Section I Activity mode and main points of coaching

航空模型活動一般包括制作、放飛和比賽三種方式，也可據此劃分為三個階段：

Aviation model activities generally include production, release and competition, which can also be divided into three stages:

制作活動的任務是完成模型制作和裝配。通過制作活動對學生進行勞動觀點、勞動習慣和勞動技能的教育。使他們學會使用工具，識別材料、掌握加工過程和得到動手能力的訓練。

The task of the production activity is to complete the model production and assembly. Through production activities, students will be educated about labor ideas, labor habits and labor skills. Make them learn to use tools, identify materials, master the processing process and get hands-on training.

放飛是學生更加喜愛的活動，成功的放飛，可以大大提高他們的興趣。放飛活動要精心輔導，要遵循放飛的程序，要介紹飛行調整的知識，要有示范和實際飛行情況的講評。通過放飛對學生進行應用知識和身體素質的訓練。

Flying is a favorite activity for students. Successful flying can greatly improve their interest. The release activities should be carefully guided, follow the release procedures, introduce the knowledge of flight adjustment, and have demonstration and actual flight situation evaluation. The students are trained in applied knowledge and physical quality through flying.

比賽可以把活動推向高潮，優勝者受到鼓舞，信心十足：失利者或得到教訓，或不服輸也會憋足勁頭。是引導學生總結經驗，激發創造性和不斷進取精神的好形式。參加大型比賽將使他們得到極大的鍛煉而終生不忘。

The competition can bring the event to a climax, and the winners are encouraged and confident: the losers will either learn a lesson or not admit defeat, and will also hold their strength. It is a good way to guide students to sum up experience, stimulate creativity and keep forging ahead. Participating in large-scale competitions will give them great exercise and never forget it.

第二節 飛行調整的基礎知識

Section II Basic knowledge of flight adjustment

飛行調整是飛行原理的應用。沒有起碼的飛行原理知識，就很難調好飛好模型。輔導員要引導學生學習航空知識，并根據其接受能力、結合制作和放飛的需要介紹有關基礎知識。同時也要防止把航模活動變成專門的理論課。

Flight adjustment is the application of flight principle. Without basic knowledge of flight principles, it is difficult to adjust the flight model well. The instructor should guide students to learn aviation knowledge and introduce relevant basic knowledge according to their acceptance ability and the needs of production and release. At the same time, it is also necessary to prevent aircraft model activities from becoming specialized theoretical courses.

一、升力和阻力

1、 Lift and drag

飛機和模型飛機之所以能飛起來，是因為機翼的升力克服了重力。機翼的升力是機翼上下空氣壓力差形成的。當模型在空中飛行時，機翼上表面的空氣流速加快，壓強減小;機翼下表面的空氣流速減慢壓強加大(伯努利定律)。這是造成機翼上下壓力差的原因。

The reason why aircraft and model aircraft can fly is that the lift of wings overcomes gravity. The lift of the wing is formed by the pressure difference between the upper and lower air of the wing. When the model is flying in the air, the air velocity on the upper surface of the wing increases and the pressure decreases; The air velocity on the lower surface of the wing slows down and the pressure increases (Bernoulli's law). This is the cause of the pressure difference between the upper and lower wings.

造成機翼上下流速變化的原因有兩個：a、不對稱的翼型;b、機翼和相對氣流有迎角。翼型是機翼剖面的形狀。機翼剖面多為不對稱形，如下弧平直上弧向上彎曲(平凸型)和上下弧都向上彎曲(凹凸型)。對稱翼型則必須有一定的迎角才產生升力。

There are two reasons for the change of the flow velocity of the wing: a. asymmetric airfoil; B. The wing and relative air flow have an angle of attack. An airfoil is the shape of an airfoil section. The wing profile is mostly asymmetrical, and the following arcs are straight and upward curved (flat and convex), and the upper and lower arcs are upward curved (concave and convex). Symmetrical airfoils must have a certain angle of attack to generate lift.

升力的大小主要取決于四個因素：a、升力與機翼面積成正比;b、升力和飛機速度的平方成正比。同樣條件下，飛行速度越快升力越大;c、升力與翼型有關，通常不對稱翼型機翼的升力較大;d、升力與迎角有關，小迎角時升力(系數)隨迎角直線增長，到一定界限后迎角增大升力反而急速減小，這個分界叫臨界迎角。

The lift is mainly determined by four factors: a. The lift is proportional to the wing area; B. The lift is proportional to the square of the aircraft speed. Under the same conditions, the faster the flight speed, the greater the lift; C. The lift is related to the airfoil. Generally, the lift of asymmetric airfoil wings is large; D. The lift is related to the angle of attack. At a small angle of attack, the lift (coefficient) increases linearly with the angle of attack. When the angle of attack increases, the lift decreases rapidly. This boundary is called the critical angle of attack.

機翼和水平尾翼除產生升力外也產生阻力，其他部件一般只產生阻力。

The wing and horizontal tail generate drag in addition to lift, and other components generally only generate drag.

二、平飛

2、 Level flight

水平勻速直線飛行叫平飛。平飛是基本的飛行姿態。維持平飛的條件是：升力等于重力，拉力等于阻力。

Horizontal uniform straight flight is called level flight. Level flight is the basic flight attitude. The conditions for maintaining level flight are that lift equals gravity and pull equals drag.

由于升力、阻力都和飛行速度有關，一架原來平飛中的模型如果增大了馬力，拉力就會大于阻力使飛行速度加快。飛行速度加快后，升力隨之增大，升力大于重力模型將逐漸爬升。為了使模型在較大馬力和飛行速度下仍保持平飛，就必須相應減小迎角。反之，為了使模型在較小馬力和速度條件下維持平飛，就必須相應的加大迎角。所以操縱(調整)模型到平飛狀態，實質上是發動機馬力和飛行迎角的正確匹配。

Since the lift and drag are related to the flight speed, if the horsepower of a model in the original level flight is increased, the pull will be greater than the drag to speed up the flight speed. As the flight speed increases, the lift will increase, and the model with lift greater than gravity will gradually climb. In order to maintain the level flight of the model at higher horsepower and flight speed, the angle of attack must be reduced accordingly. On the contrary, in order to maintain the level flight of the model under the condition of small horsepower and speed, the angle of attack must be correspondingly increased. So controlling (adjusting) the model to level flight is essentially the correct match between engine horsepower and flight angle of attack.

三、爬升

3、 Climb

前面提到模型平飛時如加大馬力就轉為爬升的情況。爬升軌跡與水平面形成的夾角叫爬升角。一定馬力在一定爬升角條件下可能達到新的力平衡，模型進入穩定爬升狀態(速度和爬角都保持不變)。穩定爬升的具體條件是：拉力等于阻力加重力向后的分力(F=X十Gsinθ);升力等于重力的另一分力(Y=GCosθ)。爬升時一部分重力由拉力負擔，所以需要較大的拉力，升力的負擔反而減少了。和平飛相似，為了保持一定爬升角條件下的穩定爬升，也需要馬力和迎角的恰當匹配。打破了這種匹配將不能保持穩定爬升。例如馬力增大將引起速度增大，升力增大，使爬升角增大。如馬力太大，將使爬升角不斷增大，模型沿弧形軌跡爬升，這就是常見的拉翻現象。

As mentioned earlier, when the model is in level flight, if it increases the horsepower, it will change to climbing. The included angle between the climb path and the horizontal plane is called the climb angle. A certain horsepower may reach a new force balance under a certain climbing angle, and the model enters a stable climbing state (both speed and climbing angle remain unchanged). The specific condition for stable climbing is that the pulling force is equal to the backward component of resistance plus gravity (F=X X Gsin θ); Lift equals another component of gravity (Y=GCos θ)。 When climbing, part of the gravity is borne by the pull force, so it needs a larger pull force, and the lifting force burden is reduced. Similar to peace flight, in order to maintain a stable climb at a certain angle of climb, the proper matching of horsepower and angle of attack is also required. Breaking this match will not maintain stable climbing. For example, an increase in horsepower will cause an increase in speed, lift and climb angle. If the horsepower is too high, the climbing angle will increase continuously, and the model will climb along the arc path, which is a common phenomenon of pull-over.

四、滑翔

4、 Glide

滑翔是沒有動力的飛行。滑翔時，模型的阻力由重力的分力平衡，所以滑翔只能沿斜線向下飛行。滑翔軌跡與水平面的夾角叫滑翔角。

Gliding is flight without power. When gliding, the resistance of the model is balanced by the component of gravity, so gliding can only fly downward along the oblique line. The angle between the glide path and the horizontal plane is called the glide angle.

穩定滑翔(滑翔角、滑翔速度均保持不變)的條件是：阻力等于重力的向前分力(X=GSinθ);升力等于重力的另一分力(Y=GCosθ)。

The condition for stable glide (glide angle and glide speed remain unchanged) is that the resistance is equal to the forward component of gravity (X=GSin θ); Lift equals another component of gravity (Y=GCos θ)。

滑翔角是滑翔性能的重要方面。滑翔角越小，在同一高度的滑翔距離越遠。滑翔距離(L)與下降高度(h)的比值叫滑翔比(k)，滑翔比等于滑翔角的余切滑翔比，等于模型升力與阻力之比(升阻比)。Ctgθ=1/h=k。

Gliding angle is an important aspect of gliding performance. The smaller the gliding angle, the farther the gliding distance at the same height. The ratio of the glide distance (L) to the descent height (h) is called the glide ratio (k). The glide ratio is equal to the cotangent glide ratio of the glide angle, and is equal to the ratio of the lift to the drag of the model (lift-drag ratio). Ctg θ= 1/h=k。

滑翔速度是滑翔性能的另一個重要方面。模型升力系數越大，滑翔速度越小;模型翼載荷越大，滑翔速度越大。

Gliding speed is another important aspect of gliding performance. The higher the lift coefficient of the model, the smaller the glide speed; The greater the model wing load, the greater the glide speed.

調整某一架模型飛機時，主要用升降調整片和前后移動來改變機翼迎角以達到改變滑翔狀態的目的。

When adjusting a certain model aircraft, the wing angle of attack is mainly changed by using the lifting adjustment piece and the center of gravity moving forward and backward to achieve the purpose of changing the glide state.

五、力矩平衡和調整手段

5、 Torque balance and adjustment means

調整模型不但要注意力的平衡，同時還要注意力矩的平衡。力矩是力的轉動作用。模型飛機在空中的轉動是自身的，所以重力對模型不產生轉動力矩。其它的力只要不通，就對產生力矩。為了便于對模型轉動進行分析，把繞的轉動分解為繞三根假想軸的轉動，這三根軸互相垂直并交于。貫穿模型前后的叫縱軸，繞縱軸的轉動就是模型的滾轉;貫穿模型上下的叫立軸，繞立軸的轉動是模型的方向偏轉;貫穿模型左右的叫橫軸，繞橫軸的轉動是模型的俯仰。

Adjusting the model requires not only the balance of attention, but also the balance of torque. Moment is the rotational action of force. The rotation center of the model aircraft in the air is its own center of gravity, so gravity does not produce rotation torque on the model. As long as other forces do not reach the center of gravity, they will produce torque to the center of gravity. In order to facilitate the analysis of model rotation, the rotation around the center of gravity is decomposed into rotation around three imaginary axes, which are perpendicular to each other and intersect at the center of gravity. The longitudinal axis runs through the front and back of the model, and the rotation around the longitudinal axis is the rolling of the model; The vertical axis runs through the top and bottom of the model, and the rotation around the vertical axis is the direction deflection of the model; The horizontal axis runs through the left and right of the model, and the rotation around the horizontal axis is the pitch of the model.

對于調整模型來說，主要涉及四種力矩;這就是機翼的升力力矩，水平尾翼的升力力矩;發動機的拉力力矩;動力系統的反作用力矩。

For the adjustment model, it mainly involves four kinds of moments; This is the lift moment of the wing, the lift moment of the horizontal tail; Tensile torque of engine; Reaction torque of power system.

機翼升力力矩與俯仰平衡有關。決定機翼升力矩的主要因素有縱向位置、機翼安裝角、機翼面積。

The wing lift moment is related to the pitch balance. The main factors that determine the wing lift moment are the longitudinal position of the center of gravity, the wing installation angle, and the wing area.

水平尾翼升力力矩也是俯仰力矩，它的大小取決于尾力臂、水平尾翼安裝角和面積。

The lift moment of the horizontal tail is also the pitching moment, and its size depends on the installation angle and area of the tail arm and the horizontal tail.

拉力線如果不通過就會形成俯仰力矩或方向力矩，拉力力矩的大小決定于拉力和拉力線偏離距離的大小。發動機反作用力矩是橫側(滾轉)力矩，它的方向和螺旋槳旋轉方向相反，它的大小與動力和螺旋槳質量有關。

If the tension line does not pass through the center of gravity, it will form pitching moment or directional moment. The magnitude of the tension moment depends on the magnitude of the distance between the tension line and the center of gravity. The reaction torque of the engine is the lateral (rolling) torque, its direction is opposite to the rotation direction of the propeller, and its magnitude is related to the power and the mass of the propeller.

俯仰力矩平衡決定機翼的迎角：增大抬頭力矩或減小低頭力矩將增大迎角;反之將減小迎角。所以俯仰力矩平衡的調整為重要。一般用升降調整片、調整機翼或水平尾翼安裝角、改變拉力上下傾角、前后移動未實現。

The angle of attack of the wing is determined by the balance of the pitching moment: the angle of attack will be increased by increasing the heading moment or decreasing the bow moment; Otherwise, the angle of attack will be reduced. Therefore, the adjustment of pitch moment balance is very important. Generally, it is not achieved by adjusting the installation angle of the wing or horizontal tail, changing the pull up and down inclination, and moving the center of gravity forward and backward.