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#11
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would an AOA indicator be helpful in a glider?
On Jun 4, 10:25*am, "
wrote: This has all been hashed out before (some interesting threads, those!) but here is my 2 cents: AOA can be derived from pressure differential, best way would be to have sensor ports in both wings (enough to be redundant and avoid yaw problems. *Nose might also work, but it's the wing you care about, really. AOA is really only needed at high angles: Stall, Min Sink, L/D max, recommended approach speed. *Since these speeds vary with weight and bank angle, AOA is better than airspeed. *So to keep it simple, with gear up show min sink (for thermalling) tied to flap setting, and maybe have an index at L/D max (not really used that often). *Gear down, show desired approach speed, with warning approaching stall. I think the military chevrons and doughnut indicator would work just fine: *On-speed (desired AOA) when center g(green) circle is lit. Slightly slow when circle and lower up (red) chevron are both lit. Slow when only red up chevron is lit, slightly fast when circle and upper down (yellow) chevron is lit, and fast when only down chevron is lit. Electronics would need input from gear and flaps, if present, of course. Easy to see if on top of panel. Kirk I think Kirk's idea would work but it is generally accepted that an accurate AoA probe should be as far forward of the wing and its near- field flow effects as possible. I don't think top and bottom nose pressure ports would be sensitive to yaw since they should both be affected the same and cancel out cross flow signals. A probe in the fuselage would have the advantage that there wouldn't be anything to connect when rigging. Clearly, there's a need for some experimentation. |
#12
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would an AOA indicator be helpful in a glider?
On Jun 4, 9:25*am, "
wrote: This has all been hashed out before (some interesting threads, those!) but here is my 2 cents: AOA can be derived from pressure differential, best way would be to have sensor ports in both wings (enough to be redundant and avoid yaw problems. *Nose might also work, but it's the wing you care about, really. AOA is really only needed at high angles: Stall, Min Sink, L/D max, recommended approach speed. *Since these speeds vary with weight and bank angle, AOA is better than airspeed. *So to keep it simple, with gear up show min sink (for thermalling) tied to flap setting, and maybe have an index at L/D max (not really used that often). *Gear down, show desired approach speed, with warning approaching stall. I think the military chevrons and doughnut indicator would work just fine: *On-speed (desired AOA) when center g(green) circle is lit. Slightly slow when circle and lower up (red) chevron are both lit. Slow when only red up chevron is lit, slightly fast when circle and upper down (yellow) chevron is lit, and fast when only down chevron is lit. Electronics would need input from gear and flaps, if present, of course. Easy to see if on top of panel. Kirk I think the tricky part will be calibration. The device needs to be set up to a fraction of a degree so I suspect you'll have to do some fancy measuring of a series of flight tests. You'll also need some data from the factory about lift coefficient versus alpha. 9B |
#13
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would an AOA indicator be helpful in a glider?
On Jun 4, 11:13*am, Andy wrote:
On Jun 4, 9:25*am, " wrote: This has all been hashed out before (some interesting threads, those!) but here is my 2 cents: AOA can be derived from pressure differential, best way would be to have sensor ports in both wings (enough to be redundant and avoid yaw problems. *Nose might also work, but it's the wing you care about, really. AOA is really only needed at high angles: Stall, Min Sink, L/D max, recommended approach speed. *Since these speeds vary with weight and bank angle, AOA is better than airspeed. *So to keep it simple, with gear up show min sink (for thermalling) tied to flap setting, and maybe have an index at L/D max (not really used that often). *Gear down, show desired approach speed, with warning approaching stall. I think the military chevrons and doughnut indicator would work just fine: *On-speed (desired AOA) when center g(green) circle is lit. Slightly slow when circle and lower up (red) chevron are both lit. Slow when only red up chevron is lit, slightly fast when circle and upper down (yellow) chevron is lit, and fast when only down chevron is lit. Electronics would need input from gear and flaps, if present, of course. Easy to see if on top of panel. Kirk I think the tricky part will be calibration. *The device needs to be set up to a fraction of a degree so I suspect you'll have to do some fancy measuring of a series of flight tests. You'll also need some data from the factory about lift coefficient versus alpha. 9B Actually, calibration is the easy part. Just load the glider to maximum gross weight, fly it at the Calibrated Air Speed (From tables in the POH) for best L/D, for minimum sink and for stall and note the readings for each. You probably don't care about actual AoA is in degrees. If you want a fancy color LED display that changes color/shape precisely at each, the electronics package should have adjustments built in. Alternatively, choose a 10 element LED bargraph display where each element can be red, yellow or green depending on which pins are used. Once the position of each AoA of interest is known, switch pins to produce the color desired. You can also wire in a warning horn to sound when the red stall LED lights up and the gear is down. |
#14
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would an AOA indicator be helpful in a glider?
On Jun 4, 11:22*am, bildan wrote:
On Jun 4, 11:13*am, Andy wrote: On Jun 4, 9:25*am, " wrote: This has all been hashed out before (some interesting threads, those!) but here is my 2 cents: AOA can be derived from pressure differential, best way would be to have sensor ports in both wings (enough to be redundant and avoid yaw problems. *Nose might also work, but it's the wing you care about, really. AOA is really only needed at high angles: Stall, Min Sink, L/D max, recommended approach speed. *Since these speeds vary with weight and bank angle, AOA is better than airspeed. *So to keep it simple, with gear up show min sink (for thermalling) tied to flap setting, and maybe have an index at L/D max (not really used that often). *Gear down, show desired approach speed, with warning approaching stall. I think the military chevrons and doughnut indicator would work just fine: *On-speed (desired AOA) when center g(green) circle is lit. Slightly slow when circle and lower up (red) chevron are both lit. Slow when only red up chevron is lit, slightly fast when circle and upper down (yellow) chevron is lit, and fast when only down chevron is lit. Electronics would need input from gear and flaps, if present, of course. Easy to see if on top of panel. Kirk I think the tricky part will be calibration. *The device needs to be set up to a fraction of a degree so I suspect you'll have to do some fancy measuring of a series of flight tests. You'll also need some data from the factory about lift coefficient versus alpha. 9B Actually, calibration is the easy part. *Just load the glider to maximum gross weight, fly it at the Calibrated Air Speed (From tables in the POH) for best L/D, for minimum sink and for stall and note the readings for each. *You probably don't care about actual AoA is in degrees. If you want a fancy color LED display that changes color/shape precisely at each, the electronics package should have adjustments built in. Alternatively, *choose a 10 element LED bargraph display where each element can be red, yellow or green depending on which pins are used. Once the position of each AoA of interest is known, switch pins to produce the color desired. *You can also wire in a warning horn to sound when the red stall LED lights up and the gear is down.- Hide quoted text - - Show quoted text - I think you all miss the point that a panel mounted AoA indicator is not the right way to get this critical information. I don't want some boob looking in the cockpit while thermaling!! That's why we create audio variometers! I have been considering this for some time and unless we want two channels of audio in the cockpit, or we have a very good heads up display, the AoA info is wasted when you need it most. Mike |
#15
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would an AOA indicator be helpful in a glider?
I think the GLIDER is a pretty good angle of attack indicator.
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#16
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would an AOA indicator be helpful in a glider?
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#17
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would an AOA indicator be helpful in a glider?
On Jun 4, 8:32*pm, Mike Bamberg wrote:
On Jun 4, 11:22*am, bildan wrote: On Jun 4, 11:13*am, Andy wrote: On Jun 4, 9:25*am, " wrote: This has all been hashed out before (some interesting threads, those!) but here is my 2 cents: AOA can be derived from pressure differential, best way would be to have sensor ports in both wings (enough to be redundant and avoid yaw problems. *Nose might also work, but it's the wing you care about, really. AOA is really only needed at high angles: Stall, Min Sink, L/D max, recommended approach speed. *Since these speeds vary with weight and bank angle, AOA is better than airspeed. *So to keep it simple, with gear up show min sink (for thermalling) tied to flap setting, and maybe have an index at L/D max (not really used that often). *Gear down, show desired approach speed, with warning approaching stall. I think the military chevrons and doughnut indicator would work just fine: *On-speed (desired AOA) when center g(green) circle is lit. Slightly slow when circle and lower up (red) chevron are both lit. Slow when only red up chevron is lit, slightly fast when circle and upper down (yellow) chevron is lit, and fast when only down chevron is lit. Electronics would need input from gear and flaps, if present, of course. Easy to see if on top of panel. Kirk I think the tricky part will be calibration. *The device needs to be set up to a fraction of a degree so I suspect you'll have to do some fancy measuring of a series of flight tests. You'll also need some data from the factory about lift coefficient versus alpha. 9B Actually, calibration is the easy part. *Just load the glider to maximum gross weight, fly it at the Calibrated Air Speed (From tables in the POH) for best L/D, for minimum sink and for stall and note the readings for each. *You probably don't care about actual AoA is in degrees. If you want a fancy color LED display that changes color/shape precisely at each, the electronics package should have adjustments built in. Alternatively, *choose a 10 element LED bargraph display where each element can be red, yellow or green depending on which pins are used. Once the position of each AoA of interest is known, switch pins to produce the color desired. *You can also wire in a warning horn to sound when the red stall LED lights up and the gear is down.- Hide quoted text - - Show quoted text - I think you all miss the point that a panel mounted AoA indicator is not the right way to get this critical information. *I don't want some boob looking in the cockpit while thermaling!! *That's why we create audio variometers! * I have been considering this for some time and unless we want two channels of audio in the cockpit, or we have a very good heads up display, the AoA info is wasted when you need it most. Mike You seem to assume a pilot would be fixated on the AoA display. That's not how it's used. Find the airspeed that corresponds to the desired AoA and hold that airspeed. The AoA won't change if you don't change the airspeed or bank angle. You should be able to hold airspeed, and by extension the AoA by the sound of the glider and control forces just like you do now - except, with an AoA indicator, you'd know you were flying exactly the right airspeed for minimum sink. wby0n: "I think the GLIDER is a pretty good angle of attack indicator." This sounds suspiciously like someone is confusing pitch attitude with AoA. |
#18
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would an AOA indicator be helpful in a glider?
On Jun 4, 7:32*pm, Mike Bamberg wrote:
I think you all miss the point that a panel mounted AoA indicator is not the right way to get this critical information. *I don't want some boob looking in the cockpit while thermaling!! *That's why we create audio variometers! * I have been considering this for some time and unless we want two channels of audio in the cockpit, or we have a very good heads up display, the AoA info is wasted when you need it most. Mike An AOA indicator, like the airspeed indicator or even the yaw string, can easily be used by just glancing at it. Once you have established the correct AOA, then it's easy to maintain by looking at your glider's nose position vs the horizon - just as you do now, with that inaccurate airspeed indicator. The whole point is that you can quickly set the correct AOA for the bank angle and wingloading you are flying at (without having to guess what airspeed to use based on some chart or graph in the flight manual - quick, what is your gliders min sink speed with 20 gallons of water in a 37 degree bank?). What would be real nice - and might save a life in the pattern - would be to have aural Fast/Onspeed/Slow tones that would replace the vario tones when the spoilers an/or landing flaps are extended (assuming that once those are out, you are no longer really concerned with climbing!). Then you could focus all your attention outside the cockpit on your approach, without having to glance into the cockpit to check airspeed. That's how we used to land F-4s, and it was a really comfortable way to fly a visual approach. What is amusing is that pilots who have never had the opportunity to fly an AOA-indicator equipped aircraft seem to be reluctant to accept it's advantages and cling to their old ways, while pilots who have used AOA gauges love them. Kirk 66 |
#19
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would an AOA indicator be helpful in a glider?
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