M11.2 Flashcards
What is the main disadvantage of the fail safe concept?
It adds a lot of weight
What is fatigue?
Failure after a series of cyclic loads
What are the three classifications of aircraft structure?
- primary
- secondary
- tertiary
What is classified as primary structure?
It is critical load bearing structure that requires immediate repair
What is classified as secondary structure?
It is not a load carrying members structure and requires repair as soon as possible
What is classified as tertiary structure?
Does not carry any loads
What must be used to classify an aircrafts structure classification?
The structural repair manual or AMM
What are the five main structural units for an aircraft?
- fuselage
- wings
- stabiliser
- flight control surfaces
- landing gear
What are the six main types of stress that affect the structure?
- tension
- compression
- torsion
- shear
- bending
- hoop stress
How do you work out tensile strength?
The load of the material
————————
Cross sectional area
What is tension and compression measured in?
Psi
What is meant by torsion stress?
Stress caused by twisting
When does torsion stress occur?
When the rudder is deflected
What is shear stress?
When unaligned forces push in opposite directions
Shear strength of a material is usually either equal or less than what?
It’s tensile or compressive strength
What is bending stress a combination of?
Compression and tension
What is hoop stress?
When the aircraft pressurises it causes it to expand in all directions
What are the three reference planes?
- vertical
- horizontal
- longitudinal
What units do Boeing use to measure things?
Inches
What units do airbus use to measure things?
Cm or mm
What are the body coordinates called on Boeing’s aircraft?
- Body stations (BS)
- body buttocks (RBBL/LBBL)
- body water lines (BWL)
On Boeing aircraft what are the wing coordinates?
- Wing reference plane
- wing buttock lines
- wing stations
Why is the wing reference plane inclined?
So that it is the same as the dihedral of the wing
On Boeing aircraft the nacelle coordinates are divided into what?
- nacelle stations
- nacelle buttock lines
- nacelle waterlines
What is special about the nacelle station zero on Boeing aircraft?
It’s in front of the nacelle depending on engine type
What are the horizontal stabiliser coordinates on Boeing aircraft?
- the stabiliser chord plane
- buttock lines stations
- leading edge stations
- elevator stations
On Boeing aircraft the vertical stabiliser coordinates are divided into what?
- fin stations
- waterlines
- leading edge stations
- rudder stations
What coordinates do airbus use?
X,Y,Z
What is zone 100?
Lower half of the fuselage
What is zone 200?
Upper half of the fuselage
What is zone 300?
The empennage
What is zone 400?
Power plants and struts
What is zone 500?
Left wing
What is zone 600?
Right wing
What is zone 700?
Landing gear and the landing gear doors
What is zone 800?
The doors
What are major zones divided into?
Sub-major zones
Why are sub-major zones used?
For more precise location of assemblies and components
How are major zones identified?
By the first digit of the zonal system
How are sub-major zones identified?
By the second digit of the zonal system
What type of numbers are found on the right hand side of the aircraft?
Even numbers
What type of numbers are found on the left hand side of the aircraft?
Odd numbers
How are zones identified?
By the third digit of the zonal system
How are zones numbered?
From forward to aft, inboard to outboard, bottom to top
When are letters used in zone identification?
When assemblies need to be identified
What does the first letter in the zonal system mean?
Shows the position from forward to aft, inboard to outboard, bottom to top
What does the second letter of the zonal system mean?
If its on the left or right side
Where are drain holes located?
Lower fuselage
What are the two types of lightning damage?
Direct and indirect
What is lightning direct damage?
When the surface is burned or damaged
What is lightning indirect damage?
Damage to electrical components
What areas are most likely for lightning strike damage?
Nose and aerofoil trailing edge
What is the highest resistance you should get from a bonding lead and structure?
0.025Ω
How many grounding points should be in a fuel vapour area?
Two
How many ground terminals can go to one stud?
Maximum 4
How should grounding points be separated?
AC, DC, and shields
What is a longeron?
Main longitudinal member of the fuselage or nacelle
What is a tie rod (tension rod)?
Member taking tensile load
What is a strut?
Member taking a compression load
What is meant by stressed skin?
Structure where loads are shared between skin and framework
What is a frame?
Lateral fuselage or nacelle member giving cross-sectional shape
What is a rib?
A fore-and-aft structural member of an aerofoil
What is a spar?
The main spanwise member of the aerofoil
What is a stringer?
A stiffener which assists sheet materials to carry lads along their length
What is a bulkhead??
A partition within the structure
What is a station number?
Numbers allocated to certain components to indicate their position
What is meant by the term safe life?
The period which it is considered that failure of a component is extremely unlikely
What is a crack stopper?
A reinforcing member placed in the path of a crack to reduce rate of cracking
What is aerodynamic loading?
The loads imposed on an aircraft in flight
What is static loading?
The loads imposed on an aircraft when stationary
What are the two types of fuselage construction?
- truss type
- monocoque type
What is truss type framework?
A rigid framework made up of members that carry the stress
What is monocoque type framework?
A rigid framework covered in skin that takes most of the stress
What is semi-monocoque construction?
A strong skin reinforced by strong framework
What is the skin riveted to?
Longerons or bulkheads
What are floorboards made from?
Honeycomb composite
How are floorboards secured down?
By fasteners screwed into nutclips or nutplates attached to aluminium beams
Why are the floorboards around he toilets and gallies sealed?
To prevent corrosion
What is used to attach the wings to the aircraft?
A wing box
What is the strongest part of the fuselage?
The wing box
How does the wing box prevent the wings from wobbling or bending?
By absorbing some of the stress and distributing it across supportive framework
How is the horizontal stabiliser attached to the empennage?
By using a box section
How is the vertical stabiliser attached to the fuselage?
By large machined fittings that align with the fuselage frames
What is the pylon also known as?
The strut
What are nacelles?
Streamlined enclosures used to primarily house the engine and its components
What do composites use to bond together?
Adhesive
When are bolts used?
When high strength is needed
When are screws substituted for bolts?
When high strength isn’t needed
When should aluminium bolts not be used?
In tension applications or high wear areas
What are the different groups of protective treatment?
- pretreatment
- paint coatings
- special coatings
What are the two types of paint coating?
Primer and top coat
Why is primer used?
To give the surface the correct protection and gives a good surface for the top coat
Why is a top coat used?
To protect the the layers of primer and aesthetics
What are the two types of special coatings?
Type 1 and type 2
What is type 1 coating used for?
Water repellent
What is type 2 coating used for?
Heavy duty corrosion prevention
What type of water should be used for cleaning purposes?
- PH between 7 and 8
- chloride level less than 100ppm
