(D) placing stiffeners farther and decreasing internal pressure.
2012 AEROSPACE ENGINEERING - AE
AE 7/12
Common Data Questions
Common Data for Questions 48 and 49:
A wing and tail are geometrically similar, while tail area is one-third of the wing area and distance between
two aerodynamic centres is equal to wing semi-span ( b/2). In addition, following data is applicable:
0.3, 1.0, 0.08 / deg., 2.5 , 30 , 0, 1.
acLL M tCC c m b m C
αα η∈= = = = = = = The symbols have their usual
aerodynamic interpretation.
Official Answer Key:
A
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE AE 2012 Q.47)**
**1. Governing Concept & Theory**:
Governed by principles of **Atmospheric Flight Mechanics** (Aircraft Performance & Stability, 2 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 **A**.
**3. Official Answer Verification**:
- **Official Result**: **A**
- **Evaluation Status**: Matches official GATE 2012 master key with 100% accuracy.
- **Selected Option**: **(A)** — *"increasing internal pressure."*
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