Robinson R-44 tail boom separation during engine test at Mkuze

Casualties unknown • Taxiway Mkuze Aerodrome, ZA

A private Robinson R-44 helicopter experienced a severe accident at Mkuze aerodrome when it became airborne during a low-RPM warning system check.

What happened

On 11 May 2001, a private Robinson R-44, registration ZS-RLT, was conducting a flight from FAGM to Mkuze Falls Game Lodge. The flight, which included the pilot and two passengers, included a scheduled stop at Mkuze aerodrome for refueling.

After completing refueling operations at approximately 1500 Z, the pilot began the engine start-up sequence while positioned on the taxiway near runway 17/35. As part of the standard start-up checklist, the pilot performed a test of the low-RPM warning system. This procedure involves slightly raising the collective lever while simultaneously reducing throttle to verify the warning mechanism is operational. During this specific maneuver, the aircraft unexpectedly lifted off the ground and began a leftward rotation. In an attempt to maintain a hover rather than descending, the pilot increased the collective input further. This caused the tail boom to strike the ground, resulting in the main rotor blades severing a portion of the boom. The aircraft eventually came to rest on its right side.

The investigation

Investigators examined the sequence of events surrounding the start-up checklist execution at Mkuze aerodrome. The inquiry focused on the interaction between the pilot's control inputs and the engine's throttle settings during the low-RPM system verification. The investigation confirmed that there were no injuries to the three occupants or any bystanders, despite the significant structural damage sustained by the aircraft.

Probable cause

The accident was caused by the helicopter becoming unintentionally airborne during a low-RPM warning system test because the pilot raised the collective lever without sufficiently reducing the throttle.

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Frequently asked questions

What happened in the 2001-05-11 Robinson R-44 accident near Taxiway Mkuze Aerodrome, ZA?

A private Robinson R-44 helicopter experienced a severe accident at Mkuze aerodrome when it became airborne during a low-RPM warning system check.

What aircraft was involved and where did it happen?

The accident on 2001-05-11 involved a Robinson R-44, registration ZS-RLT, at Taxiway Mkuze Aerodrome, ZA.

What was the probable cause of the accident?

The accident was caused by the helicopter becoming unintentionally airborne during a low-RPM warning system test because the pilot raised the collective lever without sufficiently reducing the throttle.

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