MOD 7 UNIT 1 ENGINE THEORY
What is the indicated Horsepower of a 12 cylinder engine with a Bore of 5.5 inches, a Stroke of 6 inches and producing an IMEP of 165 PSI at 3,000 RPM?
1,069 HP
A nine (9) cylinder radial engine with a Bore of five and one-half (5.5) inches and a Stroke of six (6) inches will have a Total Piston Displacement (CID) of:
1,283 Cubic Inches
Normally, the ignition event on the reciprocating engine occurs at:
10 to 35 degrees BTC on the Compression Stroke
After ignition occurs in a cylinder, the normal speed of the Flame Front across the combustion chamber is approximately:
100 FPS
What kind of test is performed on an aircraft engine to prove its reliability?
150 hour Certification Test Run
How much heat energy is contained in one pound of Aviation Gasoline?
20,000 BTU's
What is the Thermal Efficiency of an engine producing 130 BHP, while burning 11.13 gallons of fuel per hour?
24.77%
A 6 cylinder aircraft engine with a 5 inch Stroke, and a 5 inch Bore is producing an IMEP of 125 PSI at 2,750 RPM with an internal loss of 25 horsepower. What is the indicated Horsepower?
255.7 HP
How many Foot-Pounds of Work must be done in one minute to produce one Horsepower?
33,000
At what speed must a crankshaft turn, if each cylinder of a Four-Stroke/Cycle engine fires 200 times per minute?
400 RPM
How many degrees of crankshaft rotation does it take to complete all events in the Four-Stroke/Cycle
720 Degrees
The Volume of a Cylinder is 70 Cubic Inches when the piston is at BDC. When the piston is at TDC, the Volume is 10 Cubic Inches. What is the Compression Ratio?
7:1
The Mechanical Efficiency for most reciprocating aircraft engines is about?
90 %
What is the Mechanical Efficiency of an engine which is delivering 450 HP to the propeller and has an internal loss of 50 HP?
90 %
Valve Overlap will:
Allow better cooling of the piston and exhaust valve
Whose name is commonly associated with the development of the Four-Stroke/Cycle principle used in the reciprocating engine?
August Otto
In what way does Valve Overlap affect engine operation?
Better Exhaust Scavenging
The actual power delivered to the propeller of an aircraft reciprocating engine is called:
Brake Horsepower
Most aircraft engines are classified according to:
Cylinder arrangement and method of cooling
What term best describes the explosion of the Fuel/Air Mixture in the Combustion Chamber?
Detonation
Valve Overlap is defined as the number of degrees of Crankshaft Rotation:
During which both valves are open
The primary concern when determining the Cylinder Firing Order for an opposed engine is:
For balance and eliminate vibration as much as possible
There are five events that occur during the operation of a Four-Stroke/Cycle horizontally opposed engine. The third event is:
Ignition
The horsepower developed within the cylinders of a reciprocating engine is known as the:
Indicated Horsepower
The events of a Four-Stroke/Cycle engine, in the order of their occurrence are:
Intake, Compression, Ignition, Power, Exhaust
The majority of reciprocating aircraft engines are:
Internal Combustion, Heat Engines, Otto Cycle
In the Internal Combustion Aircraft Engine, a large portion of the combustion heat is lost through the exhaust. A portion is lost through cooling, and a small amount through friction. The remainder:
Is converted into engine power to drive the propeller
Engine speed:
Is expressed in Revolutions Per Minute
When a reciprocating engine is properly timed, the Combustion process should be completed and peak pressure reached:
Just after TDC on the Power Stroke
(1) Pre-Ignition is caused by improper Ignition Timing:(2) Detonation occurs when an area of the Combustion Chamber remains glowing red hot and ignites the Fuel/Air Mixture in advance of the Normal Times Ignition.
Neither #1 nor #2 are true
The Exhaust Valve has just opened on a Four-Stroke/Cycle engine. Which stroke is it on?
Power
What term best describes the ignition of the fuel/air mixture before the Spark Plug normally fires?
Pre-ignition
What can cause Pre-Ignition to occur in a reciprocating aircraft engine?
Red-Hot Sparking Electrodes
When is the Fuel/Air Mixture ignited in the reciprocating aircraft engine?
Shortly before the piston reaches T.D.C. on the Compression Stroke
The definition of Valve Overlap is the number of degrees of crankshaft rotation:
That both valves are open
In the engine designation O-290-D:
The 290 is the approximate CID of the engine
Which statement is correct regarding a four-stroke/cycle aircraft engine?
The intake valve closes on the compression stroke
In aircraft engine design, why does engine smoothness of operation improve as cylinders are added?
The power impulses occur closer together
Air cooled engines are used on most modern aircraft rather than liquid cooled engines because:
They have better power-to-weight ratios
Why are the Intake and Exhaust valves of most engines designed to overlap?
To improve the Volumetric Efficiency
For each revolution of the Crankshaft in a Four-Stroke/Cycle engine, there will be:
Two strokes of the piston
When is an aircraft engine considered to be reliable?
When it does what it's designed to do
Compression ratio is the ratio between the:
cylinder volume with piston at bottom dead center and at top dead center
The primary purpose in setting proper valve timing and overlap is to:
obtain the best volumetric efficiency and lower cylinder operating temperatures
