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Pilots depend on simple, quickly applied remedies to any loss of
control. Since we are not always afforded the luxury of examination, analysis, and consideration of options as a preamble to action, any flight condition where these simple rules of recovery do not work demands closer examination and appropriate training to recognize symptoms and take appropriate actions. Modern aircraft are designed to meet well-defined controllability requirements. For example, in the United States, the recommended recovery (generic) for any impending or developed stall is to move the control column forward while applying coordinated aileron and rudder to halt an un-commanded roll. The Flight Manual for my S-H Ventus 2bx states on page 3.4: --On stalling whilst flying straight ahead or in a banked turn, normal flying attitude is regained by firmly easing the control stick forward and, if necessary, applying opposite rudder and aileron.-- Page 3.5 (Spin Recovery) continues... --Note: Spinning may be safely avoided by following the actions given in section 3.4 "Stall Recovery"- During the past several years, I have made it a point to experiment with various applications of controls throughout the stall break (and in a variety of makes and models). In all cases where I maintained coordination, either paying attention to the yaw string or through application of equal amounts of aileron and rudder, the aircraft did not spin, even if I held the stick firmly against the rear stop. Instead, it would transition from stall to spiral dive. In a recent RAS thread (Nimbus 4DT accident 31 July 2000 in Spain), I was introduced to a maneuver practiced by BGA instructors to demonstrate that a quick transition from coordinated flight into a spin can take place while recovering from a winch launch cable break. This was pointed out to refute my comment in that thread that modern gliders need to be "helped" into a spin (by either intentional or inadvertent abuse of the controls). Chris Reed described the following: --One of my favourite exercises for my annual checkouts as a UK Basic Instructor is the spin off a simulated winch launch (only try this at height with an appropriate instructor with you!). Simulate a winch launch by diving to 90 kt and then pulling up at 45 degrees. As the speed drops to about 60 kt cry "BANG - cable break", and push over into the normal flying attitude. The moment normal attitude is reached, begin a co-ordinated turn. All will be fine for a second or so, as you are flying at reduced G. However, once the G comes back on many gliders will roll smoothly (no buffeting) into a spin so fast that there is little you can do about it (though the purpose of the exercise is to show the spin entry and then a recovery, so I've not tried reducing back pressure as the wing drops). The Puchacz is excellent for this.-- For me, this raised an immediate alarm. It indicates that there are flight regimes (whether experienced during a cable break recovery, during an aggressive thermal entry, or as a result of turbulence) where normal control movements may result in an immediate and unannounced spin entry. Since such matters are best examined in the air, I put together an informal flight test plan to measure just how sudden the spin entry is and whether there might be mitigating factors. To prepare for the test, I set up the following limits: First, I would at no time during the maneuver bring the stick back all the way to the stop. We must assume that all pilots meet a base level of competency, and under no circumstance would any competent pilot resort to full up elevator to maintain attitude during a cable break recovery. I would consider such control usage an abuse of the controls. Second, I would remain coordinated (as indicated by my yaw string) throughout the maneuver per the instructions of my flight manual. Third, at stall break, I would hold the controls firm and visually verify their positions, then wait for the sailplane to assume its new state (either spin or spiral dive) then clearly identify that state before making an appropriate recovery. I began the test sequence with a series of four dives and recoveries just as Chris described, but without introducing a bank. At 60 knots, I called out "Bang - cable break - recover!" I pushed the stick firmly forward. Three out of the four, I briefly suspended loose dirt in the cockpit. As soon as the nose passed through the horizon into a normal flying attitude, I moved the stick quickly back to its normal position for that attitude. Of course, this did not entirely halt the downward pitch of the nose. However, it was clearly apparent through the feel of the controls that the sailplane was either stalled or on the edge of a stall as a result of my quick application of stick from well forward to neutral. It was very clear that bringing the stick straight back to the stop would result in a full stall. I began the dives in flap position -1, moving the flaps to position +1 as I slowed through 70 knots, as I might if I were entering a thermal, though my recovery (pitch over) was much more aggressive than any I would use during cross-country flight. Once I was comfortable with my ability to keep myself from making an immediate recovery from any stall, I stopped to thermal, then found a clear patch of sky and warned off others away, as I fully expected to spin the sailplane. In order to force an immediate turn, I imagined that there was an obstruction preventing a straight ahead landing. As soon as the nose came down, I determined that I would have to make an immediate turn to the right, which I did, without adverse results. The sailplane rolled sluggishly and felt on the edge of stall, but there was no loss of control, and certainly no sudden yaw and entry into a spin. I thought perhaps I had waited too long to initiate the turn, so with the next pull and recovery, I made the decision, before the nose came fully over, that I would land to the left in an adjoining field. I rolled to about 30 degrees, then as the nose reached normal flying attitude, I brought the stick right back to neutral... and braced myself against making an immediate recovery. As before, there was a sense of mushing through the air, but no tendency for the glider to yaw itself into a spin. For the next pull and recovery, I delayed saying "Bang - cable break - recover!" until 50 knots. Given the additional delay, I was much more aggressive with the stick, both moving it forward and returning it to neutral once I reach normal flying attitude. And once again, the sailplane demonstrated a sluggish, heavy feel as the g force came back on, but without any tendency to "fall" into the direction of the turn. It was clear to me that I could have easily induced a spin during this maneuver. A little too much rudder or stick against the turn coupled with bringing the stick full aft would have tipped the sailplane right over. But my intent was to produce an unanticipated spin, even though I was, ostensibly, doing everything right. I repeated this maneuver several more times, making slight adjustments to angle of bank, but without adverse effects. My conclusions: This is an interesting flight regime. I suspect that it would prove useful for producing spins in typically resistant aircraft, and require significantly less control abuse among those gliders that are inclined to spin. However, for my make and model (which can be easily coaxed to incipiency), normal attention to stall warning signs and application of coordinated aileron and rudder are adequate. There does not appear to be any tendency for the glider to spin suddenly or unpredictably, though I would caution that if the stick is used to catch a dropping wing without appropriate application of rudder, the spin entry could be significantly accelerated. The greater the span, the more pronounced the effects of a tip stall would be, but greater span is usually compensated for by a longer tail boom and larger vertical stabilizer. Some designs may choose to underpower the vertical stabilizer to increase glide performance, but hopefully these would include appropriate warnings and recovery procedures in their respective flight manuals. As far as thermal entry is concerned, I would give the same warning: if you delay your pushover on thermal entry to the point where G and airspeed are significantly reduced below the norms (generally not the most efficient way to enter a thermal), extra attention should be paid to coordination. I wouldn't expect the glider to snap into a spin, but it is entirely possible that the now underpowered vertical stabilizer may not adequately compensate if you have any tendency towards sloppiness. I intend to experiment with this maneuver some more over the coming weeks. As I discover anything interesting, I'll add my comments to the thread. Also, I uploaded my FR trace to the OLC, but my sampling was 4 seconds, hardly adequate for analysis. However, just in case you are tempted to make an armchair assay, be my guest! http://www2.onlinecontest.org/olcphp...823e438ec30ed8 The test run began at 1454 ET (UTC-4) and ended at 1503 ET. |
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It is not obvious to me, why, in a cable break scenario, you would be close
to stalling when you push the nose down to a normal attitude while you maintain 60 knot airspeed. This sounds like you are flying significantly above stall speed. Could you elaborate? Thanks, Mike Schumann wrote in message oups.com... Pilots depend on simple, quickly applied remedies to any loss of control. Since we are not always afforded the luxury of examination, analysis, and consideration of options as a preamble to action, any flight condition where these simple rules of recovery do not work demands closer examination and appropriate training to recognize symptoms and take appropriate actions. Modern aircraft are designed to meet well-defined controllability requirements. For example, in the United States, the recommended recovery (generic) for any impending or developed stall is to move the control column forward while applying coordinated aileron and rudder to halt an un-commanded roll. The Flight Manual for my S-H Ventus 2bx states on page 3.4: --On stalling whilst flying straight ahead or in a banked turn, normal flying attitude is regained by firmly easing the control stick forward and, if necessary, applying opposite rudder and aileron.-- Page 3.5 (Spin Recovery) continues... --Note: Spinning may be safely avoided by following the actions given in section 3.4 "Stall Recovery"- During the past several years, I have made it a point to experiment with various applications of controls throughout the stall break (and in a variety of makes and models). In all cases where I maintained coordination, either paying attention to the yaw string or through application of equal amounts of aileron and rudder, the aircraft did not spin, even if I held the stick firmly against the rear stop. Instead, it would transition from stall to spiral dive. In a recent RAS thread (Nimbus 4DT accident 31 July 2000 in Spain), I was introduced to a maneuver practiced by BGA instructors to demonstrate that a quick transition from coordinated flight into a spin can take place while recovering from a winch launch cable break. This was pointed out to refute my comment in that thread that modern gliders need to be "helped" into a spin (by either intentional or inadvertent abuse of the controls). Chris Reed described the following: --One of my favourite exercises for my annual checkouts as a UK Basic Instructor is the spin off a simulated winch launch (only try this at height with an appropriate instructor with you!). Simulate a winch launch by diving to 90 kt and then pulling up at 45 degrees. As the speed drops to about 60 kt cry "BANG - cable break", and push over into the normal flying attitude. The moment normal attitude is reached, begin a co-ordinated turn. All will be fine for a second or so, as you are flying at reduced G. However, once the G comes back on many gliders will roll smoothly (no buffeting) into a spin so fast that there is little you can do about it (though the purpose of the exercise is to show the spin entry and then a recovery, so I've not tried reducing back pressure as the wing drops). The Puchacz is excellent for this.-- For me, this raised an immediate alarm. It indicates that there are flight regimes (whether experienced during a cable break recovery, during an aggressive thermal entry, or as a result of turbulence) where normal control movements may result in an immediate and unannounced spin entry. Since such matters are best examined in the air, I put together an informal flight test plan to measure just how sudden the spin entry is and whether there might be mitigating factors. To prepare for the test, I set up the following limits: First, I would at no time during the maneuver bring the stick back all the way to the stop. We must assume that all pilots meet a base level of competency, and under no circumstance would any competent pilot resort to full up elevator to maintain attitude during a cable break recovery. I would consider such control usage an abuse of the controls. Second, I would remain coordinated (as indicated by my yaw string) throughout the maneuver per the instructions of my flight manual. Third, at stall break, I would hold the controls firm and visually verify their positions, then wait for the sailplane to assume its new state (either spin or spiral dive) then clearly identify that state before making an appropriate recovery. I began the test sequence with a series of four dives and recoveries just as Chris described, but without introducing a bank. At 60 knots, I called out "Bang - cable break - recover!" I pushed the stick firmly forward. Three out of the four, I briefly suspended loose dirt in the cockpit. As soon as the nose passed through the horizon into a normal flying attitude, I moved the stick quickly back to its normal position for that attitude. Of course, this did not entirely halt the downward pitch of the nose. However, it was clearly apparent through the feel of the controls that the sailplane was either stalled or on the edge of a stall as a result of my quick application of stick from well forward to neutral. It was very clear that bringing the stick straight back to the stop would result in a full stall. I began the dives in flap position -1, moving the flaps to position +1 as I slowed through 70 knots, as I might if I were entering a thermal, though my recovery (pitch over) was much more aggressive than any I would use during cross-country flight. Once I was comfortable with my ability to keep myself from making an immediate recovery from any stall, I stopped to thermal, then found a clear patch of sky and warned off others away, as I fully expected to spin the sailplane. In order to force an immediate turn, I imagined that there was an obstruction preventing a straight ahead landing. As soon as the nose came down, I determined that I would have to make an immediate turn to the right, which I did, without adverse results. The sailplane rolled sluggishly and felt on the edge of stall, but there was no loss of control, and certainly no sudden yaw and entry into a spin. I thought perhaps I had waited too long to initiate the turn, so with the next pull and recovery, I made the decision, before the nose came fully over, that I would land to the left in an adjoining field. I rolled to about 30 degrees, then as the nose reached normal flying attitude, I brought the stick right back to neutral... and braced myself against making an immediate recovery. As before, there was a sense of mushing through the air, but no tendency for the glider to yaw itself into a spin. For the next pull and recovery, I delayed saying "Bang - cable break - recover!" until 50 knots. Given the additional delay, I was much more aggressive with the stick, both moving it forward and returning it to neutral once I reach normal flying attitude. And once again, the sailplane demonstrated a sluggish, heavy feel as the g force came back on, but without any tendency to "fall" into the direction of the turn. It was clear to me that I could have easily induced a spin during this maneuver. A little too much rudder or stick against the turn coupled with bringing the stick full aft would have tipped the sailplane right over. But my intent was to produce an unanticipated spin, even though I was, ostensibly, doing everything right. I repeated this maneuver several more times, making slight adjustments to angle of bank, but without adverse effects. My conclusions: This is an interesting flight regime. I suspect that it would prove useful for producing spins in typically resistant aircraft, and require significantly less control abuse among those gliders that are inclined to spin. However, for my make and model (which can be easily coaxed to incipiency), normal attention to stall warning signs and application of coordinated aileron and rudder are adequate. There does not appear to be any tendency for the glider to spin suddenly or unpredictably, though I would caution that if the stick is used to catch a dropping wing without appropriate application of rudder, the spin entry could be significantly accelerated. The greater the span, the more pronounced the effects of a tip stall would be, but greater span is usually compensated for by a longer tail boom and larger vertical stabilizer. Some designs may choose to underpower the vertical stabilizer to increase glide performance, but hopefully these would include appropriate warnings and recovery procedures in their respective flight manuals. As far as thermal entry is concerned, I would give the same warning: if you delay your pushover on thermal entry to the point where G and airspeed are significantly reduced below the norms (generally not the most efficient way to enter a thermal), extra attention should be paid to coordination. I wouldn't expect the glider to snap into a spin, but it is entirely possible that the now underpowered vertical stabilizer may not adequately compensate if you have any tendency towards sloppiness. I intend to experiment with this maneuver some more over the coming weeks. As I discover anything interesting, I'll add my comments to the thread. Also, I uploaded my FR trace to the OLC, but my sampling was 4 seconds, hardly adequate for analysis. However, just in case you are tempted to make an armchair assay, be my guest! http://www2.onlinecontest.org/olcphp...823e438ec30ed8 The test run began at 1454 ET (UTC-4) and ended at 1503 ET. |
#3
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If you imagine that you are climbing at 55kts no probs
and the cable breaks. The glider starts to decelerate so the immediate action is to push the stick forward to pitch the nose down. The glider flies a parabolic arc and while it's mass remains the same the weight that the wing has to support is dramatically reduced at the top of the arc. So the glider can be at 45kts or less and the wing has not stalled, the AoA is still below the stalling angle and the airspeed is sufficient with the reduced G to keep the glider flying. The harder the push the greater the reduction in G and effective weight the wing has to support. Because of inertia the glider will take time to accelerate to sufficient speed to generate the lift necessary to support the glider as the G increases to 1. If aileron is applied to turn before this acceleration takes place the increasing G can mean that in effect the wing is stalled and application of aileron could initiate the spin. It is important to remember that it is the attitude of the glider to the relative airflow that determines the angle of attack, not the relationship of the glider to the horizon. The picture the pilot sees in these circumstances could well be one where the nose is well below the horizon (approach attitude) but acceleration has not taken place and the wing is stalled. Once the glider accelerates it is then safe to use the ailerons as normal. It is a reversal of the situation where high G increases the stalling speed, the further stalling exercise. I have seen as little as 20 kts at the top of a push over with no ill effect provided the ailerons remain central. Try it sometime at a safe height, this will be a far better way of seeing the problem than my explanation. At 14:36 30 June 2005, Mike Schumann wrote: It is not obvious to me, why, in a cable break scenario, you would be close to stalling when you push the nose down to a normal attitude while you maintain 60 knot airspeed. This sounds like you are flying significantly above stall speed. Could you elaborate? Thanks, Mike Schumann wrote in message roups.com... Pilots depend on simple, quickly applied remedies to any loss of control. Since we are not always afforded the luxury of examination, analysis, and consideration of options as a preamble to action, any flight condition where these simple rules of recovery do not work demands closer examination and appropriate training to recognize symptoms and take appropriate actions. Modern aircraft are designed to meet well-defined controllability requirements. For example, in the United States, the recommended recovery (generic) for any impending or developed stall is to move the control column forward while applying coordinated aileron and rudder to halt an un-commanded roll. The Flight Manual for my S-H Ventus 2bx states on page 3.4: --On stalling whilst flying straight ahead or in a banked turn, normal flying attitude is regained by firmly easing the control stick forward and, if necessary, applying opposite rudder and aileron.-- Page 3.5 (Spin Recovery) continues... --Note: Spinning may be safely avoided by following the actions given in section 3.4 'Stall Recovery'- During the past several years, I have made it a point to experiment with various applications of controls throughout the stall break (and in a variety of makes and models). In all cases where I maintained coordination, either paying attention to the yaw string or through application of equal amounts of aileron and rudder, the aircraft did not spin, even if I held the stick firmly against the rear stop. Instead, it would transition from stall to spiral dive. In a recent RAS thread (Nimbus 4DT accident 31 July 2000 in Spain), I was introduced to a maneuver practiced by BGA instructors to demonstrate that a quick transition from coordinated flight into a spin can take place while recovering from a winch launch cable break. This was pointed out to refute my comment in that thread that modern gliders need to be 'helped' into a spin (by either intentional or inadvertent abuse of the controls). Chris Reed described the following: --One of my favourite exercises for my annual checkouts as a UK Basic Instructor is the spin off a simulated winch launch (only try this at height with an appropriate instructor with you!). Simulate a winch launch by diving to 90 kt and then pulling up at 45 degrees. As the speed drops to about 60 kt cry 'BANG - cable break', and push over into the normal flying attitude. The moment normal attitude is reached, begin a co-ordinated turn. All will be fine for a second or so, as you are flying at reduced G. However, once the G comes back on many gliders will roll smoothly (no buffeting) into a spin so fast that there is little you can do about it (though the purpose of the exercise is to show the spin entry and then a recovery, so I've not tried reducing back pressure as the wing drops). The Puchacz is excellent for this.-- For me, this raised an immediate alarm. It indicates that there are flight regimes (whether experienced during a cable break recovery, during an aggressive thermal entry, or as a result of turbulence) where normal control movements may result in an immediate and unannounced spin entry. Since such matters are best examined in the air, I put together an informal flight test plan to measure just how sudden the spin entry is and whether there might be mitigating factors. To prepare for the test, I set up the following limits: First, I would at no time during the maneuver bring the stick back all the way to the stop. We must assume that all pilots meet a base level of competency, and under no circumstance would any competent pilot resort to full up elevator to maintain attitude during a cable break recovery. I would consider such control usage an abuse of the controls. Second, I would remain coordinated (as indicated by my yaw string) throughout the maneuver per the instructions of my flight manual. Third, at stall break, I would hold the controls firm and visually verify their positions, then wait for the sailplane to assume its new state (either spin or spiral dive) then clearly identify that state before making an appropriate recovery. I began the test sequence with a series of four dives and recoveries just as Chris described, but without introducing a bank. At 60 knots, I called out 'Bang - cable break - recover!' I pushed the stick firmly forward. Three out of the four, I briefly suspended loose dirt in the cockpit. As soon as the nose passed through the horizon into a normal flying attitude, I moved the stick quickly back to its normal position for that attitude. Of course, this did not entirely halt the downward pitch of the nose. However, it was clearly apparent through the feel of the controls that the sailplane was either stalled or on the edge of a stall as a result of my quick application of stick from well forward to neutral. It was very clear that bringing the stick straight back to the stop would result in a full stall. I began the dives in flap position -1, moving the flaps to position +1 as I slowed through 70 knots, as I might if I were entering a thermal, though my recovery (pitch over) was much more aggressive than any I would use during cross-country flight. Once I was comfortable with my ability to keep myself from making an immediate recovery from any stall, I stopped to thermal, then found a clear patch of sky and warned off others away, as I fully expected to spin the sailplane. In order to force an immediate turn, I imagined that there was an obstruction preventing a straight ahead landing. As soon as the nose came down, I determined that I would have to make an immediate turn to the right, which I did, without adverse results. The sailplane rolled sluggishly and felt on the edge of stall, but there was no loss of control, and certainly no sudden yaw and entry into a spin. I thought perhaps I had waited too long to initiate the turn, so with the next pull and recovery, I made the decision, before the nose came fully over, that I would land to the left in an adjoining field. I rolled to about 30 degrees, then as the nose reached normal flying attitude, I brought the stick right back to neutral... and braced myself against making an immediate recovery. As before, there was a sense of mushing through the air, but no tendency for the glider to yaw itself into a spin. For the next pull and recovery, I delayed saying 'Bang - cable break - recover!' until 50 knots. Given the additional delay, I was much more aggressive with the stick, both moving it forward and returning it to neutral once I reach normal flying attitude. And once again, the sailplane demonstrated a sluggish, heavy feel as the g force came back on, but without any tendency to 'fall' into the direction of the turn. It was clear to me that I could have easily induced a spin during this maneuver. A little too much rudder or stick against the turn coupled with bringing the stick full aft would have tipped the sailplane right over. But my intent was to produce an unanticipated spin, even though I was, ostensibly, doing everything right. I repeated this maneuver several more times, making slight adjustments to angle of bank, but without adverse effects. My conclusions: This is an interesting flight regime. I suspect that it would prove useful for producing spins in typically resistant aircraft, and require significantly less control abuse among those gliders that are inclined to spin. However, for my make and model (which can be easily coaxed to incipiency), normal attention to stall warning signs and application of coordinated aileron and rudder are adequate. There does not appear to be any tendency for the glider to spin suddenly or unpredictably, though I would caution that if the stick is used to catch a dropping wing without appropriate application of rudder, the spin entry could be significantly accelerated. The greater the span, the more pronounced the effects of a tip stall would be, but greater span is usually compensated for by a longer tail boom and larger vertical stabilizer. Some designs may choose to underpower the vertical stabilizer to increase glide performance, but hopefully these would include appropriate warnings and recovery procedures in their respective flight manuals. As far as thermal entry is concerned, I would give the same warning: if you delay your pushover on thermal entry to the point where G and airspeed are significantly reduced below the norms (generally not the most efficient way to enter a thermal), extra attention should be paid to coordination. I wouldn't expect the glider to snap into a spin, but it is entirely possible that the now underpowered vertical stabilizer may not adequately compensate if you have any tendency towards sloppiness. I intend to experiment with this maneuver some more over the coming weeks. As I discover anything interesting, I'll add my comments to the thread. Also, I uploaded my FR trace to the OLC, but my sampling was 4 seconds, hardly adequate for analysis. However, just in case you are tempted to make an armchair assay, be my guest! http://www2.onlinecontest.org/olcphp...info.php?ref3= 197828&ueb=N&olc=olc-usa&spr=en&dclp=c9701de37223903b6f823e438ec30 ed8 The test run began at 1454 ET (UTC-4) and ended at 1503 ET. |
#4
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![]() Mike Schumann wrote: It is not obvious to me, why, in a cable break scenario, you would be close to stalling when you push the nose down to a normal attitude while you maintain 60 knot airspeed. This sounds like you are flying significantly above stall speed. Could you elaborate? Thanks, Mike Schumann Mike; I don't think Chris means he maintain 60 knots. Starts at 60 knots, but with the nose up speed decays..... Push the nose over to an *attitude* that in normal flight would give around 60 knots and the trap is set.... Real speed is ~ Vs (say 40k) but attitude is good and she IS flying (as G 1) once the G reverts to 1 you either have a good angle of attack/speed and you are flying or you don't and you arent. thats my take - Vs increases in a tight turn as g1. so... when G1 (bunt/top of loop etc.) Vs *reduces* ;-) Jonny. |
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Someone taught me a pretty effective way to put almost "all" the
gliders in a spin. It consist in just flying straight at a speed just a little over the stall speed. Then use the ailerons only to slightly bank the wings, say ten or fifteen degrees. At that moment if you push the rudder on the side of the low wing you _will_ enter a spin. I remember that during instruction we had to use the ASK13 for the spins, because the Grob Twin Astir was not really spinning. Years after I have then tried the Twin with this system, and geez down it goes... |
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And I should add that I was explaining the exercise from memory and may
have got the speeds wrong. 90 kts is definitely over the top for starting - pull up from 65 or 70 into a 45 degree climb so as not to throw more height away at the outset. In the case of a real cable break, climbing at 45 at 60 kt you *will* take a second or two before you begin the pushover (and if you have quick reactions pretend to be an out of practice, early solo pilot). Then it will take the aircraft another second or two to complete the pushover, which will mean the speed decays further. Performing this exercise, I'd expect to see the normal gliding attitude with a speed of perhaps 30kt or even as low as 20kt, but you're still flying because of reduced G. Mike is quite right that the controls don't feel quite right, but you're concerned to make the turn as early as possible because you're just at that awkward height where you can't get in ahead but are low for an abbreviated circuit (say 450ft at my airfield) so you turn, the G comes back on, and the wing drops. Whether you enter a spin will depend on the aircraft - our K21 won't spin, even in this exercise, so falls out into a spiral dive. The Puchacz rolls smoothly into the spin without any buffeting or other warning, and I suspect most Polish gliders would do the same. Our K13 used to do the same, though in a more stately fashion, but since re-covering seems more reluctant. My point was not that a spin is inevitable, but that many gliders will spin from this even though you are flying co-ordinated. jonnyboy wrote: Mike Schumann wrote: It is not obvious to me, why, in a cable break scenario, you would be close to stalling when you push the nose down to a normal attitude while you maintain 60 knot airspeed. This sounds like you are flying significantly above stall speed. Could you elaborate? Thanks, Mike Schumann Mike; I don't think Chris means he maintain 60 knots. Starts at 60 knots, but with the nose up speed decays..... Push the nose over to an *attitude* that in normal flight would give around 60 knots and the trap is set.... Real speed is ~ Vs (say 40k) but attitude is good and she IS flying (as G 1) once the G reverts to 1 you either have a good angle of attack/speed and you are flying or you don't and you arent. thats my take - Vs increases in a tight turn as g1. so... when G1 (bunt/top of loop etc.) Vs *reduces* ;-) Jonny. |
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Chris Reed wrote:
And I should add that I was explaining the exercise from memory and may have got the speeds wrong. 90 kts is definitely over the top for Watch the limits: The LS 4 for example is limited to 77 knots on the winch. In the case of a real cable break, climbing at 45 at 60 kt you *will* take a second or two before you begin the pushover (and if you have Two seconds? Never! If it takes you two seconds to react on the winch, then you are not winch worthy. Hanging at the winch is not the place to be dozing. quick reactions pretend to be an out of practice, early solo pilot). An out of practice, early solo pilot isn't sent solo at the winch. Never. In our club, even the most experienced pilots are required to do the first winch launch of the year with an instructor. (Club rule. And yes, before you ask, for the instructors it's a catch 22 situation. It works for us.) reduced G. Mike is quite right that the controls don't feel quite right, but you're concerned to make the turn as early as possible because you're just at that awkward height where you can't get in ahead but are low for an abbreviated circuit (say 450ft at my airfield) so you turn, Nothing awkward with this height: There's plenty of time for a safe downwind landing. In fact, you *must* take your time for that downwind landing. Turn too early, and you'll find yourself with the (now in fact awkward) problem of 200 ft height over the runway with possibly a tailwind. Stefan |
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At 20:54 30 June 2005, Stefan wrote:
Chris Reed wrote: And I should add that I was explaining the exercise from memory and may have got the speeds wrong. 90 kts is definitely over the top for Watch the limits: The LS 4 for example is limited to 77 knots on the winch. As you are fond of pointing out, read the thread. What Chris is describing is an upper air excercise (no winch involved), Va and Vne are relevant, the max winch speed is of no concern (personally I favour 70-75kts as an entry speed, 60 isn't quite enough to get the glider into the winch launch attitude, push over and then stop the nose dropping on the horizon, 90 would work but you'd be wasting height). To simulate the situation which kills people (namely spinning as a result of commencing a turn before flying speed is regained after a cable break) you dive to acquire speed, pull up into the winch launch attitude then, at the appropriate moment, shout 'bang' and recover, but check the pitch down at the normal gliding attitude for 60kts, then immediately start a co-ordinated turn. A Puchacz will immediately spin off this if you get it right (the speeds are quite critical), too slow you can't hold the nose up, too fast and it gets 'untidy'. Trying to do this demo off a real winch launch would hurt. |
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![]() "Andrew Warbrick" wrote in message ... At 20:54 30 June 2005, Stefan wrote: Chris Reed wrote: And I should add that I was explaining the exercise from memory and may have got the speeds wrong. 90 kts is definitely over the top for Watch the limits: The LS 4 for example is limited to 77 knots on the winch. As you are fond of pointing out, read the thread. What Chris is describing is an upper air excercise (no winch involved), Va and Vne are relevant, the max winch speed is of no concern (personally I favour 70-75kts as an entry speed, 60 isn't quite enough to get the glider into the winch launch attitude, push over and then stop the nose dropping on the horizon, 90 would work but you'd be wasting height). To simulate the situation which kills people (namely spinning as a result of commencing a turn before flying speed is regained after a cable break) you dive to acquire speed, pull up into the winch launch attitude then, at the appropriate moment, shout 'bang' and recover, but check the pitch down at the normal gliding attitude for 60kts, then immediately start a co-ordinated turn. A Puchacz will immediately spin off this if you get it right (the speeds are quite critical), too slow you can't hold the nose up, too fast and it gets 'untidy'. Trying to do this demo off a real winch launch would hurt. You guys do this a little bit more subtly than I did it. I just asked the student to deliberately botch the simulated wire break by doing nothing at first. Just leave the glider pointed at the sky until it runs out of energy and the nose falls through on it own and THEN, just as the nose falls through the horizon, yank hard back on the stick while attempting a turn. Almost any spinable glider will spin with enthusiasm under those conditions. Of course, I'm talking about doing this at a safe altitude. Fiveniner's point that this is abnormal use of controls is a fact but a rusty or inexperienced pilot already unnerved by a wire break and now seeing the nose fall toward the earth may just do it this way if not for this sort of explicit training. It would appear that there are several cases in the BGA accident database where this might have happened. Just in case there are lurkers reading this who are getting the impression that this is a sort of trap for the unwary should carefully read fiveniner's flight test report. It DOES require the pilot to use very abnormal, in fact illogical, control inputs. The training just reinforces the very basic idea that the pilot must see a safe airspeed for the glider being flown before establishing a normal glide or attempting a turn. No rocket science here, just mind your airspeed and use smooth, logical control inputs. Bill Daniels |
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At 00:48 01 July 2005, Bill Daniels wrote: (snip)
Just in case there are lurkers reading this who are getting the impression that this is a sort of trap for the unwary should carefully read fiveniner's flight test report. It DOES require the pilot to use very abnormal, in fact illogical, control inputs. The training just reinforces the very basic idea that the pilot must see a safe airspeed for the glider being flown before establishing a normal glide or attempting a turn. No rocket science here, just mind your airspeed and use smooth, logical control inputs. Unfortunately Bill that is just what it is, a trap for the unwary. You can be in a situation where everything looks normal, the nose is down in the approach attitude you put in aileron and rudder and voila, spin/spiral dive. I have always taught that the decision whether to land ahead or turn should never be made until both conditions are met, attitude and airspeed. You cannot rely on attitude in the same way as we do for 'normal' flying. It is a trap easily avoided by thinking rather than acting instictively. It's a bit like the turn on finals - open the airbrake syndrome, people do it until it bites. |
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