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#61
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#62
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At 15:06 02 January 2011, n7ly wrote:
.. =A0'Actually the only totally reliable sysmptom of being stalled is that the elevator will no longer raise the nose.' HUH? =A0 Many cases possible where we could have full elevator and not be stalled. =A0(I demonstrate this is 2-33 and grob 103 and ask-21. All you need is heavy pilot (forward CG) and gentle stick back to the stop. =A0Glider will mush, but not stall. =A0Elevator will not raise the nose........wing does not have angle to stall. .. whoa - depends on who's defining "stall". The FAA definition is indeed that when the aircraft does not respond in the direction of the control input that it's done. When you can no longer move the elevator up, you're done. Nose doesn't respond in direction of aft stick deflection, you're stalled. I don't remember exactly the way they word it, but the result is that touch the elevator limit, that's it. Slow entry rates result in higher stall speeds. Forward cg's give higher stall speeds. Trim settings (on some configs) affect stall speeds. Weight, etc., etc. The scene that seems the most insidious is the slow entry rate. They sneak up on you, kind of like a slow tow. Not necessarily - have the CG too far forward, and you'll run out of elevator before you stall. Admittedly that is still a stall according to FAR23/25 definitions "a stall is produced, as shown by either: (1) An uncontrollable downward pitching motion of the airplane; (2) A downward pitching motion of the airplane that results from the activation of a stall avoidance device (for example, stick pusher); or (3) The control reaching the stop." |
#63
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At 15:06 02 January 2011, n7ly wrote:
.. =A0'Actually the only totally reliable sysmptom of being stalled is that the elevator will no longer raise the nose.' HUH? =A0 Many cases possible where we could have full elevator and not be stalled. =A0(I demonstrate this is 2-33 and grob 103 and ask-21. All you need is heavy pilot (forward CG) and gentle stick back to the stop. =A0Glider will mush, but not stall. =A0Elevator will not raise the nose........wing does not have angle to stall. .. whoa - depends on who's defining "stall". The FAA definition is indeed that when the aircraft does not respond in the direction of the control input that it's done. When you can no longer move the elevator up, you're done. Nose doesn't respond in direction of aft stick deflection, you're stalled. I don't remember exactly the way they word it, but the result is that touch the elevator limit, that's it. Slow entry rates result in higher stall speeds. Forward cg's give higher stall speeds. Trim settings (on some configs) affect stall speeds. Weight, etc., etc. The scene that seems the most insidious is the slow entry rate. They sneak up on you, kind of like a slow tow. Not necessarily - have the CG too far forward, and you'll run out of elevator before you stall. Admittedly that is still a stall according to FAR23/25 definitions "a stall is produced, as shown by either: (1) An uncontrollable downward pitching motion of the airplane; (2) A downward pitching motion of the airplane that results from the activation of a stall avoidance device (for example, stick pusher); or (3) The control reaching the stop." |
#64
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On Jan 2, 1:20*pm, "
wrote: *'Actually the only totally reliable sysmptom of being stalled is that the elevator will no longer raise the nose.' HUH? * Many cases possible where we could have full elevator and not be stalled. *(I demonstrate this is 2-33 and grob 103 and ask-21. All you need is heavy pilot (forward CG) and gentle stick back to the stop. *Glider will mush, but not stall. *Elevator will not raise the nose........wing does not have angle to stall. On tow the only additional "weight component" would be a downward component to the tow rope (thrust). *Since the tension on the tow rope is fairly low........it should *not have a big effect, but there is some effect. But yeah, that extra 10 knots makes all the difference in the world. (I remember occasionally getting a "slow tow" when flying a 2-32 with three aboard..........what a handful!!! Cookie I know that you have some 'persons of size' out in the States, but I have never flown a glider that could not stalled in straight flight with a legal weight (less than 110kg, 242lbs) person in the front seat. This includes the K21 and the G103. Sometimes you run out of trim when circling in a thermal with such folk. I weigh about 190lbs by the way. Derek C |
#65
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At 18:34 02 January 2011, kirk.stant wrote:
On Jan 1, 12:44=A0pm, Free Flight 107 wrote: On Jan 1, 3:21=A0am, Doug Greenwell wrote: At 0= 6:24 01 January 2011, Anne wrote: I've certainly sparked some interest here - considering it's New Year :-)- Hide quoted text - And I mignt add this is a very fast moving discussion too! While I was loging in 2 messages were posted.. Concerning the Tow Plane position while on tow, two of my CFIs have said to position yourglider as if you were going to Machine Gun the pilot of the Tow Plane. this is equivelent of aligning the horizontal of the TP with a portion of his foweward fuslage, like the wheels on a Pawnee. Works great in all conditions I've come accross in 15 years flying 8 different types from 2-33 to Duo Discuss. Never been criticized for it either in BFRs. Wayne Without a gunsight, how do you do that? ;^) I don't understand why the high tow position is taught by reference to the towplane or horizon, when what should be taught is how to find the correct tow position (just above or below the wake, which is actually the propwash). Simple - once safely airborne (usually before the towplane), just ease down until you feel the towplanes turbulence, then ease up a bit. THEN look at the towplane and pick whatever convenient references you need to maintain this vertical alignment. Any significant change in towplane speed will require a readjustment of the tow position (normally only a factor if on an aerotow retrieve). Obviously, if you only tow behind the same towplane on every flight, you will quickly learn where to position your glider. But if you have a variety of towplanes, or are towing behind something different (Agcat, Wilga, AN-2, whatever) for the first time, you can use this process to find the correct position quickly. Many US instructors seem to only teach HOW to do something without going into WHY it is done. As a result, there are a lot of "shortcuts" being taught, and a lot of poorly trained pilots, IMHO. A result of not having a standardized curriculum, a la BGA, perhaps? Kirk 66 This is what I was taught - once I'd done a few tows it seemed pretty straightforward even for an inexperienced pilot like me. |
#66
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I know that you have some 'persons of size' out in the States, but I
have never flown a glider that could not stalled in straight flight Not that this adds to the main discussion, but... 160lb (normal sized) pilot here... my SZD-59 couldn't be stalled straight ahead without 'tricking' it (ease nose up till *near stall and yank the stick for the last bit of travel). No mods were done to plane to cause this, and a reliable W&B with me in it determined C/G to be at 37%, well within the limits (it's JAR22 cert'd...). This is actually common with this ship as well as the Jantar Std3 from which it's derived. I added 5.5lbs to the tail via a brass/lead tailwheel and now fly it at 50%, where it flies much nicer, with an honest (and predictable) stall and a more usable trim range. At some point I'm going to make an externally visible, removable weight set (replacement rudder hinge access panels milled out of brass or tungsten) to add up to 3 more lbs, to get it to 65% for mid-late season flying but plan on leaving it at 50% for early season. -p |
#67
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On Jan 3, 12:01*am, Derek C wrote:
Actually the only totally reliable sysmptom of being stalled is that the elevator will no longer raise the nose. But that is neither necessary nor sufficient! If you put enough weight in the front cockpit then there are plenty of gliders where you reach the back stop while they are still flying just fine. Conversely, there are also plenty of gliders with sufficiently powerful elevators that the wing can be stalled and you're mushing at 500+ fpm but you still have perfect control over the attitude of the nose and can raise or lower it at will. Not to mention other aircraft such as the F/A-18 which can be flown in perfect control with the wing stalled at huge angles of attack. I see in another post the definition: Admittedly that is still a stall according to FAR23/25 definitions "a stall is produced, as shown by either: (1) An uncontrollable downward pitching motion of the airplane; (2) A downward pitching motion of the airplane that results from the activation of a stall avoidance device (for example, stick pusher); or (3) The control reaching the stop." Without having that document in front of me I will hazard a guess that this is not a definition of a stall, but rather a definition of the standards for what a pilot should do in order to pass a practical flight examination. They're not going to fail him when the aircraft fails to actually stall because the elevator reaches its stop first, so they explicitly allow that as a signal that the pilot is allowed to terminate the "stall" attempt and commence the stall recovery procedure. The only true definition of a stall is when the wing is at an angle of attack such that a further increase of AoA produces a decrease of lift. *Usually* this will be accompanied by a large increase in drag such that the combination of lift and drag is easily capable of supporting the aircraft against gravity at a low speed and steep nose up descent angle, but that may not necessarily always be the case and some aircraft might speed up while stalled (perhaps at high altitude?). |
#68
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The discussion of forces surrounding a climb on high tow has been
interesting. However, has anyone considered descent on tow? A SGS 2-33 glider descending on tow behind a Cessna 182 has some interesting lateral control issues. * Descending behind a 182 with 10 degrees of flap at 65 mph in high tow with full spoilers is reasonably stable. * At 40 degrees of flap the 2-33 is almost uncontrollable. You need full stick and some patience to recover from the frequent level flight excursions. The 182 high lift/high drag wake is the obvious difference. Would anyone care to venture an analysis or opinion? Cheers, John Chapman, 1DG |
#69
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On Jan 2, 1:34*pm, "kirk.stant" wrote:
On Jan 1, 12:44*pm, Free Flight 107 wrote: On Jan 1, 3:21*am, Doug Greenwell wrote: At 06:24 01 January 2011, Anne wrote: I've certainly sparked some interest here - considering it's New Year :-)- Hide quoted text - And I mignt add this is a very fast moving discussion too! While I was loging in 2 messages were posted.. Concerning the Tow Plane position while on tow, two of my CFIs have said to position yourglider as if you were going to Machine Gun the pilot of the Tow Plane. this is equivelent of aligning the horizontal of the TP with a portion of his foweward fuslage, like the wheels on a Pawnee. Works great in all conditions I've come accross in 15 years flying 8 different types from 2-33 to Duo Discuss. Never been criticized for it either in BFRs. Wayne Without a gunsight, how do you do that? ;^) I don't understand why the high tow position is taught by reference to the towplane or horizon, when what should be taught is how to find the correct tow position (just above or below the wake, which is actually the propwash). *Simple - once safely airborne (usually before the towplane), just ease down until you feel the towplanes turbulence, then ease up a bit. *THEN look at the towplane and pick whatever convenient references you need to maintain this vertical alignment. Any significant change in towplane speed will require a readjustment of the tow position (normally only a factor if on an aerotow retrieve). Obviously, if you only tow behind the same towplane on every flight, you will quickly learn where to position your glider. *But if you have a variety of towplanes, or are towing behind something different (Agcat, Wilga, AN-2, whatever) for the first time, you can use this process to find the correct position quickly. Many US instructors seem to only teach HOW to do something without going into WHY it is done. As a result, there are a lot of "shortcuts" being taught, and a lot of poorly trained pilots, IMHO. *A result of not having a standardized curriculum, a la BGA, perhaps? Kirk 66- Hide quoted text - - Show quoted text - This is one of my pet peeves.........I don't like to use the term "high tow" because beginners seem to assume it means that the glider is flying higher than the tow plane. I use the terms "normal tow" and low tow. (because around here we noramlly tow above the wake.) But I do take the time to explain to my students that "high" tow means "high" compared to the wake(not campared to the tow plane), and you need only to be above the wake a little, and low tow is "low" compared to the wake, and you want ot be just barely below the wake. Also that flying "too high" on tow is a "mortal sin", and extremely dangerous. In rough air gliders seem more prone to "bounce up" than to "bounce down" so if your already running toward the high side on tow, one or two good bounces will make you too high. If you fly just above the wake, you have room to "bounce up" once or twice, and have time to re- position, before getting "too high" giving the tow pilot a hard time. As far as visual reference....there are several....some pilots and some instructors seem to prefer some or one more than others. I like to use the tow plane compared to the horizion. Another is the position of the tow plane in the glider's canopy...if the towplane appears low in the canopy, like under the inst panel, the glider is too high......if the tow plane appears way high above the inst panel, the glider is too low. My least favorite visual is lining up stuff on the tow plane itself, like top of fin to pilot's head, or stab to strut or whatever.....every make and modlel of tow plane is different, and tow pilot may change pitch attitude........The problem with the horizon method is if in hilly or mountainous terrain, the horizon is not always visible, students sometimes use the wrong reference then...The best is to use a sort of combination of all the visual references at once......not hard after the student has a few flight under the belt. On X-C retreive, I find that once the towplane levels out, that the wake goes way high, and to fly above the wake makes the glider too high.......I recommend, and usually go to low tow then...and since the wake is way up there, the low tow is not very low at all. In fact I've done low tow retreives that were higher than some high tows behind a strong tow plane! Cookie |
#70
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On Jan 2, 3:13*pm, Derek C wrote:
On Jan 2, 1:20*pm, " wrote: *'Actually the only totally reliable sysmptom of being stalled is that the elevator will no longer raise the nose.' HUH? * Many cases possible where we could have full elevator and not be stalled. *(I demonstrate this is 2-33 and grob 103 and ask-21. All you need is heavy pilot (forward CG) and gentle stick back to the stop. *Glider will mush, but not stall. *Elevator will not raise the nose........wing does not have angle to stall. On tow the only additional "weight component" would be a downward component to the tow rope (thrust). *Since the tension on the tow rope is fairly low........it should *not have a big effect, but there is some effect. But yeah, that extra 10 knots makes all the difference in the world. (I remember occasionally getting a "slow tow" when flying a 2-32 with three aboard..........what a handful!!! Cookie I know that you have some 'persons of size' out in the States, but I have never flown a glider that could not stalled in straight flight with a legal weight (less than 110kg, 242lbs) person in the front seat. This includes the K21 and the G103. Sometimes you run out of trim when circling in a thermal with such folk. I weigh about 190lbs by the way. Derek C- Hide quoted text - - Show quoted text - I didn't say you "can't" stall these gliders. What I did say was that you "can" get the stick back to the rear stop, without stalling, if you are gentle, and if the GC is forward. But then again.....a couple of new (to me) definitions of "stall" have come up. I just attended a FAA seminar on stalls, and nobody defined stall as "stick all the way back and nose won't come up". I still go by the definition of stall as "when the angle of attack of the wing reaches or exceeds the critical angle. " Cookie |
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