Aero 318 Flashcards
Ultimate Loads
The loads that a structure must be able to support without failure/rupture for at least 3 seconds. Often the limit load multiplied by 1.5.
Primary structure
Those that would endanger the aircraft upon failure.
Secondary structure
Those that do not cause immediate danger upon failing. Non load-bearing structure.
Spars
Carry loads by bending and provide foundation for attaching skins.
Spar web
Carry shear stresses and resist shear and torsional loads. Divide the skin into small panels, and increase the buckling and failure stress.
Spar caps/flanges
Capable of supporting large compressive loads from axial bending effects.
Ribs
Maintain the aerodynamic shape of the cross-section, and act with the skin in resisting the distributed aerodynamic load. Also distribute concentrated loads into the structure.
Formers
Establish the shape of the fuselage and reduce the column length of stringers to prevent instability.
Name three types of fuselage
Truss, monocoque and semi-monocoque.
Truss type fuselage
Made up of beams, struts and bars that all carry tensile and compressive loads.
Monocoque type fuselage
Rings (formers) establish the shape and prevent instability. The skin forms an impermeable surface for supporting the aerodynamic pressure and transmitting aerodynamic forces to the internal structure. There are no bracing members.
Semi-monocoque type fuselage
The skin is reinforced by longitudinal members called longerons and stringers, which prevent tension and compression from bending the fuselage. Most common for commercial aircraft.
What does the wing structure of an aircraft contain?
Spars, ribs, stringers and a skin.
Three types of aircraft fuel tank
Integral tanks, rigid removable tanks and bladder tanks.
Integral fuel tank
Non-removable. Areas in the aircraft structure that have been sealed, often in the wing.
Rigid removable fuel tank
A metal construction that doesn’t contribute to the aircraft’s structural integrity.
Bladder fuel tank
Constructed from two or more plies of rubber coated fabric.
Nacelles
Streamlined enclosures used to house the engine and its components. Have a rounded profile to reduce aerodynamic drag. Protect the engine from damage.
Four causes of loading on the airframe
Manoeuvres (inertial loads), wind gusts, cabin pressure and landing.
Load path
A path that links the applied load to equilibrium forces.
When do the maximum loads on the components of an aircraft’s structure generally occur?
When the aircraft undergoes some form of acceleration or deceleration.
Newton’s 2nd law vs D’Alembert’s principle
For Newton’s 2nd law, the acceleration should be measured with respect to an inertial axes system. For D’Alemebert, the reference axes system must be changed from an inertial one to fixed within the body and accelerating with it.
Load factor, n
Total lift/ weight = 1 + a/g
Symmetric manoeuvre
The motion of the aircraft initiated by movement of the control surfaces in a plane of symmetry.