AE 440 Structures Discipline Lecture 6 Eric Loth

AE 440 Structures Discipline Lecture 6 Eric Loth For AE 440 A/C Lecture 1

Structures Responsibilities a. b. c. d. e. f. Determine V-n relationships and establish a V-n diagram Establish and maintain load paths Determine component materials (weights and dimensions to configuration) and consider environmental impact of acquisition, production and operations Determine landing gear configuration Carry out a detailed structural design of the wing box and wing attachment and structurally design landing gear (weights & dimensions to configuration) Employ FEM Analysis 2

Three Primary Structural Loads 3

Typical Aircraft Loads 4

Limit Load Factors 5

V-n Diagram http: //rgl. faa. gov/Regulatory_and_Guidance_Library/rg. FAR. nsf/Main. Frame? Open. Frame. Set 6

Load Paths • How loads are transferred from one structural member to another • Wing skin—torsion and shear stress • Wing ribs—maintain shape and rigidity, transfer loads from skin to spars • Wing spars—bending moments • Fuselage—bulkheads, framers, stringers 7

Lift Distribution 8

Spanwise Load Distribution 9

Typical Wing Box (AE 441) 10

Major Fuselage Loads • Empennage loads due to trim, maneuvering, turbulence and gusts • Pressure loads due to cabin pressurization • Landing gear loads due to landing impact, taxiing and ground maneuvering • Loads induced by the propulsion installation when the latter is attached to the fuselage 11

Fuselage Structure 12

Structural Components • • • Spars Ribs Skin Beam shear Beam bending Torsion Cessna Citation II 13

Materials • Selection criteria – – Strength Stiffness Density Cost • Typical materials – – Aluminum Composites Steel Titanium • Mini-UAV materials – Plastic – Balsa – Fiber (cloth) 14

Stress vs. Strain= Stiffness 15

Landing Gear Loads • Vertical loads primarily caused by non-zero touchdown rates and taxiing over rough surfaces • Longitudinal loads primarily caused by braking loads and rolling friction loads • Lateral loads primarily caused by ‘crabbed landings, ’ cross-wind taxiing and ground turning 16

Common Landing Gear Configurations 17

Samples of Structural Results from Previous CDRs 18

V-n Diagram 19

Spanwise Lift Distribution 20

Spanwise Load Distribution 21

Moment Distribution 22

Structural Weight and Deflection 23

Structural Configuration (441 level) I-beam gives good resistance to shear (web) and bending (caps) 24

Structural Details (441 level) 25