Aeronautics Flashcards
How was the term aeronautics derived?
Aero – referring to flight
Nautics – referring to ships and sailing
How does NASA define aeronautics?
The science of atmospheric flight
What are the three types of lift?
Buoyant
Aerodynamic
Direct
What is buoyant lift?
When an object is less than the weight of the medium it is displaced in, it will experience a buoyant force
Done with hot air, hydrogen or helium
How does helium weigh compared to air?
Helium is 1/5 weight of air
How does hydrogen weigh compared to air?
Hydrogen is 1/7 weight of air
How are balloons manipulated?
By manipulating how hot the air is, various altitudes can be reached
No control surfaces
Used for recreation and adventure sectors
What are the two types of airships?
Blimps - Gas bags that maintain their shape through internal pressure of the bag
Dirigibles - Rigid frames with gas cells split throughout the aircraft
Controlled with engines and control surfaces
Advantages of LTA?
Most efficient type of lift
Versatile to design
VTOL capability
Some safety aspects (engine failure less consequence, and collision is absorbed by frame)
Disadvantages of LTA?
Slow Helium is inert but expensive Hydrogen is cheap but flammable Low alt limit Public safety concerns Wind issues Large hangar spaces required
Cause of the Hindenburg disaster?
Lacquer used on the fabric ignited under static discharge with the mooring mast
What is a monoplane?
One wing structure
Lift generaated through aerofoils of the wing
What is a biplane?
Two wing design with aerofoils
De Havilland Tiger Moth
What is a triplane?
Three wings with aerfoil shapes
Fokker Triplane
What is a multiplane?
Multiple wings with aerofoil shapes
Advantages of aeroplanes?
Design allows fastest out of the categories Not alt limited (except by engine) Long range More efficient than direct lift less wind effect
Disadvantages of aeroplanes?
Limited design by shape Cannot Hover Can only go fast Restricted view Require runways
What theory is direct lift based on?
Newton’s third law - every action has an equal and opposite reaction
Aircraft generates a down forces, thus producing an upwards reaction
Purpose of main & tail rotors on helicopters?
Main - direct lift
Tail - at a tangent to counter the rotational effect of the main rotor (anti-torque)
Characterisitics of the chinook? CH47
Counter rotating rotors to eliminate need for anti-torque tail rotor
Largest helicopter in the world?
Military Mi-26
90 Pax
20 tonnes of cargo
What is a gyrocopter?
Direct lift
Instead of having an engine power the top rotor directly, a propeller at the front or back will be powered and also provide rotation for the top rotor.
Advantages of rotorcraft?
Hovering ability
VTOL (Helos)
STOL (Gyros)
Wide view
Disadvantages of rotorcraft?
Fuel inefficient
Limited range & endurance
What is hybrid lift?
This is where lift is generated using a combination of two or more of the three types
Types of hybrids?
Gyrodynes - eurocopter x3
Tilt rotors - Bell Boeing V-22 Osprey
Hybrid airships - Airlander 10
Four forces of flight?
Lift
Weight
Thrust
Drag
Newtons first law?
An object at rest will stay at rest unless acted upon by an external force. An object in motion will continue moving at a steady speed unless acted upon by an external force.
Newtons second law?
Explains how the velocity of an object changes when it is subjected to an external force.
Newtons third law?
Thethird lawstates that for every action (force) in nature there is an equal and opposite reaction
Factors affecting lift?
Density
Velocity
Surface area
Co-efficient of lift
What makes up the co-efficient of lift?
Number to represent the lifting capability of the wing
AOA
Camber
What is lift?
Lift is a mechanical aerodynamic force produced by the motion of the airplane through the air.
According to Bernoulli’s Principle, the air passing over the top of an aerofoil or wing must travel further and hence faster that air the travelling the shorter distance under the wing in the same period but the energy associated with the air must remain the constant at all times. The consequence of this is that the air above the wing has a lower pressure than the air below below the wing and this pressure difference creates the lift.
Three primary control surfaces?
Aileron, Rudder, Elevator
Primary effects of control surfaces?
Pitch - Lateral axis
Roll - Longitudinal Axis
Yaw - Normal Axis
Purpose of trim?
Small tab on the edge of the control surface deflected into airflow to relieve control stick pressure
Effect of Flap?
Increase in lift - ability to fly slower while producing the same amount of lift
Slower landing speed
Shorter landing distance
Types of flaps?
Plain
Split
Fowler
Slotted
What is drag?
Drag is a force acting opposite to the direction of travel
As air is a viscous fluid, when an aircraft moves through the air, resistance is encountered
Types of drag?
Induced Drag
Parasite drag
What is induced drag?
Product of an aerofoil generating lift, caused by rearward tilt of the lift vector
Caused by wingtip vortices from downwash
How to reduce induced drag?
High aspect ratio (glider) Tapering towards wingtip Winglets (spanwise flow is blocked) Wing fences Washout (reducing the angle of incidence at the wingtip compared to the wing root.)
What is parasite drag? What is it broken up into?
Caused by shape/size of the aircraft’s surfaces.
Interference, - conflicting air flows (reduced by blending and filleting)
Skin friction - shear forces between layers of air
Form - caused where a shape is not streamlined
What is the relationship between parasite & induced drag
As speed increases, Parasite will increase, lift induced will decrease
What is thrust?
Mechanical force generated by engines to move the a/c through the air
Key is newtons third law
Most efficient way to produce thrust?
Propeller (spinning aerofoil)
Problem with windmilling prop?
Produces huge amounts of drag - feather to reduce
What would you do in a engine fail in twin engine a/c?
Bank into the good engine, ‘raise the dead’ reduces yawing moment
