigation
CENIPA's investigation examined the sequence of events and the mechanical behavior of the landing gear during the ground excursion. Investigators considered two primary hypotheses regarding the cause of the gear retraction. The first hypothesis suggested a hard landing may have occurred; a heavy impact, particularly with the right wing low, could have provided enough force to rupture the right gear's locking mechanism. Such an impact could also explain the subsequent failure of the left gear and nose gear during the ground loop.
An alternative hypothesis considered by investigators was that the landing gear assembly might have been unlocked prior to touchdown. In this scenario, the retraction of the right gear would have created an asymmetrical configuration, causing the left wing to rise and subjecting the left gear to extreme forces, leading to the wing puncture.
Findings
- The pilot was properly licensed and experienced in the aircraft type.
- The aircraft was airworthy, with all maintenance records up to date.
- The pilot had never previously landed at the Hotel Baiazinha grass runway.
- The hard landing or an unlocked gear mechanism served as the primary mechanism for the gear retraction and subsequent loss of control.