Transcript Week 4 Lecture

AVAT11001: Course Outline
1. Aircraft and Terminology
2. Radio Communications
3. Structure, Propulsion, Fuel Systems
4. Electrical, Hydraulic Systems and Instruments
5. Air Law
6. Aerodynamics: Basics
7. Aerodynamics: Performance
8. Human Factors
9. Meteorology
10. Loading
11. Take-off and Landing Performance
12. Navigation
Stuff to read
• Required Reading: BAK Chapter 4, pp.
106-132
Sources of Electricity
• Battery
– Provides initial electrical power to start the
engine
– Provides back-up power in case of failures
– Is recharged by the alternator during flight
• Alternator
– Driven by the engine
– Generates current
Gauges and Instruments
• Ammeter
– Indicates electrical current level
– Load-type Ammeter
• Shows alternator output only
• See Figure 4-68 page 107
– Centre-Zero Ammeter
• Shows flow to and from the battery
• See Figure 4-69 page 108
• Voltmeter
– Indicates the system voltage
• About 27.5 Volts indicated for a 28-Volt system
• About 13.75 Volts indicated for a 14-Volt system
Abnormal Electrical System
Operations
• Ammeter indicates
– Too little current
•
•
•
•
Likely cause is alternator failure
The battery will be drained
Reduce electrical usage
Consider landing at nearest aerodrome
– Too much current
• Likely caused by faulty voltage regulator
• May cause battery to overheat
• Voltmeter indicates
– Too little voltage
• Likely cause is alternator failure
• Voltage level provides some indication of remaining battery life
Switches and Fuses
• Master Switch
– For normal operation, both switches are on
– Switching off the battery will automatically switch off the
alternator
– If you must switch off either during flight, land as soon as
possible
• Fuses
– A fuse is an over-current protection device
– Can not be reset
• Metal conductor melts when current is too high
• Circuit Breakers
– A circuit breaker is an over-current protection device
– Can be reset
• Pilot should wait 90 seconds before attempting to reset
• Only attempt one reset
• If you smell smoke or detect burning, do not attempt a reset
Hydraulic Systems
• Hydraulic systems use fluid pressure to create
motion
– On General Aviation aircraft, these system most often
are used to operate the wheel brakes and retract
landing gear
– On larger and more complicated aircraft, hydraulic
systems are used to move many different surfaces
• Leading Edge Flaps
• Horizontal Tails
• Hydraulic fluid is a very hazardous material and
should be handled with great care
Heating and Ventilation
• See Figure 4-75 page 113
• Be familiar with the airflow in the cabin and
the controls a pilot has to change the
heating and ventilation
3 Types of Pressure
• Static Pressure
– Caused by random motion of gas molecules
– Equal in all directions
– For the atmosphere, this translates to function of altitude
• Dynamic Pressure
– Caused when gas molecules have a net resultant velocity (not
just random motion)
– It is a function of the number of molecules (expressed as density,
mass/volume)
– It is a function of the resultant net velocity
• Pdynamic = 0.5 r V2
• Total Pressure
– Total pressure is the sum of static and dynamic pressure
• Ptotal = Pstatic + Pdynamic
Pressure Instruments
• The Pitot-Static system measures the total pressure and
the static pressure
– Since dynamic pressure is the difference between total and static
pressures, all three can be known by measuring any 2
• Altimeter
– See Figure 4-84 page 119
– Uses static pressure to indicate altitude
– Uses a model of the atmosphere to predict altitude based on
static pressure
– You must correctly set the subscale (QNH)
• Vertical Speed Indicator (VSI)
– Uses the rate of change of static pressure to predict altitude rate
Pressure Instruments 2
• Air Speed Indicator (ASI)
– See Figure 4-82 page 118
– Uses dynamic pressure to indicate airspeed
– Colour coded to rapidly convey important
speeds
• See Figure 4-83 page 118
– Assumes a constant air density
• Indicated speed will differ from true airspeed as
altitude changes
• See Figure 4-78 page 115
Gyroscopic Instruments
• Gyroscopes use the principles of angular momentum to
maintain an orientation
– Powered by electricity or a vacuum system
• See Figure 4-90 page 123 for vacuum system details
– For more info on gyros see:
 http://science.howstuffworks.com/gyroscope4.htm
• Follow the links to see more information
• The “NASA: Guidance, Navigation and Control” contains some good
info on how gyros are used in aerospace applications
• Attitude Indicator
– See Figure 4-92 page 124
– Uses a gravity aligned gyroscope to indicate pitch angle and
bank angle
Gyroscopic Instruments 2
• Heading Indicator
– See Figure 4-93 page 124
– Uses a gyroscope to indicate heading angle
– Must be occasionally realigned due to drift
• Turn Indicator
– See Figure 4-94 page 125
– Uses a gyroscope to sense the rate of turn (heading
change)
• Turn Coordinator
– See Figure 4-95 page 126
– Uses a gyroscope to sense both roll and yaw rates
Other Instruments
• Balance Ball
– Uses gravitational and inertial forces to coordinate a turn
• Magnetic Compass
– You might think this would be a pretty simple and easy
instrument to use: compass points north, gives you your heading
– However, there are many precautions you must take when using
your compass
• Magnetic north is not true north
– Know what variation to use
• Metal and electrical equipment in the cabin can affect the compass
– Know what deviation to use
• Turns and accelerating can affect compass indications
For next week…
• Required Reading: BAK Chapter 5, pp.
133-168