Wings

Question 1

Wings support what in the aircraft

Answer 1

supports its weight in the air

Question 2

what should the wings be to be able to support

Answer 2

stiff and strong

Question 3

how can the wings be stiff and strong

Answer 3

• based on thickness of the wings
• based on the type of construction

both are dependent on the speed requirements of the aircraft

Question 4

the 3 types of construction for wings

Answer 4

Biplane

Braced monoplane

Cantiliver monoplane

Question 5

Biplane

Answer 5

**very low air load **

mainly found on aircraft with TRUSS/FRAMEWORK type FUSELAGE

Covered in fabric skin

The upper & lower mainplanes, INTERPLANE STRUT, BRACING WIRES = create** high rigidity** and resistant to twisting and bending

Question 6

Braced Monoplane

Answer 6

used on low speed aircrafts

Top mainplanes with struts connected to fuselage (no bracing wires)

Question 7

Cantiliver Monoplane

Answer 7

when wings are built around one or more load bearing members called SPARS

Question 8

What are spars helpful for:

Answer 8

In Air
* Helps the mainplane absorb stresses from **drag & lift **
* The wing not only has to have the flexibility to bend upwards (tension on lower skin, compression on upper skin) but needs enough stiffness to resist the torsional loads which will cause twisting.

On ground
* Helps the aircraft handle its own weight on ground by absorbing the downwards bending stresses when the aircraft is on the ground (Tension in upper surface/compression in lower surface)

Question 9

what’s a spar made up of

Answer 9

Aluminium girders/cap (top and bottom)
Alumium Web plate

arranged in ‘I’ shape

Question 10

components of a wing set up** (TORSION BOX)**

Answer 10

spars
* the mainplanes may be of single spar, twin spar or multi-spar construction.
* A conventional structure would consist of front and rear spars, the metal skin attached to the spar booms, the ribs and stringers.

skin
* takes the loads due to differences in air pressures and the mass and inertia of the fuel (if any) in the wing tanks.
* It generates direct stresses in a spanwise direction as a response to bending moments reacts against twisting (torsion) .

stringers
* spanwise members giving the wing rigidity
* ** stiffen the skin in compression.**

Ribs
* Gives shape to the wing
* supports stringers, skin and spars from buckling
* passes load from engine, landing gear, etc to spars and skin
*

Question 11

what else helps with bend stress relief on the wing?

Answer 11

Aileron up-float

engine mounted on the wings

fuel tanks in the wing

Question 12

where is the last bit of fuel used?

Answer 12

from the wings

Question 13

Most bending moment happens at which part of the wing

Answer 13

the root of the wing

Question 14

wings are made with what materials?

Answer 14

• aluminium alloys
• composite materials such as GRP (glass reinforced plastic), CRP (carbon reinforced plastic)
• honeycomb structures used for fairings, control surfaces, flaps etc.

Question 15

what is flutter

Answer 15

uncontrolled oscillation occuring on a fixed surface (a movement of up and down)

caused by **aerodynamics forces, inertia forces and the elastic properties of the surface **

can lead to the catastrophic failure of the structure.

Question 16

when an aircraft is on cruise, which direction is the wing bent?

Answer 16

wings are bent upwards

Question 17

what happens when wings are subjected to gust (along with their natural flutter)?

Answer 17

If the aircraft is subjected to a gust it will shake up and down with the wings flapping at a certain frequency.

If the vibration is similar to that of the structure of the wing then it will begin to resonate.

** The resonance will amplify the flutter** and may well **lead to failure **of the structure.

Question 18

how to prevent flutter

Answer 18

Flutter must not occur within the normal flight operating envelope of the aircraft.

Flutter can be prevented by:

1)mass balancing control surfaces to alter the moment of inertia of the surface and therefore the period of vibration (move the control surface C of G closer to the hinge).

2) maintain the aircraft

3) using the engines as mass balances, placing them on pylons forward of the wing leading edge.

Poorly maintained aircraft, particularly those with excessive control surface backlash (play) or flexibility may mean that flutter could occur at speeds below the limit airspeed.

Flutter of the mainplanes may be prevented by

Question 19

Aileron deflection on a wing structure can cause?

Answer 19

Torsion

Question 20

If the wings are bend up, what do the Aileron do?

Answer 20

Airleron deflect downwards

because the airleron centre of gravity lies behind the hinge line

Flutter will occur

Question 21

If the wings are bend down, what do the Aileron do?

Answer 21

Airleron deflect upwards

Question 22

2 deformation modes happen to the wing during flutter

Answer 22

Bending (highest on wing root)

Torsion (due to aireleron deflection)

Question 23

to control flutter, the balance mass must be located:

Answer 23

IN FRONT of the control surface hinge

Question 24

when engine under a wing is in thrust, wing is subject to bending moments from drag/thurst.

Answer 24

the loading **on the front spar of the torsion box from win root to wing tip is **

compression to tension