powerplant ch 1 flash cards

chp1.json

[
  {
    "q": "What is the fundamental requirement for an aircraft's wings to provide lift or for vertical takeoff?",
    "a": "Aircraft require thrust to produce enough speed for the wings to provide lift or enough thrust to overcome the weight of the aircraft for vertical takeoff."
  },
  {
    "q": "According to Newton's third law of motion, how is propulsive force developed by an aircraft engine?",
    "a": "By displacing air in a direction opposite to that in which the aircraft is propelled, thrust can be developed. For every action there is an equal and opposite reaction."
  },
  {
    "q": "What is the primary difference between a rocket engine and other aircraft powerplants regarding the working fluid?",
    "a": "The rocket must provide all the fuel and oxygen for combustion and does not depend on atmospheric air; it carries its own oxidizer."
  },
  {
    "q": "How do propellers on reciprocating or turboprop engines generate thrust?",
    "a": "They accelerate a large mass of air at a relatively lower velocity by turning a propeller."
  },
  {
    "q": "What type of engines accelerate a smaller quantity of air through a large velocity change, and what is a common problem associated with them?",
    "a": "Turbojets, ramjets, and pulse jets; a problem is the noise made by the high velocity air exiting the engine."
  },
  {
    "q": "What is the current common term used to describe most turbine engines, replacing the former term \"turbojet\"?",
    "a": "\"Gas turbine engine\""
  },
  {
    "q": "List three general requirements that all aircraft engines must meet.",
    "a": "Efficiency, economy, and reliability."
  },
  {
    "q": "Besides fuel consumption, what other economic factors must an aircraft engine consider?",
    "a": "Cost of original procurement and cost of maintenance."
  },
  {
    "q": "What ratio is critical for an aircraft engine, allowing for a greater useful load and improved performance?",
    "a": "Low weight-to-horsepower ratio (specific weight)."
  },
  {
    "q": "What is required for an aircraft engine's ignition system to operate reliably in various conditions?",
    "a": "Ignition systems that deliver the firing impulse to the spark plugs at the proper time in all kinds of weather and under other adverse conditions."
  },
  {
    "q": "What is the useful output of all aircraft powerplants?",
    "a": "Thrust, the force which propels the aircraft."
  },
  {
    "q": "How is the gas turbine engine typically rated, as opposed to a reciprocating engine?",
    "a": "Gas turbine engines are rated in thrust horsepower (thp), while reciprocating engines are rated in brake horsepower (bhp)."
  },
  {
    "q": "What is the formula for calculating thrust horsepower (thp)?",
    "a": "Thp=375 mile-pounds per hour thrust × aircraft speed (mph)​"
  },
  {
    "q": "Why is it not practical to rate or compare the output of a turbine engine solely on a horsepower basis?",
    "a": "Horsepower varies with speed, so it is necessary to calculate horsepower for each speed of an aircraft."
  },
  {
    "q": "What is the basic parameter for describing the fuel economy of aircraft engines?",
    "a": "Specific fuel consumption."
  },
  {
    "q": "How is specific fuel consumption calculated for gas turbine engines?",
    "a": "Fuel flow measured in (lb/hr) divided by thrust (lb)."
  },
  {
    "q": "How is specific fuel consumption calculated for reciprocating engines?",
    "a": "Fuel flow (lb/hr) divided by brake horsepower."
  },
  {
    "q": "What is the difference between reliability and durability in terms of engine performance?",
    "a": "Reliability is measured as the mean time between failures, while durability is measured as the mean time between overhauls."
  },
  {
    "q": "What is \"operating flexibility\" for an aircraft engine?",
    "a": "The ability of an engine to run smoothly and give desired performance at all speeds from idling to full-power output, and to function efficiently through all variations in atmospheric conditions."
  },
  {
    "q": "Why is compactness important for an aircraft engine, especially in single-engine aircraft?",
    "a": "To allow proper streamlining and balancing of an aircraft, and in single-engine aircraft, it affects pilot visibility and reduces drag from a large frontal area."
  },
  {
    "q": "What are two common ways aircraft engines can be classified?",
    "a": "By operating cycles, cylinder arrangement, or method of thrust production."
  },
  {
    "q": "What type of combustion process do most current aircraft engines use?",
    "a": "Internal combustion, where the combustion process takes place inside the engine."
  },
  {
    "q": "List the four common cylinder arrangements for reciprocating engines.",
    "a": "Inline, V-type, radial, and opposed."
  },
  {
    "q": "What is the primary method for transferring excess heat in air-cooled reciprocating engines?",
    "a": "Direct heat transfer from the cylinders to the air, aided by thin metal fins on the cylinders."
  },
  {
    "q": "What is the main drawback of liquid-cooled engines compared to air-cooled engines?",
    "a": "The added weight of coolant, heat exchanger (radiator), and tubing."
  },
  {
    "q": "Describe an inverted inline engine.",
    "a": "An inline engine designed to operate with the cylinders below the crankshaft."
  },
  {
    "q": "What are two advantages of the inline engine type?",
    "a": "Small frontal area, better adapted to streamlining, shorter landing gear, and greater pilot visibility when inverted."
  },
  {
    "q": "What is the typical cylinder arrangement for an opposed-type engine?",
    "a": "Two banks of cylinders directly opposite each other with a crankshaft in the center."
  },
  {
    "q": "What are two advantages of the opposed-type engine, making it ideal for certain aircraft applications?",
    "a": "Low weight-to-horsepower ratio, narrow silhouette (ideal for horizontal installation on wings), and low vibration characteristics."
  },
  {
    "q": "How are cylinders typically arranged in V-type engines?",
    "a": "In two inline banks, generally set 60 degrees apart."
  },
  {
    "q": "How is a V-type engine designated?",
    "a": "By a V followed by a dash and the piston displacement in cubic inches (e.g., V-1710)."
  },
  {
    "q": "Describe the cylinder arrangement of a radial engine.",
    "a": "A row, or rows, of cylinders arranged radially about a central crankcase."
  },
  {
    "q": "What type of aircraft commonly still use radial engines today?",
    "a": "Some older cargo airplanes, war birds, and crop spray airplanes."
  },
  {
    "q": "List the basic major components of a reciprocating engine.",
    "a": "Crankcase, cylinders, pistons, connecting rods, valves, valve-operating mechanism, and crankshaft."
  },
  {
    "q": "What is the fundamental purpose of the crankcase in an engine?",
    "a": "It contains the bearings and bearing supports for the crankshaft, provides a tight enclosure for lubricating oil, supports internal and external mechanisms, and supports the cylinder assemblies and powerplant attachment to the aircraft."
  },
  {
    "q": "What material is commonly used for crankcase construction due to its light weight and strength?",
    "a": "Cast or forged aluminum alloy."
  },
  {
    "q": "What are \"cylinder pads\" on a crankcase?",
    "a": "Accurately machined surfaces where the cylinders are attached."
  },
  {
    "q": "What is the function of the nose section oil sump in some larger radial engines?",
    "a": "To collect oil on the bottom of the nose section."
  },
  {
    "q": "What is the primary purpose of the crankshaft in a reciprocating engine?",
    "a": "To transform the reciprocating motion of the piston and connecting rod into rotary motion for rotation of the propeller."
  },
  {
    "q": "What three main parts does every crankshaft have?",
    "a": "A journal, crankpin, and crank cheek."
  },
  {
    "q": "What is the function of flyweights and dampers on a crankshaft?",
    "a": "To reduce engine vibration."
  },
  {
    "q": "What is the \"crankpin\" section of a crankshaft?",
    "a": "The section to which the connecting rod is attached, often called the throw."
  },
  {
    "q": "How does a crankshaft achieve \"static balance\"?",
    "a": "When the weight of the entire assembly of crankpins, crank cheeks, and flyweights is balanced around the axis of rotation."
  },
  {
    "q": "What is the purpose of dynamic dampers on a crankshaft?",
    "a": "To reduce vibration to a minimum during engine operation."
  },
  {
    "q": "What is the function of the connecting rod in an engine?",
    "a": "To transmit forces between the piston and the crankshaft."
  },
  {
    "q": "List the four types of connecting-rod assemblies.",
    "a": "Plain, fork and blade, master and articulated, and split-type."
  },
  {
    "q": "Which type of connecting rod assembly is commonly used in radial engines?",
    "a": "Master-and-articulated rod assembly."
  },
  {
    "q": "What is the function of the piston in a reciprocating engine?",
    "a": "It acts as a moving wall within the combustion chamber, drawing in air-fuel mixture, compressing it, being forced downward by expanding gases, and expelling exhaust gases."
  },
  {
    "q": "From what material are most aircraft engine pistons machined?",
    "a": "Aluminum alloy forgings."
  },
  {
    "q": "What are \"cam ground pistons\" and what is their benefit?",
    "a": "Pistons that are a larger diameter perpendicular to the piston pin, which helps keep the piston straight in the cylinder as the engine warms up and reduces cocking or slapping."
  },
  {
    "q": "What are \"ring lands\" on a piston?",
    "a": "The portions of the piston walls that lie between the ring grooves."
  },
  {
    "q": "What is the function of the piston pin?",
    "a": "It joins the piston to the connecting rod."
  },
  {
    "q": "What are the two primary functions of piston rings?",
    "a": "To prevent leakage of gas pressure from the combustion chamber and to reduce the seepage of oil into the combustion chamber."
  },
  {
    "q": "What material are most piston rings made of?",
    "a": "High-grade cast iron."
  },
  {
    "q": "What is the purpose of compression rings?",
    "a": "To prevent the escape of combustion gases past the piston during engine operation."
  },
  {
    "q": "Where are oil control rings typically placed on a piston?",
    "a": "In the grooves immediately below the compression rings and above the piston pin bores."
  },
  {
    "q": "What problems can occur if too much oil enters the combustion chamber?",
    "a": "It burns and leaves thick carbon deposits on combustion chamber walls, piston head, spark plugs, and valve heads, which can cause sticking, spark plug misfiring, detonation, pre-ignition, or excessive oil consumption."
  },
  {
    "q": "What is the \"cylinder\" in an engine?",
    "a": "The portion of the engine where power is developed, providing a combustion chamber and housing the piston and connecting rod."
  },
  {
    "q": "What are the two major parts of an air-cooled engine cylinder assembly?",
    "a": "Cylinder head and cylinder barrel."
  },
  {
    "q": "What is the purpose of thin metal fins on air-cooled cylinder heads?",
    "a": "To increase the surface area for sufficient heat transfer and rapid cooling."
  },
  {
    "q": "What material is typically used for cylinder barrels due to its strength and wear resistance?",
    "a": "Steel alloy forging, often surface-hardened by nitriding."
  },
  {
    "q": "What process can be used to repair worn cylinder barrels?",
    "a": "Chroming (plating chromium on the surface)."
  },
  {
    "q": "How are inline and V-type engine cylinders usually numbered?",
    "a": "From the rear."
  },
  {
    "q": "What is the \"firing order\" of an engine?",
    "a": "The sequence in which the power event occurs in the different cylinders, designed for balance and vibration elimination."
  },
  {
    "q": "What type of valves are commonly used in aircraft engines?",
    "a": "Conventional poppet type, sometimes referred to as mushroom or tulip shaped."
  },
  {
    "q": "Why are exhaust valves typically made of more heat-resistant materials than intake valves?",
    "a": "Exhaust valves operate at higher temperatures."
  },
  {
    "q": "What material is applied to valve faces to make them more durable?",
    "a": "Stellite or nichrome."
  },
  {
    "q": "What is the purpose of the machined groove near the tip of a valve stem?",
    "a": "It receives the split-ring stem keys to hold the valve spring retaining washer in place."
  },
  {
    "q": "What material is sometimes used to partially fill hollow valve stems, and why?",
    "a": "Metallic sodium, because it is an excellent heat conductor, circulating to carry heat away from the valve head."
  },
  {
    "q": "What is \"valve overlap\"?",
    "a": "The period when both the intake and exhaust valves are open simultaneously (at the end of the exhaust stroke and beginning of the intake stroke)."
  },
  {
    "q": "What are the benefits of valve overlap?",
    "a": "Permits better volumetric efficiency, lowers cylinder operating temperature, increases the amount of air-fuel mixture inducted, and aids in scavenging combustion byproducts."
  },
  {
    "q": "What determines the valve lift and valve duration?",
    "a": "The shape of the cam lobes."
  },
  {
    "q": "What is the function of the \"ramp\" on a cam lobe?",
    "a": "To gently start the valve operating mechanism moving, reducing shock load."
  },
  {
    "q": "How is the valve mechanism of a radial engine typically operated?",
    "a": "By one or two cam rings."
  },
  {
    "q": "At what speed does the camshaft in an opposed engine always rotate in relation to the crankshaft?",
    "a": "One-half the crankshaft speed."
  },
  {
    "q": "What is the primary function of the tappet assembly?",
    "a": "To convert the rotational movement of the cam lobe into reciprocating motion and transmit it to the push rod, rocker arm, and then to the valve tip, opening the valve at the proper time."
  },
  {
    "q": "What is the benefit of using hydraulic valve tappets/lifters?",
    "a": "They automatically keep the valve clearance at zero, eliminating the need for manual adjustment, and operate more quietly."
  },
  {
    "q": "How many helical springs are typically used to close each valve, and why?",
    "a": "Two or three, to eliminate vibration or surging at certain speeds, as each spring vibrates at a different engine speed, and to reduce the danger of failure."
  },
  {
    "q": "What is the physics definition of \"work\"?",
    "a": "Force times distance."
  },
  {
    "q": "What is the standard unit of mechanical power in the English system of measurement?",
    "a": "Horsepower (hp)."
  },
  {
    "q": "How much work is equivalent to one horsepower?",
    "a": "550 ft-lb per second, or 33,000 ft-lb per minute."
  },
  {
    "q": "What is \"piston displacement\"?",
    "a": "The volume displaced by the piston when it moves from BDC to TDC."
  },
  {
    "q": "What is \"compression ratio\" in an engine?",
    "a": "A comparison of the volume of space in a cylinder when the piston is at the bottom of the stroke to the volume of space when the piston is at the top of the stroke."
  },
  {
    "q": "What are \"pre-ignition\" and \"detonation\"?",
    "a": "Pre-ignition is when the fuel air charge starts to burn before the spark plug fires. Detonation occurs when the fuel air charge is ignited by the spark plug, but instead of burning at a controlled rate, it explodes."
  },
  {
    "q": "What is \"indicated horsepower (ihp)\"?",
    "a": "The power developed in the combustion chambers without reference to friction losses within the engine, calculated from the indicated mean effective pressure."
  },
  {
    "q": "What is \"brake horsepower (bhp)\"?",
    "a": "The power delivered to the propeller for useful work, which is indicated horsepower minus the power lost overcoming friction."
  },
  {
    "q": "What is \"friction horsepower\"?",
    "a": "The horsepower used by an engine in overcoming the friction of moving parts, drawing in fuel, expelling exhaust, driving oil and fuel pumps, and other engine accessories."
  },
  {
    "q": "What is \"brake mean effective pressure (BMEP)\"?",
    "a": "That portion of IMEP (indicated mean effective pressure) that produces brake horsepower."
  },
  {
    "q": "What is \"thrust horsepower\"?",
    "a": "The result of the engine and the propeller working together, determining the performance of the engine-propeller combination."
  },
  {
    "q": "What is \"thermal efficiency\" of an engine?",
    "a": "The ratio of useful work done by an engine to the heat energy of the fuel it uses."
  },
  {
    "q": "What is the approximate thermal efficiency of reciprocating engines?",
    "a": "About 34 percent."
  },
  {
    "q": "What is \"mechanical efficiency\"?",
    "a": "The ratio that shows how much of the power developed by the expanding gases in the cylinder is actually delivered to the output shaft (bhp to ihp)."
  },
  {
    "q": "What is the approximate mechanical efficiency of an average aircraft reciprocating engine?",
    "a": "Approaches 90 percent."
  },
  {
    "q": "What is \"volumetric efficiency\"?",
    "a": "A ratio comparing the volume of air-fuel charge (corrected for temperature and pressure) inducted into the cylinders to the total piston displacement of the engine."
  },
  {
    "q": "List four factors that decrease volumetric efficiency.",
    "a": "Part-throttle operation, long intake pipes of small diameter, sharp bends in the induction system, carburetor air temperature too high, cylinder-head temperature too high, incomplete scavenging, and improper valve timing."
  },
  {
    "q": "What is \"propulsive efficiency\"?",
    "a": "The ratio of thrust hp to bhp, indicating how much of the engine's power is converted into thrust by the propeller."
  },
  {
    "q": "What is a significant distinguishing feature of gas turbine engines compared to reciprocating engines regarding their functions?",
    "a": "In gas turbine engines, separate sections are devoted to each function (intake, compression, combustion, exhaust), and all functions are performed simultaneously without interruption."
  },
  {
    "q": "List the seven basic sections/systems of a typical gas turbine engine.",
    "a": "Air inlet, compressor section, combustion section, turbine section, exhaust section, accessory section, and systems necessary for starting, lubrication, fuel supply, and auxiliary purposes."
  },
  {
    "q": "What are the two principal types of compressors used in gas turbine aircraft engines?",
    "a": "Centrifugal flow and axial flow."
  },
  {
    "q": "What is the Brayton cycle?",
    "a": "The name given to the thermodynamic cycle of a gas turbine engine to produce thrust, also known as the variable volume constant-pressure cycle or continuous combustion cycle."
  }
]