Subtopic: Conservation Equations of Mass, Momentum & Energy
Question Statement:
In an aircraft, the dive manoeuvre can be initiated by:
Options:
(A) reducing the engine thrust alone.
(B) reducing the angle of attack alone.
(C) generating a nose down pitch rate.
(D) increasing the engine thrust alone.
Official Answer Key:
C
Step-by-Step Solution & Explanation
### **Dedicated Step-by-Step Solution (GATE AE 2012 Q.16)**
**1. Problem Statement & Parameters**:
- **Module**: Aerodynamics & Fluid Mechanics (1 Mark, MCQ)
- **Topic**: Basic Fluid Mechanics (Conservation Equations of Mass, Momentum & Energy)
- **Organizing Institute**: IIT Delhi
- **Problem Statement**:
> In an aircraft, the dive manoeuvre can be initiated by:
**2. Mathematical Derivation & Physical Analysis**:
1. **Flight Dynamics of Dive Maneuver**:
A dive maneuver requires rotating the flight path angle $\gamma$ downward (i.e. $\dot{\gamma} < 0$).
The kinematic pitch relation is $\theta = \alpha + \gamma$, where $\theta$ is the pitch angle and $\alpha$ is the angle of attack.
2. **Rotational Pitch Rate Requirement**:
To initiate an entry into a dive from steady level flight, the aircraft must generate a nose-down pitching moment ($M_{cg} < 0$), producing a negative pitch rate ($q = \dot{\theta} < 0$).
This is typically accomplished by forward deflection of the control column, causing trailing-edge-up elevator deflection ($\delta_e > 0$).
Thrust reduction or angle of attack changes alone do not initiate the rotational trajectory curvature without establishing the pitching rate.
3. **Conclusion**:
The maneuver is initiated by generating a nose-down pitch rate (**Option C**).
**3. Comprehensive Options Analysis**:
- **(A)** *"reducing the engine thrust alone."*: ❌ **INCORRECT**.
- **(B)** *"reducing the angle of attack alone."*: ❌ **INCORRECT**.
- **(C)** *"generating a nose down pitch rate."*: ✅ **CORRECT**.
- **(D)** *"increasing the engine thrust alone."*: ❌ **INCORRECT**.
**4. Official Answer Verification**:
- **Official Master Answer**: **C**
- **Evaluation Status**: Matches official GATE 2012 (IIT Delhi) master answer key with 100% precision.
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