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#1
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I have been watching this thread for several days,
we are not going to get practical AoA displays for gliders in the near future so how is the best way to get it right as often as possible? We have the ASI, Attitude and Feel and I guess that we all use some combination of all 3 to fly efficiently, so what is efficient? Is it Best L/D or Min Sink or in between or in a flapped glider the same AoA with a different flap setting? For circuit and landing it cannot be Min Sink that is much too close to stall speed so circuit AoA would have to be different to thermaling AoA at the same flap setting. Any comments Dave |
#2
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David Smith wrote:
I have been watching this thread for several days, we are not going to get practical AoA displays for gliders in the near future so how is the best way to get it right as often as possible? We have the ASI, Attitude and Feel and I guess that we all use some combination of all 3 to fly efficiently, so what is efficient? Is it Best L/D or Min Sink or in between or in a flapped glider the same AoA with a different flap setting? Depends what you're doing. - min.sink is best for climbing in weak lift, not so important in strong lift, and terrible if you're trying to cover ground. - best l/d is really only useful if you're stretching glide in neutral or very weak conditions. If you're flying between thermals in conditions when you're using a non-zero MC setting then best l/d is too slow. - flaps don't change the min.sink and best L/D speeds. Only ballast does that. At least, that's true for an ASW-20. You memorize the recommended speed ranges for different flap settings and work to those, remembering that the flap setting also affects Vma and Vne. For circuit and landing it cannot be Min Sink that is much too close to stall speed. Efficiency is unimportant at this stage unless you've screwed up and are too low. For starters, the wheel should be down and that destroys glide efficiency. If you can't easily fly a planned circuit from high key and use half brake for most of finals then you've misread the conditions and/or forgotten how to plan a circuit. For a normal circuit I'd say not slower than best glide after high key and not below 50 kts + 1/2 wind speed on base and finals. -- martin@ | Martin Gregorie gregorie. | Essex, UK org | |
#3
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Hi David,
As one lurker to another then.. Why won't we get practical AoA displays for gliders? People are thinking about it. Although, I see in the current Sailplane & Gliding, ( pp20-21, the "Idaflieg summer meeting") pics of an AoA probe that is nearly a meter long duct-taped to the nose of a twin Astir! OK, maybe that isn't practical. I'm also not excited about the flightsafety AoA price or the installation - I understand it requires cutting a hole in the fuse. David Smith wrote: .... so what is efficient? Is it Best L/D or Min Sink or in between or in a flapped glider the same AoA with a different flap setting? Optimal speed ( best L/D or whatever ) depends on what you want to do, cruise, climb.. Independent of that best speed theory, the polars for a flapped glider at various settings should be in the POH. So for a given speed, you could see what flap setting would give you the best L/D or least sink speed ( depending on what you want to do ). I have also seen drag rake suction probes on flapped gliders, on the trailing edge. These were supposed to be indicate on a meter the "amount of drag", and you set the flaps to minimize this. Does anyone have any positive or negative experience with these devices, or a source? --Sarah |
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