Cap 2 , A/c Construction Flashcards
Types of fuselage?
Circular
Double bubble
Square (for non pressurised)
Pressure between forward and rear pressure bulk?
Pressurised up to 8 or 9 psi
What stress does the pressure put on the a/c?
Axial stress (along the longitudinal axes) Hoop stress (radial)
What is the fatigue life?
Is mesasured in flight cycles
Types of wing?
> High mounted ( require external bracing,reduce visibility)
> Low mounted (good visibility,can;t use gravity for fuel distribution)
Cantilever wings mean no supports structures
Wing construction?
Stressed wing construction>Main spar,rear spar,ribs and skin
D spar construction>front spar ,inner skin,wing ribs,outer skin
Fail safe spar?
Where crack no can propagateacroos the structure
Wing ribs what does it provide?
Provide aerodynamic shape and allow the stress skin to be attached to the wing and transfer the loads into the spar
Stringers ?
Combine with ribs to share loads and transfer load to spars
Centre wing box>
Forms part of the fuselage and provides the attachment point for the wings
Wing covers?
Form the upper and lower aerodynamic surface of the wing
Wing box?
Main component structure of the wing
Empennage construction
Composites material are often used and sometimes used to store fuel.
Attached to the fuselage by 3 or 4 lugs and pins
Why the empennage is. placed in a strategic place?
To keep the tail away from the turbulent air from the wings/engines
T tailplane advantages?
Smooth airflow for control surfaces.can get to deep stall.
Requires stronger structure to support them
Engine pylon?
Carries engine load,not part of the wing structure.
Weight thrust forces carried from engine mounts to pylon by by STRUT BRACES.
Designed to break at an excess load
Critical engine?
Outboard engine where the wind is coming from is the critical engine.
Or in propeller the one creating the force further away from the cg
Torsional forces?
Twist the wings for lift ,weight ,thrust,aileron forces
Why the engines are mounted in front?
To bring the cg forward.
Torsional stress is caused by the difference between cg and cp.
This forms a couple which twist the wing around it flexural axis.the greater the distance between cg and cp the greater the torsional stress
What is flutter?
Lack of torsional stiffness in a wing structure .
Is an undamped oscillation .
Flutter increases with aerodynamic force and can lead to rapid structural failure
Torsional stresses ?
Forward mounted engines to reduce the cg/cp couple .
This can move the flexural axis closer to the cp.
Inboard ailerons to reduce the arm/moment
