Fuselage structures

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Transcript of Fuselage structures

Introduction

Forms main body of aircraft to which wings, tail plane, engines and gears are attached

In modern aircraft forms a tube structure housing flight deck, pax cabin, hold and equipment

Also acts as a pressure hull in pressurized aircraft

TypesFrame structure:

A box frame made up of a series of vertical, horizontal, diagonal and longitudinal tubular steel pipes

Design produces a square profiled fuselage

Used in old aircraft and light modern aircraft

Frame takes up all the loads

Types

Heavier if shape

altered

Covered with

fabric, fiberglass,

aluminum,

Kevlar e.t.c.

Types

TypesMonocoque structure:

Skin takes up all flight and ground loads and shape gives structure its rigidity

Any damage to skin directs effects its load carrying capacity

Complications in designing doors windows and hatches

Types Inherently heavy and fragile by design, not used in

airliners.

TypesSemi-Monocoque structure:

Loads shared by skin,

frames, stringers and

formers

Tolerant to damage

Good strength to

weight ratio

More redundancy then

monocoque construction

TypesReinforces shell structure:

Best redundancy in shell structure

Reinforced windows, doors and hatch attachment points

Longerons added for further load distribution, prevent crack propagation

Joining methodsRiveting:

Old process, time

consuming, more drag

Bonding:

Using an adhesive to attach metallic parts

Joining methodsMilling:

To remove unnecessary material

Material retention adds rigidity

Joining methodsEtching:

Using chemicals to remove material or create design or shapes in billets

Pressure bulkheads Pressure cabin terminates at the front and rear

bulkheads

Usually dome shaped for better pressure distribution

In some designs floor part of pressure hull, un-pressurised hold in this case

Cabin floors

In modern designs are not used as bulkheads

Series of panels attached to supporting beams of aircraft

Honeycomb panels

used for best

weight to strength

ratio

Blow out bungs

Plastic blowout bungs to equalize pressure in case of decompression

WindowsFlight deck:

Heated for de-icing

JAR approved for bird strikes

Laminated like car windscreens

Stepped nose profile used in most subsonic airliners

Helps in:

Aerodynamic profiling

Windows (flight deck)

Better ground and forward visibility

Reduction in size of screen windows

Sheds water better

Reduces impact force

Reduces pressure loads

Windows (flight deck)Stepped:

Windows (flight deck)Exception:

WindowsDirect vision window:

For maintaining clear vision

Opened from inside

Can also be used as

emergency exits

Windows Passenger cabin windows:

Form a part of pressure shell of fuselage

Reinforced surrounding structure

Windows fitted from inside and larger then apertures

Two panes with air filled gap in between them

Windows

Doors Commonly plug type doors used in commercial

aircraft

Closed from inside with locking pins engaging into door frame

Open by pulling back on inside and turning/sliding sideways

Doors

DoorsSome requirements are:

Must not be located near propellers

Must be able to open with people surrounding it

In emergency, external handle must be able to unlock door

Must open from both sides, handles to be flushed to skin

Doors

Must be a visual indication of doors being secured and locked, both externally and internally. E.g. flushing handle on outside, warning light on the crew warning panel

Must not jam in emergencies

Must b a means of safe-guarding against inadvertent operation in flight

Sealing

Pressurization costs fuel/energy

Every item passing through a hole is sealed

Seat mountings

Must withstand loads e.g.

Forward 3.0g

Upward 9.0g

Downward 6.0g

Sideward 4.0g

Seat mountings attached to crossbeams below floor structure

Spar attachment The strongest part of fuselage where wings are

attached

All flight loads converge at this point

Fuselage shapes

Streamlined tapering design

Suitable undercarriage/fuselage

for smaller payloads

Fuselage shapes Fuselages became more

cylindrical to carry more

payloads

Engines had to be added

which added weight

penalties

Large piston engines

give diminishing returns

Fuselage shapes Jet engine:

With its advent fuselage became cylindrical with rounded nose and a tapered tail

Advantages:

Easy manufacturing

Lower operating costs

Fuselage shapes

Better power to weight ratio

Greater cargo and passenger capacity

Easier loading and unloading of aircraft

Fuselage shapesTricycle undercarriage: Upward tapering tail till reaching the tip of tailcone

Top of fuselage remains unchanged

Tail bumper:

For protection during

rotation

Fixed or retractable

Fuselage mounted engines

Front mounted engines act as a tractor, pull aircraft

Support frame takes vibrations and engine loads

Fuselage mounted engines Rear bulkhead mounted act as pusher

Fuselage mounted engines Jet engines can also be mounted in fuselage, usually

reserved for combat aircraft

Fuselage mounted engines

For twin engine aircraft, engines can also be mounted to sides of fuselage

Mounted on stub wings

Reduces drag and cabin noise as compared to wing mounted aircraft

But early onset of stall

Fuselage mounted engines