Airframe Structure And Control Systems Flashcards
Main parts of a plane
- Fuselage
- Wings
- Empennage
- Landing gear
- Engine mount (engine is not apart of the airframe)
Manoeuvring loads
Forces due to the mass of the aircraft and its acceleration or deceleration. Particularly significant during manoeuvres where the forces can be several times the weight of the aircraft.
Aerodynamic loads
Loads applied on the aircraft by the air moving over the surfaces of the airframe by the air moving over the surfaces of the airframe. Include life, drag, and side forces.
Gusts loads
Needs to be able to withstand gusts
Control surface loads
When the control surfaces are deflected, it induces a force on the wing or the airframe.
Pressurisation loads
Internal pressures applied to the airframe, particularly in the fuselage , when the aircraft is pressurised for high-altitude flight.
Ground loads
Forces acting on the aircraft when it is on the ground e.g. during landing, taxiing, or take-off. Transferred to the airframe through the landing gear.
Stress
A measure of the internal resistance of a material to deformation due to applied forces.
- Measure in PSI of Pascals
Tensile stress
When a material is subjected to a stretching force. When an aircraft is in flight, various parts of the airframe are subjected to tensile stress.
Compressive stress
Opposite of tensile stress and occurs when a material is subjected to a squeezing force. For example, the landing gear of an aircraft experiences compressive stress during landing.
Bending stress
When a material is subjected to a load that causes it to bend. One side of the material gets compressed (compressive stress) while the other side is stretched (tensile stress).
E.g.
An example in aviation is the wings of an aircraft, which undergo bending stress during flight. The top of the wing is under compression as it bends upward, while the bottom of the wing is under tension.
Shear stress
Two forces act parallel to each other but in opposite directions. This can occur in an aircraft’s skin during turbulence or manoeuvres
Tortional stress
When a material is subjected to a twisting force, known as torque.
E.g.
One example in aviation is the fuselage of an aircraft during a roll manoeuvre, which can be subjected to torsional stress.
Strain
Measure of the deformation of a structure.
- Dimensionless quantity
- Generally described as a percentage
- Might not result in immediate failure, but repeated can weaken materials over time potentially leading to failure
Elastic strain
- Temporary deformation
- Once the load has been removed, it will go back to its normal state
Plastic strain
- Permanent deformation
- After the load is removed, the material doesn’t return to its original state
Truss
- Fuselage construction that utilises a framework of beams (longerons and stringers), struts etc.
- Covered with fabric, plywood, or metal
- Used in early aircraft designs
- A lot of extra weight and takes up space
Monocoque
- Skin of the aircraft bears the major part or all of the stress
- Streamlined
- Ends up being really heavy for the amount of strength you get
Semi-monocoque (stressed skin)
- Most commonly used
- Has a substructure to support the sin including longerons and frames.
- Shares the load with the skin
- Skin can be thinner and lighter than a full monocoque design
Composite
- Modern aircraft
- Use carbon fibre or fibreglass
- Strong, lightweight
- Moulded into complex aerodynamic shapes
Biplane
- Two wings, one above the other
- Connected by struts and wires
- Common in early aircraft
- More drag
Braced monoplane
- Singled winged aircraft
- Has additional structural supports e.g. struts or wires
- Addational bracing provides more strength
- Common in early monoplanes
- High lift, low-speed wing
Unbraced monoplane
- AKA cantilever monoplane
- Wing attached to fuselage without additional external bracing
- Strength comes from its internal structure
- Less drag compared to braced monoplane and biplanes
Wing spars
- Runs span wise - length of the wing from fuselage to the wingtip.
- Bears the most load that the wing experiences during flight
- Typical design, two spars, a front (leading edge) spar and a rear (trailing edge) spar.
Ribs
- Provide the aerofoil shape and help distribute the loads to the spars.
- Run chord wise, from the leading edge to the trailing edge of the wing
Stringers
- Longitudinal structural members in an aircraft’s wings and fuselage that provide additional support and rigidity.
- Secondary load-bearing structures - but are still vital to maintaining the structural integrity.
- Run parallel to the spars
- Distributes the loads acting on the skin
- Help maintain the shape of the wing
