曝光台 注意防骗
网曝天猫店富美金盛家居专营店坑蒙拐骗欺诈消费者
Substituting and simplifying, we get
(C,p)WtB) = -0.061CX (~78~) [1+0.1705 * (1 + 0.7853)] (1 + O 72853)
X (~)+ _;.:b_796 +(,)4'3l+35(1.0560*10_4
- 0.0000261) + 0.009105 - -0.001725CN + 0.000816
From the solution ofExample 3.8, for M - 2.0, we have ay - 1.8338lrad, k =
On6, (i+[au/ap])~ = 1.2012, Sv/S - 0.1909, z, - 3.8290 m,/u = 7.7561 m,
and b - 17.3228 m. Substituting these values in Eq. (3.374), we get
(Cip)v - -0.001233 + 0.000044ct
where a is in degrees. Then, summing up wing and tail contributions,
Clp = ct(0.000044 - 0.001725CLa) - 0.000417
where a is in degrees and CLu iS given in Fig. 3.60. Thus, we observe that this
vehicle has adequate lateral stability at subsonic and supersonic speeds. It should
be remembered that these results are based on crude approximation of vertical tail
contribution to lateral stability at supersonic speeds.
3.7 Summar\t
In this chapter, we have studied the concepts of static stability and control. The
airplane was assumed to be a rigid body and possess a vertical plane of symmetry.
The aerodynamic forces and moments were assumed to be linear functions of angle
of attack/sideslip and control surface deflections. We assumed that the longitudinal
control deflections do not produce lateral-directional forces or moments and vice
versa. The effect of power was ignored. Under these assumptions, it was possible
to assume that the longitudinal and lateral- directional motions of the airplane are
indepcndent of each other, and we could study the associated concepts of static
stability and control separately.
The static stability is the inherent capability (open-loop stability) of the airplane
to counter a disturbance in angle of attack or sideslip. The stability with respect
to a disturbance in angle of attack is called the longitudinal stability. We have two
types ofstabilities, lateral and directional, with respect to a disturbance in sideslip.
Usually, the lateral and directional motions are always aerodynamically couple9:
Everything else remairung the same, the location of the center of gravity has a
312 PERFORMANCE, STABILITY, DYNAMICS, AND CONTROL
significant influence on the level of the static Iongitudinal stability. The center of
gravity location has some effect on the static directional stability but very little or
no infiuence on the static lateral stability.
The methods of analyses of static longitudinal stability were extended to simple
maneuvers like pull-up in a vertical plane and steady turns in a horizontal plane.
For an airplane to be safely flyable,it must be capable oftrim and have adequate
levels of longitudinal, lateral, and directional stabilities. In this chapter, we have
studied how these stabilit)r levels are related to various geometric, aerodynamic,
and mass properties (center of gravity location). We have also presented meth-
ods suitable for prelinunary estimation of these characteristics at subsonic and
supersonic speeds for typical air:plane configurations.
Quite often, to improve the performance, the inherent stability of the airplane is
compromised. For safe flyability, such airplanes have to be provided with artificial
(closed-loop) stability. This forms the subject matter of automatic flight control
systems, which we will study in Chapter 6.
The controllability of the airplane is inversely proportional to the level of stabi-
lity. The elevator is the primary longitudinal control, and the ailerons and rudder
are the primary roll and yaw control devices. We found that the stick or pedal
forces associated with the defiection of these control surfaces are direcdy related
to their hinge-moment characteristics. For adequate feel and ease of flying, the
stick or pedal forces must lie within normally acceptable limits.
In Lhe next chapters, we will study the dynamic motions of the airplane. The
basic concepts we have studied here will be very usefulin understanding the more
complex subject of airplane dynamics and control.
References
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：
PERFORMANCE, STABILITY, DYNAMICS, AND CONTROL2(89)
