Circumstances:
The pilot reported that the aircraft was taking off downhill from a one-way agricultural strip with a load of superphosphate. The strip consisted of 300 metres of gravel, followed by about 100 metres of pasture. A gully crossed beyond the strip end. The pilot reported that the wind in the loading area at the top of the strip was a very light quartering tailwind from the left. The aircraft became airborne at the end of the gravel strip, with the engine apparently delivering full power. Almost immediately the aircraft encountered sink, with the mainwheels touching momentarily on the pasture. At that stage, the pilot commenced dumping the load, but the aircraft failed to respond. Full dump was initiated. However, the aircraft stalled, dropping the right wing before striking the ground on the far side of the gully with the wing, which broke off. The aircraft then skidded through a fence in a semi-inverted attitude for about 70 metres before coming to rest upright. The pilot advised that the wind funnelling down the valley was gusting 12 to 15 knots from the left, considerably different to that in the loading area.
