Funny this came up now. I have just been going over deHavilland data for STOL performance in the Twin Otter. It turns out that STOL is not a universally accepted term and only applicable in certain jurisdictions. STOL supplement is omitted in two of the three certification versions of the Twin Otter. STOL operations where only granted to a handful of 121 operators, the most notable was downtown London with the Dash 7.
In the Twin Otter, again. Its operation in the STOL regime is quite different from operating in a more traditional manner. In the classic STOL approach, the nose is so high that your actual intended point of landing is obscured by the long nose version. So it is pick the spot, aim about 100 yards in front when your energy and wind compensation point you figured in your head comes about, and haul back on the elevator and hold it at a very nose high attitude and you will float to the point and gently touch the ground (!). Brakes and reverse when the nose is on the ground. Even more important in the DHC-5 Buffalo, it had nose wheel brakes as well as the mains (in addition to ground actuated spoilers and other wizardry on the wing). I've brought a fully loaded Buff down in 365' in Southern Sudan in Max hot, deep mud conditions.
One of the classic mistakes in STOL, in the deHavilland nose draggers, is failure to keep that nose high attitude. You tend to land on the nosewheel in a "wheelbarrow" mode, a dangerous and rather uncontrollable configuration. Then again, most of the times you do this, you will most likely snap the nose wheel off above the fork. It happens often enough that deHavilland (now Viking) offers a station 60 repair kit.
I've got to offer a complete STOL syllabus for the DHC-6 for one of our government clients in the next couple of weeks. So I have been dusting off all the old material.
