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On Thu, 21 Jul 2011 10:31:18 -0400, "vaughn"
wrote: "Mike Rhodes" wrote in message news ![]() By simple geometry the forward wing of a dihedraled pair in a skid will have the steepest angle of attack, and the greatest amount of lift, and therefore the one most likely to stall. (Not the wing inside inside of the skid.) Aileron use will not change that -- except they force the aircraft to remain in a skid when operated "crossed controlled." Aileron use affects the effective angle of attack of a wing. One way to turn mere wing drop (caused by a stall or near-stall) into a real spin is to use aileron to try to raise the stalled wing. This is one of thse disturbing cases where a pilot's instinctive reaction can kill! So the adverse yaw on a wing on the verge of a stall will pull the aircraft into a dangerous spin, when it would have been just a stall. The slow, draggy aileron will yaw the aircraft like a rudder. Wing dihedral will cause the opposite wing to rise into the yaw. Still, full ailerons may be applied to counter the roll. But the aircraft rolls over surprisingly in the direction opposite of the applied aileron. This is because of wing dihedral (and inherent aircraft stability); not because of wing stall, or because the aileron changes the angle of attack of that wing to cause it to stall. The aileron is acting like a rudder to yaw the aircraft. Dihedral stability then rolls the aircraft -- oppositely. But since the aircraft has rolled then the elevator no longer has gravity (or the inertia of a bank) to push against, so angle of attack rises rapidly. Then the wings stall. The aircraft is in an aerobatic attitude. The tail feathers will ensure the nose will then point down. The problem with uncoordinated controls and the stall is that, in a coordinated bank, the elevator pushes 'up' against the COG properly. But when the turn is not coordinated (when the aircraft just rolls over) then the elevator lift is no longer restrained by the load of the COG, and can raise the nose of the aircraft rapidly such that the wings then stall. Slips and skids, however, do not generally cause the plane to roll. In those conditions elevator control of the COG is not usually in doubt. When an aircraft is slow then a lot of elevator is applied to hold the nose up. Other than the flare, this condition is most likely to occur when doing stalls. It is could also occur during the turn when a pilot has overshot final from base. That is the danger point on final. And the roll into a spin probably came while using coordinated controls. The aircraft just stalled in the turn. It does not typically happen during a level approach while using crossed controls to skid the aircraft to align with the runway. (Which students may instinctively do to fine-tune their approach, which instructors may instinctively hate. It seems a matter of prejudice.) -- Michael |
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On Jul 22, 12:47*am, Mike Rhodes wrote:
On Thu, 21 Jul 2011 10:31:18 -0400, "vaughn" wrote: "Mike Rhodes" wrote in message news ![]() By simple geometry the forward wing of a dihedraled pair in a skid will have the steepest angle of attack, and the greatest amount of lift, and therefore the one most likely to stall. *(Not the wing inside inside of the skid.) *Aileron use will not change that -- except they force the aircraft to remain in a skid when operated "crossed controlled." Aileron use affects the effective angle of attack of a wing. *One way to turn mere wing drop (caused by a stall or near-stall) into a real spin is to use aileron to try to raise the stalled wing. *This is one of thse disturbing cases where a pilot's instinctive reaction can kill! So the adverse yaw on a wing on the verge of a stall will pull the aircraft into a dangerous spin, when it would have been just a stall. The slow, draggy aileron will yaw the aircraft like a rudder. *Wing dihedral will cause the opposite wing to rise into the yaw. *Still, full ailerons may be applied to counter the roll. But the aircraft rolls over surprisingly in the direction opposite of the applied aileron. *This is because of wing dihedral (and inherent aircraft stability); not because of wing stall, or because the aileron changes the angle of attack of that wing to cause it to stall. *The aileron is acting like a rudder to yaw the aircraft. *Dihedral stability then rolls the aircraft -- oppositely. But since the aircraft has rolled then the elevator no longer has gravity (or the inertia of a bank) to push against, so angle of attack rises rapidly. *Then the wings stall. *The aircraft is in an aerobatic attitude. *The tail feathers will ensure the nose will then point down. The problem with uncoordinated controls and the stall is that, in a coordinated bank, the elevator pushes 'up' against the COG properly. * *But when the turn is not coordinated (when the aircraft just rolls over) then the elevator lift is no longer restrained by the load of the COG, and can raise the nose of the aircraft rapidly such that the wings then stall. * *Slips and skids, however, do not generally cause the plane to roll.. In those conditions elevator control of the COG is not usually in doubt. When an aircraft is slow then a lot of elevator is applied to hold the nose up. *Other than the flare, this condition is most likely to occur when doing stalls. * *It is could also occur during the turn when a pilot has overshot final from base. *That is the danger point on final. *And the roll into a spin probably came while using coordinated controls. *The aircraft just stalled in the turn. * *It does not typically happen during a level approach while using crossed controls to skid the aircraft to align with the runway. (Which students may instinctively do to fine-tune their approach, which instructors may instinctively hate. *It seems a matter of pree patjudice.) -- You're over-thinking this. The only times in a the pattern I'd even consider uncoordinated flight is a slip -- not a skid -- to lose altitude, or when landing in a cross wind. If you find yourself cross controlling, add throttle, get coordinated, tell the tower you're going around and try again. If I have to slip to lose altitude it means my planning has been bad unless the slip was part of the landing plan (that does not often happen unless the approach end has something intruding on the flight path, or it's a failed engine landing and I carried some altitude as insurance on short final. A competent pilot, from the time he or she is on downwind, until on the taxiway, will only have to reduce throttle -- he or she should not have to increase it unless there's an unusual circumstance. Further, the competent pilot, speaking of ground reference, will not be aiming for the numbers, but for perhaps a thousand feet from his (or her) turn off. If you only have to retard the throttle from downwind to turn off, plan your exit from the active correctly, you're my kind of pilot. I have too often seen a 152 touch down on the numbers and taxi 1500 feet to exit the active. You may be a student pilot, perhaps a 'sophomore'. The literal of that word means 'wise fool'. There's lots to learn about being a safe pilot, and it's not all in books. For example: when this was an active newsgroup a discussion led me to accept that I should use oxygen above 11,000 feet, especially at night. It keeps vision better. Something I learned after 2k house of PIC. Ditto, clearing turns when on the 45 degree entry to downwind. I have a low winged airplane, an M20J, and there might be a Cessna below me. As such I tend to fly at pattern altitude from a mile out on entry leg so I can see who might be descending from above me. If I had a high wing airplane I would come in higher. And I fly en route altitudes at nominal less 50 or 75 feet, especially if VFR, and I consider it bad form to pass directly over a VOR because too many guys have their auto pilot on and will pass dead center, a possible meeting grounds. Other real pilots, add your favorite bits of wisdom, we may learn from one other. Or, a 'wise fool' might learn something that could be life saving. |
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![]() "Mike Rhodes" wrote in message ... On Thu, 21 Jul 2011 10:31:18 -0400, "vaughn" wrote: Aileron use affects the effective angle of attack of a wing. One way to turn mere wing drop (caused by a stall or near-stall) into a real spin is to use aileron to try to raise the stalled wing. This is one of thse disturbing cases where a pilot's instinctive reaction can kill! So the adverse yaw on a wing on the verge of a stall will pull the aircraft into a dangerous spin, Did I say anything above about adverse yaw? I actually said that aileron use affects the AOA. A stall happens...when? I even gave you a reference, which you apparently snipped. The rest of your crazy stuff is snipped unread. Frankly, many of your ideas are downright dangerous. Perhaps you are terribly uninformed, or perhaps you are trolling, but please read up on this subject before posting any further. I highly suggest the classic text in that field, "Stick and Rudder" by Wolfgang Langewiesche, but there are thousands of others. Visit your local public library. For anyone else reading this thread, please don't take piloting advice from Internet "experts". (Even from me.) Go to trusted sources for your information. You are far more likely to live longer and die in bed that way. Vaughn CFI |
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![]() " The aircraft does not actually stall into a roll from a skidding turn. It has only been rolled into a bank (which could be quite steep) in an unusual manner -- yet it is still flying." And at 200' AGL, the pilot's physical reaction is typically to pull up. The only visualization you need to know is very simple: In a skid--especially in a low-wing--much of the root of the inside wing is in the shadow of the fuselage, and is not providing lift. IF This would be a fascinating academic exercise, perhaps, if so many people hadn't witnessed these types of crashes happen. But what you really need to know is that if the inside wing drops in a skid, you will very likely strike the ground before you have time to flip through all of your Kershner books and internet theories. Odds are, you're four or five seconds from your own fireball. |
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....fat-fingered and hit Send by accident. To clarify:
In a skidding, cross-controlled turn, particularly in a low-wing, the root of the inside wing is in the shadow of the fuselage and is not generating lift. The inboard wing is thus closer to a stall. IF the plane stalls in that condition, the low wing stalls and drops first, and you've already got 30 degrees of bank in, you'll be at 50, 60 or 90 degrees before you even have time to react, and you're losing altitude. If the high wing stalls and drops, on the other hand, it's going to drop through wings-level before that wing becomes low, giving you more of your precious remaining seconds to recover. That's all you need to know. If you're inside, low wings stalls turning final, you could very easily die before you recognize the problem. The rest is just hangar talk, and it's particularly dangerous because you don't want to spend the last five seconds of your life reviewing all the physics theories you've heard. Chris G Commercial Pilot, CFI |
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On Aug 1, 1:17 pm, Alpha Propellerhead wrote:
...fat-fingered and hit Send by accident. To clarify: In a skidding, cross-controlled turn, particularly in a low-wing, the root of the inside wing is in the shadow of the fuselage and is not generating lift. The inboard wing is thus closer to a stall. IF the plane stalls in that condition, the low wing stalls and drops first, and you've already got 30 degrees of bank in, you'll be at 50, 60 or 90 degrees before you even have time to react, and you're losing altitude. Nope. Not even close. In a descending turn the inside wing is at a higher angle of attack than the outside wing. If we skid the airplane the difference becomes greater. If we slip it, it becomes less. I built a machine for my students so they could see it easily. Go to Pilots of America and see it: http://www.pilotsofamerica.com/forum...873#post672873 Dan |
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