P Piston Engine Power, Efficiency and Control Flashcards
What 2 factors dictate the power of an engine?
- The mass of charge
- The numbers of times per second that the charge is put into the cylinders
What is the power equation?
Power = (force x distance)/time
What does power = plane mean?
Power = Pressure x Length of stroke x Area x Number of cylinders x rpm/2
What is the total volume of a cylinder?
Volume of cylinder at BDC
What is the clearance volume of a cylinder?
Volume of the cylinder at TDC
What is the swept volume?
Volume of the cylinder between TDC and BDC
Total volume - Clearance volume = Swept volume
What is the compression ratio?
A relationship between total volume and clearance volume
What is mechanical efficiency?
Measures the effectiveness of an engine turning the input power to output power. Taking into account friction and vibration most engines are 90-95% mechanically efficient. When factoring in thermal efficiency this falls to around 80%
What is thermal efficiency?
Defines how effective the engine is at converting fuel energy into producing mechanical work. All combustion engines are heat engines and heat is always lost, meaning thermal efficiency is 25-35% for a standard engine
What is the relationship between thermal efficiency and compression ratio?
As thermal efficiency increases, the compression ratio increases
What does the RPM gauge do?
Measures crankshaft RPM
What dos the manifold pressure gauge do?
Measures manifold pressure in InHg
What does the boost pressure gauge do?
Measures manifold pressure in PSI relative to sea level pressure
What does the oil pressure gauge do?
Measures the oil pressure just after the filter
What does the oil temperature gauge do?
Measures the oil temperature in the oil return line
What does the CHT (cylinder head temperature) gauge do?
Measures the temperature of the hottest cylinder
What does the EGT (exhaust gas temperature) gauge do?
Measures the temperature in the exhaust gas stream
What does the fuel pressure gauge do?
Measures fuel pump output pressure
What does the induction temperature gauge do?
Measures the temperature are the carburettor inlet
How to engine controls differ?
By colour and shape
What colour and shape is the throttle?
On a panel: round
On a quadrant: cylindrical
Colour: black
What colour and shape is the propeller control?
On a panel: round with large grooves
On a quadrant: crown shape with large grooves
Colour: blue
What colour and shape is the mixture control?
On a panel: round with small protrusions
On a quadrant: round with small protrusions
Colour: red
Why do we check the fuel pre-start?
Check for water contamination
Why do we pull through inverted or radial engines before start?
To prevent hydraulicing
3 starting procedure precautions
- Shut down if the start warning light remains on for 30 seconds or more after start
- Positive engine oil pressure should be indicated within 30 seconds of engine start
- In very cold conditions increased oil viscosity may make starting more difficult
Which 3 after-start checks do we consider?
- Individually check magnetos to ensure ignition circuits are functional
- Carburettor heat should be off whilst the engine is running on the ground
- Prolonged idling should be avoided to reduce risk of spark plug fouling
What are the 3 procedures for changing power settings?
- Slow, smooth throttle movement to reduce engine stress
- Reduce to max continuous as soon as safely possible after take off
- Constant speed propellers (rev up, throttle back)
(Rev leads throttle when increase, throttle leads revs when decrease power)
2 shut down procedures
- Allow engine to cool at low rpm before shut down
2. Do a dead cut check to confirm both ignition circuits are properly earthed
What does black smoke indicate?
Excessively rich mixture
What does blue smoke indicate?
Burning oil - worn or broken piston rings
What does a high CHT indicate?
Cowl flaps may be closed
What could cause excessive CHT?
Excessively lean mixture
What can cause rough running?
- Carburettor icing
- Moisture in the ignition circuit
- Problems with fuel delivery
- Uneven compression in the cylinder
