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#11
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At 18:24 27 January 2004, Mike Lindsay wrote:
3) 'Always fly flatter close to the ground' - Now here is one that REALLY bothers me. This is probably the WORST misconception that insists in lingering around hangar talk, internet talk and in other media with many 'experts'. It should be replaced with 'Always fly coordinated !' or 'Fly with the right amount of bank for the turn you want to make'. That's the simple, naked, honest truth. Instilling fear of banking close to the ground is one of the worst things you can do to your students. I really hate people who insist on this one. Gliders will not Stall or Spin due to bank angles. They will do so because of angle of attack (pitch) not angle of bank. Since most of us don't have an AOA indicator in our gliders, we use Speed as an easy way to determine it. OTOH if you do a well banked turn close to the ground and there is a steepish wind gradient, its liable to be the last one you ever do. If you are flying on a day that has a strong wind gradient, surely you would actually have compensated for that with a higher approach speed? I personally have never had any problem with steeply banked, cordinated final turns, even under conditions of severe turbulence or rotor. Spin and stall avoidance is all about the speed you have. I take it from your comment you have never explored the stalling characteristics of any aircraft you have flown under different angles of bank? |
#12
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Then it may be a different matter if you are _just_
making it back from a cross country and are so low that you might hit the ground with the wingtip. Though I have never been there myself I have heard about people making their final turn 'with the rudder' in that situation. I just wonder whether it would help at all, since there'd be quite a penalty in height for the unclean flying involved. (Apart from the fact that there will have been some fairly poor airmanship involved to end up in that situation in the first place.) CV Hmmm, did'nt realise you could 'make a turn' with the rudder! Who ever the instructor is that taught this wonderful technique, and who ever their CFI is that alow them to continue to practice this technique, they both should be sacked and banned from ever instructing again. While there maybe secondary roll effects when you yaw your glider, the whole purpose of the rudder is to align the glider with the airflow. It is the ailerons which instigate a turn by rolling the wings. The rudder is used to 1) correct the adverse yaw 2) control any slide or skid 3) align the airframe with the airflow as you roll. The elevator is used to maintain a constant speed through out. If you chose to fly at or near the stall, and your glider has a strong incipient spin characteristic, it makes no odds whether you are turning or flying straight and level. Assume that if you touch that rudder near the stall you will spin, and you will die! |
#13
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First line of defence: Have sufficient airspeed and
fly coordinated when you are low. Second line of defence: Be able to quickly recognise and recover from an incipient spin. Souldnt that be.... 1) airspeed Airspeed AIRSPEED 2) ALWAYS fly coordinated 2) dont get low and try hard not to land out 3) dont fly so slow you have to worry about an incipient spin |
#14
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Geir Raudsandmoen om wrote:
I know at least one pilot who was saved from serious injury or death by his ability to quickly recover from an incipient spin at very low altitude (probably below 50 m). I watched it happen. Woow! He must have experienced the fear of his life. I am probably also in that category myself, having once unintentionally started to spin a LS7 when flying a very turbulent thermal close to a mountainside near Orcierres in the Alps, and being saved by quick recovery action. Sure, ridge flying is one of the most spin prone activities if one gets into the habit of flying too slow and too "flat". As we are not perfect, we should try to have two (or more) lines of defence whenever possible: First line of defence: Have sufficient airspeed and fly coordinated when you are low. Second line of defence: Be able to quickly recognise and recover from an incipient spin. You are perfectly right. Regarding the value of training fully developed spins: I think the main benefits are to (hopefully) eliminate the panic effect in a spin, and also to learn how to avoid overspeeding or overstressing the sailplane in the pull-out phase. This is the point of concern to me. A lot of modern single seater glasses don't like very much the pull-out phase, and tend to take horrendous speeds in the dive. Hence my own opinion to avoid as much as possible entering spin and if incipient spin either appears, get out immediately. Of course on a good old Ask13 one can play the game as much as one likes it. I seem to remember examples where people *have* indeed overstressed glasses in the pull-out phase, unfortunately for them. -- Michel TALON |
#15
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Arnold Pieper wrote: Ok, Here is to Mike and CV. Apparently both of you aren't listening. Hmmm. Surprising reaction, considering my post mainly supported your views. If you make a turn with just the rudder and the wings level or almost level, in other words, an uncoordinated turn, close to the ground, THAT will be your last turn. If you don't have height abouve the ground enough to perform a coordinated turn, you SHOULD NOT be turning. Here's the bottom-line : THAT level turn with the rudder-only, performed at 10 or 15ft height, is what produces the first part of a Spin and results in gliders hitting the ground with the nose and wingtip first, usually crippling the pilot. My gosh, you guys don't seem to get it, or read enough accident reports. As Ian already pointed out I reported this as something that other people claim to do, and I was in fact questioning it. On the other hand your claim that any uncoordinated flying automatically leads to a spin is just ridiculous. It rather detracts from your credibility and otherwise sensible views. And I must say, in all kindness, that you would benefit by trying not to be so pompous. These discussions are much more interesting and helpful if we can air our views and experiences on an equal footing rather someone dishing out "bottom-lines" and "simple, naked, honest truths" from their preacher's pulpit. Cheers CV |
#16
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we all know, from the accident statistics, just how
safe competition pilots are, don't we? Ian, I am assuming you are being sarcastic? Where are you getting your competition vs. normal flying accident statistics from? I am interested because the vast majority of accident reports I read are nothing to do with competitions. Owain |
#17
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Geir Raudsandmoen wrote:
... Regarding the value of I think the main benefits are to (hopefully) eliminate the panic effect in a spin, and also to learn how to avoid overspeeding or overstressing the sailplane in the pull-out phase. The pull-out is normally very different after a fully developed spin vs. after the typical quarter-turn incipient spin. Maybe there is another benefit of training fully developed spins. A pilot told me how this training and the way it was done saved his life. The instructor who trained him insisted on practising fully developed spins, with exit after a precise number of turns in a precise direction, this varying with each exercise. Later he was once ridge flying in front of a cliff when he has a spin departure. He was about to attempt the recovery when he realized that this would bring the glider just facing the cliff at exit with no way to avoid crashing onto it, so he delayed this recovery for a half turn as he was taught and made the exit in the proper direction. |
#18
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On Wed, 28 Jan 2004 12:37:49 UTC, Owain Walters
wrote: : we all know, from the accident statistics, just how : safe competition : pilots are, don't we? : : I am assuming you are being sarcastic? Yup. : Where are you : getting your competition vs. normal flying accident : statistics from? Reading the blood-and-gore pages of S&G : I am interested because the vast majority of accident : reports I read are nothing to do with competitions. Well of course not. When you stuff up landing a glider in a field after pressing on, too late, too low and too tired, you don't have to compound things by owning up ... Incidentally, note that I said "competition pilots" and not "pilots flying in competitions" ... Ian |
#19
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Arnold Pieper wrote:
Therefore, if you're maintaining the correct Speed in the traffic pattern, you can (and SHOULD) bank the glider as appropriate for the turn. ALWAYS. There is no exception. A glider will not Stall/Spin from a coordinated turn with the proper speed. This begs the question: a glider will NOT stall/spin from an UNcoordinated turn with the proper speed, either. It will do so always from an uncoordinated turn, usually with the Wings close to level in a skidding turn and the stick aft. Remember what I said about Wings level and the stick full aft. I've routinely stalled our club's Blanik from coordinated turns, and other gliders, too. Establish a shallow banked turn (10-15 degrees, say), then simply slow down while maintaining a coordinated turn. At some point, the inner wing falls and the spin begins. Coordination is important, but not sufficient to protect you from a spin. -- ----- change "netto" to "net" to email me directly Eric Greenwell Washington State USA |
#20
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Geir Raudsandmoen om wrote:
I am probably also in that category myself, having once unintentionally started to spin a LS7 when flying a very turbulent thermal close to a mountainside near Orcierres in the Alps, and being saved by quick recovery action. I read in one of his notes that Carl Herold doesn't ridge soar any more, because he thinks it is too dangerous. After I read that, I had a little talk with myself about how close I came to ridges a few times... As we are not perfect, we should try to have two (or more) lines of defence whenever possible: First line of defence: Have sufficient airspeed and fly coordinated when you are low. OK, I've got to agree with PART of this, but in detail. The US FAA Glider Flying Handbook, although it's nice to have one, is edited poorly, in my opinion. It has a lot of different definitions of a skid vs. slip, in different chapters (clearly written by different people). The editor should have seen this and standardized it. I think a slip is an uncoordinated manuever where both wings are at the same airspeed. A skid is an uncoordinated manuever where the wings are at different airspeeds. Straight flight is a coordinated manuever where both wings are at the same airspeed. Banked, turning flight is a coordinated manuever where both wings are at different airspeeds. Beyond this, I do a lot of training where the glider is uncoordinated. Boxing the wake, slips (on the takeoff roll and on landing), slack line recovery. I don't worry at all because neither wing ever stalls. What is coordinated? Well, if the yaw string or ball were at the CG, and centered, that would be coordinated. But the string isn't. It is often in front of and higher than the CG. When this is the case, at high roll rates, and steep banks, keeping the yaw string perfectly centered means I am in a skid. Think about a string on the end of a pole 20 feet long at 45 degrees up from the nose. Would you want to use this? Now let's make the wingspan really long and put your CG back 4 inches, and leave your top of the canopy yawstring in the same place. Now what happens? With that high aspect ratio where the difference between min sink angle-of-attack and stall is just a few degrees? Now I assume I actually have a yawstring right at the CG instead. I fly my Lingus with the 300 foot wingspan, which stalls at 38 knots. I decide to put it into a coordinated 60 degree bank, and fly at 53 knots. The "G" chart says this is the correct speed, and the radius of turn is 144 feet. Does anyone see anything wrong with this idea? I certainly do. Some of the wing is actually flying backwards. A glider with a 20 foot wingspan vs. a 300 foot wingspan is going to get a different result. Even in coordinated flight, the wings are at different airspeeds. Then I can just imagine the amount of opposite aileron one would need... Using the same "G" loading chart for airspeeds for aircraft with different wingspans seems puzzling to me. Now I go up in my glider, and I get in straight flight, and I pull the stick back to the stop, and hold it perfectly centered for about a minute. If the CG or design don't allow a continual stall, the glider bucks up and down in pitch. I try my best to keep it straight, but eventually a wing drops, and it goes into a bucking spin/spiral. If the CG or design allow a continued stall, I try my best to keep it straight, and a wing drops, and it goes into a spin. If I keep the stick all the way back and centered, I can change the direction of the spin with rudder (including a momentary straightness) but can't keep it straight consistently. The only aircraft I've been able to do a true full stall straight falling leaf is in Cezzna 150/152/172s. Washout, dihedral, huge vertical stab, huge rudder, CG hanging low. I've never been able to do a straight ahead stall, stick back and centered for a full minute, in any glider. So from my way of thinking, keeping the yaw string straight and using the airspeed indicator are a poor man's way of trying to keep either wing from stalling. Then applying airspeed rules for bank with no consideration for wingspan or aileron drag is another poor man's technique. If I flew a nice schmancy L/D one billion glider with long sexy wings, I'd invest in AOA indicators for each wing (maybe halfway or more along). I'd either rig them for worst case (worst flaps, worst aileron deflection, worst spoilers) or I'd link in the flap and aileron position info somehow. The Beech Duchess has an stall horn/AOA indicator on each wing (one side is for flaps up, the other for flaps down), so this isn't entirely novel (although it isn't specifically for spin avoidance). An AOA indicator on each wing wouldn't be perfect (bugs and ice and stuff still wouldn't get factored in), but I'd sure like it Seriously, how much drag would a couple of these cause? Until then, I fly little short-wingspan things with low aspect ratio and sacrifice performance. And I use wide patterns, slow roll rates, excessive airspeed, medium or less banks, and gentle control inputs when close to the ground. Second line of defence: Be able to quickly recognise and recover from an incipient spin. I'd say be able to quickly recognise and recover from an incipient stall. Since I've not been able to maintain a straight stall, I assume a stall = spin. If I'm uncoordinated, it just happens faster. |
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