I assisted with clearing airstrips for MAF in Tanzania several years ago.
Basically the target was 1000 metres long, reasonably flat, 20 metres wide and a further 10 metres or so either side clear of bushes & trees suitable for the wings of an aircraft (e.g. a high wing Cessna) to pass over.
Not really an answer to your question, but there you go.....!
[ 04 December 2001: Message edited by: topunicyclist ]