Airframes Flashcards
What are the 4 types of airframes?
1) Truss
2) Semi-monocoque (MONO-COKE) or Stressed Skin
3) Pure monocoque
4) Composite
What is a truss type fuselage made of?
Steel or aluminum tubes, which are welded and bolted together in the shape of a ‘truss’ design. This is the heaviest of the four designs.
It is these steel truss tubes that give stregnth to this design
The truss may then be covered with metal, fabric, or composite for aerodynamic purposes
Because truss designs are quite blocky, what is usually added to add curves for aerodynamic purposes?
Bulkheads
In a truss design, with or without bulkheads, where is the ‘structural loading’ contained?
Within the truss itself. All of the stregnth is in the tube frame itself. (Quizz wording)
What is a semi-monocoque design?
The frame consists of a series of ‘formers’ and bulkheads spaced out and held together by ‘stringers’ that run lengthwise.
The frame is then wrapped tightly with a skin, this is called Stressed Skin, because the airframe loads travel through the skin (unlike a truss design where the loads travel through the frame itself)
The majority of AC today are manufactured with the semi-monocoque design
Why are the bulkheads so important in a semi-monocoque design?
It creates the ‘pressure vessel’ in an aircraft, which allows that section to be pressurized while the rest of the AC is not.
What is a pure monocoque design?
Same as the semi but without the stringers. Even more lightweight, and almost all the load goes through the skin.
Like a semimoncoque design, it also employs Stressed Skin.
What is the biggest con about a pure monocoque design?
It is very strong until there is even a small bit of damage.
Like a pop can or egg is hard to crush from top to bottom. But if there is a small crack or dent, the whole thing crumbles very easily
What is a ‘composite’ airframe?
An apoxy and fiberglass/cabon fiber/kevlar mixed together, spread over a mold, then cured, and hardened (DA-20 / DA-40). Several layers will be done of this proccess.
Can be molded into very smooth and aerodynamic shapes.
Is very strong and very light.
Dont get fatiqued like metal and fabric and wood
What is a con of composite airframes?
It is hard to detect damage. And impact damage in one spot can spread outward through the layers without the pilot being able to see it.
Extremem heat can melt/damage them (this is why many composite planes are white)
Unlike metal, which will permanantly deform before they break, which gives you a heads up. Composite will just snap without warning.
Damage to composite is difficult to fix and more expensive.
How do machanics test composite airframes for damage?
They can tap along leading edges. If there is a change in the sound, it indicates there may be damage inside.
