GearDropSim A Tool for simulating landing gear drop tests.Dr. Dan Retief PhD (Mech. Eng.)

Background / History 1982 – BE Mechanical – University of Pretoria 1983-1985 National Service in SA Air Force 1985 – Complete ME at University of Pretoria 1989 – PhD Mechanical Engineering. 1983 – 1986 Armscor – A-Vehicles. 1987 – 1990 Armatron Systems . 1990 – 1993 Aero Projects and Epsilon Eng. 1994 Settle in NZ – Computer Programming Fisher & Paykel Laundry – Washer Dynamics and

Structures Pacific Aerospace Ltd – 750 XL Ag conversion, IFR,

electric upgrade. Alpha Aviation – Chief Designer 2009 – Started Aero Design Ltd

Tyre Model

Windmill Blade Development

Mirage F1 Dive Brake

UAV Seeker Head Cooling Design and Mechanicals

Aero Design’s Office400 Raynes RoadRD 2Hamiltonwww.aerodesign.co.nz

F18 Landing Gear Drop Test

Component Element Method

Fmvdt

d)(

Fdt

ydm

dt

dvm

2

2

Newton’s Second Law

Reference: The Component Element Method in DynamicsSamuel LevyAndJohn Wilkinson

Component Modelling Elements Mass Spring Damper

Simple mass-spring-damper system.

Free body diagram.

ymyckyF

Finite Differences

t

y

dt

dydt 0lim

t

yy

dt

dy

tt

211

0

2101

0

2

2 2

t

yyy

dt

yd

tt

Finite Difference Equations

0011

2101

2)(

2Fky

t

yyc

t

yyym

Solving for y1

01202

2

1 )(2)(

2

2)(

1Fy

t

m

t

cyk

t

m

tc

tm

y

Multiple mass systems

Algorithm

Masses as objects with attach points Force elements as objects with nodes Calculate starting values for all object

positions and velocities Calculate attach point location and

velocities from mass location and orientation.

Calculate forces in force elements Calculate mass acceleration, velocity

and next position from sum of forces on it.

Landing Gear Simulation

Open Model File

Tyre Characteristics

Simulation Parameters

Oleo Damping Characteristics

Oleo Spring Characteristics

Load Factor Results

Oleo Displacement

Tyre Displacement

Applications

Landing Gear Design Optimisation Oleo stroke length and diameter Oleo Damping Characteristics Oleo Inflation Pressure Tyre Inflation Pressure

Calculation of landing gear fatigue forces based on sink rate.

Reduce design iterations and avoid expensive mistakes in hardware.