Microlight Crash in Mokopane Mountains Caused by Rotor Turbulence

Casualties unknown • Mokopane mountains 7,8 nm from Mokopane town, ZA

A Windlass Aquila microlight crashed into a mountain ridge in Limpopo, resulting in one fatality and one serious injury.

What happened

On 18 November 2017, a Windlass Aquilla microlight, registration ZU-CIU, was participating in a scenic flight through the Mokopane mountains in Limpopo Province. The flight, conducted under visual flight rules, involved the pilot and a passenger traveling from Potgietersrus Airport toward Microland airport.

While flying in formation with another aircraft, the crew of ZU-CIU was utilizing thermals to gain altitude, a technique that involved reducing engine power to idle. As the aircraft transitioned through a mountain valley and attempted a left turn toward the west, it encountered severe rotor turbulence on the lee side of the ridge. The sudden downward force caused the aircraft to lose altitude rapidly, resulting in a nose-down impact against the mountain edge at an elevation of approximately 5,655 feet. The pilot sustained fatal injuries, while the passenger suffered serious injuries.

The investigation

An investigation by the SACAA AIID examined the flight conditions, aircraft maintenance, and pilot experience. The investigation confirmed that the engine and propeller were fully operational and that the aircraft's maintenance records were current and compliant with regulations. Meteorological data indicated clear weather with light winds, but the investigation focused on the complex aerodynamic phenomena present near the terrain.

Investigators determined that the aircraft was flying with the engine at idle power to take advantage of rising air. When the aircraft turned into the lee side of the mountain, it was caught by unexpected downward air currents. Because the engine power was at idle, the pilot lacked the immediate thrust necessary to overcome the descending air and maintain altitude.

Findings

  • The aircraft encountered rotor turbulence which led to a rapid loss of height and subsequent impact.
  • The pilot was operating the aircraft with the engine power set to idle while maneuvering near terrain.
  • The pilot lacked sufficient experience in mountain flying and the specific use of thermals in such environments.
  • The aircraft's position on the lee side of the ridge made it vulnerable to the downward forces of the mountain waves.

Probable cause

The accident was caused by the aircraft encountering rotor turbulence that forced it into the mountainside, compounded by the pilot's lack of experience in mountainous terrain and the use of idle engine power during the maneuver.

Frequently asked questions

What happened in the 2017-11-18 Windlass Aquila accident near Mokopane mountains 7,8 nm from Mokopane town, ZA?

A Windlass Aquila microlight crashed into a mountain ridge in Limpopo, resulting in one fatality and one serious injury.

What aircraft was involved and where did it happen?

The accident on 2017-11-18 involved a Windlass Aquila, registration ZU-CIU, at Mokopane mountains 7,8 nm from Mokopane town, ZA.

What was the probable cause of the accident?

The accident was caused by the aircraft encountering rotor turbulence that forced it into the mountainside, compounded by the pilot's lack of experience in mountainous terrain and the use of idle engine power during the maneuver.

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