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#11
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What this exercise really does is demonstrate how angle of attack is
decoupled from attitude. It's unfortunate that the concept of pitch control by reference to angle attack is only taught at a basic theoretical level in most gliding instruction - undoubtedly due to the lack of any angle of attack indicator on gliders! (unless you count the pitot mast -mounted yaw string on a 2-33). I really wish there was a simple, reliable and easy to read angle of attack (AOA) gauge available for gliders, optimized for efficient thermalling (no adjustment needed for water ballast or bank angle - unlike airspeed) and safe pattern speeds (instant response to wind gradient and shear; and again automatically adjusts for landing right off tow while still full of water). Then you could use this exercise to show how to drive the AOA way past the stalling AOA while still appearing to be in a level "flying" attitude. Kirk |
#12
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#13
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wrote in message oups.com... I really wish there was a simple, reliable and easy to read angle of attack (AOA) gauge available for gliders, optimized for efficient thermalling (no adjustment needed for water ballast or bank angle - unlike airspeed) and safe pattern speeds (instant response to wind gradient and shear; and again automatically adjusts for landing right off tow while still full of water). Then you could use this exercise to show how to drive the AOA way past the stalling AOA while still appearing to be in a level "flying" attitude. Kirk I agree that an AoA indicator would be very useful in general and in winch launch in particular. A VERY cheap AoA indicator can be made with two red yarns taped to the sides of the canopy as far forward and as low a possible yet where the pilot can still see them. You need two yarns to insure that the pitch angle is not affected by a yaw angle. Calibrate the yarns with a flight at best L/D, Min Sink and stall. Those are the only AoA you are interested in. The $99 Dynon AoA probe looks like it might work in gliders. It's just a pitot probe with a 45 degree angled flat face below the pitot opening with a pressure port in the middle of the flat face. Some clever electronics convert the pressure differential into an AoA display. If you have a flapped glider, the electronic smarts will need to know the flap position. If the electronics have the correct AoA, then the best flap setting for that AoA is also known and can be displayed too. Bill Daniels |
#14
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wrote in message oups.com... What this exercise really does is demonstrate how angle of attack is decoupled from attitude. It's unfortunate that the concept of pitch control by reference to angle attack is only taught at a basic theoretical level in most gliding instruction - undoubtedly due to the lack of any angle of attack indicator on gliders! (unless you count the pitot mast -mounted yaw string on a 2-33). I really wish there was a simple, reliable and easy to read angle of attack (AOA) gauge available for gliders, optimized for efficient thermalling (no adjustment needed for water ballast or bank angle - unlike airspeed) and safe pattern speeds (instant response to wind gradient and shear; and again automatically adjusts for landing right off tow while still full of water). Then you could use this exercise to show how to drive the AOA way past the stalling AOA while still appearing to be in a level "flying" attitude. Kirk Hey Kirk.....I thought that you had experimented with placing "yaw strings" on the sides of the canopy at one point....any input re how that went for a poor man's AOA? Casey |
#15
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Yeah, I tried a "yaw string" AoA setup, and while it did show AoA, it
was extremely sensitive to yaw, and wasn't really in the correct position to help a pilot while thermalling or during landing. Plus the range from "cruise" to "min sink" to "too slow" wasn't very big (on my LS6, using about 8 inch long "AoA strings") - less than 2 inches, if I remember right, and the ends are always moving making holding a particular AoA a bit problematical. Plus one of the strings (the upwind one, obviously) was always getting caught in the canopy... Heck, JJ, I figure that since the F-4 came equipped with both a real live mil-spec yaw string (there is actually a hole in front of the windscreen for the string to exit after being tied off inside the nose - and a black stripe painted in front of the canopy for reference) and a really nice visual and aural AoA system, we should have the same thing in a glider. An aural "fast - on speed - SLOW" AoA tone that would replace the audio vario when the gear is down would be nice... JJ, it was 3 to 8 units until the jet started to fly again - pointy end first. Otherwise, the F-4 departure bold face was (I think...) "STICK - FORWARD, AILERONS AND RUDDER - NEUTRAL, IF NOT RECOVERED MAINTAIN FULL FORWARD STICK AND DEPLOY DRAG CHUTE" And I think the the spin recovery bold face was: "STICK - MAINTAIN FULL FORWARD, AILERONS - FULL WITH SPIN (TURN NEEDLE), AIRCRAFT UNLOADED - AILERONS NEUTRAL" Departures were interesting, but spins were a bad thing! Off to fly! Kirk |
#16
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#18
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Dear Mr (or Mrs or Ms or Miss) Soarski,
Whoever you are, please remind me not to stand on or near any airfield where you are flying, as I don't want a glider falling on top of me. Feeding in full rudder after a rope or cable break almost guarantees a spin and once you are in one you will lose at least 150 ft per turn plus another 300ft to recover. I do hope you were not being serious! The correct recovery from a winch launch cable break is to lower the nose fairly rapidly to slightly below the normal approach attitude, allow the speed to build up to the correct approach speed for the day and then decide what to do, depending on your height and landing options ahead. It is usually safer to land ahead if you can. While you are waiting for the nose to come down it is also a good idea to pull the cable release twice to get rid of any remaining broken cable, so it can't get caught round any trees, power lines, etc. From aerotow you are usually in a more level attitude and usually have plenty of speed. If the rope breaks just lower the nose slightly and monitor your airspeed. If you are low you have to land more or less straight ahead. With a bit more height - say 200 ft or more, a 180 degree turn is possible, but must be flown accurately - not skidded round on the rudder. Regards Derek C (UK Instructor) 05:18 02 July 2005 'Soarski' wrote: I have never been in that predicament. Never seen a cable break or lost power at below 200 ft or the tow rope on aero tow. I do have 1000s of hours and acro time. If I would want to land downwind on the runway I was taking off I could be inclined to just kick in full rudder, and make the 180 Turn via a "Hammerhead" I think it is called a "Kehre" in German, or a "Turn? There would be mostly rudder work required, some back preasure on coming out of a dive following the wingover, which is really half a spin. Has anyone ever seen that done? Actually, come to think of it, I have, in an airshow, a long time ago in a clipped wing Cub. I will have to try at altitude, what will need more altitude to recover |
#19
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On 1 Jul 2005 22:00:34 -0700, "soarski" wrote:
If I would want to land downwind on the runway I was taking off I could be inclined to just kick in full rudder, and make the 180 Turn via a "Hammerhead" I think it is called a "Kehre" in German, or a "Turn? There would be mostly rudder work required, some back preasure on coming out of a dive following the wingover, which is really half a spin. Has anyone ever seen that done? Actually, come to think of it, I have, in an airshow, a long time ago in a clipped wing Cub. Jmmm... I never ever heard of such a maneuvre. The closer to the ground, the more important it is to keep the yaw string centered. Kicking in full rudder is regarded as censored. We simply fly a 180 degrees turn at the end of the runway. Pushing over forward very hard after cable break, you could get into a negative flight regime, possibly into an inverted spin? No. Not even if you puished the stick to the forward stop. Bye Andreas |
#20
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Hi Tom
Just because the gilder is at a 40 to 50 degree nose up attitude with respect to the ground does not mean it has the energy for a stall turn. There was a recent fatality in New Zealand where someone inadvertently tried this. Assume you were joking, but in case you were serious, please feel free to try it - the outcome would be merely predictable, if a little sad. Since I live nearly 9 000 miles away I am confident you will not impact on my personal safety... Bruce soarski wrote: I have never been in that predicament. Never seen a cable break or lost power at below 200 ft or the tow rope on aero tow. I do have 1000s of hours and acro time. SNIP MAINTAIN FULL FORWARD STICK AND DEPLOY DRAG CHUTE' And I think the the spin recovery bold face was: 'STICK - MAINTAIN FULL FORWARD, AILERONS - FULL WITH SPIN (TURN NEEDLE), AIRCRAFT UNLOADED - AILERONS NEUTRAL' Departures were interesting, but spins were a bad thing! Off to fly! Kirk Differs from the SEPECAT Jaguar where the action is much simpler. SEIZE BLACK AND YELLOW HANDLE, PULL HARD :-) -- Bruce Greeff Std Cirrus #57 I'm no-T at the address above. |
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