Aerospace & Aeronautical Engineering / Directional & Lateral Stability
FREE TO EXPLORE
LABORATORY 24 · AEROSPACE & AERONAUTICAL ENGINEERING

Lateral-Directional Weathercock Stability and Dihedral Effect

Measure yawing moment derivative C_n_beta (weathercock stability) and rolling moment derivative C_l_beta (dihedral effect) across a wind tunnel sideslip sweep. Explore interactive wind tunnel simulation, flight dynamics, and aerospace engineering telemetry.

AERODYNAMICS · PROPULSION · FLIGHT DYNAMICS

Your virtual aerospace engineering laboratory.

YAWING MOMENT C_N X 10^3—
FLIGHT & TEST CELL TELEMETRY

Ready to sample with beta = 4.0 deg.

4.0 deg
Wing span b: 600 mm

Adjust beta, then execute aerospace trial.

Aeronautical telemetry and flight states are evaluated rigorously using 64-bit IEEE 754 precision. Residuals reflect ordinary least-squares regression across successive observations. Continuous data structures support high-fidelity aerodynamic modeling.

Aeronautical assumptions and boundary condition limits

Linear derivative C_n_beta is valid for attached flow on the vertical fin (beta < 12 deg); high sideslip causes vertical fin stall. Linear regression of yawing moment coefficient against sideslip angle yields a weathercock derivative C_n_beta x 10^3 = 1.8000 deg^-1 with R^2 > 0.999999.

Aeronautical apparatus & wind tunnel sensors.

Complete Aircraft Model with Vertical Fin

Wind tunnel model (b = 600 mm) with modular vertical tail surfaces and geometric wing dihedral.

Precision Computerized Yaw Turntable

Rotates model in yaw from beta = -15 to +15 degrees with 0.02 degree angular resolution.

6-Component Internal Strain-Gauge Balance

Simultaneously measures yawing moment N, rolling moment L_roll, and side force Y.

Subsonic Wind Tunnel Test Section

Maintains uniform airspeed V_inf = 30.0 m/s with low free-stream turbulence intensity.

Dynamic Pressure Sensor

Monitors free-stream dynamic pressure q_inf to normalize moments into non-dimensional coefficients.

Digital Lateral-Directional DAQ Workstation

Calculates C_n and C_l and extracts stability derivatives C_n_beta and C_l_beta.

FOLLOW THE METHOD

A reason behind every step.

Measure yawing moment derivative C_n_beta (weathercock stability) and rolling moment derivative C_l_beta (dihedral effect) across a wind tunnel sideslip sweep. Standardized parameter settings: 1.0, 3.0, 5.0, 7.0, 8.5, 10.0 deg.

01

Balance Taring in Zero Sideslip

Align model symmetrically with tunnel axis (beta = 0 deg) and perform wind-off tare across all six balance channels.

02

Wind Tunnel Speed Stabilization

Run the wind tunnel to V_inf = 30 m/s, stabilizing dynamic pressure at q_inf = 551 Pa.

03

Zero-Sideslip Symmetry Check

Verify that measured side force Y, yawing moment N, and rolling moment L_roll are zero within balance noise at beta = 0 deg.

04

Systematic Sideslip Angle Sweep

Rotate the turntable through beta = 1.0, 3.0, 5.0, 7.0, 8.5, and 10.0 degrees, sampling 2000 points per channel at each step.

05

Coefficient Normalization

Compute non-dimensional yawing moment coefficient C_n = N / (q_inf * S * b) and rolling moment coefficient C_l = L_roll / (q_inf * S * b).

06

Weathercock Derivative Linear Regression

Plot C_n x 10^3 versus beta, perform linear regression to determine the weathercock derivative C_n_beta, and verify positive stability.

YOUR NOTEBOOK · 0 OBSERVATIONS

Turn measurements into aerodynamic insight.

See a complete example report ↗

Points are your recorded observations. The solid regression line validates Directional & Lateral Stability mathematical scaling.

LINEAR REGRESSION FIT · y = mx + b
C_n = C_{n\beta} \cdot \beta \implies C_n \times 10^3 = m \cdot \beta_{\text{deg}} + b
#Sideslip Angle beta (deg)Yawing Moment C_n x 10^3 (dimensionless)Sideslip Angle beta (deg)Yawing Moment Coefficient C_n x 10^3Remove

No readings yet. Execute an aerodynamic trial and record it.

Calculate it yourself.

CHECK YOUR UNDERSTANDING

Explain what the aerodynamic metrics mean.

What mathematical condition is required for positive directional (weathercock) static stability?

What aerodynamic surface provides the primary contribution to positive weathercock stability C_n_beta?

Why does a positive sideslip angle (wind from right) require a negative rolling moment derivative (C_l_beta < 0)?

For a measured weathercock slope C_n_beta = 0.00180 deg^-1 and sideslip beta = 5.0 deg, what is the yawing moment coefficient C_n x 10^3?