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发表于 2014-1-10 21:05:30
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So (to establish the basics) we can see that in high-power, low-airspeed situations like takeoff, the combined prop effects tend to swing the nose of the aircraft left. We can also see that this causes a pilot a lot of work to keep the aircraft tracking straight.
In model aviation, we can see this same effect upon takeoff. I think anyone who has ever spend much time at an RC flying field has seen this go down:
所以（建立基础）我们可以看到，在大功率，低空速的情况下起飞，混合的螺旋桨效应趋向将飞机鼻子往左转。我们也可以看到，这使飞行员费好大劲保持飞机走直。
在模型飞行中，我们在起飞时可以看到同样的效果。我认为任何人都曾经在飞场花太多的时间看了这下去：
In 3D flying, however, we have other common circumstances that include high power and low airspeed, particularly hovering. All of these high-power, low-airspeed situations and the attendant prop effects cause more work for the pilot, because the pilot has to use the rudder actively to cancel out the left-turning tendency. So, what can an aircraft designer do to assist the pilot and take some work off of his thumbs?
然而，在3D飞行中，我们有其他常见的情况，包括高功率和低空速，特别是在起飞时。所有这些大功率，低空速的情况和随之而来的模型效果，导致飞行员做更多的工作，因为飞行员不得不实时的用舵来抵消左转弯的倾向。所以，什么模型设计师用他们的手指可以做一些什么来协助飞行员？
Most RC pilots already know that the typical aircraft design includes right-thrust, that is, the motor or engine and propeller point slightly to the right of the center line of the aircraft. On 3D aircraft, this angle is usually set by the shape of the motor mounting box. Typically, on most 3D aircraft, the motor or engine points 2.5-3 degrees to the right, and this dimension is called "Right thrust angle". This directs approximately 5% of the total thrust to the right to counteract the left-turning tendency, and reduces the amount of right rudder needed in high-power/low-airflow situations. Because it is an angle applied to the power system, the amount of right thrust increases as power and RPM increases and decreases as power decreases.
大多数的RC飞行员已经知道典型的飞机设计有右拉，即，电机或发动机和螺旋桨和方向略有点向飞机中线的右侧偏离。3D飞机，这个角度通常是由电机安装盒的形状设计好了。通常情况下，大多数的3D飞机，电机或发动机有2.5-3度的指向右，这是所谓的“右拉角”。这将使总推力的约5%来抵消左转弯的倾向，并降低右满舵在大功率/低的空速情况下的需要量。因为它是动力系统的角度，它的量随着功率和转速的增加而增加和随着功率降低而降低。
All good and fine, right? A genius solution, and now we know and can all go back to flying. Not quite. We really need to know two more aspects of right thrust to use it to our advantage. Firstly, (and most importantly) we need to know that the right thrust angle on any quality ARF aircraft or set of professionally-drawn plans is going to be sufficient for the aircraft to fly reasonably well. You can fly a 3D aircraft, as a matter of fact, with zero degrees of right thrust. The effect is subtle, and except for takeoff and hovering and certain maneuvers, you might not even notice for a while. I say that this is important to know because right thrust angle is one of those things which is often blamed for poor aircraft behavior when in fact it is almost never the culprit.
好的，好的，对吗？一个天才的解决方案，现在我们知道了，一切又都可以回到飞行。不太。我们真的需要知道两个右拉带来的好处。首先，（最重要的）我们需要知道任何好的ARF飞机或一组专业装机方案右拉角将能够使飞机飞的足够好。事实上，0度的右拉角，你也可以很好的飞3D飞机。影响是微妙的，除了起飞和悬停需要一定的技巧外，你甚至不会注意到这些。我说这是重要的是因为要知道因为右拉角的是经常被指责为飞机性能差时许多事情之一，实际上它不可能是罪魁祸首。
The scenario is very common at every flying field - A pilot is having a problem with his aerobatic airplane. It is most likely caused by a center of gravity issue or control surface throws like 95% of tuning problems, but during the course of diagnosis it is inevitable that someone will suggest right thrust as the culprit. Nope. (BTW, the problem is also not lateral balance. It never is, but someone always suggests it too). If the pilot starts changing his right thrust around to try to fix some problem, he will waste time, get confused, and possibly make things worse.
这样的场景在每一个飞行场都是非常常见的，一个飞行员的飞机遇到了问题。它是最有可能通过重心问题或控制面像95%控制量问题，但是在诊断过程中某些人会猜测右拉角是罪魁祸首，这样的情况是不可避免的。不是的。（顺便说一句，这个问题也不是横向不平衡造成的。不可能是，但总有人会这样认为）。如果飞行员开始改变自己的右拉角来尝试解决一些问题的话，他会浪费时间，最后还乱了，感到困惑，很可能使事情变得更糟。
For this reason, I recommend that new 3D aerobatic pilots ignore right thrust angle as a setup variable on their aircraft. New 3D pilots should be buying well-known quality aircraft anyway so that they can concentrate on learning 3D flight instead of re-engineering bad planes - leave that to other people. As such, new guys should put right thrust out of their minds and if someone suggests they should change the right thrust on their plane, say "Thanks very much" and completely ignore the suggestion. Concentrate on CG location, choosing the right prop, correct control throws, and practice, practice, practice!
Secondly, for more advanced pilots, it is important to know that right thrust angle is a compromise. There is no "correct" right thrust angle, only an approximation based upon a variety of factors. Once in a while, we get a call or email from a pilot who took one of our aircraft and added a ton of right thrust (sometimes it looks like 9 or 10 degrees) and finds out that the airplane is easier to hover and tells us that our right thrust angle is "wrong". This pilot has not yet learned that right thrust is a compromise. The consensus angle of 2.5-3 degrees represents a setting that takes some work off of the pilot at low speed and helps to keep the airplane from turning left at moderate speed but still allows the airplane to track straight with one rudder trim setting at a variety of speeds. The pilot who puts in a ton of right thrust to make his plane easier to hover will find that his plane no longer tracks straight in high speed flight and that the rudder trim he needs is speed-dependent.
正是因为这个原因，我建议新的3D特技飞行员忽略掉右拉角做为他的飞机的设置参量。新3D飞行员应该购买著名质量的飞机，以使他们能够集中精力学习3D飞行，而不是再修理差的飞机，把那些工作留给其他人来做。这样，新人应该把右拉角从头脑中去除，如果有人建议他们应该改变他们飞机上的右拉角的话，你就说“非常感谢”，然后完全忽略的他们的建议。集中精力在在重心位置、选择合适的螺旋奖、正确控制量，实践，实践，再实践！
其次，对于更优秀的飞行员来说，了解右拉角是一种妥协是很重要的。没有“完全正确”的右拉角，基于多种因素只有一个近似角。有时，我们接到email或电话，飞行员买了我们的飞机并给飞机和增加了很大的右拉角（有时看起来像是9或10度），发现飞机更容易悬停了，就告诉我们说我们的右拉角是“错误的”。这个飞行员还没有领悟到右拉角只能是一种妥协。比较一致的角度是2.5-3度，这样的设置帮助飞行员在低速时省掉一些工作，且有助于在适当的速度范围内保持飞机从避免左转弯，还能允许飞机只用一个方向舵的微调值来适应很宽范围的速度。那个加了一吨的右拉角就可以很容易的悬停的飞行员会发现他的飞机飞高速时不再会飞直线而且他的方向舵微调值随着速度要变化的。
So, when would someone maybe want to change their right thrust? As an example, if you have an airplane that can use a wide variety of prop sizes (like for instance our 48" Vyper, I fly it on 11x8, 12x6, 13x6.5, and 14x7 props, a diameter difference range of 27%) then it probably has a compromise right thrust angle intended for the middle of the size range. A very large diameter prop will likely benefit from a slight increase in the right thrust angle, although the effect will be subtle, but again this is for advanced pilots.
好，什么时候需要改变他们的右拉角呢？作为一个例子，如果你有一架飞机，它能使用很多尺寸的螺旋桨（比如像我们48”vyper，我飞上11x8，12x6，13x6.5，和14x7的桨，有27%的直径差范围）那么它可能有一个折中的右拉角范围的中间值。一个特别大的直径的螺旋螺旋桨将可能从微小的右拉角的改变中得到好处，虽然效应是微妙的，但这只是对优秀的飞行员而言。
The standard, classic test prescribed for testing your amount of right thrust is to first fully trim the airplane (this is the first step of every trimming test - get the plane flying straight hands-off) and then to fly the airplane at full throttle away from yourself and pull up to a vertical climb and watch the airplane during the vertical climb. As the aircraft slows, watch to see how long until the aircraft starts to veer to the left from prop effects. If you are tuning for a pattern or IMAC sequence, then you use the altitude of your uplines you will fly in competition as the standard for this test. If you want it to go farther up the upline before veering left, add more right thrust. Now, can anyone see any problem with using this test on a 3D airplane? Yep, for starters, a lot of our planes don't really slow down on a vertical climb. Secondly, since we're not flying a prescribed pattern routine, we don't have a set distance of vertical climb to work with as a standard. So, this test can be less than completely useful for us. However, we can see the principle contained within the method of this test - the amount of right thrust you need is determined by what you are doing with the aircraft. If literally all you did all day with your aircraft was to hover and you didn't care how wacky it flew at higher speed, then perhaps adding a bunch of right thrust is the ticket, however, most of us use the full speed envelope of our planes and so we will be forced to make this compromise.
做为标准，所描述的经典的测试验合适的右拉角的试验是这样的，首先完全配平你的飞机（这是每个微调测试的第一步-让飞机自由离手直飞），然后在全油门情况下让飞机远离自己并拉起垂直爬升。当飞机减速时，看需要多长时间飞机开始出现从螺旋桨效应中开始左旋。如果你是在用iMac序列模式做花样的话，然后你用上升线的高度做为竞争的话，这是一个标准的测试。如果你想让飞机上升得更远而又不左转的话，添加更多的右拉角。现在，谁能看出3D飞机用这样的测试有任何问题了吗？是的，对初学者来说，我们很多的飞机在垂直爬升过程中不能真的慢下来。其次，因为我们飞的不是如上描述的模式和飞得轨迹，我们没有设定一套距离垂直爬升而作为一个标准。所以，这个测试对于我们来说没有多大用处。然而，我们可以看出这个测试中的原理——你需要的右拉角大小是根据你要在飞机上做什么。如果你整天都让你的飞机做悬停动作，你从不在意空速，那么你就添加大大的右拉角，然而，我们大多数人是要让飞机飞全速的，所以我们将不得不做出折中。
So, if we are very familiar with our aircraft and we want to play with right thrust value to see if we can extract more performance for our particular flying style, we can certainly change our right thrust. Sometimes at the field, you will see people with their cowl off, adding washers to their motor mount to try different right thrust angles in flight. Usually, pilots are disappointed by the small effect this has (especially in proportion to the work required to take off the cowl and dismount the motor) but sometimes they make a positive change to their plane for themselves. Here's a tip - if you want a quick and easy way to simulate what your plane would be like with a little more right thrust angle, instead of taking it apart, use your transmitter. Program in a 2% right rudder to full throttle mix. While not exact, this is a very close approximation of the performance of the plane with a slight addition of right thrust. If you want to try less right thrust, use a 2% left rudder to full throttle mix. In this way, you can experiment without taking the plane apart. If you find you like the change, you can always actually change the thrust angle on the plane, just remember to then remove the transmitter mix!
所以，如果我们非常熟悉我们的飞机，我们想设这样一个右拉角的值，它可以让我们的特技飞行花样表现出更多的精华，当然，我们可以改变我们右拉角。有时在现场，你会看到有些人摘掉整流罩，给马达安装座加入垫圈以尝试不同的右拉角。通常，飞行员对小的效果很失望（尤其是对不成比例的大的工作量来说，因为要脱掉整流罩并拆卸电机）但是他们有时会做出积极的改变他们自己的飞机。这里有一个提示-如果你想找一个快速简单的方法来模拟你的飞机增加一点右拉角，就用你的遥控发射机而不必把飞机拆开。编程序加2%的右舵和全油门时混控。虽然不完全准确，但相当于是稍微增加一点右拉角时的近似值。如果你想减小右拉角，使用2%左舵和全油门混控。以这种方式做实验，你可以不必拆开你的飞机。如果你发现了适合的角度，你总是最终要实际改变飞机上右拉角的，记得要把发射器混控取消了啊！
So, to sum up:
Props are thrust producers, but they also impart a lot of other forces into our airplanes, like gyroscopic force and many others.
These forces are strongest when the prop RPM (engine power) is high.
At high airspeeds, the tail of the plane counteracts these prop forces effectively, but not at low speeds.
Therefore, at high power at low airspeed (like takeoff and hovering) we feel prop forces most.
The net effect of these forces is usually to make our aircraft turn left.
To take some work off of our left thumb, we mount our power system and prop at an angle pointing right so that at high power it balances the left turning force with a right turning force.
This angle is a compromise based upon the need for the airplane to handle well at a variety of airspeeds.
Any decent quality aerobatic ARF already has an adequate right thrust angle, changing it is only for advanced pilots.
Applying the classic test to check right thrust can be difficult on a modern 3D airplane since our planes power right past the limits used in the classic test.
So, we might need to experiment to find perfection, and this is easiest done by experimenting first with rudder to throttle mixes before taking your plane apart.
I hope this little discussion of right thrust has been helpful. For a lot of pilots, especially newer ones, it remains mysterious (as evidenced by the calls and emails we get) but it is only a detail meant to make our job as pilots a bit easier. We should know about it, but not be obsessed about it, since any decent aircraft designer will basically take care of it for you.
Ben Fisher
www.3DHobbyShop.com
This article was originally published in forum thread: "Right Thrust" and Prop Effects started by Blucor Basher View original post
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发表于 2014-1-10 21:05:04
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