直升機(jī)飛行力學(xué)復(fù)習(xí)題答案

1、Chapter OneA helicopter of central articulated rotor makes a level flight with cruse speed. In this flight condition, the pitching attitude angle is : - -20, longitudinal cyclic pitching angle is Bi 70, rotor longitudinal flapping angle is a1s = -30. Assuming the tilted angle of rotor shaft is :. =

2、00, please determining the following angles: Helicopter climb angle1二 Fuselage attack angle ;二 Rotor attack angle : s =Rotor flapping due to forward speed a10 =中心較式旋翼直升機(jī)以巡航速度前飛。俯仰角 -2。，縱向周 期變距7 ,縱向揮舞角-3 ,旋翼軸前傾角0 平飛，爬升角0機(jī)身迎角-2 槳盤平面迎角-2 吹風(fēng)揮舞4Chapter Two1. For the main/tail rotor configuration helicopt

3、er, the pilot applies which stick or rudder to control what kind of surfaces and corresponding aerodynamic forces?2. Why the gradient of control stick forces can t be too large or small?3. Co-axis, tandem and tilted-rotor helicopters have no tail rotor. How to change the direction in hover for these

4、 helicopters?1. 操縱一一氣動面一一響應(yīng)P13表2-1前推/后拉桿縱向周期變距，槳盤前傾/后倒前飛/后飛，俯仰左推/右推桿操操橫向周期變距，槳盤側(cè)倒操操側(cè)飛，滾轉(zhuǎn)油門/總距桿操操改變總距操操改變垂向速度腳蹬操操改變尾槳總距操操改變航向2. 為什么桿力梯度不能太大也不能太小P16太大時(shí)大操縱較吃力，太小了不易感覺當(dāng)前位移量。桿力梯度適中有利于精確操縱。3. 共軸、縱列、傾轉(zhuǎn)旋翼機(jī)如何懸停轉(zhuǎn)彎？共軸操操上下旋翼總距差動縱列操操前后橫向周期變距一個(gè)向左一個(gè)向右傾轉(zhuǎn)旋翼操操一側(cè)后倒一側(cè)前倒Chapter Three1. The rotation direction of Black ha

5、wk helicopter rotor is anticlockwise from the top view. Please answer the following questions:How the rotor flaps when the helicopter comes up gust in hover?How to adjust the controller to keep the hover condition?How the blade changes its feathering angle following the pilot s adjustment?2. During

6、left and right turn flights with constant speed and altitude, is there any different for pilot controls?3. Is there flapping motion for hinge-less rotor?1 . 黑鷹直升機(jī)旋翼右旋懸停時(shí)遇到陣風(fēng)旋翼如何揮舞，此時(shí)如何操縱前方來的陣風(fēng)會導(dǎo)致旋翼后倒，右倒。應(yīng)向前、向左推桿。前推桿導(dǎo)致90槳距變小，270槳距變大左推桿導(dǎo)致180槳距變小， 0槳距變大2 .不改變高度和速度時(shí)，左轉(zhuǎn)彎和右轉(zhuǎn)彎有區(qū)別沒？以右旋直升機(jī)為例，左轉(zhuǎn)時(shí)需要增加尾槳總距，為了平衡

7、尾槳拉力的增加需要左推桿以增加側(cè)向力，這卻導(dǎo)致了旋翼拉力的降低，進(jìn)而需要提總距，又導(dǎo)致向前拉力的增加，因而需要后拉桿?？傊?，右旋直升機(jī)前飛左轉(zhuǎn)彎的操縱為，踩腳蹬左壓桿提總距后拉桿。同理， 右旋直升機(jī)右轉(zhuǎn)彎的操縱為：松腳蹬減小左壓桿減總距減小前推桿3 .無鉸式旋翼有揮舞嗎？沒有揮舞鉸但是通過槳葉根部的柔性段或者槳榖柔性件的彈性變形實(shí)現(xiàn)揮舞運(yùn)動。Chapter FourWhich items in the linear equations of helicopter motion reflect the longitudinal and lateral cross-coupling effect?

8、直升機(jī)線化運(yùn)動方程中哪些項(xiàng)體現(xiàn)了橫縱向的耦合P53操縱輸入系數(shù)矩陣C 中， FX 對橫向周期變距A1 、 FZ 對縱向周期變距B1 的導(dǎo)數(shù)均不為0，即橫向周期變距對后向力有影響，而縱向周期變距對側(cè)向力也有影響。Chapter Five1. What is the mission of helicopter trim calculation?2. In order to keep the center of helicopter mass in the specified range it is necessary to check the helicopter loadings before

9、flight. Why the center of helicopter mass must be in the specified range?3. The tail rotor of some helicopters is lower than main rotor. What is the advantagesand disadvantageswhen the tail rotor is lower than main rotor?4. Bell-412 helicopter releases left and right buoys for making an urgent ladin

10、g on the water surface. Compare the differences of pilot controls and helicopter attitude before and after releasing buoys.配平的任務(wù)是什么根據(jù)平衡條件確定直升機(jī)穩(wěn)定飛行所需的操縱量和直升機(jī)的姿態(tài)角。為什么重心在特定的范圍內(nèi)重心太前抑制直升機(jī)后飛及懸停低速性能，而太靠后則影響大速度前飛性能以及穩(wěn)定性，因此重心需要限制在一定的范圍內(nèi)。尾槳低于旋翼的好處及壞處P70好處：尾梁扭轉(zhuǎn)載荷不大，不需要加固垂尾以安裝尾槳?？傊梢詼p小結(jié)構(gòu)重量。Chapter Six壞處：前飛時(shí)尾槳槳盤

11、處于旋翼下洗流中，直升機(jī)需側(cè)傾一個(gè)角度以平衡尾槳、旋翼高度差所引起的滾轉(zhuǎn)力矩。比較有無浮筒時(shí)駕駛員的操縱增加浮筒，相當(dāng)于在前飛時(shí)增加一個(gè)作用于重心以下的后向力，相比于無浮筒時(shí)駕駛員的操縱，需要增加縱向周期變距、提高總距、減小橫向周期變距、增加尾槳總距。1. The feathering angle of horizontal tail is negative. Analysis the speed stability and pitch damping if the feathering angle of horizontal tail is positive.2. Analysis the

12、effect of flapping hinge offset on the speed stability, attack angle stability, diheadral effect and yaw stability.3. What is the different of longitudinal hover oscillation from lateral hover oscillation?4. Why co-axis helicopter always uses two vertical tails?分析速度穩(wěn)定性及俯仰阻尼，當(dāng)平尾正裝的時(shí)候穩(wěn)定前飛時(shí)，前方來流速度的增量將導(dǎo)

13、致平尾上產(chǎn)生一個(gè)額外的低頭力矩，因而是速度不穩(wěn)定的。當(dāng)直升機(jī)以俯仰角速度繞Z 軸轉(zhuǎn)動時(shí)，比如抬頭，將使得平尾的迎角增加，產(chǎn)生額外的低頭力矩，阻礙直升機(jī)抬頭，因而是阻尼力矩。分析揮舞鉸偏置量對速度穩(wěn)定性、迎角穩(wěn)定性、上反效應(yīng)及航向穩(wěn)定性的影響。當(dāng)飛行速度增加時(shí)，來流左右不對稱性增加導(dǎo)致槳尖平面后倒，所引起的槳榖力矩使得直升機(jī)抬頭，因而揮舞鉸偏置量對速度的變化是起靜穩(wěn)定作用的。當(dāng)機(jī)身迎角增加時(shí)，前行槳葉升力增加的多些，后行槳葉升力增加的少些，導(dǎo)致槳尖平面后倒，所附加的槳裁力矩也使 得直升機(jī)抬頭，因而揮舞較偏置量是迎角靜不穩(wěn)定的。當(dāng)直升機(jī)向右傾斜時(shí)，拉力分量導(dǎo)致直升機(jī)向右移動，進(jìn)而 導(dǎo)致旋翼前后氣流

14、不對稱引起槳尖平面左倒，所附加的槳裁 力矩也使得機(jī)身左傾，因而是靜穩(wěn)定的?？v向懸停振蕩模態(tài)與橫向懸停振蕩模態(tài)的區(qū)別縱向懸停振蕩：該模態(tài)類似于單擺運(yùn)動，表現(xiàn)為速度與俯仰 角兩個(gè)運(yùn)動變量之間的耦合，但由于旋翼是迎角靜不穩(wěn)定 的，該模態(tài)往往是振蕩發(fā)散的。橫向懸停振蕩：與縱向懸停振蕩類似，但由于尾槳垂尾的存 在，該模態(tài)除了滾轉(zhuǎn)角與側(cè)向速度兩個(gè)變量的耦合，還附加 了航向的擺動；如果尾槳垂尾提供的側(cè)向阻尼足夠大，該模 態(tài)將是振蕩收斂的。為什么共軸雙旋翼需要兩個(gè)垂尾因?yàn)闆]有尾槳，共軸雙旋翼需要更大面積的垂尾來提供航向 穩(wěn)定性、橫向運(yùn)動阻尼、航向運(yùn)動阻尼。從減輕結(jié)構(gòu)重量的 角度上講，需要面積相同時(shí)，雙垂尾比單

15、垂尾更有利。Chapter Seven1. What is the physical meaning of helicopter control bandwidth?2. Analysis the effects of following factors on the damping, control sensitivity and time constant of helicopter vertical motion.Increasing rotor solidityIncreasing rotor rotational speed3. There is no oscillation for

16、 the response of helicopter to collective pitch control, while the responses of helicopter to stick or rudder are oscillation. Why?帶寬的物理含義直升機(jī)對于低頻操縱有較好的跟隨性，操縱響應(yīng)幅值與操縱量成正比，相位之后也較??；在進(jìn)行高頻操縱時(shí)，直升機(jī)跟 隨性變差，滯后變大且響應(yīng)幅度減小。因而直升機(jī)存在一個(gè) 操縱頻率的適應(yīng)范圍，稱為帶寬。分析下列因素對直升機(jī)垂直運(yùn)動的阻尼、操縱靈敏度及時(shí)間常數(shù)的影響增加實(shí)度增加槳尖速度僅僅考慮旋翼的作用Fy 4?，1R2 R2 1(vy) 2322Fy 7 J DR2-：R2H ，6_V1_2Fy =D JR 二R ra.4d. Vy VmFyy Vy Fy，：7dt. ：Vy(S)Fy 7 k=v 二17(s) ms -Fyy Ts 1其中 k=-Fy*/F：y =|cR, T=mF：y當(dāng)旋翼實(shí)度增加時(shí)，運(yùn)動阻尼增加，操縱靈敏度不變，時(shí)間常數(shù)減小。當(dāng)槳尖速度增加時(shí)，運(yùn)動阻尼增加，操縱靈敏度增加，時(shí)間 常數(shù)減小。直升機(jī)對總距控制的