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#71
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Tony Verhulst wrote:
Slightly off topic but the following is pretty good reading, IMHO. http://home.comcast.net/~verhulst/GB...r_landings.htm It really points out one of the largest differences between power and glider flight: the increased need for no altimeter approaches. The Airplane Flying Handbook (AFH) suggests rectangular field engine failure landouts just for this reason (to eliminate the problem, just fly further on base). I must say, however, that I vaguely recall that other countries don't fly rectangles, but a V and then a 45 deg turn onto final. Is this true? It seems like a better way to avoid looking back over the shoulder for the touchdown spot... -- ------------+ Mark Boyd Avenal, California, USA |
#72
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Kirk Stant wrote:
I like the BGA's idea of the angled base leg, which approaches my preferred military-style one turn to final pattern. Yep, I think this is a better pattern too. I wonder where the rectangle came from in the USA? -- ------------+ Mark Boyd Avenal, California, USA |
#73
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Andy Durbin wrote:
(Kirk Stant) wrote in message Not the same as max performance low altitude turning (thermalling), which are definitely NOT ground reference maneuvers. Thermalling close to the ground is not intended to be a ground reference maneuver, but the visual feedback from the ground can have a strong influence on control inputs. It is very important to keep airspeed in the scan and not to be influenced by ground speed. The input from ground reference can be very compelling, and misleading, when thermalling low in a strong wind. We had this discussion before. If the thermal is coming from a stationary ground source, and the best performance is zero sink in the thermal, doing it exactly as a ground reference manuever (shallow upwind, steep tailwind) is correct. Otherwise one is blown downwind of the thermal. This was well discussed in threads about a year ago. If one starts at 60 degree banks on the upwind, with 10+ knots of wind and zero sink, trying to core the thermal on the downwind will be exciting... -- ------------+ Mark Boyd Avenal, California, USA |
#74
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Andy Blackburn wrote:
I have often used somewhat higher speeds on approach as well. The logic is simple: trade a little altitude for airspeed and you will get a better perspective on field slope, power lines and other features that my not be visible at higher view angles. I know this flys in the face of the traditional stabilized approach philosophy - so I'm interested in counterpoints. Effective airbrakes do a great job of dissapating speed too. In a Lancair IVP recently, without them it was really a headache to land. The glide angle even with power off was at such a high speed that to clear terrain we were way too fast every time. Speed brakes 4 miles out got us to the airport at the right approach speed every time. Having extra energy is great, if you can get rid of it when you need to. But I've seen some manuals where the best full spoiler descent rate is at a pretty slow speed. And it seems different gliders respond very differently to slips. So I'd definitely test out the slips too... Some of my more exciting landings have been when I got a lot of unforseen lift right before touchdown, rather than problems with sink. At shorter runways, or with weak spoilers, this could have been a big issue. You guys in your flap only PIKs and such get my respect. Adjustments on short final must be "interesting." -- ------------+ Mark Boyd Avenal, California, USA |
#75
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Chris OCallaghan wrote:
I've found over the years that my critical decision point to stop searching for lift is between 400 and 200 feet agl, depending on conditions. This is not when I enter the pattern, but when I put the gear down and focus ENTIRELY on landing safely. Typically, I'll be at least half way through a modified downwind (still looking for lift). This means that I am viewing the field from less than 400 feet above and 400 feet displaced from my intended centerline. Yep, this is what happened to me. On downwind got a sniff of a thermal. Was VERY leery. Always assess the field after you've landed. What didn't you see? What did you see that wasn't really a problem? This review will serve your assessment of the next field you find yourself falling into. Or while climbing away. I've found roads really suck, because they always seem to have fences and signs and wires. Dirt roads in fields are a little better, because if I don't like it (POLE!), I can go left or right and still land in the field. On this one particular downwind, and then climb away, I was most surprised by my misjudgement of the wind. A flag below showed I had set up for a tailwind landing. The winds aloft over the ridge I'd gotten into the lee of were SW, and a nearby flag (which I noticed only climbing away) said Northerly. Maybe the field had convergence too, eh? But I was very concerned that I'd not found any wind cues on the approach, although I'd looked hard... I think figuring out wind direction visually is sometimes VERY hard. With no lakes, no flags, no tilling, no smoke, no leaves on the trees, and no cow butts, I've sometimes been visually stumped... -- ------------+ Mark Boyd Avenal, California, USA |
#76
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Andy Blackburn wrote:
I have often used somewhat higher speeds on approach as well. The logic is simple: trade a little altitude for airspeed and you will get a better perspective on field slope, power lines and other features that my not be visible at higher view angles. I might not be visulizing this right: as you go down final approach, you reduce the spoilers and speed up, so you end up on a lower glide path but with an a more shallow approach? At what altitude do you begin this speed/altitude trade? There is practically nothing worse than having those hidden power lines pop up above the horizon when you are at 30' and 50 kts on final (this is the voice of experience from the person who had to pick up the wreck). So, the lines are hidden in the ground clutter, but by coming in at a more shallow angle, you can see them above the horizon sooner (i.e., from farther away than with steeper approach)? -- Change "netto" to "net" to email me directly Eric Greenwell Washington State USA |
#77
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Kirk Stant wrote:
(which probably takes a bit more than one second, I would think) will corkscrew the nose down and around, but you are not flying backward! I agree. I don't think I am flying backward. I think I am, to some degree, flying backward. What I mean is that some of the momentum carrying me into the spin will cause a reduction of airspeed which is most pronounced at 180 degrees from the entry heading. including Maverick's F-14 spinning out to sea after departing over the desert - I would have loved to have seen that for real!) Art Scholl lost his life in a fatal inverted spin into the Pacific Ocean with no parachute (while filming for Top Gun). Some say the weight of the cameras on the wingtips made the spin unrecoverable... Still a bad analogy, in my opinion. Think of the snap roll example - at what point do you stop "rolling" and start "frisbeeing"? You don't, your flightpath just curves more downward as you initiate the spin slower. At the 180 snap-roll point from entry, the nose isn't pointing in the other cardinal direction. It simply isn't comparable. It sure would be fun to take up a nice spinning glider (a 2-32 for example), instument it, then take turns trying to make each other sick! Hmmm...on a calm wind day with a cheap GPS with a time track set to every 1 second, if the GPS is synchronised with a stopwatch and observer, it may get interesting. A logger might do the same... But don't you ever wonder why the most nose down part of a positive spin is at the 1/2 spin point? Lowest airspeed perhaps? And why IS that... Broken glass ships have the same problem with weight in the tail... G-103s are notorious for it. Othewise, instruments, batteries, cheeseburgers, and beer tend to move the CG forward. You have a BBQ and beer cooler in the nose? How inventive... I suppose your landouts are quite a party... Again, the aft CG doesn't cause the spin, it just make it easier to initiate, and maybe harder to recover. NASA thought it sometimes made it easier, and sometimes harder to recover, depending on the aircraft. Go figure. You still have to exceed the stalling AOA, regardless of CG location. Winch launching is probably a lot safer overall than aerotowing (from my limited experience in Germany), with fewer potential gotcha's - plus it's really hard to kill the winch operator (unless you crash on the winch, of course). I must say it's a LOT of fun teaching aerotow. Formation flight where you don't have to worry about airspeed is a real thrill for a lot of folks. But yep, aerotow might be more complicated... But I wouldn't know, I've never done a wench launch... are not really "max performance" turns, and are usually no more than 90 - 100 degrees (unless you prefer the 180 degree one turn to final approach, which I do). I do rectangular bases, so others know I'm landing instead of thermalling at the end of the runway :PPP Well, most glider landing accidents only break the glider, or maybe a bush or two - and the reasons are usually pretty consistent. Shoulder harnesses probably have brought the stats down a huge amount, and the lower stall speed, and fuselage shape, of gliders compared to, say a Cherokee. Trike landing gear and rough fields do not mix... Not necessarily - the key is the lack of outside references, coupled with moving the head too much so as to confuse the inner ear. In an aileron roll, the head is moved. In max dutch rolls 45 to 45, the head is moved. So again, I guess you are agreeing with me that high roll rates and steep banks can induce vertigo. If you don't agree. Take a pax at night cover all instruments. Head perfectly straight ahead. Close eyes. Then max roll rate left 45 bank, then 90 degrees of turn, slow roll right, and tell them to open eyes while level and recover. Fun, huh? And yes, lack of coherent outside reference is important too. Pretty easy to get when looking at clouds and fog and mountainsides... And sometimes tough to correct without... wait for it...moving your head I have had the leans in formation in cloud - interesting when you pop out and your internal gyros cage up! I've had them almost uncontrollably on several occasions, night IMC, and straight and level on a rollout to a heading. Absolutely bloodcurdling... I fly my pattern based on where I want to touch down, and adjust the pattern accoding to my altitude and the wind. I prefer low, tight, fast patterns, so I can see what I'm getting into during a landout! It helps that my glider can get rid of a lot of energy fast when I need to. The only disadvantages I can find of very effective spoilers a 1) If they ain't locked for takeoff, a gnarly pio 2) If they don't have very fine controls, hard to be precise about glide slope. 3) If at max out, landing flare is VERY fast, and stall speed increased -- ------------+ Mark Boyd Avenal, California, USA |
#78
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Eric Greenwell wrote:
Andy Blackburn wrote: I have often used somewhat higher speeds on approach as well. The logic is simple: trade a little altitude for airspeed and you will get a better perspective on field slope, power lines and other features that my not be visible at higher view angles. I might not be visulizing this right: as you go down final approach, you reduce the spoilers and speed up, so you end up on a lower glide path but with an a more shallow approach? At what altitude do you begin this speed/altitude trade? There is practically nothing worse than having those hidden power lines pop up above the horizon when you are at 30' and 50 kts on final (this is the voice of experience from the person who had to pick up the wreck). So, the lines are hidden in the ground clutter, but by coming in at a more shallow angle, you can see them above the horizon sooner (i.e., from farther away than with steeper approach)? I think he's saying to use a flatter, faster glide slope on far out final, until 50-100 ft AGL, and then use a steeper glide slope. Remember he mentioned it wasn't a stabilized approach. -- ------------+ Mark Boyd Avenal, California, USA |
#79
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#80
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Mark got it right.
Rather than fly from IP to the threshold at 55 knots with, say, 1/2 spoiler, I will fly at 70-75 knots at 1/4 spoiler. This way I make all my turns at well above stall speed and can handle gusts, etc better. I end up on short final at a lower angle (better view), but with more energy. If everything looks good, I go to 3/4 spoiler and bleed the energy down at constant altitude (say 50-75'), then land as usual. If there is some obstacle or other issue, I can close the spoilers and have enough energy to pick a different touchdown point. This requires that you have good spoilers and that you don't over-do the extra speed - that could run up the risk of over-shooting. This is how I normally land, so it's not making everything different just for outlandings. Thoughts? 9B At 04:30 27 August 2004, Mark James Boyd wrote: Eric Greenwell wrote: Andy Blackburn wrote: I have often used somewhat higher speeds on approach as well. The logic is simple: trade a little altitude for airspeed and you will get a better perspective on field slope, power lines and other features that my not be visible at higher view angles. I might not be visulizing this right: as you go down final approach, you reduce the spoilers and speed up, so you end up on a lower glide path but with an a more shallow approach? At what altitude do you begin this speed/altitude trade? There is practically nothing worse than having those hidden power lines pop up above the horizon when you are at 30' and 50 kts on final (this is the voice of experience from the person who had to pick up the wreck). So, the lines are hidden in the ground clutter, but by coming in at a more shallow angle, you can see them above the horizon sooner (i.e., from farther away than with steeper approach)? I think he's saying to use a flatter, faster glide slope on far out final, until 50-100 ft AGL, and then use a steeper glide slope. Remember he mentioned it wasn't a stabilized approach. -- ------------+ Mark Boyd Avenal, California, USA |
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