Zurück zur Übersicht Allgemein, Deutsch, pll_6724b17cd4d1a The High-Speed Spiral Dive is dangerous. That's why it's less formally called the Graveyard Spiral. Pilots are taught to avoid it -- not usually difficult, although people get it wrong quite often. But can we do anything else about it? Read on. In March 1974 I was flying a Schweizer 1-34 in a SW wave over San Francisco Bay. It was cloudy, but I was in clear air at 10,000’. Then more cloud approached: it was time to go home. I duly set full airbrakes, and entered a 40°-50° spiral. Then suddenly I realised I was doing nothing. The trusty 1-34 was flying itself. This was a puzzle, because we expect aircraft to be unstable. I intended to look into this, but never got round to it. Then Einar Enevoldson (of The Perlan Project and much else) ran a letter in Soaring for September 2018 on the topic. This re-awakened my interest. My method has been twofold. First, I try as many aircraft types as I can, to check that they really do spiral stably — the „Benign Spiral“, as many call it. Secondly, I’m trying to understand the aerodynamics, to see where this stability comes from. This thinking led me (with others) to try out over a dozen aircraft – real and simulated — during the last few years. Among these there are two doubtful cases: an Arcus M self-launching motor-glider, which was stable only if the stick was held fixed; and a Boeing 737 Simulator, which refused to spiral at all and therefore could not be tested. All other types, ranging up to a five-tonne An-2, spiralled stably. Vertical speeds were comparable to parachute descent speeds (about 1400 fpm) or less. Why is all this interesting? It could be very useful to pilots caught above an overcast. It would be easy to set up a Benign Spiral, and then descend hands-off through the cloud. If there is enough clear air below, it should not be difficult to recover the aircraft as soon as it emerges from the cloud. And even if there isn’t, the occupants are in a much better position spiralling comfortably down than they would be in a fully developed Graveyard Spiral. Beyond that, it has been suggested that General Aviation pilots might teach it to those who fly with them, but who have little piloting experience themselves. There have been cases in which the only qualified pilot had a medical emergency, leaving other occupants in an awful position. I would encourage any pilot to try it. What I usually do is open the flaps/airbrakes fully, set the power (if any) to idle, trim (I think) for cruise or somewhat slower, and turn it loose. It should start out into a spiral, but then stabilise in a fairly steep bank; if necessary, I normally stop at about 60°, where aerobatic flight starts. But please be aware that this is not in the POH. In effect you’re test flying; this is a Work in Progress. Ultimately, I want to get it into everyone’s bag of tricks, in Soaring and General Aviation. I’m trying to build up as large a database of types as I can, and answer a big question: Are there any bugs in all this? Then I want to generate publicity for it: If it’s useful, it’s very wrong that only some pilots know it. Report: John Crawford, Würenlingen AG