What is the primary structure of an aircraft called?
The airframe
What are the primary functions of the airframe structure?
- Survive the rigors of flight
- House, protect and sustain the occupants
- Crashworthiness
- Provide best aerodynamic performance
- Carry the control surfaces and systems to provide safe reliable flight.
What are the major sub assemblies of the airframe?
- Fuselage
- Wings
- Empennage (tail assembly)
- Undercarriage
- Engine/prop installation
What are the 5 aircraft design factors that specify the role and desired flight envelope?
- Mission
- Speed
- Altitude
- Range
- Payload
What are the compromising goals in A/C design?
- Weight
- Cost
- Efficiency
- Reliability
- Safety
What materials are the aircraft structure constructed with?
- Metals
- Plastics
- Composites
What material is the primary structure of an aircraft mostly made from?
Aluminum alloy
What are some adverse factors relating to service operating conditions that an aircraft must take into account?
- Strength/load factors
2 Cyclic loads
3.Corrosion - Battle/other damage
Aircraft structural strength specified as?
‘Load factor limit’ (e.g. 4g)
What are the 3 different types of load factor limits?
- Design limits
- Ultimate limits
- Operating limits
What are the 5 engineering forces that act on the aircraft and influence the design?
- Tension
- Compression
- Torsion
- Shear
- Bending
What are tension and compression forces?
Compressing or pulling the object axially (top –> bottom).
What is the torsion force?
When the object is twisted
What is a shearing force?
Sliding force on a material in the direction the force is being applied.
What is a bending force?
An external load is applied perpendicularly to the longitudinal axis of the element.
What do the ultimate and operating limits of an aircraft mean? When can you find these limits?
- Ultimate limits are those that if exceeded could result in permanent structural deformation or structural failure.
- Operating limits are those that the pilot can routinely apply while maneuvering the aircraft without exceeding the limitations or integrity of the airframe structure.
- Both can be found in the AFM (Aircraft Flight Manual).
What is a type of fuselage structure construction and what does it consist of?
Warren truss consisting of longerons, diagonal web members, vertical web members.
What is a full monocoque fuselage?
Fuselage skin carries all of the structural stresses.
What is a semi monocoque structure fuselage? What does it consist of?
- Skin is attached to a substructure.
- Substructure consists of longerons, stringers, bulkheads, frame and skin.
What does the empennage/tail assembly structure consist of?
- Horizontal stabilizer
- Vertical stabilizer
- Movable control surfaces (rudder, elevators, trim tabs)
What is the purpose of the horizontal stabiliser?
Provide stability in the pitch axis.
What is a stabilator? Why are they normally fitted with anti-balance tab?
- Combined horizontal stabilizer and elevators.
- Anti balance tab moves in same direction as the stabilator but moves further, increasing control force which can help prevent inadvertent overstress.
What is the vertical stabiliser (fin) and what is its purpose?
- Provides directional stability for the aircraft
- Moveable rudder is attached to the rear of the stabilizer, operated by foot pedals.
What loads must the wings be able to handle?
Aircraft weight and the stresses and strains that are imposed during flight.
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Airframe Structure29
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PC-21 Aircraft Introduction65
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Engine Systems Introduction97
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PC-21 Engine Systems104
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Fuel Systems Introduction35
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PC-21 Fuel System72
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PC-21 Propeller System45
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Hydraulic Systems Introduction29
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PC-21 Hydraulic System39
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Landing Gear Introduction26
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PC-21 Landing Gear27
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PC-21 Nose Wheel Steering (NWS) and Brakes21
