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Engine Cessna 172 With 93 Questions
When is carbarator icing most likely to happen? - โ โ Descents When checking the mags, how much should they drop and how much of each other? - โ โ They should drop no more than 175 and be within 50 of each other What does no drop mean? - โ โ Bad connection What 3 things cool the engine? - โ โ Oil Fuel Air What is the perfect ratio of fuel to air? - โ โ 14.7 air to 1 fuel What 3 things does the engine need to operate? - โ โ Fuel Air Spark What does it mean for the mixture to be rich? - โ โ The density of fuel entering stays the same but the density of air entering has decreased A rich mixture can do what to the engine? - โ โ Have engine roughness and an appreciable loss of power Why does roughness occour during a rich mixture? - โ โ It is due to a spark plug fouling from excessive carbon build up on the plugs
Why does carbon build up on the plugs? - โ โ It builds up because the rich mixture lowers the temperature inside the cylinder, inhibiting complete combustion of the fuel When is a rich mixture likely to happen? - โ โ During the runup prior to takeoff at high elevation airports and during climbs or cruise flights at high altitudes When should you enrich the mixture? - โ โ During a decent from high altitudes Why should you enrich the mixture control from docents from high altitudes? - โ โ If not then it might become to lean What can an overly lean mixture cause? - โ โ It may cause detonation which may result in rough engine operation, overheating, and/or a loss or power What can you use to get the best fuel economy for fuel injected engines? - โ โ Exhaust gas temperature gauge (EGT) What thing causes spark plug fouling? - โ โ Tetraethyl lead in aviation fuel What can happen when lead deposits form on spark plug electrodes? - โ โ Misfiring How can you clear a fouled spark plug? - โ โ Run engine RPM at 2000 Lean 50 RPM of peak Let it run for 30 seconds
Why are the crankshaft and the camshaft geared together? - โ โ So they remain synchronized Which one spins faster, crankshaft or camshaft? - โ โ The crankshaft Why does the camshaft spin slower? - โ โ The camshaft is geared to spend 1/2 as fast which allows the valves to open twice during the 4 stroke cycle What does the throttle control? - โ โ The amount of fuel/air that goes into the cylinders What does the mixture control? - โ โ How much fuel is mixed with the air (controls the ration between fuel and air) Where does the air enter for the fuel/air mixture? - โ โ The air filter usually found in the front of the plane What happens once the air enters the air filter? - โ โ The air is then metered and sent to the cylinders What are the 2 types of systems that control the fuel/air mixure? - โ โ Carburetor system Fuel injection system How does the carburetor system work? - โ โ Fuel arrives and sits in the float chamber which is next to the venturi. There is a fuel discharge nozzle at the bottom of the venturi where air comes in. This draws the fuel out of the flute chamber through the nozzle and mixes with the air. Just past the venturi, the throttle controls how much fuel/air is being sent to the cylinders
How does the fuel injection system work? - โ โ Fuel from the tank gets drawn from the fuel pump into the fuel control unit. It gets regulated there based on the settings. It is then sent to the fuel manifold valve to be dispersed to the head of the nozzles of each cylinder. The fuel does not mix with the air until immediately entering the combustion chamber What is a magneto? - โ โ A rotating magnet surrounded by a coil of wire that generates sparks of electricity which is independent of the airplanes electrical system If the airplane's electrical system were to fail, would the magnetos stop working? - โ โ No, they produce their own sparks that are sent to the engine Where is the energy from the magneto's sent? - โ โ It is sent to the spark plugs which allows them to ignite the fuel/air mixture and produce power How many magneto's are on the plane? - โ โ 2 How many spark plugs are on the plane? - โ โ 2 per cylinder so 8 If one magneto was to fail, would the other still work? - โ โ Yes but the power output will be slightly reduced What are some abnormal conditions that can affect the performance of the engine? - โ โ Detonation Pre-ignition What is detonation? - โ โ The uncontrolled explosive ignition of the fuel air mixture inside of the cylinders
What is a compression ignition? - โ โ They first compress the air in the cylinder, raising its temperature to a degree necessary for automatic ignition when fuel is injected into the cylinder Describe the characteristics of the Cessna 172 engine - โ โ Normally aspirated Direct driven Air-cooled Horizontally opposed Fuel injected Four cylinder 360 cu. in. displacement Horsepower 180 2700 RPM What does normally aspirated mean? - โ โ The engine has no supercharger or turbocharger to maintain sea level atmospheric pressure at higher altitudes What does direct driven mean? - โ โ The propeller is bolted to, and turns at the same speed as, the crankshaft What is a constant speed propeller? - โ โ The pilot can adjust the blade angle of the propeller to obtain maximum performance for different conditions of flight
What does air-cooled mean? - โ โ The engine is cooled by air movement instead of liquid What does horizontally opposed mean? - โ โ The cylinders are lying down flat, and arranged on either side of a central crankshaft What does fuel injected mean? - โ โ A system that directs an exact amount of fuel into the engine when it is needed What does four cylinder mean? - โ โ The cylinders are housing the pistons and there are 4 of them What are the 4 stroke cycles that the cylinders undergo? - โ โ Intake Compression Power (combustion) Exhaust What happens during the intake process? - โ โ The piston moves away from the cylinder head, the intake valve opens and lets fuel/air in What happens during the compression process? - โ โ Intake valve closes and the piston moves back towards the cylinder head What happens during the power process? - โ โ 2 spark plugs at the head of the cylinder each let off a spark to combust and pushes the piston down and turning the crankshaft What is pre-ignition? - โ โ The fuel/air mixture is ignited prior to its normal time What are two major ways we cool out engine? - โ โ Oil
Is the propeller straight or twisted? - โ โ Twisted Why is the propeller twisted? - โ โ To create equal thrust along the propeller blade What is a propeller? - โ โ A rotating airfoil, subject to induced drag, stalls, and other aerodynamic principles that apply to any airfoil What rotates the propeller? - โ โ Engine power, which in turn generates thrust The amount of thrust produced depends on what? - โ โ The shape of the airfoil, AOA of the blade, and revolutions per minute (rmp) of engine Where on the propellers is the highest angle of incidence, or highest pitch? - โ โ The hub Which part of the propeller travels the fastest and why? - โ โ The tip of the blade travel faster because the tip travels a greater distance than the hub in the same length of time Why do we lean on the ground? - โ โ So the carbon doesn't build up and foul the spark plugs and lead from the 100LL doesn't damage cylinders What is EGT? - โ โ Exhaust Gas Temperature What is the best economy? - โ โ Peak EGT on 75% power setting or lower What is best power? - โ โ 50ยฐF rich of peak EGT or peak on tachometer
