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#31
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Tom Knauff's newsletter
I'm extremely happy to see the text in parenthesis on point no.3. I have
called attention to this to the Soaring Safety Foundation. In coaching a new tow pilot (I am not one) he made his first couple of attempts at this at a somewhat slow but vigorous rate. The result was a large yaw and the Pawnee with its large dihedral looked almost like rocking the wings. At 18:35 02 July 2008, Uncle Fuzzy wrote: On Jul 2, 10:12=A0am, George Knight wrote: Yes, =A0I'd like to know what the third one is! At 02:33 02 July 2008, Mike Schumann wrote:If you really want to help edu= cate the pilots that need it, why not include what the signals are in your post! Mike Schumann- Hide quoted text - - Show quoted text - 1. Tow plane Wing rock - release immediately 2. Tow plane yawing back and forth - towplane unable to release rope 3. Tow plane rudder waggle (too quickly to significantly yaw the airplane) - check glider for extended spoilers. |
#32
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Tom Knauff's newsletter
On Jul 1, 8:26*pm, "Bill Daniels" bildan@comcast-dot-net wrote:
Q#3: *Any uniform green color indicates a growing crop. *This could be alfalfa, corn or something else. *You can land in freshly cut alfalfa or hay but not much else. *Green usually means some form of irrigation which adds additional hazards like sprinkler pipes. *Landing in a crop is likely to cause some irritation among the farm folk. *Dirt, if it's reasonably smooth, level and large enough, is always landable. *(Answer: C) I agree with most of that but it may be too simple an answer. You need to know what crop is grown in the area you are flying and how tall it is likely to be at that particular time of year. You also need to know how it is watered or irrigated. Landings in siphon irrigated cotton fields, that are common in Arizona, can be made safely with no crop damage if you are able to keep both wheels in the same furrow and if the cotton is still short. On the other hand I know of a glider that sufferered significant fuselage damage on landing in a recently plowed field. The dirt clods were as hard as concrete and up to a foot across. Of all the landouts I have made I think the best field surfaces were mown alfapha and wheat stubble. One of the worst was a fallow dirt field that was so soft it was almost impossible to roll the glider to the trailer as it sank six inches deep in powder. Nice short landing roll though! So I don't know what answer Tom wanted to that question. My answer would be to make a choice based on size, slope, surface and a knowledge of local crop conditions. The best choice could be either green or brown but I'd take a look at the brown one first and hope it had a thermal. You can see why I don't like multiple choice tests Andy |
#33
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Tom Knauff's newsletter
Andy wrote:
I agree with most of that but it may be too simple an answer. You need to know what crop is grown in the area you are flying and how tall it is likely to be at that particular time of year. You also need to know how it is watered or irrigated. Landings in siphon irrigated cotton fields, that are common in Arizona, can be made safely with no crop damage if you are able to keep both wheels in the same furrow and if the cotton is still short. On the other hand I know of a glider that sufferered significant fuselage damage on landing in a recently plowed field. The dirt clods were as hard as concrete and up to a foot across. Wow - does this mean I need to get an endorsement for agricultural science on my certificate before I solo, or just before attempting a cross country? ;-) |
#34
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Tom Knauff's newsletter
"Jim Logajan" wrote in message .. . Andy wrote: I agree with most of that but it may be too simple an answer. You need to know what crop is grown in the area you are flying and how tall it is likely to be at that particular time of year. You also need to know how it is watered or irrigated. Landings in siphon irrigated cotton fields, that are common in Arizona, can be made safely with no crop damage if you are able to keep both wheels in the same furrow and if the cotton is still short. On the other hand I know of a glider that sufferered significant fuselage damage on landing in a recently plowed field. The dirt clods were as hard as concrete and up to a foot across. Wow - does this mean I need to get an endorsement for agricultural science on my certificate before I solo, or just before attempting a cross country? ;-) Wouldn't hurt. I agree with what Andy wrote. A freshly cut crop like a wheat stubble field is a great runway. Fallow wheat fields are nice too. Wheat stubble is usually brown, however, not green. Uncut wheat looks almost the same until you are low enough to see the "waves of grain" and then it may be too late to pick something else. If you land in standing wheat, close the air vents. I didn't and got a very upset hornet in the cockpit with me. Big, hard clods in a plowed field are a problem for gear doors if not more. |
#35
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Tom Knauff's newsletter
On Wed, 02 Jul 2008 18:13:30 -0600, Bill Daniels wrote:
"Jim Logajan" wrote in message Wow - does this mean I need to get an endorsement for agricultural science on my certificate before I solo, or just before attempting a cross country? ;-) Wouldn't hurt. Agreed. As an easier alternative, the information in this site may also be useful outside the UK: http://www.field-landings.co.uk/ I think the paired air-ground pictures (click 'CROP IMAGES') should be useful almost anywhere round the world if you translate the time of year to suit your seasons. -- martin@ | Martin Gregorie gregorie. | org | Zappa fan & glider pilot |
#36
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Tom Knauff's newsletter
At 03:26 02 July 2008, Bill Daniels wrote:
Examples of the questions include: snip During a steep, continuous left hand turn, how are the controls held? A. Left Aileron, right rudder, back stick B. Left aileron, left rudder, back stick C. Right aileron, right rudder, back stick D. Right aileron, left rudder, back stick Q#2: This one needs a some qualification since it depends on the glider. Obviously, into-the-turn aileron (left in a left turn) would never be used in a continuous turn so the choice is between C and D. I find many gliders, once stabilized in a turn, will track nicely with the string centered with my feet off the pedals indicating no rudder is needed at all. Only opposite aileron (right in this case) is used to hold off the overbanking tendency - this right aileron provides all the left yaw (adverse yaw) needed to center the string. Gliders with less adverse yaw will need some into-the-turn rudder (Answer: D). Gliders with a lot of adverse yaw may need a little out-of-the-turn rudder (right) (Answer: C). One must add that the Dick Johnson technique of using a slight slip also works nicely and adds a little to the performance. Dick holds out-of-the-turn rudder to oppose overbanking and keeps the stick centered. In my experience, this works best on gliders with generous dihedral and without winglets or polyhedral. snip Bill Daniels I notice from the back seat in a left turn that the yaw string for the front cockpit is slightly more to the right than the one in the back; I believe this to be because the front one is farther from the center of lift -- or the tangent of the turning radius. This leads me to believe that the rudder, also displaced from the center of lift would likely align itself with its own relative wind and would thus be slightly to the left if unattended. I do not think of this as holding bottom rudder. I was taught to hold a little top rudder and it might just be that a bit of pressure on the top rudder would place it somewhere between the place it would naturally seek and perfect alignment with the fuselage if not actually to the outside. I do note that if the nose drifts too low in a turn it is much easier to move it back to the proper position by applying top rudder than it is to add more back pressure on the stick. I believe this is also much safer -- a little bit of slip instead of lowering the airspeed with the stick while holding top aileron and bottom rudder, the classic setup for spin entry. React, Bill? |
#37
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Tom Knauff's newsletter
Nyal Williams wrote:
I notice from the back seat in a left turn that the yaw string for the front cockpit is slightly more to the right than the one in the back; I believe this to be because the front one is farther from the center of lift -- or the tangent of the turning radius. I suspect not. Assuming the following: 1. on a 2 seater, the front yaw string is about 6 ft (2m) ahead of the center of lift. 2. According to the American Soaring handbook, a 45 degree banked turn at 60 mph (52 kts) has a radius of 240 feet (73m). High school level geometry and trigonometry (I've been out of high school for a looong time :-) ) shows that this results in an error of only 1.4 degrees - small enough to be ignored for all practical purposes. I suspect that a yaw string, typically taped to the canopy, may have errors because the string is in the boundary layer. Tony V. |
#38
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Tom Knauff's newsletter
I suspect that a yaw string, typically taped to the canopy, may have errors because the string is in the boundary layer. Tony V. Closer than the OP, but still doesn't seem quite right. The front yaw string is much more subject to 'crossflow effect' (on most ships) than the back one due to canopy shape and the string's relative placement on a compound curve that is sometimes splitting air striking it (besides, both strings are in the boundary layer...) With this in mind, it is not a bad idea to "calibrate" ones yawstring by comparing it's position relative to a panel mounted slip-skid ball when flying a new ship, perhaps even marking the coordinated positions (at 45 deg banks?) with pinstripe tape if they are far off center. Jonson also covers this in the previously mentioned article about mildly slipping during thermalling turns (named "Circling the Holighaus Way" http://www.owp.us/Johnson/CirclingTheHolighausWay.pdf ). He explains it much more elegantly than I and it is worth reading if you have not already seen it. -Paul |
#39
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Tom Knauff's newsletter
sisu1a wrote:
With this in mind, it is not a bad idea to "calibrate" ones yawstring by comparing it's position relative to a panel mounted slip-skid ball.... But the 2 instruments measure different things. The yawstring (in theory) measures airflow angle at the fuselage. The inclinometer measures the difference between gravity and the opposite centripetal force - when in balance, the ball is centered. The question is, which is a better measure of coordination? Or, IOW, which is more important? Because of the difference in drag at the wingtips during the turn, the nose may yaw away from the center of the turn. The yaw string would show that, while at the same time, the inclinometer would be centered. I understand that some believe that that's the way it should be. Others believe that you need to hold rudder into the turn to minimize the drag. I should experiment in my LS6. Lord knows that I'm tired of looking up at the gaggle :-). Tony V. |
#40
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Tom Knauff's newsletter
Martin Gregorie wrote:
As an easier alternative, the information in this site may also be useful outside the UK: http://www.field-landings.co.uk/ I think the paired air-ground pictures (click 'CROP IMAGES') should be useful almost anywhere round the world if you translate the time of year to suit your seasons. Thanks for link - I've bookmarked it for futurer reference. |
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