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

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

3 Three Primary Structural Loads

4 Typical Aircraft Loads

Limit Load Factors 5

6 V-n Diagram

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

8 Lift Distribution

9 Spanwise Load Distribution

10 Typical Wing Box (AE 441)

11 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

12 Fuselage Structure

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

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

15 Stress vs. Strain= Stiffness

16 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

Common Landing Gear Configurations 17

18 Samples of Structural Results from Previous CDRs

19 V-n Diagram

20 Spanwise Lift Distribution

21 Spanwise Load Distribution

22 Moment Distribution

23 Structural Weight and Deflection

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

25 Structural Details (441 level)