What happened
On 3/30/2018, a Robinson R44 helicopter, registration ZS-PYG, was conducting a domestic charter flight departing from Virginia Airport (FAVG) in KwaZulu-Natal. The flight, which included the pilot and three passengers, was intended to return to the same airport. During the final approach to runway 23, the aircraft was descending from 500 feet above ground level at a rate of 200 feet per minute.
As the helicopter slowed its forward speed, the pilot experienced a loss of transitional lift, causing the aircraft to descend more rapidly than anticipated. Although the pilot attempted to pull the collective to stop the sinking motion, the rate of descent could not be arrested. The helicopter struck the ground near the runway with significant force, producing a loud screeching noise. The impact resulted in substantial damage to the tail boom and main rotor blades, though there were no injuries to the four occupants.
The investigation
SACAA AIID investigators examined the aircraft's performance and the pilot's actions leading up to the impact. The investigation confirmed that the aircraft's weight and balance were within legal limits for takeoff. At the time of the incident, the helicopter was carrying 46.5 gallons of fuel and three passengers, with a total takeoff weight of 2342.8 lbs, well below the maximum allowable 3200 lbs.
Technical analysis of the engine performance revealed that the manifold pressure was at 23 inches. Given the ambient temperature of 25°C, this represented the maximum continuous power available. Investigators determined that because the engine was already operating at its maximum power limit, the pilot lacked the additional power necessary to counteract the increased rate of descent caused by the loss of transitional lift.
Findings
- The primary cause of the accident was an incorrect approach technique.
- The loss of transitional lift during the deceleration phase led to an unmanageable rate of descent.
- The pilot was unable to arrest the descent because the engine was already operating at its maximum continuous power capacity.
- The impact was severe enough to cause the main rotor blades to sever the tail boom.