Prof. E.G. Tulapurkara

Chapter 1 Introduction (Lectures 1,2 and 3)

Keywords : Importance of stability and control analysis ; brief historical background ; basic concepts – static stability, dynamic stability, longitudinal, lateral and directional stability, control fixed and control free stability ; controllability; subdivisions of the subject; course outline. Topics 1.1 Opening remarks 1.2 Brief outline of historical developments 1.2.1 Early developments 1.2.2 Subsequent developments 1.3 Basic concepts about airplane stability and control 1.3.1 Stable, Unstable and neutrally stable states of equilibrium 1.3.2 Types of motions following of disturbance – subsidence, divergence, neutral stability, damped oscillations, divergent oscillation and undamped oscillation. 1.3.3 Static stability and dynamic stability 1.3.4 Recapitulation of some terms – body axes system, earth fixed axes systems, attitude, angle of attack and angle of sideslip 1.3.5 Longitudinal and lateral stability 1.3.6 Control fixed and control free stability 1.3.7 Subdivisions of stability analysis 1.4 Controllability 1.5 General remarks 1.5.1 Examples of stability in day-to-day life 1.5.2 Airplane stability depends on flight condition 1.5.3 Stability and controllability are not the same 1.5.4 Stability is desirable but not necessary for piloted airplanes 1.5.5 Small disturbance analysis of stability

Dept. of Aerospace Engg., IIT Madras

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Flight dynamics –II Stability and control 1.5.6 Rigorous definition of terms 1.6 Course content 1.7 Back ground expected References Exercises

Prof. E.G. Tulapurkara

Dept. of Aerospace Engg., IIT Madras

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Flight dynamics –II Stability and control

Prof. E.G. Tulapurkara

Chapter 1 Lecture 1 Introduction – 1 Topics

1.1 Opening remarks 1.2 Brief outline of historical developments 1.2.1 Early developments 1.2.2 Subsequent developments 1.3 Basic concepts about airplane stability and control 1.3.1 Stable, Unstable and neutrally stable states of equilibrium 1.3.2 Types of motions following of disturbance – subsidence, divergence, neutral stability, damped oscillations, divergent oscillation and undamped oscillation.

1.1 Opening remarks In the introduction to flight dynamics-I, it was mentioned that flight dynamics deals with the motion of objects moving in earth‟s atmosphere. The attention in that course and the present one is focused on the motion of the airplane. Helicopters, rockets and missiles are not covered. Flight dynamics is subdivided into two main topics viz. (a) airplane performance and (b) airplane stability and control. Airplane performance was dealt with in flight dynamics-I.This course, deals with stability and control. Stability and control of airplane is one of the fascinating subjects in aeronautics. This is because of the following reasons. A detailed theoretical analysis of the stability and control of an airplane requires sophisticated mathematical techniques while its experimental

assessment calls for sophisticated wind tunnel and flight test techniques. Hence, this topic has an appeal for both the theoretician and the experimentalist. Further, the importance of stability and control analysis can be judged from the fact that

Dept. of Aerospace Engg., IIT Madras

3

Flight dynamics –II Stability and control

Prof. E.G. Tulapurkara

the lack of adequate stability and control was the cause for the failure of early heavier than air machines to sustain themselves in air. The historical developments in this subject are briefly dealt with in the next section, which is followed by (a) discussion of the basic concepts of airplane stability and control,(b) course content and (c) back ground expected from the reader. 1.2 Brief outline of historical developments 1.2.1 Early developments The first attempts to study the stability of vehicles in flight were made by Sir George Cayley (1774-1857) who also carried out experiments on...