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List the components of the Powerplant and what they do for the aircraft.
The powerplant includes the Engine and the Prop. They provide thrust, electrical power, a vacuum for instruments, and heat for people.
What translates rotating force into thrust?
What is the 4 stroke cycle of a reciprocating engine?
- Intake of fuel air mixture
- Compression of mixture
- Ignition of mixture
What is the difference between spark ignition and compression ignition?
- Spark ignition uses a spark plug to ignite the mixture in the cylinder.
- Compression ignition first compresses air in the cylinder, raising its temp to a degree necessary for automatic ignition when fuel is injected into the cylinder.
A) A radial engine
B) A v-type engine
C) An opposed engine
D) An in-line engine
C) N68767 has a horizontally opposed engine.
(this multiple choice question has been scrambled)
Why has the use of a two stroke engine been limited in aviation?
- A two stroke engine has a power stroke each revolution and so has a high power-to-weight ratio.
- Due to it's inherent inefficiency and disproportionate emissions it's use has been limited.
Continuous operation of the engine depends on the simultaneous operation of what systems?
Induction, Ignition, Fuel, Oil, Cooling, and Exhaust Aystems.
The Prop is a rotating airfoil, subject to induced drag, stalls, and other aerodynamic principles that apply to any airfoil.
The amount of thrust produced by the prop is dependent on what factors?
- Shape of the airfoil.
- AOA of the prop blade.
- RPM of the engine.
Why is the prop twisted?
- To produce uniform lift throughout the blade.
- The greatest angle of incidence, or highest pitch, is at the hub (The slowest moving part of the blade) and the smallest AOI, or smaller pitch, is at the tip of the blade. (The fastest moving part of the blade.)
What type of prop is set by the manufacturer and cannot be changed?
The fixed pitch prop.
The fixed pitch prop is used when low weight, simplicity, and low cost are considered.
In a fixed pitch prop, the ___________ is the indicator of engine power.
Tachometer. The engine rpm is indicated on the tachometer.
What prop has blades that can be adjusted on the ground but not in flight?
Adjustable pitch prop, aka ground adjustable prop.
What prop is a controllable pitch prop whose pitch is automatically varied in flight by a governor maintaining constant rpm?
Constant speed prop.
- Most common type adjustable prop
- More efficient because it allows selection of most efficient engine rpm for given conditions.
In a constant speed prop, what are the two controls?
How are their outputs measured?
A constant speed prop has two controls:
- Throttle- engine power output measured on Manifold Pressure gauge.
- Prop control- Regulates rpm.
What is the #1 rule in flying an a/c with a constant speed prop?
- Keep the prop on top!!
- (Manifold pressure should always be reduced first and increased last. RPM should always be on top to avoid engine stress and damage.)
The system that brings air in from the outside, mixes it with fuel, and delivers it to the cylinder is the __________ system.
Where does the outside air come in?
- Indiction system.
- The outside air comes in through the intake port on the front of the cowling. This port normally contains the air filter.
Is there an alternate source of air incase the air filter becomes clogged?
Yes. The alternate air source for the engine is under the cowling.
Some alternate air sources function automatically, while others operate manually. (carb heat)
What are the two main types of induction systems used in small a/c engines? How are they different?
The carburetor system- mixes fuel and air before it enters the intake manifold. (cylinder)
The fuel injection system- mixes fuel/air immediately before entry int each cylinder, or injects fuel directly into each cylinder.
Float or Pressure are two types of what a/c system?
The carburetor, induction system.
What is the basic difference between the float and pressure type carburetor systems and which is most common?
The main difference between float and pressure carburetors is the fuel delivery system. The pressure delivers fuel via a pump.
The float type carburetor is the most common of all carburetor types.
What does the float in the carburetor do?
The float rests on the fuel in the fuel chamber, like a toilet float, a needle attached to the float opens and closes an opening at the bottom of the carburetor bowl. The needle valve opens when the float gets low and lets more fuel into the chamber.
What regulates the flow of mixture to the combustion chambers?
The throttle valve, controlled by the throttle in the flight deck.
Why does carb ice form in the venturi?
Fuel vaporization and decreasing air pressure in the venturi cause temperature to drop and water vapor can condense causing ice to form.
When can carb ice happen?
Carb ice can happen at any time but is most likely when temp is below 70 degrees F or 21 degrees C and relative humidity is above 80%.
What would indicate you have carb ice?
Fixed pitched prop- Drop in rpm followed by engine roughness.
Constant speed prop- Drop in manifold pressure, rpm will remain the same, and engine roughness.
What controls the fuel to air mixture ratio?
The mixture controls the fuel to air ratio.
When does the condition of the engine make carb ice more probable?
Carb ice is more probable when the throttle valve is closed. The engine cools rapidly and vaporization of fuel is less complete. Otherwise, carb ice may not be detected until power is added back in. (Think descending, then needing power but no fuel due to carb ice...)
Why does the use of carb ice cause a decrease in rpm? How can you tell if you did have carb ice once you have initiated heat?
Heated air is less dense, the mixture is enriched, and the engine doesn't run as efficiently.
In a fixed pitch prop, once heat ha been applied to carb ice there will be a drop in rpm followed by a gradual increase in rpm as the ice melts. If there is no ice, the rpm will drop and remain constant.
In a constant speed prop, a decrease in manifold pressure followed by a gradual increase in mp will occur if there was ice and heat was applied. If there is no ice the mp will drop and remain constant.
Your notice a loss in power, altitude and airspeed and a vibration so you apply carb heat which results in a further loss of power, altitude, airspeed and increased roughness. Should you stop using carb heat since the conditions worsened?
No. These symptoms can last from 30 seconds to several minutes and only verify that carb ice has accumulated.
What is the OAT gauge?
Outside Air Temperature gauge. Provides outside ambient air temp. for calculating true airspeed but is helpful in detecting icing conditions.
List the six basic components of the fuel injection system.
- Engine driven fuel pump
- Fuel/Air control unit
- Fuel Manifold (fuel distributor)
- Discharge nozzles
- Auxiliary fuel pump
- Fuel pressure/flow indicators
Since the master switch is on, the engine driven fuel pump provides fuel for starting the engine in a fuel injected a/c.
The auxiliary pump provides fuel for engine start and emergencies.
Even though there is no carburetor in a fuel injected a/c there is still a chance for icing.
Impact icing occurs when ice forms on the exterior of the a/c and blocks openings such as the air intake for the injection system.
I have an a/c that doesn't start easily on hot days, can vapor lock on hot days, and has trouble starting after fuel starvation. I have a __________.
Fuel injected a/c.
Benefits include reduction in evaporative icing, better fuel flow, faster throttle response, better control of mixture, better fuel distribution, and easier to start in cold weather.
What does the fuel control unit do?
The fuel control unit meters fuel based on the mixture control and sends it to the manifold valve. (fuel injected a/c)
What is the fuel manifold valve and is there one on Zero Five Papa?
The fuel manifold valve distributes fuel into individual fuel discharge nozzles.
No, 05P has a carburator and has an intake manifold, but no fuel manifold valve.
This system is made up of magnetos, spark plugs, high tension leads, and the ignition switch.
What is the Ignition system.
Magnetos are part of the electrical system.
Magnetos use a permanent magnet to generate an electrical current independent of the electrical system.
What are the RPM requirements while checking the mags?
When testing the Left or Right mag the rpm may not drop more then 125rpm, and there may not be a difference greater then 50 rpm between the rpm of the left and the rpm of the right.
What are the mags?
Magnetos. Engine driven mini alternators that supply the spark that ignites the fuel air mixture.
What are the main functions of the oil system?
- Lubrication of moving parts
- Cooling by reducing friction
- Removes heat from cylinders
- Provides seal between cylinder walls and pistons
- Carry away contaminants
What is the difference between a wet sump oil system and a dry sump oil system?
In a wet sump system the oil is kept in the sump in the engine and pumped around.
In a dry sump system the oil is kept in a tank located external to the engine and is pumped around. This allows for more oil to be supplied to the engine and is more suitable for very large reciprocating engines.
What gauge gives a direct indication of the oil system operation?
Any abnormal reading, high or low, consult POH immediately.
- The oil pressure gauge gives a direct indication of the oil systems operation.
- Measures pressure in psi, pounds per square inch.
The oil temp gauge is slow to change and should be rechecked periodically.
What could a high oil temp reading indicate?
High oil temp could mean a plugged line, low oil, or defective oil gauge.
How is the engine of your C152 trainer cooled?
It is normally aspirated. Air is funneled by the cowling and cools the external components of the engine. Oil helps cool the internal components of the engine.
Detonation can occur due to high engine temp.
High engine temp can cause loss of power, excessive oil consumption, detonation, and serious engine damage.
What are the main functions of the exhaust system?
The engine exhaust system vents burned gases, provides heat for the cabin, and defrost for the windscreen.
How does cabin heat work?
Outside air is drawn from the air inlet and ducted through a shroud around the muffler, where it's heated by contact with the outside of the muffler.
What does grounding the mags do?
Grounding the mags breaks the electrical circuit and grounds it to the exterior of the a/c. (so the a/c won't start while towing, pushing, or moving the prop.)
What is detonation?
Detonation is an uncontrolled, explosive ignition of the fuel/air mixture.
Caused by use of lower grade fuel then specified, high manifold and low rpm, high power settings with lean mixture, maintaining extended ground ops or climbing with reduced cylinder cooling.
What is preignition?
Preignition occurs when the fuel/air mixture ignites prior to the normal ignition event.
Caused by a residual hot spot in the chamber, a small carbon deposit on spark plug or other damage to the cylinder.
Describe the gravity fed fuel system.
Fuel tank is above the carburetor. High wing a/c. Fuel is under positive pressure (gravity.)
Describe the pressure fed fuel system.
Engine drived the fuel pump, with an auxiliary pump run by the electrical system in case of failure.
Which fuel is red?
80 octane fuel is red.
What fuel does the C152 take?
The C152 takes 100 LL, and it's blue.
What color is 100 octane fuel?
100 octane is green.
If you stain the fuel in your C152 and it's clear, what fuel do you have in your a/c? Is it safe to use?
Jet fuel is clear and is not okay to use in a C152.
100 octane and 100LL mixed makes clear fuel as well and it is okay to use. Jet fuel smells different and is oily.
How much fuel does your C152 hold?
13 gallons in each wing = 26 gallons total, but .75 gallons on each side is unusable because it's below the fuel drain. So my C152 has 24.5 gallons usable fuel total.
What are the minimum and maximum oil requirements for your C152?
Minimum 4 quarts oil and maximum 7 quarts oil.
Describe the break system in the C152.
Pump mushy breaks to build pressure.
- Hydraulically actuated- look for red break fluid
- Master cylinder behind breaks on each side.
- Disk breaks
- Parking break above primer
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