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1、Ch. 4 Flight Performance transport aircraft performance： take-off performance 起飞性能 climb performance 爬升性能 cruise performance 巡航性能 descending performance 下降性能 landing performance 着陆性能 turning performance 盘旋性能 engine-out performance 发动机失效后性能 stalling performance 失速性能4.1 take-off performance Consider a
2、n airplane standing motionless at the end of a runway. The pilot releases the brakes and pushes the throttle to maximum take-off power，and the airplane accelerates down the runway. At some distance from its starting point，the airplane lifts into the air.4.1.1 Forces acting on an aircraft in take-off
3、 The forces acting on an aircraft in take-off are weight W、lift L、thrust T、drag D and a rolling resistance R caused by friction between the tires and the ground. This resistance force is given by the coefficient of rolling friction and the net normal force（W-L）exerted between the tires and the groun
4、d.4.1.2 take-off distance The sum of Sg and Sa is the total take-off distance for the airplane. The Sg is called the ground roll（or sometimes the ground run）which is covered along the runway before the airplane lifts into the air. The Sa is the take-off distance in airborne over the obstacle which i
5、s generally defined to be 50ft for military aircraft and 35ft for commercial aircraft. The ground roll Sg is further divided into intermediate segments. These segments are defined by various velocities，as follows：1,Vstall stalling speed 失速速度2,Vmcg minimum control speed on the ground 地面最小可操纵速度 This i
6、s the minimum speed at which enough aerodynamic force can be generated on the vertical fin with rudder deflection while the airplane is still rolling along the ground to produce a yawing moment sufficient to counteract that produced when there is an engine failure for a multiengine aircraft.3,Vmca m
7、inimum control speed in the air空中最小可操纵速度 If the airplane were in the air（without the landing gear in contact with the ground）, the minimum speed required for yaw control in case of engine failure is slightly greater than Vmcg. For the ground roll shown in Fig.，Vmca is essentia1ly a reference speed-t
8、he airplane is still on the ground when this speed is reached. 4,V1 decision speed 决断速度 This is the speed at which the pilot can successfully continue the take-off even though an engine failure（in a multiengine aircraft）would occur at that point. This speed must be equal to or larger than Vmcg in or
9、der to maintain control of the airplane. If an engine fails before V1 is achieved，the take-off must be stopped. If an engine fails after V1 is reached，the take-off can be achieved.5,VR take-off rotational speed 起飞抬前轮速度 At this velocity, the pilot initiates by elevator deflection a rotation of the ai
10、rplane in order to increase the angle of attack, hence to increase CL. Clearly, the maximum angle of attack achieved during rotation should not exceed the stalling angle of attack. Actually, all this is needed is an angle of attack high enough to produce a lift at the given velocity larger than the
11、weight, so that the airplane will lift off the ground. However, even this angle of attack may not be achievable because the tail may drag by the ground.（Ground clearance for the tail after rotation is an important design feature for the airplane, imposed by take-off considerations.）6, Vmu minimum un
12、stick speed 最小松杆速度If the rotation of the airplane is limited by ground clearance for the tail, the airplane must continue to accelerate while rolling along the ground after rotation is achieved，until a higher speed is reached where indeed the lift becomes lager than weight. This speed is called the
13、minimum unstick speed.7,VLO liftoff speed 起飞速度，离地速度 For increased safety, the angle of attack after rotation is slightly less than the maximum allowable by tail clearance, and the airplane continues to accelerate to a slightly higher velocity, called the liftoff speed, denoted by VLO. This is point
14、at which the airplane actually lifts off the ground. The total distance covered along the ground to this point is the ground roll Sg. 4.1.3 Factors affecting take-off performance The design parameters have an important effect on take-off ground roll. Sg depends on wing load W/S, thrust-to-weight T/W
15、 and maximum lift coefficient（CL）max, the ambient density wind and ground conditions. Sg increases with an increase in W/S.Sg decreases with an increase in（CL）max.Sg decreases with an increase in T/W.Sg increases with a decrease in .Sg increases with a tailwind，and decreases with a headwind.4.2 Climb performance zooming 急跃升 power required 需用功率 thrust required 需用推力 power available 可用功率 thrust available 可用推力excess power 富裕功率 excess thrust 富裕推力A climb is an ascending flight path at constant speed.It is usually a straight path but, sometimes, a climbing turn is necess
