As mentioned several of the Nepal STOL ports where not long enough to meet the ICAO STOL requirements. This mainly due to the terrain which didn´t allow the construction of STOL PORTs according to the standard criteria at many places. It was simply impossible to build a long enough runway in Himalaya. The most known sample is Lukla, the gateway to Everest. That many of the STOL Ports where at a high altitude with thin air and a hot climate parts of the year added to the problems. This is due to the fact that flying in thin air demands higher speeds in take-offs and landings, while at the same time the engines produced less power. This was partly compensated by the construction of the Pratt and Whitney PT6 engines which was used on the Twin Otter Aircrafts. The PT6 engines which were «Flat Rated», i.e. they had more power at altitude than other engines. The downside of this was that the engine used more fuel at low altitudes. This was not a big issue in Nepal, where most of the flights were at relatively high altitudes.
We are soon going to add pictures and videos to our blog! 🙂