Engine failure leads to aircraft capsize during emergency landing in Benavente

Casualties unknown • Benavente, PT

A Sky Ranger ultralight aircraft experienced an unexpected engine failure during climb-out, resulting in a forced landing and subsequent capsize after striking a tree stump.

What happened

On January 30, 2005, at approximately 15:15 UTC, a Sky Ranger V.FUN ultralight aircraft, registration CS-UKW, was performing a recreational flight from Benavente aerodrome. Shortly after takeoff from runway 10, while climbing through approximately 500 feet, the engine stopped unexpectedly and the propeller ceased rotation.

Recognizing the emergency and being at a low altitude, the pilot identified a nearby field that appeared suitable for an emergency landing. During the descent, the pilot attempted to maneuver away from obstacles; however, as the aircraft neared the ground, the pilot discovered several tree stumps protruding from the surface, left over from recent clearing operations. While attempting to avoid these obstacles, the aircraft struck a eucalyptus stump, causing the nose gear to collapse and the aircraft to capende and come to rest in an inverted position.

The investigation

The GPIAAF investigation examined the engine, fuel, and the landing site. The engine was manually rotated after the accident without any mechanical obstruction being detected, and no issues were found with the fuel supply or ignition system. The fuel tanks were nearly full with a standard 50:1 gasoline/oil mixture.

Investigators noted that the engine had recently undergone maintenance. While there was an unverified suggestion from a maintenance technician that a richer oil mixture (50:2) should have been used temporarily following the overhaul, no such requirement was found in the Rotax manufacturer manuals. The investigation also noted that the landing site had been recently burned, and the subsequent removal of trees had left stumps that were not clearly visible from the air during the pilot's initial decision-making process.

Findings

  • The pilot and passenger were uninjured due to the low speed of the impact and the use of seatbelts.
  • The aircraft sustained significant damage, including a broken nose gear, propeller, and engine cowlings, as well as damage to the wings and fuselage.
  • The unexpected engine failure during the initial climb was the primary cause of the accident.
  • The presence of tree stumps, which were not perceptible during the approach, forced the pilot into a collision that led to the aircraft's capsize.

Probable cause

The primary cause of the accident was the sudden and unexpected failure of the engine during the initial climb following takeoff. This forced the pilot to perform an emergency landing on unprepared terrain, where the aircraft subsequently struck a tree stump that was not visible from the air.

Frequently asked questions

What happened in the 2005-01-30 Sky Ranger V.Fun accident near Benavente, PT?

A Sky Ranger ultralight aircraft experienced an unexpected engine failure during climb-out, resulting in a forced landing and subsequent capsize after striking a tree stump.

What aircraft was involved and where did it happen?

The accident on 2005-01-30 involved a Sky Ranger V.Fun, registration CS-UKW, at Benavente, PT.

What was the probable cause of the accident?

The primary cause of the accident was the sudden and unexpected failure of the engine during the initial climb following takeoff. This forced the pilot to perform an emergency landing on unprepared terrain, where the aircraft subsequently struck a tree stump that was not visible from the air.

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