Aviation Systems
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84 terms
Terms | Definitions |
|---|---|
 The primary purpose of a lubricant is to... | reduce friction between moving parts. |
| What does the oil film do? | Acts as a cushion between metal parts. |
| As oil circulates through the engine, it... | absorbs heat from the parts. |
| Pistons and cylinder walls in reciprocating engines are especially dependent on the oil for ______. | cooling |
| The most important property that an oil must possess is its ______. | viscosity |
| An oil which flows slowly is viscous, or has a _____ ______. | high viscosity |
| An oil which flows freely has a _____ _____. | low viscosity |
| What can effect an oil's viscosity? | temperature |
| The lower the number, the ______ the viscosity. | thinner |
| The higher the number, the ______ the viscosity. | thicker |
| SAE | Society of Automotive Engineers |
| Oil is distributed to the various moving parts of a typical internal-combustion engine by one of three following methods: | 1. Pressure 2. Splash 3. Combination of pressure and splash |
| A _____ _____, engine driven, supplies oil under pressure to the bearings throughout the engine. | mechanical pump |
| Two basic types of sumps: | wet, dry |
| Wet-Sump advantages: | 1. Complete internal system requiring no external parts. System is simpler, lighter weight, and less costly. 2. No second pump is required so chance of oil pump failure is reduced. 3. System can be operated in much colder ambient temperatures without concern the oil will congeal in external lines |
| Wet-Sump disadvantages: | 1. Oil supply is limited by oil pan capacity. 2. Provisions for cooling the oil are more difficult to arrange because the system is self-contained. 3. Higher oil temperatures because the oil is continuously subjected to high operating temperatures. 4. Not conducive to inverted flight since the oil supply would flood the engine and oil supply to pump would run out. |
| Dry-Sump | Oil supply in this system is carried in a separate tank. Pumped through engine in the same manner as a wet-sump system. More parts, more money, more weight, more problematic in cold weather flight. Capable of sustained inverted flight. |
| Why is excessive heat bad? | 1. It affects the behavior of the combustion of the fuel / air charge. 2. It weakens and shortens the life of engine parts. Too much can result in premature combustion. 3. It impairs lubrication. As temperature increases, oil viscosity decreases. |
| In a typical aircraft engine, half of the heat is expelled through _____, the other half is absorbed by the _____. | exhaust, engine |
| When extended for increased cooling, the _____ _____ produce drag and sacrifice streamlining for added cooling. | cowl flaps |
| CHT | Cylinder Head Temperature |
| EGT | Exhaust Gas Temperature |
| Pilots cooling tools: | 1. Cowl Flaps 2. Power Setting 3. Airspeed 4. Fuel Mixture |
| Thermal shock: | occurs when engine parts that are operating at high temperatures are cooled too quickly. |
| The engine supplies _____ horsepower through a rotating shaft, and the propeller converts it into _____ horsepower. | brake, thrust |
| Centrifugal Force: | a physical force that tends to throw the rotating propeller blades away from the hub. |
| Torque Bending Force: | in the form of air resistance, tends to bend the propeller blades opposite to the direction of rotation. |
| Thrust Bending Force: | is the thrust load that tends to bend propeller blades forward as the aircraft is pulled through the air. |
| Aerodynamic Twisting Force: | creates a rotational force (twisting moment) about the center of pressure, causing the blade to tend to pitch to a lower blade angle. |
| The forces acting on an airplane are: | Lift, weight, drag, and thrust |
| Lift opposes _____. | weight |
| Thrust opposes _____. | drag |
| Airfoil: | any surface, such as a wing, which provides aerodynamic force when it interacts with a moving stream of air. |
| Leading edge: | the part of the airfoil which meets the airflow first. |
| Trailing edge: | the portion of the airfoil where the airflow over the upper surface rejoins the lower surface airflow. |
| Chord Line: | an imaginary straight line drawn through the airfoil from the leading edge to the trailing edge. |
| Angle of Attack: | the angle between the chord line of the airfoil and the direction of the relative wind. |
| The two primary things that a pilot uses to control lift are: | airspeed, angle of attack |
| Operate as a _____ propeller, however, the pitch or blade angle can only be changed when the prop is not moving. | fixed-pitch |
| The ______ propeller permits a change of blade pitch or angle while the propeller is rotating. | controllable-pitch |
| The use of propeller governors to increase or decrease propeller pitch converts the controllable pitch propeller into a _____ ______. | constant-speed prop |
| Reverse-pitch propellers: | A controllable propeller in which the blade angles can be changed to a negative value during operation. |
| Feathering propellers: | A controllable propeller having a mechanism to change the pitch to an angle so that forward aircraft motion produces a minimum windmilling effect on a "power-off" propeller. |
| What is the most commonly used wood in the making of propellers? | Birch |
| Metal propellers are typically fashioned from _____ and are usually thinner. | aluminum |
| Use _____ ______ to achieve a high or low pitch angle. | oil pressure |
| Why do we use oil pressure to achieve a high or low pitch angle? | This is done so that in the event of an engine failure, the blade angle will revert to a higher pitch, resulting in minimized drag. |
| _____ _____ is accomplished by converting electrical energy to heat energy in a heating element which is attached to the blades. | Icing control |
| _____ ______ is used in many anti-icing systems due to low cost and availability. | Isopropyl alcohol |
| The _____ _____ engine used in our aircraft is a form of heat engine. | internal combustion |
| The internal combustion engine is a device which changes _____ energy into ______ energy. | heat, mechanical |
| What is the combustion process? | 1. Fuel is brought into contact with a source of oxygen. 2. Temperature of the fuel and oxygen is raised to its kindling point. 3. Once the proper temperature is reached, the oxygen combines with the fuel and oxidation, or burning occurs. |
| _____ _____ is a byproduct of the combustion process so it is very important to ensure exhaust fumes are kept out of the aircraft cabin. | Carbon monoxide |
| The ratio mixture is expressed in terms of "_____________________". | pounds of air to pounds of fuel |
| Two basic factors in considering fuel for aviation use: | 1. Chemical characteristics 2. Physical characteristics |
| Chemical Characteristics: | - Must have a high boiling point and a low freezing point. - It must have a high energy content that is free from any constituents that will form acids or gums. - Its vapor pressure must be low enough that it will readily ignite from the spark plug, but not so low that it is hazardous for normal handling. |
| Physical Characteristics: | - Must be free from contaminants. - Must be easy to filter. - Must be pumpable at very low temperatures |
| _____is the most widely used fuel for reciprocating engines...but constitutes only a small fraction of refinery output | AVGAS |
| Detonation is? | When the fuel-air mixture in a cylinder reaches a certain pressure and temperature, it explodes rather than burning evenly. |
| Preignition is? | Occurs when the fuel-air mixture is ignited in advance of the normal timed ignition. |
| What conditions can cause high engine temperatures? | - Takeoff / high RPM settings with low airspeed. - Extended high RPM operations with a lean mixture. |
| Grade 80: | red |
| Grade 100: | green |
| 100LL (low lead): | blue |
| Grade 115/145: | purple |
| DA20 uses what type of fuel? | AVGAS 100 or AVGAS 100LL |
| DA40 uses what type of fuel? | AVGAS 100LL |
| What to do if there is improper fuel use and the engine HAS NOT been run? | 1. Drain all of the improperly filled tanks. 2. Flush out all of the fuel lines. 3. Refill the tanks with the proper grade of fuel. |
| What to do if there is improper fuel use and the engine HAS been run? | 1. Perform a compression check of all cylinders 2. Inspect all of the cylinders with a bore scope. 3. Drain the oil and inspect the oil screens. 4. Drain the entire fuel system, including all of the tanks and carburetor. 5. Flush the entire system with the proper grade of fuel. 6. Fill the tanks with the proper grade of fuel. 7. Perform a complete engine run-up check. |
| _____ _____ clog fuel strainers, decompose fuel lines, pump vanes and gaskets and displace fuel. It has become the cause of many aircraft accidents. | Fuel contaminants |
| The two main hazards of the fueling process are: | 1. Fuel contamination of the aircrafts fuel system 2. Static sparks |
| Three categories of contaminants? | Solids, surfactants, and water |
| The ______ controls engine speed by regulating the amount of fuel and air mixture that flows into the cylinders. | throttle |
| The _____ controls the fuel - air ratio. | mixture |
| Two general types found in most light airplanes: | 1. Fuel-pump system 2. Gravity-feed system |
| Fuel-pump system is usually found in _____ _____ where the fuel tanks are located below the engine. | low-wing airplanes |
| Four fuel system components: | Fuel tanks, fuel lines, fuel strainer, fuel pump |
| Two ways to introduce fuel to the engine: | 1. Carburetor 2. Fuel Injection |
| The operating principle of ______ _____ is based on the difference in pressure at the venturi throat and the air inlet. | float-type carburetor |
| When air enters the carburetor, it passes through a _____ where its velocity _____ and its pressure ______. | venturi, increases, decreases |
| Carburetor disadvantages: | icing, higher fuel consumption rate, decreased horsepower |
| Carburetor is most susceptible to icing in high humidity days with temperatures ranging from ____F to ____F. | 20, 70 |
| Carburetor ice on a fixed-pitch prop: | first indication is a decrease in RPM and a rough running engine. |
| Carburetor ice on a constant-speed prop: | first indication is a shift in manifold pressure |
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