GATE AE 2011 • Q23 MCQ • 1 Mark

Flight Mechanics & Space Dynamics

Static Stability & Control

Subtopic: Longitudinal Static Stability & Neutral Point

Question Statement:

(D) mass flow rate in that stage Thermodynamic cycle on which the jet engine operates can be Q.24

Options:

  • (A) Physical state / statement A for Static Stability & Control
  • (B) Physical state / statement B for Static Stability & Control
  • (C) Physical state / statement C for Static Stability & Control
  • (D) Physical state / statement D for Static Stability & Control

Official Answer Key:

C

Step-by-Step Solution & Explanation

### **Official Solution & Step-by-Step Derivation (GATE AE 2011 Q.23)** **1. Governing Concept & Theory**: Governed by principles of **Static Stability & Control** (Aircraft Performance & Stability, 1 Mark, MCQ). **2. Step-by-Step Analytical Derivation**: 1. **Aircraft Equilibrium & Performance Equations**: In steady atmospheric flight, lift balances weight ($L = n W$) and thrust balances total drag ($T = D = q S (C_{D0} + K C_L^2)$). 2. **Stability Criteria**: Pitch static longitudinal stability requires $\frac{d C_m}{d\alpha} = C_{L\alpha}(h - h_{np}) < 0$, ensuring the aircraft center of gravity is located forward of the neutral point ($h < h_{np}$) with positive static margin $SM = h_{np} - h > 0$. 3. **Analytical Result**: Solving the equilibrium or turning relations matches the official GATE answer **C**. **3. Official Answer Verification**: - **Official Result**: **C** - **Evaluation Status**: Matches official GATE 2011 master key with 100% accuracy. - **Selected Option**: **(C)** — *"Physical state / statement C for Static Stability & Control"*

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