The pilot-in-command, accompanied by the co-pilot, aircraft loader and 18 passengers, departed on a World Food Programme (WFP) flight from Marial Bai Aerodrome in Southern Sudan to Rumbek Aerodrome in Sudan at approximately 09:30Z. The intention was then to fly from Rumbek Aerodrome to Lokichoggio in Kenya. During the VFR flight to Rumbek Aerodrome, the crew experienced a north-easterly wind with extremely turbulent conditions. Prior to landing at Rumbek Aerodrome, the crew calculated the approach and landing indicated air speeds (IAS) to be 85 kts and 75 kts respectively. The crew then joined the circuit accordingly for landing on runway 01. Approximately 4 nm away from landing, the co-pilot warned the pilot-in-command of a whirlwind in the area, close to the threshold of runway 01. The whirlwind appeared to have dissipated and the pilot-in-command continued with the landing with full flaps. At approximately 100 ft above ground level and 100 m before the threshold of runway 01, the IAS suddenly decreased to 70 kts. The pilot-in-command said that he immediately selected full power in order to arrest the rate of descent as wind shear in Southern Sudan and especially at Rumbek at this time of the year was a common factor. The aircraft nevertheless continued to descend and the left-hand propeller and left-hand main landing gear collided with a tree approximately 20 m before the threshold of runway 01. The tree was approximately 6 ft high and on an embankment. The aircraft then struck a drainage ditch before the threshold, causing the left-hand main landing gear to collapse. The airplane bounced and landed on the runway. The co-pilot immediately retracted the flaps and the aircraft continued down the runway on the right-hand main landing gear, but as its speed decayed, the left-hand propeller impacted with the runway surface. The aircraft veered to the left off the runway and entered a drainage ditch parallel to the runway. Both left and right-hand main landing gear were torn out of their attachment points and the aircraft eventually came to rest on its lower fuselage section. The crew and passengers sustained no injuries and evacuated the aircraft safely through the emergency exits and rear main entry door. The aircraft was substantially damaged: both left and right-hand main landing gear were damaged; the left-hand outboard aileron was forced out of the outboard hinge point, and the lower fuselage frame and attachment stringers subsequently collapsed and were damaged. The aircraft was temporary repaired on site by replacing two main landing gear, tailwheel, two engines, two props, one aileron and some skin repair. It was flown back to South Africa on 17 April 2003.