11.2 Airframe Structures - General Flashcards
What must be done if a defect is found on an aircraft
It must be noted in the logbook so it can be rectified with an approved drawing
What type of loads do structural members usually carry
End loads rather than side loads
Tension or compression rather than bending
Rather than taking structural loads what qualities are required from fairings and cowlings
They need to have a neat appearance and streamlined shape
Every part of the aircraft must be planned to take the load to be imposed on it what is this process called
Stress analasys
To ensure the aircraft structure is capable of taking all of the stresses it will experience in flight what is done in the initial design phase
Fail safe load transfer, damage tolerance and fatigue indexing
What does the fail safe method rely on
Duplication of certain structural members. If one fails the other will take the load
What is the damage tolerance method
Requires an assessment to see if the damage sustained will lead in failure
This method is old and outdated
What is a further method of damage tolerance
By using crack limited joints. The joints will limit the spread of cracks
What is fatigue known as
Fracturing after a series of cyclic loads, may be much less than the ultimate load
What are the 3 categories of aircraft structure
- Primary structure
- Secondary structure
- Tertiary structure
What are the characteristics of the primary structure
Critical load baring structure. Requires immediate repair if damaged as it can affect the structural integrity of the aircraft
What are the characteristics of the secondary structure
Not load baring and the failure of a secondary structure would not affect the structural integrity of the aircraft
These consist of things like access panels and require repair as soon as possible
What are the characteristics of a tertiary structure
Not load baring and do not make up an integral part of the airframe. They consist of things like wing root fairings and landing gear fairings
What are the 5 main structural units of an aircraft
- The fuselage
- The wings
- The stabilisers
- Flight control surfaces
- The landing gears
What main structural members make up an aircrafts structure
Stringers, frames, bulkheads, ribs, skin and other members
How are structural members fixed together
With brackets, rivets, bolts, screws and nuts which add strength to the fuselage
What are structural members designed to do
Carry a load or resist stress
How is stress created
By the internal force of a substance which opposes or resists deformation
What are the 6 major types of stress that can effect aircraft structure
- Tension
- Compression
- Torsion
- Shear
- Bending
- Hoop stress
Give the definition of tension
Stress that resits the forces trying to pull it apart
How do you calculate tensile strength
Divide the load (in pounds) with by the cross sectional area
The result is PSI
What is the definition of compression
Stress that resists a crushing force. Causes aircraft parts to be squeezed together
Usually measured in PSI
What type of stress is torsion
A twisting stress. For example when the rudder is deflected
What is shear stress
Unaligned forces pushing one part of a body in one direction and another part in the opposite direction