Unexplained Engine Shutdown Leads to Forced Landing of Cessna Caravan

Casualties unknown • 3 miles South of Hoedspruit Aerodrome in the Limpopo Province, ZA

A domestic charter flight involving nine passengers required an emergency landing near Hoedspruit after an unidentified engine shutdown and reports of a burning smell.

What happened

On 11 July 2006, a Cessna C208 Caravan, registration ZS-ORR, was conducting a domestic charter flight from Ngala Lodge to Johannesburg International Aerodrome. The aircraft was carrying a crew of two and nine passengers. During the flight, the crew reported a burning smell within the cockpit. At the same time, a large-scale fire was visible in the nearby Blyde River Canyon, leading the crew to suspect the odor might be originating from the ground rather than the aircraft.

Shortly after noticing the smell, the crew heard a grinding noise lasting approximately four seconds. In response to the perceived emergency, the pilot began deactivating electrical systems, leaving only the radios active for communication. During this process, the engine was inadvertently shut down. The pilot opted not to attempt a restart due to concerns regarding potential internal engine damage and fire risks. After feathering the propeller to extend the glide, the crew identified an uneven airstrip approximately four miles south of Hoedspruit and executed a successful forced landing. There were no injuries to the passengers or crew, and the aircraft sustained no damage.

The investigation

SACAA AIID investigators conducted an extensive examination of the engine and the aircraft's electrical systems. A detailed teardown of the Pratt & Whitney PT6A-114A engine was performed at a maintenance facility. The inspection included borescope examinations of the compressor and turbine modules, as well as an analysis of the oil and fuel filters. All internal components, including the power section, turbine blades, and accessory gearbox, were found to be in satisfactory condition. Subsequent bench testing of the engine confirmed it was operating normally with no unusual vibrations or leaks.

Further investigation into the aircraft's electrical systems revealed that an avionics cooling fan located behind the instrument panel had been producing excessive noise due to dry motor bushings. While this could account for the grinding noise reported by the crew, no evidence of electrical burning or chafing was found.

Findings

  • The primary cause of the engine failure could not be definitively established.
  • It is possible that the engine was inadvertently shut down while the crew was deactivating electrical components.
  • The reported burning smell was likely caused by the massive ground fire in the Blyde River Canyon rather than an aircraft malfunction.
  • The grinding noise heard by the crew was likely attributed to a malfunctioning avionics cooling fan.

Probable cause

The exact cause of the engine shutdown remains undetermined, though it is suspected that the engine was accidentally deactivated during the crew's attempt to switch off electrical systems in response to a perceived fire.

Frequently asked questions

What happened in the 2006-07-11 C208 (Caravan) accident near 3 miles South of Hoedspruit Aerodrome in the Limpopo Province, ZA?

A domestic charter flight involving nine passengers required an emergency landing near Hoedspruit after an unidentified engine shutdown and reports of a burning smell.

What aircraft was involved and where did it happen?

The accident on 2006-07-11 involved a C208 (Caravan), registration ZS-ORR, at 3 miles South of Hoedspruit Aerodrome in the Limpopo Province, ZA.

What was the probable cause of the accident?

The exact cause of the engine shutdown remains undetermined, though it is suspected that the engine was accidentally deactivated during the crew's attempt to switch off electrical systems in response to a perceived fire.

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