AMT 287 Exam 1 Makana
What kind of a lever is your forearm?
3rd class lever
Many general aviation aircraft have cowl flaps installed. These flaps provide a means of decreasing or increasing the exit are at the rear of the engine cowling. Closing the flaps increase cooling and opening the flaps decrease cooling of the engine. A. True B. False
A. False decreases cooling
A bearing is any surface that supports or is supported by another surface. Bearings are used in aircraft engines to produce minimum friction and max wear resistance. A. true B. False
A. True
Although it is good practice to use the same brand and grade of oil already in the engine, if it is necessary in order to have the correct level/quantity of oil, brands of different oil types can be mixed. A. True B. False
A. True
As the engine temperature rises excessively, oil viscosity decreases, oil is not pumped as easily, oil pressure decreases and the lubricating qualities of the oil film decrease. A. True B. False
A. True
Engine baffles direct the cooling of the air close around the cylinders to prevent forming hot spots on the cylinders and provide as uniform cooling as possible. A. True B. False
A. True
Excessive heat is undesirable in any internal combustion engine or turbojet engine. Exceeding temperature limits is the single biggest threat to any aircraft engine operation. A. True B. False
A. True
Excessive temperature affects the behavior of the combustion of the fuel/air charge. If the fuel/air mixture is preheated then combustion may occur before the desired time. This can cause detonation, knocking and other undesirable conditions. A. True B. False
A. True
In addition to reducing friction, the oil film acts as a cushion between metal parts such as: engine crankshaft, connecting rods, pistons, and cylinder walls, and absorbing heat from these parts. A. True B. False
A. True
In the four-stroke aircraft engine two complete revolutions of the crankshaft are required for the four strokes, thus each cylinder in an engine of this type fires once in every two revolutions of the crankshaft. A. True B. False
A. True
Manifold pressure is the average pressure of the air or fuel/air charge in the intake manifold and is measured in units of inches of mercury (Hg). A. True B. False
A. True
With a fixed RPM, does propeller blade angle of attack increase or decrease as airspeed increases?
Decreases
T/F. The fuel air mixture enters the cylinders through the intake valve ports and burned gases are expelled through the exhaust ports. Because of this exhaust valves tend to operate lower temperatures then the intake valves.
False " because of this intake valves operate at lower temperatures than exhaust valves"
What are the advantages of the pressure carburetor over the float carburetor?
Pressure carburetors are better than flow carburetors because of the following: 1) not susceptible to icing 2) even fuel/air mixture distribution 3) not critical at high density altitudes 4) not affected by gravity
What are the states of matter? Define or describe each.
Solids: Have a definite volume and a definite shape Liquids: Have a definite volume but take the shape of vessel Gases: Have neither a definite cilium nor shape but expands Plasma: Made of very hot, ionized gases (sun and stars)
What are the advantages of a wet sump system, compared to the dry sump?
Some advantages of wet sump lubrication systems is that it is a complete system that requires no external parts, no second pump is required, and it can be operated in colder temperatures.
What is the difference between static and dynamic balancing?
Static balancing is a propeller suspended by a drawstring and dynamic balancing is an electrical machine with vibration analysis of the aircraft.
What are the advantages of a fuel injection system, as a fuel metering system?
The advantages of a fuel injecting system are that it is not susceptible to icing and has more power than carbureted systems
What are the advantages of a hydraulic lifter?
The advantages of a hydraulic valve filter or tappets is that it automatically keep the value at 0, trapping the oil in the pressure chamber. Then, a predetermined leakage occurs between the plunger and cylinder, compensating for any expansion or contraction in the valve train.
What is the purpose of the air bleed in an injector nozzle?
The air bleeds purpose in the injector nozzle is to minimize fuel bleeding
What is the purpose of the bypass valve and relief valve?
The bypass valve allows oil flow if the oil filter becomes plugged and the relief valve creates pressure in the system to compensate for wear on bearings or thinning out oil.
What provides the low pressure at the discharge nozzle of a float carburetor?
The carburetor venturi
How does the cowling contribute to engine cooling?
The cowlings are designed to force air over the cylinder cooling fins.
How are the cylinder walls lubricated in a typical opposed aircraft engine?
The cylinder walls are lubricated by oil sprayed from the crankshaft and crankpin bearings.
What are the disadvantages of a fuel injection system, as a fuel metering system?
The disadvantages is that there is possible vapor lock in the fuel lines make it difficult to start the engine
Is the lowest blade angle near the shank or the tip? Why? Was it built that way?
The lowest blade angle is near the tip to provide equal thrust along the propeller blade.
Pour point
The lowest temp at which the oil can flow or be poured.
What is the main function of a piston?
The main purpose of the piston in a reciprocating engine is to act as a moving wall within the combustion chamber. as the piston moves down, it draws in fuel/air mixture. as it moves upward, it compresses the charge, ignition occurs.
Why is viscosity important when selecting a lubricant?
The oil selected must be light enough to circulate freely but heavy enough to provide the proper oil film at various temperatures.
Describe the operating cycle of the typical aircraft reciprocating engine.
The operating cycles in general use is the (1) two-stroke cycle and the (2) four-stroke cycle. Most aircraft operate on a four-stroke cycle. Induct, compress, ignite, burn, expand the fuel/air charge in the cylinder.
What is the purpose of the process called nitriding?
The purpose of nitriding is for the steel of the cylinder barrel to soak up nitrogen for the gas which forms iron nitrides on the exposed surface.
Cloud point
The temp at which the wax begins to solidify and separate into crystals.
Name all the parts in a typical cylinder assembly: describe the function of each and what material it is made of.
There are two major parts in a cylinder assembly: 1) Cylinder head 2) Cylinder barrel. 1) The cylinder head is made out of aluminum alloy. Provides a place for the combustion of the fuel/air mixture and to give the cylinder more heat conductivity for adequate cooling. 2) The cylinder barrel is made out of steel alloy. They hold the piston, therefore, the steel alloy must be light and withstand high temperatures.
Define Thrust
Thrust it the force which propels the aircraft.
Other factors remaining equal the greater the piston displacement the greater the maximum horsepower an engine will develop. A. True B. False
True
T/F Radial engines consist of a row or rows of cylinders arranged radially about a central crankcase. The number of cylinders comprising a row may be three, five or seven or nine, but it is always and odd number.
True
T/F The oil Scraper ring usually has a beveled face and is installed in the groove of the bottom of the piston skirt.
True
T/F The purpose of the compression rings is to prevent escape of gas past the piston during engine operation. The number of compression rings used on the piston is determined by the type of engine and its design.
True
T/F The valve mechanism of an opposed engine is operated by a camshaft. The camshaft always rotates at one-half the crankshaft speed in four stroke engines.
True
T/F When the propeller tips approach the speed of sound, the efficiency of the propeller decreases rapidly. Because of high horsepower engines the crankshaft will turn the prop at excessive speeds, therefore in high horsepower engines some kind of reduction gearing is often be required.
True
T/F. An in-line engine usually has an even number of cylinders. This engine may be either liquid cooled, or air cooled and has only one crankshaft, either above or below the cylinders.
True
T/F. The opposed type of engine has two banks of cylinders opposite each other with a crankshaft in the center. This type of engine may be liquid cooled or air-cooled but the air-cooled version is used predominantly in aviation today.
True
When should carburetor heat be used on the ground (several answers)?
When engine starting in high or low temperatures and when shutting off the engine which prevents cold air from passing through
How much thrust is being used by an atreraft that is using 100 THP to go 100 MPH?
X(100mph)/375 = 100 THP X= 375 lbs of thrust
Is the fuel-air mixture enriched or leaned when the main air bleed is restricted?
it will be leaned when the air bleed is restricted
Does application of carburetor heat richen or lean the mixture? How and whv? (more than one reason).
richer a) less dense air decreases the amount of oxygen getting into the cylinder, thus increasing the fuel/air ratio b) higher air temperature will do a better job of vaporizing the fuel, thus increasing the fuel/air ratio
Show the value of temperature of the standard day atmosphere at sea level in four different units of measure.
1) 59˚ F 2) 15˚ C 3) 298.18 ˚K 4) 518.67˚ R
Show the value of pressure of the standard day atmosphere at sea level in five different units of measure.
1) 760 mm of mercury 2) 14.70 lbs/in^2 3) 1,1013.25 * 10^3 dynes 4) 1,013.25 millibars 5) 101.325 kilopascals
What distinguishes a liquid from a gas and what is a fluid?
1) Gases fill their containers completely, but liquids may not 2) Gases are lighter than equal climes of liquids 3) Gases are highly compressible, but liquids are essentially not compressible Fluid: a substance which changes its shape easily and takes the shape of the container.
The lubricating oil is distributed to the various parts of the engine by one of three ways. What are they?
1) Pressure-lubrication 2) Wet-sump 3) Dry-sump
What are the functions of the spider?
1) distributes the fuel evenly to all of the cylinders 2) provides a positive shut off when the mixture control is placed in the idle cut off position
3 Main Advantages of the wet-sump oil system (commonly found in general aviation aircraft)
1) doesn't need extra parts: simpler, lighter, cost efficient 2) no second pump is required 3) can be operated in colder climates
Why are float carburetors more susceptible to icing (at least two reasons)?
1) fuel evaporation 2) decreasing air pressure in the Venturi
3 Main Disadvantages of the wet-sump oil system (commonly found in general aviation aircraft)
1) oil supply is limited by the sump capacity 2) cooling the oil is more difficult to arrange because it's a self-contained unit 3) not readily adaptable to inverted flying
Name the three types of bearings commonly found in engines. 1.__________ 2.___________ and 3. ______________.
1) plain 2) ball 3) roller
What are the advantages of leaving the propeller in the 10/4 o clock position?
1) propeller position for hand starting 2) intake/exhaust valve opening minimized 3) less attractive for birds to perch on
Name five functions/actions the oil performs. (7)
1) reduces friction 2) cushion 3) absorbs heat 4) cooling 5) seals 6) reduces wear 7) cleansing
Name the three major types of propeller shafts. (That point at which the propeller is mated to the engine) 1.________ 2_________ 3_________.
1) tapered 2) splined 3) flanged
Name two functions of an air bleed on a float carburetor.
1) to improve fuel vaporization 2) to provide a more even mixture over a wide range of air flows 3) to decrease the size of the fuel metering force needed which decreases the amount of restriction necessary at the Venturi
Three minutes after take-off how much potential energy will the aircraft of Question #1 possess (neglet remaining fuel in the tanks)?
2,500 lb * 1000 ft.min * 3 min = 7,500,000 ft-lb PE = 7,500,000 ft-lb
What kind of a lever is a hydraulic wobble pump handle?
3rd Class lever
Under what conditions would a dry sump system be advantageous, over a wet sump?
A dry sump would be better for radial engines because oil can't be carried inside the engine itself and wet sump systems are self-contained unit.
Describe the purpose and operation of a dynamic damper.
A dynamic damper is a pendulum, fastened to the crankshaft. It is incorporated in the counterweight assembly and reduces vibration during engine operation.
What is the principal fluid used for propulsion by most heat engines?
Air is the principal fluid for propulsion
Ashless dispersant (AD) oil is used after the break-in period for a new or overhauled engine. This oil has fewer tendencies to oxide to carbon nor does it form ash sludge, additives tend to cause particle dispersion, so particles don't clump together, but repel each other, staying in suspension and being removed by the oil filter. A. True B. False
B. False not AD, straight mineral oil
Specific gravity is a comparison of the weight of a substance compared to the weight of an equal volume of distilled gasoline at a specified temperature. A. True B. False
B. False not gasoline but distilled water
What forces are used to feather a propeller?
Centrifugal force
What forces tend to twist the blade to decrease propeller angle?
Centrifugal twisting force
What three energy forms does the reciprocating engine utilize or convert?
Chemical energy into heat energy then into mechanical energy.
What type of pump is the engine oil pump?
Displacement pump and mechanical positive.
What are the differences between a two position and a ground adjustable propeller?
Ground adjustable operates as a fixed pitch propeller, cannot be changed. Two-position controllable prop permits a change of blade pitch while the prop is rotating.
Horsepower (HP)
HP = ft-lb per min/33,000 HP = ft-lb per sec/550
List all the useful function of lubricating oil within the engine.
Lubricating oils reduce friction, acts as a cushion in between metal parts, absorbs heat, reduces abrasive wear, and cleans the engine.
What limits the maximum amount of fuel which can flow from the float bowl for any given pressure differential?
Main metering jet
How much more or less thrust than the airplane of Question #5 is another aircraft using that is using 100 THP, just like the airplane of Question #5, but is going 90 KTS?
X(103.6)/375 = 100 THP X=632.0 lbs of thrust 13.0 lbs less than Q #5
Neglecting drag, how much power is needed to cause a 2500 pound airplane to climb at 1000 R2/mig Express your answer in ft-lbs/min, watts and HP.
2500 lb * 1000 ft= 2,500,000 ft-lb/min (1 HP/33,000 ft-lb/min) * (2,500,000 ft-lb/min) = 75.76 HP (746 watts/ 1 HP)*(75.7 HP) = 56,515.115 watts
What are the differences between inertia and momentum?
Inertia is the resistance offered by a body to the motion whereas momentum is the tendency of a body to continue moving.
What are the disadvantages of the pressure carburetor?
Pressure carburetors main disadvantages is that even though they are less susceptible to icing they can still have ice formations therefore fuel injection systems are the least susceptible.
On a short field takeoff, what can the pilot do to reduce FHP and thus increase BHP and THP?
Pull the alternator field circuit breaker, or open the alternator switch, and let the battery handle the electrical system until you've cleared.
What is THP (name and define, or describe it)?
THP is thrust horsepower calculated by multiplying thrust by by aircraft speed (in MPH) divided by by 375 mile-pounds per hour. (thrust* aircraft speed (mph))/ (375 miles-punters per hour) = THP
Piston rings are used as seals to prevent the loss of gases between the piston and cylinder wall during all strokes. a. TRUE b. FALSE
A. True
Radial engine design is such that the oil can't be carried inside the engine itself, therefore, radial engines have pressure dry sump lubrication systems. A. True B. False
A. True
Radial engine design is such that the oil can't be carried inside the engine itself. Other types of engines capable of sustained inverted flight share this problem. The dry sump oil system caters to these types of aircraft by scavenging oil and dispensing it from an external tank. A. True B. False
A. True
Straight mineral oil is often used in engines after overhaul or when new to facilitate break-in for most four-cycle aviation piston engines. A. True B. False
A. True
The cooling fins on a cylinder cool the engine by radiation heat as the air passes over the fins. This hot air is then carried away from the cylinder and is exhausted through the bottom of the engine compartment or through cowl flaps if installed. A. True B. False
A. True
Thermal shock occurs when engine parts that are operated at a high temperature are quickly cooled. Some of these parts such as cooling fins and exhaust ports are cooled more rapidly than others. This may cause cracks in the cylinder heads or cracked valve guide housings. A. True B. False
A. True
What forces tend to twist the blade to increase propeller blade angle?
Aerodynamic twisting force
What is the function of an augmenter tube?
Augmenter tubes provide additional cooling, especially for low speed, high power conditions.
What is BHP?
BHP is brake horsepower, measured by work per revolution.
Why is a power enrichment system also called an economizer system?
Because they allow the engine to operate with a relatively lean, economical mixture for all conditions besides full power
How does opening cowl flaps affect engine cooling? Cabin cooling?
For engine cooling, cowl flaps (when opened) increase cooling airflow over the engine and through the oil cooler. For cabin cooling, hot and cold airflow is reduced due to air pressure inside and in front of the cowling when cowl flaps are open.
What is the relationship between aviation grade numbers and SAE numbers for lubricating oil?
The Society of Automotive Engineers (SAE) rates and divides the oils into specific groups that go hand-in-hand in aviation grade numbers.
What components in the governor oppose the force of the speeder spring?
The fly weight and the pilot valve.
What does the fuel flowmeter actually measure on the fuel injection systems discussed in this chapter?
The fuel flow meter measures air pressure
Other things being equal the higher the compression ratio the larger is the proportion of the heat energy of combustion turned into useful work at the crankshaft. A. True B. False
True
T/F Oil control rings are placed in grooves immediately below the compression rings and above the piston pin bore. There may be one or more oil control rings. They regulate the thickness of oil film on the cylinder wall.
True
The crankshaft transforms the reciprocating motion of the piston and connecting rod to rotary motion for turning the propeller. a. True b. False
a. True
The four principle types of crankshafts are: 1) Single-throw, 2) double- throw, 3) Four-throw, and 4) Six-throw. a. True b. False
a. true
What is the purpose of the acceleration system on an aircraft carburetor?
temporarily enriches the mixture when the throttle is suddenly opening
Rotational velocity
w = 2pi(rpm)/60s = unit ft/s ft/s x 0.592 KTS = unit KTS KTS x 0.0015 Ma = unit Ma tan = forward velocity/linear velocity tan-1 to get degrees
