Aerospace & Aeronautical Engineering / Phugoid & Short-Period Modes
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LABORATORY 25 · AEROSPACE & AERONAUTICAL ENGINEERING

Longitudinal Dynamic Flight Modes: Short-Period and Phugoid Oscillations

Extract natural frequency omega_n and damping ratio zeta of the rapid angle-of-attack short-period mode and slow energy-exchange phugoid mode from aircraft state-space flight dynamics. Explore interactive wind tunnel simulation, flight dynamics, and aerospace engineering telemetry.

AERODYNAMICS · PROPULSION · FLIGHT DYNAMICS

Your virtual aerospace engineering laboratory.

PHUGOID RECIPROCAL FREQUENCY 1/OMEGA_N,P—
FLIGHT & TEST CELL TELEMETRY

Ready to sample with V_0 = 60.0 m/s.

60.0 m/s
Gravitational acceleration g: 9.80665 m/s^2

Adjust V_0, 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

Lanchester's analytical formula assumes zero angle of attack perturbation (Delta alpha = 0) during the phugoid cycle. Linear regression of reciprocal phugoid frequency against trim airspeed yields a slope m = 0.0721 s^2/m matching Lanchester's formula with R^2 > 0.999999.

Aeronautical apparatus & wind tunnel sensors.

6-DOF Real-Time Flight Dynamics Simulator

Executes 4th-order longitudinal state-space equations with Runge-Kutta numerical integration at 500 Hz.

Automated Elevator Doublet Input Generator

Applies standardized pitch doublet inputs (+/- 2 degrees, 1 second duration) to excite natural modes.

State Telemetry Sensor Package

Records airspeed V(t), pitch angle theta(t), angle of attack alpha(t), and pitch rate q(t) with 16-bit resolution.

Logarithmic Decrement Mode Analyzer

Extracts damped frequency omega_d and damping ratio zeta from time-domain oscillation decay envelopes.

Eigenvalue Root-Locus Visualizer

Computes state-space matrix A eigenvalues, plotting short-period and phugoid poles in the s-plane.

Flight Envelope Trim Station

Maintains constant lift-to-weight equilibrium across airspeeds from 40 to 100 m/s.

FOLLOW THE METHOD

A reason behind every step.

Extract natural frequency omega_n and damping ratio zeta of the rapid angle-of-attack short-period mode and slow energy-exchange phugoid mode from aircraft state-space flight dynamics. Standardized parameter settings: 40.0, 50.0, 60.0, 75.0, 88.0, 100.0 m/s.

01

Level Flight Trim at Initial Airspeed

Trim the aircraft in steady level flight at V_0 = 40.0 m/s, recording baseline state vectors and elevator trim angle.

02

Elevator Doublet Excitation

Trigger a standardized 1.0-second elevator pulse doublet (+2 deg / -2 deg) to excite longitudinal dynamic modes.

03

Short-Period Mode Identification

Isolate the first 5 seconds of pitch rate q(t) telemetry to determine the rapid short-period frequency and damping.

04

Phugoid Oscillation Recording

Track the subsequent 120 seconds of airspeed V(t) and altitude h(t) oscillations to record the slow phugoid cycle.

05

Systematic Airspeed Stepping

Repeat doublet excitation across airspeeds V_0 = 50.0, 60.0, 75.0, 88.0, and 100.0 m/s, calculating natural frequency omega_n,p.

06

Lanchester Phugoid Linear Regression

Plot reciprocal frequency 1/omega_n,p versus V_0, perform linear regression, and compare the slope to Lanchester's 1/(sqrt(2)*g).

YOUR NOTEBOOK · 0 OBSERVATIONS

Turn measurements into aerodynamic insight.

See a complete example report ↗

Points are your recorded observations. The solid regression line validates Phugoid & Short-Period Modes mathematical scaling.

LINEAR REGRESSION FIT · y = mx + b
\frac{1}{\omega_{n,p}} = \frac{V_0}{\sqrt{2} g} \implies \frac{1}{\omega_{n,p}} = m \cdot V_0 + b
#Trim Airspeed V_0 (m/s)Phugoid Reciprocal Frequency 1/omega_n,p (s)Trim Flight Airspeed V_0 (m/s)Phugoid Reciprocal Natural Frequency 1 / omega_n,p (s)Remove

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CHECK YOUR UNDERSTANDING

Explain what the aerodynamic metrics mean.

According to Lanchester's approximation, how does the phugoid natural frequency omega_n,p scale with trim airspeed V_0?

Which aerodynamic state variable remains virtually constant during a phugoid oscillation?

What is the typical period of the rapid longitudinal short-period mode on a transport aircraft?

For a trim airspeed V_0 = 100 m/s and g = 9.81 m/s^2, what is the theoretical phugoid reciprocal frequency 1/omega_n,p for Lanchester's slope m = 0.0721 s^2/m?