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| Member |
Speaking as a "crop duster"... Quick turns at the field ends are more of a combination of a quick stop and a pedal turn, rather than a banked turn. In fixed wing, little different; we've largely moved away from ag turns at each end of the swath run, and there's a lot more use of round-robin 180 degree turns across the ends of the field, rather than reversals, with shallower banking. It used to be different; minimize turn at each end of the swath. Times have changed. But we didn't do wingovers (a few did, but many of those eventually got hurt or killed). I worked with such a guy...and I also watched him crash, removed him from the wreckage, and put out the fire. There's just no need for it.
But he owns a P51. And he's maverick. And he threw up on his nickle ride in a Tomcat... But he owns a P51. And he's Tom Cruise. | |||
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Yeah, that guy who said a Pitts is unstable. Pshaw. Now and Zen |
The term that you are looking for is ‘accelerated stall’. ___________________________________________________________________________ "....imitate the action of the Tiger." | |||
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| Something wild is loose  |
"Departed controlled flight." "And gentlemen in England now abed, shall think themselves accursed they were not here, and hold their manhoods cheap whiles any speaks that fought with us upon Saint Crispin's Day" | |||
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| Dances With Tornados |
This is a great discussion of what makes a plane fly. What makes a plane fly? Money. If you don't have any money, the plane doesn't fly. My now deceased brother in law was a wealthy oilman and businessman. He owned a succession of private jets and this was probably one of his favorite things to say when the question came up. Sorry, I couldn't help myself, lol. I'll go to my room now. And seriously, thanks for the comments. It was quite educational and I enjoyed reading the posts. . | |||
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| Ammoholic |
Totally believe that, sorry for the poor explanation of what I was seeing. Thanks for clarifying. But if it is a quick stop and a pedal turn, how does one maintain 50mph IAS (too tired to interpolate the knots values, or divide by 1.15 apparently) as shown in airbubba’s Height Velocity Diagram?
When you say round-robin 180s, is that something like the pattern often used in disking a field? Basically, cut it in half, then do a “walking oval” that moves across the field covering everything and avoiding tight turns.
Yeah, like many things, we figure out a better, safer way to do things and use that. | |||
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| Member |
Height-velocity diagrams define the classic "dead man's curve," the premise of which is ensuring one has either airspeed or altitude to trade for rotor energy; adequate altitude to get the collective down and establish auto rotation, or adequate airspeed to trade for rotor inertia. Obviously in ag work, when spraying, one doesn't have altitude to trade, so it's airspeed; the turn and return to the field is conservation of energy. In fixed wing terms, it could be thought of as being similar to a steep turn in which one works the turn to keep from stalling. Bank too steeply too slow, or pull too much (exceed critical angle of attack), you'll buffet or stall. Likewise, in an ag turn, the concept is to manage energy such that airspeed on the spray run is traded for altitude, along with a power increase and collective increase (increase in AoA), get turned using torque to advantage (pedal turn), and return to a lower altitude again. The "round robin" method of spraying a field is similar to the disking or ploughing turns you're talking about. Divide the field into halves, or quarters; it's done using a GPS guidance system (SATLOC, AGNAV, etc). Pick a point, identify the start and stop of the first pass from A to B (the AB line), Identify the next line, and so long as the unit knows the swatch width, it will keep stepping over half a wingspan/width until you tell it to stop or signal empty, to go back for another load. | |||
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Member |
Thanks to all the SF pilots, especially sns3guppy, for answers to aviation questions. I am not a pilot but have an interest in aviation so these topics get my attention. The answers, provided by guys seriously know their stuff, are great. I also have to say across many topics, the folks on this forum readily share their knowledge. Thank you. Let me help you out. Which way did you come in? | |||
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| As Extraordinary as Everyone Else  |
My thoughts exactly. Thanks guys. ------------------ Eddie Our Founding Fathers were men who understood that the right thing is not necessarily the written thing. -kkina | |||
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| Member |
When I was a kid (eighteen) and got my first spray job after high school, I knew everything. Especially aerodynamics. I'd read everything I could find, back to the wrights, lilienthal, etc. After the boss watched me do a few turns, he suggested I use some top rudder. I thought he was nuts. After all, I knew the airplane would depart controlled flight and spin over the top. At 150' above the powerlines or trees, it seemed a ridiculous idea. The order of the day was an ag turn; fly the pass down the field, pitch over the powerline and a rolling climb downwind, then leveling and a rolling turn upwind all the way back to the the field in a descending turn, steep descent to the entry point, and do it again. We used an automatic flagman, which was a long square box on the wing full of plates of cardboard with folded streamers of crepe paper. A trigger on the stick popped one out, and that was used to mark the exit point, so we could adjust our entry the proper distance upwind on each pass. The spray booms were shaped like a wing; they actually generated lift, and reduced drag over the traditional round boom. The booms are suspended below and behind the wing, and attached to the supports, or hangars, using hose clamps. The angle of the booms was adjustable; variable incidence booms. We'd adjust them to reach a stall just before the wings did, and thus they produced a very effective, ruidmentary stall warning (of sorts). In the ag turn, all time spent turning was loss of revenue; we made money applying chemical in the field, not turning. Minimizing time in turns meant more time spraying, more acres covered. In the turn, we got really good at finding the edge of the envelope, and could tickle it in and out of the buffet, especially on the booms, before the airplane began to shake. An accelerated stall, in a steep turn, occurs at higher speed than a straight-ahead stall, and can, of course, occur more on one wing than another; a departure from controlled flight can occur rapidly, and when it gets to that point, at those altitudes, recovery is absolutely impossible. Therefore, know thy shit, and don't go there. In an accelerated stall, one can get to the stall at varying airspeds; all that counts is angle of attack. Carrying a lot of rudder in the turn, especially the wrong way, is going to end up stalling one wing more, or more precisely, increase the angle of attack more, and the result is that one may depart controlled flight sooner than one intended. It may be over the top (away from the turn), it maybe to the inside of the turn, depending on the level of one's abuse, how the wings are rigged, whether the numerous dents and dings in the wings, the hard landings, the abuse the airplane takes in it's flying, the way the booms were rigged, etc, affects the airflow. The big thing that being out of wack (not coordinated, not properly riggged, etc) does is that it robs reserve; one will get to the bad parts sooner than the other guy, and if one is careful not to go there, one ends up taking longer in the turn. The really good guys had shorter turn times. I thought I was doing really well. Because I was eighteen, and I knew everything. Lain, the bosses son, flew with me one day. We did most of our spraying in formation, as it made for much more consistent application and spacing, and saved on flags. And they could keep an eye on the eighteen year old kid. I pitched up, rolled downwind, and immediately into my reversal, drawing the stick back until I felt the airplane begin to buzz at the edge of the buffet. Lain would be tight on me and I wanted him to see that I was doing it right. I saw movement above and glanced through the eyebrow windows above the cockpit and there was Lain, inside my turn; he'd cut inside my turn and beat me back into the field, and I was pulling it as tight as I dared, and the airplane was buffeting. Yet he did it effortlessly. At the next turn, the same thing. We finished our tanks and returned to reload. When Lain told me I was taking too long, it was obvious. He'd just shown me that. Even though I already knew everything, I could see that much. But my spider senses told me that if I went any deeper, increased my angle of attack any more, I was going to wind up a grease spot. Then Lain told me to hold more top rudder. Idiot. He was crazy. I knew better than that. But on the next flight I tried it anyway. What I felt was epiphany. The buffet went away. I was flying steep, nose up, and the airplane felt like it just fell into a buttery groove, and I could tighten much more, still had good reserve, and the airplane was flying. For the first time, I was using the lift properly on the fuselage, taking advantage of corners of the envelope that I didn't know existed. Shangrila. I was excited, energized. The boss had a Cessna 150 that we'd use to go land on roads and do crop inspections; I could fly that as much as I wanted, on my own time. I got that airplane out and tore up the sky experimenting and trying this and that, seeing how far it would go. The career from there was an ongoing, dizzing disappointment of progressively learning how little I really know, until today I'm as dumb as a box of hammers...but back then, I was really smart, and knew everything. Today, I'm mostly an adherent of the church of aviate, navigate, communicate, and have an ingrained knowledge that I am not the ace of the base, having scared myself shitless enough times over the decades to be so thoroughly convinced as to lay cowering under the blanket, awaiting my next flight with fear and trepidation. Fear God (he's in the thunderstorm). Fear the airplane (it tries to kill you). Fear yourself (you're a dumb ass). Mostly in that order. It's worked, so far. I'm terrified of myself.This message has been edited. Last edited by: sns3guppy, | |||
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| Ammoholic |
It does seem like in aviation, as in life, the more one learns, the more he realizes how little he knows. Some days the depth of my ignorance astounds me. Top rudder wouldn’t have occurred to me, but considering lift from the fuselage, it makes a lot of sense. Thanks for the enlightenment! | |||
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| Member |
sns3guppy, this is some excellent info. Thanks | |||
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| Member |
i agree + knowing that aviation can be very unforgiving, even if you do everything right. listening to other pilots, absorbing how to's, scaring yourself to death but vowing to not do that again, is part of the harsh learning curve, making it to the finish line, to retire. doing it wrong, not learning from mistakes too many times, can lead to "he died doing what he loved" on the tombstone"! | |||
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