QB_AE_FLIGHT_009 Section Question Bank NAT · 1 Mark
Flight Mechanics & Space Dynamics • Static Stability & Control • Static Margin & Stick-Fixed/Free Stability

An aircraft has a mean aerodynamic chord $\bar{c} = 2.5\text{ m}$. The stick-fixed neutral point is located at $x_{np} = 3.65\text{ m}$ from the reference datum, and the center of gravity is located at $x_{cg} = 3.40\text{ m}$. What is the stick-fixed static margin $K_n$ (expressed as a dimensionless decimal fraction of $\bar{c}$)?

Answer Key:
0.1

Step-by-Step Verified Solution

### 5-Stage Derivation & Analytical Solution: 1. **Stage 1: Static Margin Definition:** $K_n = \frac{x_{np} - x_{cg}}{\bar{c}}$. 2. **Stage 2: Substitution:** $x_{np} - x_{cg} = 3.65 - 3.40 = 0.25\text{ m}$. 3. **Stage 3: Normalization:** $K_n = 0.25 / 2.5 = 0.10$. 4. **Stage 4: Result:** 0.1 (range 0.09 to 0.11).
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