Cap 2 , A/c Construction

Question 1

Types of fuselage?

Answer 1

Circular
Double bubble
Square (for non pressurised)

Question 2

Pressure between forward and rear pressure bulk?

Answer 2

Pressurised up to 8 or 9 psi

Question 3

What stress does the pressure put on the a/c?

Answer 3

Axial stress (along the longitudinal axes)
Hoop stress (radial)

Question 4

What is the fatigue life?

Answer 4

Is mesasured in flight cycles

Question 5

Types of wing?

Answer 5

> High mounted ( require external bracing,reduce visibility)

> Low mounted (good visibility,can;t use gravity for fuel distribution)

Cantilever wings mean no supports structures

Question 6

Wing construction?

Answer 6

Stressed wing construction>Main spar,rear spar,ribs and skin

D spar construction>front spar ,inner skin,wing ribs,outer skin

Question 7

Fail safe spar?

Answer 7

Where crack no can propagateacroos the structure

Question 8

Wing ribs what does it provide?

Answer 8

Provide aerodynamic shape and allow the stress skin to be attached to the wing and transfer the loads into the spar

Question 9

Stringers ?

Answer 9

Combine with ribs to share loads and transfer load to spars

Question 10

Centre wing box>

Answer 10

Forms part of the fuselage and provides the attachment point for the wings

Question 11

Wing covers?

Answer 11

Form the upper and lower aerodynamic surface of the wing

Question 12

Wing box?

Answer 12

Main component structure of the wing

Question 13

Empennage construction

Answer 13

Composites material are often used and sometimes used to store fuel.
Attached to the fuselage by 3 or 4 lugs and pins

Question 14

Why the empennage is. placed in a strategic place?

Answer 14

To keep the tail away from the turbulent air from the wings/engines

Question 15

T tailplane advantages?

Answer 15

Smooth airflow for control surfaces.can get to deep stall.

Requires stronger structure to support them

Question 16

Engine pylon?

Answer 16

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

Question 17

Critical engine?

Answer 17

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

Question 18

Torsional forces?

Answer 18

Twist the wings for lift ,weight ,thrust,aileron forces

Question 19

Why the engines are mounted in front?

Answer 19

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

Question 20

What is flutter?

Answer 20

Lack of torsional stiffness in a wing structure .
Is an undamped oscillation .
Flutter increases with aerodynamic force and can lead to rapid structural failure

Question 21

Torsional stresses ?

Answer 21

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