What is an aircraft?
the one pictured above is a tecnam eaglet p92 with rotax 912 single engine, a ultralight monoplane...
my first training aircraft! that's me with my instructor, mahl oakes from fly now based at redcliffe airfield.
an aircraft is an aerial vehicle. its uses the medium of the air to carry people and freight safely and efficiently. there is different sizes and types and they are grouped together and classified dependent of how they are powered. For example: helicopter - fixed or rotary wing, gliders or sailplanes including powered versions, piston or turbine, single or multi engine
my studies will concentrate on single engine aircraft - tecnam eaglet p92 and cessna 172s models.
the aircraft is made up of many components and we have the cabin - where we are seated, seat belts, the luggage compartment at the rear of seats, doors, windows, windscreen, ventilation ports, interior lights. then to stay up in the air and overcome the force of gravity, wings are needed. the wings provided the aircraft with lift but we need and engine, propeller or rotors blades.
propulsion - Thrust - push is caused by the propeller pushing air rearwards and this reaction causes the aircraft to go forwards.
every action causes a reaction.
e.g. paddling a canoe, we push the water rearwards and this reaction causes the canoe to move forwards.
what is air?
characteristics of the environment we fly in... it's invisible, it allows us to breathe it and it allows objects to fly Air is actually a gas and made up of different elements. what we breathe consists of 78% nitrogen, 21% oxygen, 1% other. due to the oxygen in air; us, animals and the aircraft's engine can breathe.
the aircraft can fly because air has mass (substance), weight (due to gravity), density (weight vs volume), temperature and pressure (static pressure due to altitude and dynamic pressure due to movement).
air has mass and weight - the air nearest the surface of the earth is thicker, warmer and at a higher static pressure than air at higher altitudes. this is due to the air's weight pushing down or squashing the lower levels near the earth.
the engine functions by sucking in air, mixing this air with the fuel, igniting the mixture (with the oxygen in the air) and using the temperature rise and its consequent expansion to generate a force. this force is what pushes the piston which then turns the crankshaft and this turns the attached propeller.
the engine and propeller is important but the wings are a major structure and this is how the aircraft flies.
the wings are shaped to compress the air underneath and reduce the pressure of the air above. the combination of compressing underneath and reducing pressure above is what causes lift.
the plane should be in the air and away from the earth... basically your flying on a thin cushion of air.
what is a engine's thrust?
to propel forward or accelerate a object must be pushed forward by an external force.
an example: if i stand on a foot scooter and leave my feet on the base of the scooter and push down, nothing really will happen but if i place one foot on the ground and push my foot backwards along the ground, the scooter will roll forward and if i continue this action, forward movement would continue. but there is another part - friction. i need to be on a firm surface otherwise the sole of my shoe won't be able to grip the ground and thus forward movement won't be possible.
so basically the external force is my foot gripping the ground and pushing myself and scooter forward.
another example: again in the canoe, we use the paddle to push the water backwards and thus moving the canoe forward. the paddle is the pressure differential. the paddle operates by compressing and pushing the water behind causing increased pressure; it also causes an area of suction (or reduced pressure) in front of the paddle. this differance between the front and rear surfaces of the paddle surfaces is producing thrusting force and propels us.
another example: air is shoved and pushed in the air boats. the large fan is facing to the rear of the boat and this represents the paddle in the above example.
basically to move forward, something needs to be pushed backwards!
aerodynamics is the science of all motion (sucking, squashing, squeezing, blowing) through the air and its forced that is being generated by an aircraft to accelerate, lift, turn or manoeuvre.
the engine and propeller act as a continuous pump. the engine turns the propeller and the air is sucked in from the front, it is then squashed and squeezed against the air behind.
an example: picture an aircraft with engine running and propeller turning. The air is following the circle of the propellor and the air is pushed backwards and in a large spiral encircles the aircraft. air goes under the wing as the propeller moves downwards and also it can go over the wing and over the cockpit area and continue circling down the aircraft.
Think of ribbons of air coming of the propeller and circling down the aircraft.
The airflow from the propeller is a action or push.
airflow that pushes back is a reaction. this reaction is called thrust.
an example: think of a electric fan that falls backwards when its set on maximum speed. that reaction of the fan caused by the action of the blades (the pushing of air). thus this reaction is thrust.