AT103 Review Through Exam 1 Flashcards
Failed Engine Characteristics
Poor Efficiency
Lack of Dependability
High Cost
Excessive Weight
Low Power Produced
Successful Engine Characteristics
High power-to-weight ratio
Efficient
Reliable
Environmentally friendly
Who created the first practical gas engine in 1860?
Jean Joseph Etienne Lenoir of France
The first four-stroke engine was built in 1876 by ___ and ___.
August Otto and Eugen Langen of Germany
First truly successful gasoline engine was built in 1885 by ____.
Gottlieb Daimler
Wright Brothers and Charles Taylor Engine Characteristics
Water Cooled
Four Cylinders
12 Horsepower
180 Pounds
Engines developed during WWI
Radial Engines
In-Line Engines
V-Type Engines
Engines developed post WWI
Multiple Row Radial Engine
Opposed Engine
Flat Engine
Fan, H, W, and X Type Engine
First flight of a jet engine power aircraft was on ____ in _______.
1939, Germany
Gas-Turbine Engine Types
Turbojet Engine
Turbofan Engine
Turboprop Engine
Turboshaft Engine
Gas-Turbine Engine Challenges
Performance
Sound Levels
Fuel Efficiency
Ease of Maintenance
Dependability
Reliability
Types of Reciprocating Engines
Rotary-Type Radial Engines
In-Line Engines
V-Type Engines
Radial Engines
Multiple-Row Radial Engines
Opposed and Flat Type Engines
Rotary Types Radial Engines
Crankshaft is held stationary to the engine mount
Cylinders rotate about the crankshaft
Propeller is attached to the engine case
Examples of Rotary Type Radial Engines
LeRhone
Gnome
Bentley
Rotary Type Radial Engines Disadvantages
Torque and gyro effect of the engine’s large rotating mass made aircraft difficult to control
Castor oil was used as the engine lubricant. The castor oil fumes from the engine’s exhaust was often nauseating to pilots
In-Line Engines
Cylinders of an in-line engine are arranged in a row parallel to the crankshaft
Cylinders can be above or below (inverted) the crankshaft
V-Type Engines
Cylinders are arranged in two rows, formed the letter V
Angles between the rows are usually 90, 60, or 45°
There are always an even number of cylinders per row
Upright V-Type Engines
When the cylinders are above the crankshaft
Inverted V-Type Engines
When the cylinders are below the crankshaft
Single-Row Radial Engine
Odd number of cylinders extending radially from the centerline of the crankshaft
Cylinders range from 5-9
All pistons are connected to a single-throw 360° crankshaft
Double-Row Radial Engine
Resembles two single-row radial engines on a single crankshaft
Cylinders range from 14-18
A two-throw 180° crankshaft is used to allow stagger between each row of cylinders
Radial Engine Disadvantages
Large frontal area creates a lot of drag
Cooling problems
Multiple-Row Radial Engines
The largest and most powerful reciprocating engine
Examples of Multiple-Row Radial Engines
Pratt & Whitney R-4360
3,500 hp
4,300 hp using two turbochargers and one supercharger
What were Multiple-Row Radial Engines replaced by?
gas-turbine engines
Opposed and Flat Engine Type
Most popular for light conventional aircraft and helicopters
Engine Classification (In-line)
Upright, inverted
Engine Classification (V-Type)
Upright, inverted, Double V, X
Engine Classification (Opposed and Flat)
Opposed, flat
Engine Classification (Radial)
Single row, double row, multiple row
Difference between letters and numbers to determine engine designation
Letters are employed to indicate characteristics
Numerical are employed to indicate displacement
L
Left-Hand Rotation
T
Turbocharged
I
Fuel Injected
G
Geared
S
Supercharged
O
Opposed Cylinders
R
Radial Engine
#
Displacement to the nearest 5 in^3
How is excessive heat is undesirable for reciprocating engines?
Adversely affects behavior of the combustion of the air fuel charge
Weakens and shortens the life of engine parts
Impairs Lubrication
Excessive heat generated by the engine is removed from the engine by the
Convection process
Projects from the engine cylinders
Cooling fins
Used around the cylinders to direct the air flow and obtain maximum cooling
Baffles
Advantages of Air Cooling
Weight of an air cooled engine is usually less than a liquid cooled engine
Less affected by cold weather operations
Less vulnerable to gunfire (Military)
Disadvantages of Air Cooling
Requires forward movement for ram air to sufficiently cool the engine
Liquid cooling systems consists of
Liquid passage around the cylinders and specific hot spots in the engine
Radiator to cool the liquid
Thermostatic element to decide amount of cooling to the liquid
Connecting pipes and hoses
Relief valve to prevent excessive pressure
How does liquid cooling work?
Cooling liquid is circulated through the engine areas that require heat removal
Heat is transferred to the liquid
Heated liquid then passes through a heat exchanger (radiator) and cools down
The cooled liquid is then cycled back into the engine to repeat the cooling process
The Crankcase
The foundation of the engine
Must support itself
What does the crankcase provide?
Mounting to the aircraft and cylinders
Three groups of the Crankcase
Opposed-Engine Crankcases
Radial-Engine Crankcases
In-Line and V-Type Crankcases
Opposed-Engine Crankcases
Consists of two matching, reinforced aluminum-alloy castings
Castings are divided vertically at the centerline
Fastened together with studs and nuts
Lubricating system are contained in the crankcase
Oil passages are drilled in sections of the case to supply lubrication to
Crankshaft Bearings
Camshaft Bearings
Radial-Engine Crankcase
Consists of multiple sections (3-7)
The Front Section (Nose)
Main Power Section
Fuel Induction and Distribution Section (Blower or Supercharger)
Accessory Section
What is in the Accessory Section of the Radial-Engine Crankcase
Provides mounting pads for accessory units
Fuel Pump
Vacuum Pump
Lubrication Oil Pump
Starters
Magnetos
In-Line and V-Type Engine Crankcases Sections
Front Section
Power Section
Fuel Induction and Distribution Section
Accessory Section
In-Line and V-Type Engine Crankcases Front Section
May be cast as part of the power section or be a separate part
Houses the propeller shaft, propeller thrust bearing… etc.
In-Line and V-Type Engine Crankcases Power Section
May be one part or two part
Supports crankshaft bearings
Cylinders are mounted onto this section
Provides attachment points to the engine mount
In-Line and V-Type Engine Crankcases Fuel Induction and Distribution Section
Houses the diffuser vanes
Supports the internal blower impeller
In-Line and V-Type Engine Crankcases Accessory Section
Can be a separate unit mounted onto the Fuel Induction and Distribution Section or form a part of the section
Houses the accessory drives
What is in the Accessory Section of the In-Line and V-Type Engine Crankcases
Mounting pads for:
Fuel Pump
Coolant Pump
Vacuum Pump
Magnetos
Other devices operated by engine power
Bearings
A part in which devices turns or revolves on:
Journal
Pivot
Pin
Shaft
etc.
Aircraft bearings
Produces minimum friction
Maximum wear resistance
Characteristics of a good bearing
Made of material strong enough to withstand the pressure imposed on it
Permit the other surface to move with minimum wear and friction
Be held in position with very tight tolerances
Provide quiet and efficient operation while not sacrificing freedom of motion
Bearings are called Thrust Bearings when in addition to reducing friction of moving parts they also take:
Thrust Loads
Radial Loads
Combination of Thrust and Radial Loads
Plain Bearings
Low-power engines
Mainly designed to take radial loads
Can also be used as a thrust bearing when flanges added
What are plain bearings used for?
Connecting Rods
Crankshaft
Camshaft
Common Materials for plain bearings
Silver
Lead
Bronze
Combination of the above
Roller Bearing
High-power applications
Made in a variety of shapes and sizes
Tapered rollers can withstand both radial and thrust loads
Straight rollers are used for radial loads
Bearing Race
Channel where rollers travel
Hardened Steel
Rollers are situated between and inner and outer race
Ball Bearings
Provides less friction than any other bearing types
Components of Ball Bearings
Inner Race
Outer Race
Set of Polished Steel Balls
Ball Retainer
Some ball bearings have ___ rows of balls and ___ sets of races
two
_____ have grooves in them to fit the curvature of the balls
Races
_____ within the bearings are held in place by a ball retainer
Balls
The _______ maintain proper spacing between the balls preventing the balls from contacting each other
Retainers
Commonly used for thrust bearings
Ball bearings
Races can be designed with deep ________ or heavier ____ on a specific depending on intended thrust load
grooves, race
Special ball bearings can be
side critical
Crankshaft
Transforms reciprocating motion of the piston to rotary motion to turn the propeller
Parts of the crankshaft
Main Journal
Crankpin
Crank Cheek or Crank Arm
Counterweights and Dampers
Main Journal
Serves to keep the crankshaft in alignment
Crankpin
When a force is applied to the crankpin in any direction other than parallel to the crankshaft, it will rotate the crankshaft
Crankpins are usually what?
hollow
Crank Cheek/Crank Arm
Connects the crankpin to the main journal
Counterweight must offset the weight of
Single Throw
Connecting Rod
Piston assembly
Dynamic Dampeners
Relieve the whip and vibration from the rotating crankshaft
Types of crankshafts (4)
Single Throw
Double Throw
Four Throw
Six Throw
Types of propeller shafts (3)
Tapered
Spline
Flange
Tapered Shaft
has a milled slot for a key
Spline Shaft
Rectangular grooves are machined in the shaft
Flange Shaft
A short stub forward of the flange supports and center the propeller hub
What alloy is used for most connecting rods?
steel
What alloy is used for low power engines?
aluminum
Common cross sectional shapes (2)
H
I
Large End
The end of the connecting rod that connects to the crankshaft
Small End
The end of the connecting rod that connects to the piston pin
At each stroke, connecting rods goes through this 3-step process
- Stop
- Change of direction
- Start
Types of connecting rod assemblies
Plain
Fork and Blade
Master and Articulated
Plain Connecting Rod
Commonly used for in-line and opposed engines
Fork and Blade Connecting Rod
Used for V-type engines
Master and Articulated Connecting Rod
Used in radial engines
Surface of master rod must be free of (3)
Nicks
Scratches
Other surface damages
Types of Pistons (5)
Flat
Recessed
Concave
Convex
Truncated Cone
Piston Ring
are split so they can be slipped over the outside of the piston into ring grooves
Three types of ring split joints
Plain Butt
Step
Angle
Blowby
the flow of gases from the combustion chamber into the crankcase
Functions of Piston Rings (3)
Provide seal to hold the pressures in the combustion chamber
Prevent excessive oil from entering the combustion chamber
Conduct the heat from the piston to the cylinder walls
Worn or defective piston rings (4)
Loss of compression
Excessive oil consumption
Excessively high oil discharge from the crankcase breather
Excessive blue smoke from exhaust during normal operation
Types of Piston Rings (2)
Compression
Oil
Compression Rings
Prevent gases from escaping past the piston during operation
Oil Rings
Control the thickness of oil film on the cylinder walls
Types of Oil Piston Rings (2)
Oil Control
Oil Wiper
Piston Pins
Used to attach the piston to the connecting rod
Types of Piston Pins (3)
Stationary
Semi-Floating
Full-Floating
Stationary Piston Pins
Not free to move in any direction
Secured in place by a set screw
Semi-Floating Piston Pins
Securely held by a clamp screw
Full-Floating Piston Pins
Free to run or slide in the connecting rod and the piston
Used in modern aircraft engines
Piston Pin Retainers (1)
Nonferrous-Metal Plugs
Nonferrous-Metal Plugs
Inserted in the open ends of the piston pin
Cylinder Assembly (7)
Cylinder Barrel
Cylinder Head
Valve Guides
Valve Rocker-Arm Supports
Valve Seats
Spark Plug Bushings
Cooling Fins
Cylinder Barrel
Provides best conduction of heat from inside the barrel
Cylinder Head
Encloses the combustion chamber
What do cylinder heads contain? (4)
Intake Valves
Exhaust Valves
Valve Guides
Valve Seats
Methods for Joining the Cylinder Head to the Barrel (3)
Threaded-Joint Method
Shrink-Fit Method
Stud-and-Nut Method
Valves
Any device for regulating or determining the direction of flow of a liquid or gas by opening and closing a passage
Uses ports
Two types of valve ports
Intake
Exhaust
Types of valves (3)
Poppet Type
Exhaust
Intake
Types of Poppet Type Valves (4)
Flat-Headed Valve
Semi-Tulip Valve
Tulip Valve
Mushroom Valve
Valve Stem
Surface-Hardened to resist wear
Valve Tip
Designed to prevent valves from falling into the combustion chambers if the tips fail
Exhaust Valves
Operates in very high temperatures
Valve Guides
Positioned to support and guide the stems of the valves
Valve Seats
are shrunk or screwed into the circular edge of the valve opening in the cylinder head
Valve Spring
Closes the valves
What do Valve Operating Mechanisms control? (3)
Valves will open at the correct time
Remain open for the required time
Close at the proper time
Valve Mechanism Components (4)
Cam
Valve Lifter or Tappet
Pushrod
Rocker Arm
Cam
Actuates the valve lifting mechanism
Valve Lifter or Tappet
Transmits the force of the cam to the valve pushrod
Pushrod
Rod or tube between the valve lifter and the rocker arm. Transmits the motion of the valve lifter
Rocker Arm
For opening and closing the valves
Heat Engines
Utilize heat energy to produce the power for propulsion
Examples of Heat Engines (2)
Reciprocating Engines
Gas Turbine Engines
Energy
The capacity for doing work
Kinetic Energy
Energy of motion
Potential Energy
Energy of position or stored energy
When a mixture of gasoline and air is ignited the kinetic energy of the molecules _________
increases
If the gas is confined, pressure will ________
increase
The pressure will produce work when the piston is forced ________
downward
______ can be transformed from one kind to another
energy
Energy transformation chart
Mechanical energy
↓
Electric energy
↓
Heat, Light, Chemical, Mechanical energy
Boyle’s Law
𝑉1/𝑉2 = 𝑃2/𝑃1
Charles’ Law
𝑉1/𝑉2 = 𝑇1/𝑇2
Engine Cycle
Intake
Compression
Ignition
Combustion
Exhaust
Otto Cycle
Four-stroke five event cycle
Stroke
The distance which the piston travels
Compression Ratio
Ratio of the volume of space in the cylinder when piston is at Bottom Dead Center (BDC) to the volume when the piston is at Top Dead Center (TDC)
Four Stoke Five Event Cycle (SSBB)
Intake Stroke (Suck)
Compression Stroke (Squeeze)
Power Stroke (Bang)
Exhaust Stroke (Blow)
Intake Stroke
Piston starts at TDC
Intake valve is open
Exhaust valve is closed
Piston moves downward
Air fuel mixture is drawn into the cylinder
Compression Stroke
Intake valve closes
Piston moves back up
Air fuel mixture is compressed in the cylinder
Before piston reached TDC, ignition happens
Ignition is timed to happen few degrees before TDC
Ignition is caused by a sparkplug
Spark ignites the air fuel mixture
Power Stroke
Heat and pressure from ignited air fuel mixture force the piston down
Power is developed during this stroke
Exhaust Stroke
Before the piston reaches BDC on the power stroke, exhaust valve opens
Gases in the cylinder are forced out as the piston moves back up
Valve Overlap
Intake valve opens before TDC
Exhaust valve closes after TDC
