GATE 2021 AE – Question 46
Which static-stability statements are correct?
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Show answer and explanation
Correct answer: (A) The vertical tail contributes to lateral stability.; (D) The horizontal tail contributes to longitudinal stability.
Explanation
Check each statement about static stability.
- **A. The vertical tail contributes to lateral stability.** True. A vertical tail above the centre of gravity produces a rolling moment in a sideslip (a dihedral effect). ✓
- **B. The vertical tail contributes to directional instability.** False. The vertical tail is the main source of **directional stability** (weathercock effect).
- **C. Wing anhedral contributes to lateral stability.** False. Anhedral (negative dihedral) is **destabilising** in roll; dihedral is stabilising.
- **D. The horizontal tail contributes to longitudinal stability.** True. It provides a restoring pitching moment. ✓
Answer **A and D**.