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#1
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On Wednesday, May 7, 2014 1:20:44 PM UTC+12, Bill D wrote:
I can assure you that the higher a glider's performance, the safer it is. It's the old, low L/D gliders that can run out of altitude before getting lined up with the runway. It's a mystery to me why some people think you can "get away with" so much more in old gliders than in those great big heavy clumsy glass ones. Somewhere in this thread I saw a statement that you could safely turn back from 150 ft in an old glider (which I agree with), but you're a dead man if you try it below 300 ft in glass. The differences that govern such a thing just aren't that big! Let's look at some numbers for weight and wing area of typical training gliders (from Wikipedia): ASK13: 290 kg, 17.5 m^2 Blanik L13: 292 kg, 19.15 m^2 PW6: 360 kg, 15.3 m^2 ASK21: 360 kg, 17.95 m^2 Puchacz: 368 kg, 18.16 m^2 Janus: 365 kg, 17.3 m^2 G103: 390 kg, 17.9 m^2 Duo Discus: 410 kg, 16.4 m^2 DG1000: 415 kg, 17.5 m^2 There's not a lot of difference in the wing areas, with individual variations bigger than the generational differences. Yes, the glass ones weigh a bit more. How much more? Someone flying solo in an ASK21 is at about the same all up weight as someone in a ASK13 with a smaller than average instructor in the back seat. Someone flying solo in a DG1000 is at about the same all up weight as someone in a ASK13 with a largish instructor in the back seat. We expect students to be able to cope with the flying characteristic differences between having an instructor and not having one -- and to cope with that difference on their first time flying alone! |
#2
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At 02:06 09 May 2014, Bruce Hoult wrote:
On Wednesday, May 7, 2014 1:20:44 PM UTC+12, Bill D wrote: I can assure you that the higher a glider's performance, the safer it is. It's the old, low L/D gliders that can run out of altitude before getting lined up with the runway. It's a mystery to me why some people think you can "get away with" so much more in old gliders than in those great big heavy clumsy glass ones. Somewhere in this thread I saw a statement that you could safely turn back from 150 ft in an old glider (which I agree with), but you're a dead man if you try it below 300 ft in glass. The differences that govern such a thing just aren't that big! Let's look at some numbers for weight and wing area of typical training gliders (from Wikipedia): ASK13: 290 kg, 17.5 m^2 Blanik L13: 292 kg, 19.15 m^2 PW6: 360 kg, 15.3 m^2 ASK21: 360 kg, 17.95 m^2 Puchacz: 368 kg, 18.16 m^2 Janus: 365 kg, 17.3 m^2 G103: 390 kg, 17.9 m^2 Duo Discus: 410 kg, 16.4 m^2 DG1000: 415 kg, 17.5 m^2 There's not a lot of difference in the wing areas, with individual variations bigger than the generational differences. Yes, the glass ones weigh a bit more. How much more? Someone flying solo in an ASK21 is at about the same all up weight as someone in a ASK13 with a smaller than average instructor in the back seat. Someone flying solo in a DG1000 is at about the same all up weight as someone in a ASK13 with a largish instructor in the back seat. We expect students to be able to cope with the flying characteristic differences between having an instructor and not having one -- and to cope with that difference on their first time flying alone! I think you are missing the point. The difference between the perceived attitude of a Discus flying at 45kts (too slow) or 55kts (much better) in a turn is very small, easy to get wrong. The perceived attitude difference in a T21 Sedburgh between 35kts (slow) and 45kts(better) is quite large, easy to spot if you got it wrong. Bearing in mind that a T21 would not stall until you got it back to 22-25kts made low turns much more unexciting. The T21 and T31 are the gliders I was referring to. When it all turns to ratsh1t in a glass glider it happens that much more quickly than it ever did in wood. |
#3
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At 00:13 10 May 2014, Don Johnstone wrote:
At 02:06 09 May 2014, Bruce Hoult wrote: On Wednesday, May 7, 2014 1:20:44 PM UTC+12, Bill D wrote: I can assure you that the higher a glider's performance, the safer it is. It's the old, low L/D gliders that can run out of altitude before getting lined up with the runway. It's a mystery to me why some people think you can "get away with" so much more in old gliders than in those great big heavy clumsy glass ones. Somewhere in this thread I saw a statement that you could safely turn back from 150 ft in an old glider (which I agree with), but you're a dead man if you try it below 300 ft in glass. The differences that govern such a thing just aren't that big! Let's look at some numbers for weight and wing area of typical training gliders (from Wikipedia): ASK13: 290 kg, 17.5 m^2 Blanik L13: 292 kg, 19.15 m^2 PW6: 360 kg, 15.3 m^2 ASK21: 360 kg, 17.95 m^2 Puchacz: 368 kg, 18.16 m^2 Janus: 365 kg, 17.3 m^2 G103: 390 kg, 17.9 m^2 Duo Discus: 410 kg, 16.4 m^2 DG1000: 415 kg, 17.5 m^2 There's not a lot of difference in the wing areas, with individual variations bigger than the generational differences. Yes, the glass ones weigh a bit more. How much more? Someone flying solo in an ASK21 is at about the same all up weight as someone in a ASK13 with a smaller than average instructor in the back seat. Someone flying solo in a DG1000 is at about the same all up weight as someone in a ASK13 with a largish instructor in the back seat. We expect students to be able to cope with the flying characteristic differences between having an instructor and not having one -- and to cope with that difference on their first time flying alone! I think you are missing the point. The difference between the perceived attitude of a Discus flying at 45kts (too slow) or 55kts (much better) in a turn is very small, easy to get wrong. The perceived attitude difference in a T21 Sedburgh between 35kts (slow) and 45kts(better) is quite large, easy to spot if you got it wrong. Bearing in mind that a T21 would not stall until you got it back to 22-25kts made low turns much more unexciting. The T21 and T31 are the gliders I was referring to. When it all turns to ratsh1t in a glass glider it happens that much more quickly than it ever did in wood. All completely correct but there is one even bigger problem, most pilots when making a low level turn off a launch failure or to modify a circuit/pattern that has got too low, tend to be looking for/at the place they intend to land with little or no attention to spare for the ASI, attitude or slip/skid indicator, that's why these events are so productive of stall/spin accidents. Training needs to emphasise, GLANCE AT THE ASI EVERY 2 - 3 SECONDS IN THESE CIRCUMSTANCES. Attitude is un unreliable indicator very near the ground, even the smallest undulations in the terrain can give a false impression and just being low can make the attitude look more nose down than it is. |
#4
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At 07:20 10 May 2014, Chris Rollings wrote:
All completely correct but there is one even bigger problem, most pilots when making a low level turn off a launch failure or to modify a circuit/pattern that has got too low, tend to be looking for/at the place they intend to land with little or no attention to spare for the ASI, attitude or slip/skid indicator, that's why these events are so productive of stall/spin accidents. Training needs to emphasise, GLANCE AT THE ASI EVERY 2 - 3 SECONDS IN THESE CIRCUMSTANCES. Attitude is un unreliable indicator very near the ground, even the smallest undulations in the terrain can give a false impression and just being low can make the attitude look more nose down than it is. Surely best practice is simply to keep the speed on until you have got it all sorted. Certainly in modern slippery gliders. Too much speed is much safer than too little and costs very little in height through a turn. Isn't this what you taught us Chris? |
#5
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On 5/10/2014 7:24 AM, Jim White wrote:
Certainly in modern slippery gliders. Too much speed is much safer than too little and costs very little in height through a turn. From the standpoint of preventing stalls, I can only agree. But if your goal is to actually make it back to the runway, that advice should be tempered with a bit more information! Remember that turn radius increases with the SQUARE of airspeed. That means that a small increase in airspeed will result in a significant increase in turn radius. As the pilot, your goal in that situation should be to shoot for the proper airspeed for the situation. Not too much, but certainly always keeping a margin above stall speed. By all means don't risk a stall! But remember that too much airspeed could add to your troubles. |
#6
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At 11:24 10 May 2014, Jim White wrote:
At 07:20 10 May 2014, Chris Rollings wrote: All completely correct but there is one even bigger problem, most pilots when making a low level turn off a launch failure or to modify a circuit/pattern that has got too low, tend to be looking for/at the place they intend to land with little or no attention to spare for the ASI, attitude or slip/skid indicator, that's why these events are so productive of stall/spin accidents. Training needs to emphasise, GLANCE AT THE ASI EVERY 2 - 3 SECONDS IN THESE CIRCUMSTANCES. Attitude is un unreliable indicator very near the ground, even the smallest undulations in the terrain can give a false impression and just being low can make the attitude look more nose down than it is. Surely best practice is simply to keep the speed on until you have got it all sorted. Certainly in modern slippery gliders. Too much speed is much safer than too little and costs very little in height through a turn. Isn't this what you taught us Chris? Certainly a bit faster than optimum costs very little but you still need to GLANCE AT THE ASI EVERY 2 - 3 SECONDS IN THESE CIRCUMSTANCES to check what speed you are doing. |
#7
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Lots of playing with numbers but I think Chris'
airspeed checking is the most important; a well sealed modern sailplane gives no clue to the airspeed from the air noise. Furthermore you may be in turbulence/ wind shear situation. Apologies if this was said before. John F. At 11:01 11 May 2014, Chris Rollings wrote: At 11:24 10 May 2014, Jim White wrote: At 07:20 10 May 2014, Chris Rollings wrote: All completely correct but there is one even bigger problem, most pilots when making a low level turn off a launch failure or to modify a circuit/pattern that has got too low, tend to be looking for/at th place they intend to land with little or no attention to spare for the ASI, attitude or slip/skid indicator, that's why these events are so productive of stall/spin accidents. Training needs to emphasise, GLANCE AT THE ASI EVERY 2 - 3 SECONDS IN THESE CIRCUMSTANCES. Attitude is un unreliable indicator very near the ground, even the smallest undulations in the terrain can give a false impression and just being low can make the attitude look more nose down than it is. Surely best practice is simply to keep the speed on until you have got it all sorted. Certainly in modern slippery gliders. Too much speed is much safer than too little and costs very little in height through a turn. Isn't this what you taught us Chris? Certainly a bit faster than optimum costs very little but you still need t GLANCE AT THE ASI EVERY 2 - 3 SECONDS IN THESE CIRCUMSTANCES to check what speed you ar doing. |
#8
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On Sunday, May 11, 2014 5:01:08 AM UTC-6, Chris Rollings wrote:
At 11:24 10 May 2014, Jim White wrote: At 07:20 10 May 2014, Chris Rollings wrote: All completely correct but there is one even bigger problem, most pilots when making a low level turn off a launch failure or to modify a circuit/pattern that has got too low, tend to be looking for/at the place they intend to land with little or no attention to spare for the ASI, attitude or slip/skid indicator, that's why these events are so productive of stall/spin accidents. Training needs to emphasise, GLANCE AT THE ASI EVERY 2 - 3 SECONDS IN THESE CIRCUMSTANCES. Attitude is un unreliable indicator very near the ground, even the smallest undulations in the terrain can give a false impression and just being low can make the attitude look more nose down than it is. Surely best practice is simply to keep the speed on until you have got it all sorted. Certainly in modern slippery gliders. Too much speed is much safer than too little and costs very little in height through a turn. Isn't this what you taught us Chris? Certainly a bit faster than optimum costs very little but you still need to GLANCE AT THE ASI EVERY 2 - 3 SECONDS IN THESE CIRCUMSTANCES to check what speed you are doing. Being constantly aware of one's airspeed is nothing more than basic airmanship. Why and where would this not be the case? |
#9
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At 15:46 11 May 2014, Bill D wrote:
On Sunday, May 11, 2014 5:01:08 AM UTC-6, Chris Rollings wrote: At 11:24 10 May 2014, Jim White wrote: At 07:20 10 May 2014, Chris Rollings wrote: All completely correct but there is one even bigger problem, most pilots when making a low level turn off a launch failure or to modify a circuit/pattern that has got too low, tend to be looking for/at the place they intend to land with little or no attention to spare for the ASI, attitude or slip/skid indicator, that's why these events are so productive of stall/spin accidents. Training needs to emphasise, GLANCE AT THE ASI EVERY 2 - 3 SECONDS IN THESE CIRCUMSTANCES. Attitude is un unreliable indicator very near the ground, even the smallest undulations in the terrain can give a false impression and just being low can make the attitude look more nose down than it is. Surely best practice is simply to keep the speed on until you have got it all sorted. Certainly in modern slippery gliders. Too much speed is much safer than too little and costs very little in height through a turn. Isn't this what you taught us Chris? Certainly a bit faster than optimum costs very little but you still need to GLANCE AT THE ASI EVERY 2 - 3 SECONDS IN THESE CIRCUMSTANCES to check what speed you are doing. Being constantly aware of one's airspeed is nothing more than basic airmanship. Why and where would this not be the case? Maybe when you are distracted having been surprised by a launch failure. It happens, it happened on a check ride I did 2 weeks ago with a pilot who had not flown for a while. That is why a procedure needs to be formulated for a moderate level of skill and currency. An experience pilot, current and on top of his game probably does not need a procedure, he is capable of formulating and executing his own, he knows his own limitations and the limitations of his aircraft. Solly made it up as he went along, procedure dictated that he found a runway. The key is knowing what you are going to do before the worst happens. |
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