Ultralight Aircraft Crashes at Lagoa de Óbidos After Stall During Turn

Casualties unknown • Óbidos, PT

A SkyRanger ultralight aircraft crashed at Lagoa de Óbidos, resulting in two fatalities, after the pilot lost control during a turn following a takeoff with improper flap settings.

What happened

On August 29, 2010, a privately owned SkyRanger ultralight, bearing the registration CS-UAE, departed from the Lagoa de Óbidos airstrip at approximately 18:20 UTC for a local test flight. The aircraft was occupied by the pilot and one passenger.

Witnesses observed the aircraft take off with a low ground speed and an unusually high nose-up attitude. The aircraft struggled to climb, reaching an altitude of only about 30 meters AGL. Shortly after passing the end of the runway, the aircraft banked to the right and then abruptly rolled to the left, disappearing behind nearby vegetation. Spectators discovered the wreckage at the end of the runway, where the aircraft had impacted the ground in a vertical nose-down position. Both occupants sustained fatal injuries.

The investigation

The GPIAAF investigation revealed that the aircraft had undergone several unauthorized and technically unsound modifications. The engine mount had been altered, which led to an imprecise engine position and affected the aircraft's alignment and torque compensation. Additionally, the propeller had been replaced with a two-blade version that was not aerodynamically optimized for the installed reduction unit.

The investigation also found that the aircraft was not properly registered in the National Aeronautical Registry (RAN), as it was using a registration belonging to a different aircraft. Furthermore, the aircraft lacked essential documentation, including maintenance logs, flight logs, and insurance.

Findings

  • The aircraft was operating outside of its approved weight and balance limits, with a center of gravity (CG) positioned too far aft.
  • The pilot performed the takeoff using full flaps, which significantly increased drag and contributed to the low climb performance.
  • The pilot was unfamiliar with this specific aircraft model and had not received proper transition training.
  • The combination of high drag from the flaps, an aft CG, and insufficient engine power at a near-stall speed created an unrecoverable nose-up attitude.
  • While attempting to return to the runway, the pilot initiated a turn, which increased the stall speed and caused the aircraft to enter a spiral dive.

Probable cause

The probable cause of the accident was the loss of control resulting from an aerodynamic stall during a turn, exacerbated by improper flap configuration and an improper weight and balance.

Frequently asked questions

What happened in the 2010-08-29 SKY RANGER accident near Óbidos, PT?

A SkyRanger ultralight aircraft crashed at Lagoa de Óbidos, resulting in two fatalities, after the pilot lost control during a turn following a takeoff with improper flap settings.

What aircraft was involved and where did it happen?

The accident on 2010-08-29 involved a SKY RANGER, registration CS-UAE, at Óbidos, PT.

What was the probable cause of the accident?

The probable cause of the accident was the loss of control resulting from an aerodynamic stall during a turn, exacerbated by improper flap configuration and an improper weight and balance.

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