GATE 2021 AE – Question 45
Which aircraft-performance statements are correct?
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Show answer and explanation
Correct answer: (B) For a given aircraft, stall speed increases with altitude.; (C) Everything else remaining the same, a tailwind increases aircraft range.; (D) For a jet constrained to fly at constant altitude, there exists an altitude where range is maximum.
Explanation
Check each statement about aircraft performance.
- **A. The service ceiling is higher than the absolute ceiling.** False. The service ceiling (where the maximum rate of climb is 100 ft/min) is **below** the absolute ceiling (maximum rate of climb zero).
- **B. Stall speed increases with altitude.** True. The stall speed is $V_s=\sqrt{2W/(\rho SC_{L,max})}$, and as $\rho$ falls with altitude the (true) stall speed rises. ✓
- **C. A tailwind increases the range.** True. The ground distance covered per unit fuel is larger with a tailwind. ✓
- **D. For a jet constrained to constant altitude, there is an altitude with maximum range.** True. Range depends on the density and the engine performance at that altitude, so it has an optimum. ✓
Answer **B, C and D**.
Official GATE 2021 answer key: https://gate2026.iitg.ac.in/doc/download/Answer_keys2021/ae_2021.pdf