11.2b Airframe Construction Methods

Question 1

what are frames or formers ?

Answer 1

Lateral fuselage or nacelle members giving a cross sectional shape which is often circular. They are used to give shape and provide strong attachment points.

Question 2

Monocoque construction was very heavy, in order to combat this what was used?

Answer 2

Semi-monocoque construction using stringers and other components to transfer loads.

Question 3

What are bulkheads?

Answer 3

Give shape to the fuselage but do not have an aperture and usually act to close off or Partion an area. E.g pressure bulkheads or fireproof bulkheads

Question 4

What are longerons?

Answer 4

Main longitudinal member of a fuselage or nacelle.

Question 5

What type of loads do longerons take?

Answer 5

The main support for bending loads

Question 6

What can longerons be supplemented by ?

Answer 6

Stringers

Question 7

What are stringers ?

Answer 7

Smaller and lighter than longerons and serve as stiffeners that assist sheet materials to carry loads along their length however they mainly create the shape of the skin

Question 8

What are used to attach the skin to the frame and stringers?

Answer 8

Clips and cleats

Question 9

What are doublers?

Answer 9

Additional sections of material used to reinforce ares of skin that require a little extra strength

Question 10

Where are doublers often found ?

Answer 10

Around apertures such as doors or windows

Question 11

What can also be used as a crack stopper ?

Answer 11

Doublers, placed at 90° to the path of the anticipated crack, which reduces the rate of further propergation

Question 12

What are struts and what are they used for ?

Answer 12

Load bearing components that primarily handle compression forces, typically transmits loads from one part of the fuselage to another

Question 13

What are ties ?

Answer 13

Elements that handle tension forces employed to maintain the structural integrity of various parts of the fuselage

Question 14

When ties and struts are used in conjunction what can this form ?

Answer 14

Truss like structures that effectively distribute loads and provide stability

Question 15

What are ties typically made from ?

Answer 15

Steel or titanium

Question 16

What do ties ensure ?

Answer 16

Resist tension forces and rigidity

Question 17

What are floorboards made of ?

Answer 17

Honeycomb composite construction which are screwed down to floor beams made from aluminium or composite

Question 18

What do floor beams do ?

Answer 18

Primary structure that carry tension loads during pressurisation

Question 19

How are floorboards protected from corrosion ?

Answer 19

Foam tape on the underside around the edges where they contact the structure or sealed in “wet areas”

Question 20

What must be considered when considering the structure of an aircraft ?

Answer 20

Strength to weight ratio

Question 21

What ways can we reinforce structures ?

Answer 21

-doublers
-butt straps
-cleats
-gussets
-fishplates
-angles
-stiffeners

Question 22

What principle is wing construction based on ?

Answer 22

Semi- monocoque construction. With spars and ribs giving shape.

Question 23

What are ribs ?

Answer 23

a fore-and-aft structural member of an aerofoil that has the primary purpose of maintaining the correct contour of the covering but is usually also a stress-bearing component of the main structure.

Question 24

What are wings often covered with?

Answer 24

Stressed skin forming a box section that is then able to house integral fuel tanks

Question 25

What are the two types of general fuselage construction?

Answer 25

Truss type Monocoque

Question 26

What is a truss ?

Answer 26

A truss is a rigid framework made up of members of : Struts, beams and bars

Question 27

Where is the the truss type wing construction method used mostly ?

Answer 27

In fabric aircraft

Question 28

What is a strut?

Answer 28

Any rod or member designed to take compression loads

Question 29

What are the two types of monocoque construction?

Answer 29

True monocoque construction and more common semi monocoque

Question 30

What does true monocoque construction consist of?

Answer 30

Formers, frame assemblies and bulkheads to give shape

Question 31

On a monocoque construction what carries the stress?

Answer 31

The skin

Question 32

What is important about semi monocoque construction?

Answer 32

Skin is reinforced by longitudinal members and loads are shared between the skin and framework

Question 33

When a fuselage structure comes in structures, and the joints need to be reinforced, what is this called ?

Answer 33

Manufacturers joint or production break

Question 34

What is a semi monocoque type construction generally made from?

Answer 34

Aluminium alloys or steel and titanium in elevated temperatures

Question 35

What are the main advantages of a semi-monocoque construction?

Answer 35

-the bulkheads, frames, stringers and longerons give shape to the skin -because of the way stresses are distributed throughout the skin, this construction method gives a lot more strength and rigidity

Question 36

How may a frame work be skinned ?

Answer 36

-Skin can either be bonded or riveted or both -

Question 37

What is the most likely method of skinning in modern composite skin aircraft ?

Answer 37

-filament wound into the frame or preformed and fastened to the frame with special fasteners and bonding techniques

Question 38

Why is aluminium widely used throughout aircraft ?

Answer 38

For its passivation property (passive film) an it’s strength

Question 39

What surface treatments can you perform to prevent corrosion ?

Answer 39

-Painting -anodising -using sealants

Question 40

What three sections are there to a pair of wings ?

Answer 40

Left wing ,centre wing box, right wing

Question 41

How many spars do a wing have ?

Answer 41

Front spar and rear spar. Some may also have a false spar for an attachment point for the landing gear

Question 42

The spars make up a “box” and are linked by formers, what are these called ?

Answer 42

Ribs

Question 43

What else does the construction of a wing often give space for ?

Answer 43

Fuel storage

Question 44

How are control surfaces connected to the wing ?

Answer 44

Control surfaces are attached to the rear wing spar

Question 45

What supports the centre wing box?

Answer 45

The keel beam and a series of heavy frames

Question 46

Despite holding the wings what other jobs do the centre wing box do ?

Answer 46

-can provide area for fuel storage - help absorb impacts during flight such as turbulence

Question 47

How are the horizontal stabilisers attached ?

Answer 47

Following a similar construction the the wing, horizontal stabilisers attach to a centre box

Question 48

How is the vertical stabiliser attached ?

Answer 48

Attached using large machined fittings that align with the fuselage frames and longerons

Question 49

What is a engine pylon ?

Answer 49

Also known as the strut consist of a torque box, firewall, fire-seal, fairings, strut drains , a fan cowl support beam and engine attachment fittings.

Question 50

What is the primary function of an engine nacelle ?

Answer 50

To provide a streamline shape to the engine pylon, engine and all of their components