# Anna University Exam Papers BE-VI Sem-Aircraft Stability and Control

ANNA UNIVERSITY, CHENNAI 25

MODEL QUESTION PAPER

B.E. Aeronautical Engineering, VI SEMESTER

### TIME – 3 Hours                                                                                                                            MAXIMUM : 100 Marks

1.         Define static stability and dynamic stability.

2.         What do you mean by degree of freedom.

3.         What is meant by aileron reversal?

4.         What is snaking. Sketch the snaking motion of an aircraft.

5.         Difference between stick fixed and stick free.

6.         What is meant by `Weather Cock Stability’.

7.         What are the condition for longitudinal static stability.

8.         How is dihedral useful for lateral stability.

9.         What is porpoising mode?

10.       What is meant by phugoid oscillation? Explain.

PART B                                      (5 X 16 = 80 Marks)

11 (a)               Explain the significance of Routh’s discriminant.                                          (8)

(b)                 Drive an expression for the tail contribution to the pitching moment of an aircraft

if i? is the wing setting angle and it is the tail setting angle.                         (8)

12 (a)              A wing body model is tested in a subsonic wind tunnel.

?L=0 = -1.50, at ? = 50, CL is 0.52. At ? = 10 and 7.880 CMcg are -0.01 and 0.05

respectively. The c.g location is 0.35c. iw = 0 and tail volume ratio is 0.34. The

tail  setting    is 2.70 and the tail lift curve slope is 0.1 per degree. ?0 = 0 and

d?/d? =  0.35. At ? = 80, calculated CMcg for the aircraft.                            (16)

( OR )

(b)              i.          Discuss in detail the power effects on longitudinal static stability.   (8)

ii          For the problem in 12, find the neutral point location and also

static margin.                                                                                       (8)

13(a)                Write short notes on

i.          Variable incidence tail plane                                                               (8)

( OR )

(b)                i.          What is the coupling between rolling and yawing moments, explain

with suitable examples.                                                                       (8)

ii.         What is the effect of running propeller on directional stability                      (8)

14 (a)               Explain the following Phenomenon

i.          Dutch Roll                                                                                          (6)

ii.         Spiral instability                                                                                  (5)

iii.        Spin                                                                                                     (5)

( OR )

(b)               Write short notes on

i.          Stability derivatives in longitudinal dynamic stability                                   (6)

ii.         Stability quartic                                                                                   (5)

iii.        Spoils in lateral control                                                                       (5)

15 (a)               An airplane W/s = 3000 N/m2, V = 450 kmph flying at 6 km attitude

has the  characteristic equation in longitudinal mode of the form

(?2 + ? + 6) (3?2 + ? + 1) = 0. Find the period and time to dump

and comment whether oscillation can be ignored.                                          (16)

( OR )

(b)              Write short notes on

i.          Tail volume ratio                                                                                 (5)

ii.         Controls of aircraft                                                                             (6)

iii.        Rudder requirement in directional control                                          (5)