AS 356 Systems Exam 1
At what speed does the camshaft turn?
-At half the speed of the crankshaft. -At twice the speed of the crankshaft -At the same speed of the crankshaft
Briefly outline the difference in operation for a light single engine and multi‐engine aircraft propeller system.
-Single: constant speed, non‐feathering -Multi: constant speed, feathering
What is the difference between static and dynamic balancing?
-Static: a prop suspended by a drawstring -Dynamic: electrical machine with vibration analysis of the aircraft
What is THP (name and define, or describe it)?
-THP is Thrust Horsepower. It is calculated by applying the propeller efficiency factor to the brake horse power. -THP = BHP x eta (where eta is the propeller efficiency factor).
What are the differences between a two‐position and a ground adjustable propeller?
-Two position: can only be changed on the ground to one or the other position. -Ground adjustable: similar to the two position prop but can be changed to more than two positions.
What are the functions of the spider?
-Two position: permits a change of blade pitch, or angle while the prop is rotating -The spider distributes the fuel evenly to all of the cylinders and shuts off fuel delivery when mixture control is placed to idle or shut‐off. Fuel pressure pushes against the spring and delivers fuel equally to all fuel outlet ports.
For a 4 cycle, 4 cylinder horizontally opposed non‐geared aircraft engine, how many 'power strokes' will each cylinder have if the engine crank shaft turns 2 full revolutions?
1
When should carburetor heat be used on the ground (several answers)?
1. Engine starting during very cold temperatures 2. Prior to shutdown during very cold temperatures 3. High humidity and very cold or warm temperatures
What are the advantages of a fuel injection system, as a fuel metering system?
1. Meters fuel as a function of engine RPM and throttle position 2. Does not use airflow as the metering force 3. Engine‐driven pump produces the fuel metering pressure, and this pressure varies with RPM
List 5 functions of aircraft engine oil (reciprocating engine).
1.Lubricates 2.Cleans 3.Cools 4.Prevents corrosion 5.Seals
For a 4 cylinder horizontally opposed aircraft engine (such as a Lycoming IO‐360) how many types of rings are found on a piston?
2
What is the most effective propeller angle of attack for takeoff?
2 to 4 degrees
A feathered propeller will have a blade angle of approximately ______ degrees.
90
turns the blades to a high blade angle
Aerodynamic Twisting (force)
What is the principal fluid use for propulsion by most heat engines? (
Air
A turbocharger compresses _____________________.
Air Only
The angle between the relative wind and the chord line
Angle of Attack
Lubricates well and cleans interior of engine.
Ashless Dispersant (AD)
Where are the fuel injection nozzles located on a typical light aircraft engine?
At the top of the cylinder, near the valves.
The angle between the firewall vertical plane and the chord line
Blade Angle/Blade Pitch
throws the rotating blade away from the hub
Centrifugal (force)
provides mechanical linkage between the crankshaft and the piston
Connecting Rod
the foundation of the engine
Crank Case
The _______ makes the camshaft turn?
Crankshaft
houses the bore hole for the piston to do its work
Cylinder
covers the upper part of the cylinder
Cylinder head
•limits the manifold pressure below critical altitude and regulates bleed oil only at full throttle
Density Controller
What is critical altitude?
Desired power can not be maintained above this altitude •i.e., you run out of throttle •trying to operate engine at 2500 RPM but can only get 2400 RPM
What is the difference between detonation and pre-ignition?
Detonation is excess fuel and air mixture combusting spontaneously after the power stroke of the engine. It is typically caused by an overheated engine or using a lower fuel grade than recommended. Detonation requires the spark plugs to be firing. Pre-ignition is when the fuel-air mixture combusts without the spark plugs firing. It is usually caused by hot leftover carbon in the cylinder.
•functions during all positions of the waste valve other than fully open position •same as density controller - changes bleed oil pressure to control the waste gate
Differential pressure controller
The distance the propeller moves when including slippage.
Effective Pitch
On light aircraft, where does the force to operate the propeller pitch changing mechanism come from?
Engine oil system
There is a relationship between aviation grade numbers and SAE numbers for lubricating oil?
False
What component in the governor opposes the force of the speeder spring?
Flyweights
A supercharger compresses __________________ and ____________________ (carbureted engine).
Fuel & Air
The distance the aircraft would move with one full propeller rotation without any slippage.
Geometric Pitch
Aircraft reciprocating engine with a built-in supercharger or turbocharger that boosts the manifold pressure well above sea level pressure to achieve the rated horsepower of the engine
Ground boosted engine
What are the advantages of the hydraulic lifters?
Hydraulic lifters reduces or eliminates need for frequent adjustments of valve operating linkages and components. Uses engine oil instead of hydraulic fluid.
separates cylinder from fuel systems/opens to allow fuel & air mixture into the cylinder
Intake Valve
Describe the operating cycle of the typical aircraft reciprocating engine.
Intake, Compression, Combustion, Exhaust
Why is it important for the pilot to know an engine's exhaust gas temperature?
Knowing EGT values will help a pilot identify important things such as maximum power range, recommended operating range, and best economy range. Pilots can also adjust the mixture based on if the engine is running too hot or cold (lean or enrichen).
Is the lowest blade angle near the shank or the tip? Why? Was it built that way?
Lowest blade angle is near the tip to offset the faster tip speeds. Built that way so propeller lift is constant across the blade.
What forces are used to feather a propeller?
Mechanical/Spring & Counterweights
Lubricates but does not clean. Can create sludge.
Mineral Oil
No extra performance enhancing devices (turbo/supercharger or both)
Normally aspirated engine
Why is viscosity important when selecting a lubricant?
Oil will thicken on a cold day and thin out at high operating temperatures. Need to make sure the oil's viscosity covers engine operating temperatures to properly lubricate the engine.
allows burned fuel/air mixture out of the cylinder during the exhaust stroke
Outflow or Exhaust Valve
compression to mixture and feels the force of the combustion
Piston
aid with combustion and lubrication of the cylinder
Piston Rings
Which cockpit control will change the RPM on an engine?
Propeller pitch control - blue lever.
What is viscosity?
Resistance of a liquid to flow•Low viscosity is thinner liquid (water)•High viscosity is thicker liquid (honey)
Does application of carburetor heat richen or lean the mixture?
Richen
What causes the engine's intake and exhaust valves to open?
Rocker Arm
The loss of propeller efficiency.
Slip
What causes the engine's intake and exhaust valves to close?
Spring
Driven mechanically by engine •Compresses fuel & air down stream of carb
Supercharger
Great in very hot and very cold temperature conditions.
Synthetic
Altimeter setting at Flagstaff airport, field elevation 7000 ft is 30.12" Hg. What should MAP be, before engine start and during takeoff with fully opened throttle?
The MAP before the engine starts should indicate the actual outside pressure, which is 7" Hg less than the reported pressure, aka 23.12" Hg. Once the engine start, the air filter will remove an additional inch of mercury, so 22.12" Hg.
Why are float carburetors more susceptible to icing (at least two reasons)?
The air moving through the carburetor is susceptible to aerodynamic cooling because of the decreased pressure through the venturi and because of fuel evaporation.
Large power reductions in very cold air (cruise altitude) with a hot engine may cause engine damage. •Valves stick •Extreme case, cylinder(s) crack
Thermal Shock
Which cockpit control will change the MAP on an engine?
Throttle lever.
The force produced by a propeller or by a jet or rocket engine that drives a vehicle (such as an aircraft) forward
Thrust
bends the propeller blades forward as the aircraft is pushed through the air
Thrust Bending (force)
bends the propeller blades in the direction opposite that of rotation
Torque Bending (force)
Which has the higher operating speed and temperature, a turbocharger or a supercharger?
Turbocharger
•Free wheeling •Driven by exhaust •Compresses air only before it reaches the carb. or fuel injection system
Turbocharger
In what form does fuel exit the fuel nozzles on a fuel‐injected engine?
Vaporized
The _________ provides the low pressure at the discharge nozzle of a float carburetor.
Venturi
•Controls the amount of exhaust through the turbine thus regulating its speed. Automatic control, Manual control, or Fixed.
Waste Gate
What are the advantages of a wet sump system, compared to a dry sump?
Wet sump is simpler and has less moving parts (no separate tank). No splash feature.
Why does MAP increase when RPM is decreased when there is no change in throttle position?
When RPM decreases, the engine is sucking less air, causing the MAP to increase.
Under what conditions would the use of carburetor heat be detrimental?
When it is warm and dry outside at low altitude with no ice present, applying carburetor heat would supply less dense air, therefore leading to an RPM drop and making the engine run hotter.
What does a carburetor air temperature gauge permit a pilot to do?
With the gauge, a pilot can apply partial carburetor heat instead of just "full" or "none." It can help a pilot detect potential carburetor icing situations, based on humidity and temperature. It also indicates if it is time to apply carburetor heat.
What are the names for each ring on a piston?
compression oil
What are the advantages of the pressure carburetor over the float carburetor?
not as susceptible to icing, meters fuel based on mass of air, automatic mixture control on higher power engines, high pressure in fuel system maintained at all times, and inverted flight is possible.
What is the main function of a piston?
‐Acts as a moving wall within the combustion chamber ‐Draws in the fuel/air mixture ‐Compresses the charge ‐Transfers force to the crankshaft via connecting rod ‐Forces exhaust gases from the cylinder
What is BHP? How is it measured?
‐BHP is Brake Horse Power‐ the indicated horsepower corrected for loss due to friction. ‐BHP= Indicated HP‐Friction HP
With a fixed RPM, does the propeller blade angle increase or decrease as airspeed increases? What about the angle of attack?
‐Blade pitch angle increases ‐Blade AoA remains the same
What three energy forms does the reciprocating engine utilize or convert?
‐chemical ‐heat ‐mechanical
List three types of bearings used in aircraft engines
‐plain ‐ball ‐roller
Define 'over boost' for turbocharge engines.
•A state in which too much exhaust is being directed to turbine causing overspeed of turbine rotation. •The engine is producing excessive manifold pressure
Define 'stoichiometric mixture'?
•Air‐to‐fuel ratio: 15:1 •Fuel‐to‐air ratio: .067:1
In an automatic turbocharger, what provides the force to activate the waste gate?
•Rely on air density and differential pressure controllers to regulate waste gate. •Hydraulic controller opens or closes the waste gate. •When oil pressure increases on the piston, the waste gate valve closes
What are the 4 'strokes' of operation for a 4 cycle reciprocating engine?
•Stroke 1:Intake •Stroke 2:Compression •Stroke 3:Power / Combustion •Stroke 4:Exhaust
What is the purpose of an intercooler and how does it work?
•reduce the temp of turbocharger before compressed air reaches the engine .•Intercooler is much like a radiator, only built very sturdily to handle high pressure.
