Systems Review 3 ATC Chapter 4. Aim To review principals of operation of pressure, gyroscopic and...
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Transcript of Systems Review 3 ATC Chapter 4. Aim To review principals of operation of pressure, gyroscopic and...
Systems Review 3ATC Chapter 4
Aim
To review principals of operation of pressure, gyroscopic and electrical instruments
Objectives1. State what each instrument indicates and name
the power source for each instrument2. State the effect of system failures on instrument
indications
Artificial Horizon (AH or AI)Sometimes referred to as the master instrument
Indirectly, the AH is a guide to airspeed• Nose low, high or increasing airspeed• Nose high, low or decreasing airspeed
Miniaturization of the outside world means that small movements of the AH represent quite large changes in pitch and bank attitudes
Indicates both pitch and bank attitude directly (in miniature) against the artificial horizon
Most commonly driven by an engine driven vacuum pump but can be electrically driven or venturi driven
1. Instruments indications and source
Airspeed indicator (ASI)Directly indicates the aircrafts speed through the air by measuring the difference between total pressure from the Pitot tube and the static pressure from the static source
The ASI is driven by the Pitot static system and requires both dynamic and static pressure.
Indirectly indicates the pitch attitude of the aircraft• Low or decreasing airspeed, nose
high• High or increasing airspeed, nose
low
Total pressure – Static pressure = Dynamic pressure
1. Instruments indications and source
AltimeterDirectly indicates the aircrafts height above a datumIn Australia below 10,000ft AMSL seal level is set as the datum
The altimeter is driven by the aircrafts static vent
Indirectly indicates pitch attitude• Altitude decreasing, nose low• Altitude increasing, nose high
1. Instruments indications and source
Altimeter – Incorrect subscale settingsBelow 5,000ft every 1 hPa that the altimeter is in error is equal to 30ft error displayed on the altimeterIf the subscale is set too low the altimeter will read lowIf the subscale is set too high the altimeter will read high
1. Instruments indications and source
Vertical Speed Indicator (VSI)Directly indicates the rate of change of altitude.
The vertical speed indicator is driven by the aircrafts static vent
Indirectly it indicates pitch attitude• VSI decreasing, nose low• VSI increasing, nose high
Useful as a trend indicator
1. Instruments indications and source
Heading Indicator
Can be a Direction Gyro (DG) or Horizontal Situation Indicator (HSI)
Electronically driven or driven by vacuum pump
Indirectly it indicates Bank angle• HSI decreasing, left turn• HSI increasing, right turn
DG must be manually aligned with aircraft compass. HSI automatically aligns with the Earths magnetic field
Allows direct reading of heading
1. Instruments indications and source
Turn Coordinator (TC)
Usually powered by an electrically driven Gyro.
Indirectly it can indicate limited angles of bank usually to 35 degrees
Directly indicates the rate of change of direction
1. Instruments indications and source
3. Instrument IndicationsBalance Indicator
Powered by gravity
Indirectly indicates aircraft yaw
Directly indicates balance
Usually incorporated with the turn co-ordinator
Slipping Turn Skidding Turn Co-ordinated Turn
1. Instruments indications and source
Tachometer
Driven by the engine via mechanical linkage
Indirectly indicates pitch in aircraft without a CSU• Increase RPM, nose low• Decrease RPM, nose high
Directly indicates engine RPM
1. Instruments indications and source
Primary navigation aid for most light aircraft
Magnetic Compass
Indirectly it indicates Bank angle• Compass decreasing, left turn• Compass increasing, right turn
Allows direct reading of heading
Susceptible to a number of errors
1. Instruments indications and source
When we look at the compass we are reading the back of it. This means the compass in our aircraft reads backwards
Magnetic CompassReading the compass
This is best shown on a boat compass. If we are heading 300 and wanted to turn onto 270 we know the shortest turn will be to the left.
When we are looking top down on the compass we can see 270 is to the left of 300. However when we look at the front of the compass card 270 is to the right of 300
1. Instruments indications and source
Angular difference between true north and magnetic north
Magnetic CompassVariation
The magnet in the compass aligns itself with the earths lines of magnetic flux (magnetic north)
1. Instruments indications and source
Occurs when the compass magnet is acted upon by a magnetic field other than the Earths. Can be caused by electronic or metal objects near the compass.
Magnetic CompassDeviation
The error is displayed on a compass deviation card produced by an engineer after they carry out a compass swing
1. Instruments indications and source
At the equator the earths magnetic field is parallel with the earths surface, the magnetic bar of the compass also lies parallel with the Earths surface
Magnetic CompassDip
1. Instruments indications and source
Magnetic CompassDipAs you travel closer to the poles the lines of magnetic flux begin to dip, so to does the magnetic bar of the compass
To help reduce this error the compass magnet is suspended from a pivot point.
This now means the center of gravity of the compass magnet is always going to be displaced from the pivot point
1. Instruments indications and source
Because the center of gravity of the magnet is displaced from the pivot point, when we Bank the aircraft there is a horizontal component of gravity that acts on the compass resulting in a change of heading indicated
Magnetic CompassTurning Errors
To remember which way it will rotate we use the acronym ONUS
ONUS
vershootorth
outhndershoot
This error is maximum on North and South, nil on East or West
1. Instruments indications and source
Because the center of gravity of the magnet is displaced from the pivot point, when we accelerate or decelerate the compass will lag behind the aircraft and will rotate. This error is maximum on East or West, nil on North or South
Magnetic CompassAcceleration Errors
SAND
outhccelerate
ecelerateorth
When we accelerate the compass will swing towards the south, when we decelerate the compass will swing towards the north
To remember which way it will rotate we use the acronym SAND
1. Instruments indications and source
G1000
Information is generated by the air data computer, AHRS and magnetometer
Directly indicates all of the above parameters
All indications are displayed on the PFD and MFD
1. Instruments indications and source
• Artificial horizon• Direction Gyro
Vacuum FailureInstruments affected
Indicated by:
Troubleshooted by:
• low VAC pressure reading• Annunciator
• Can get false indications at low RPM
2. System failures
Vacuum FailureArtificial Horizon
Failure indicted by:• The gyro toppling, may happen over an
extended period of time as the gyro slows down• Red warning flag
Direction Gyro
• Red warning flag• Inaccurate readings, check against compass
Failure indicted by:
2. System failures
Pitot Static System2. System failures
• Airspeed indicator
Pitot BlockageInstruments affected
Indicated by:
Troubleshooted by:
• No airspeed increase during takeoff roll
• If failure is identified during the takeoff roll abort the takeoff if it is safe to do so
• If failure occurs airborne Pitot heat may be required, refer to flight manual
2. System failures
Pitot BlockageAirspeed Indicator
Failure indicted by:• No airspeed increase during take off roll• If Pitot tube blockage occurs during
flight the ASI is only read correctly at blockage altitude- If aircraft climbs above blockage
height ASI over-reads- If aircraft descends below blockage height ASI under-reads
2. System failures
• Airspeed indicator• Altimeter• Vertical speed indicator
Static BlockageInstruments affected
Indicated by:
Troubleshooted by:
• ASI over or under reading• Altimeter not increasing with an increase in altitude• VSI reading zero with an increase in altitude
• Alternate static source may be required, refer to flight manual
2. System failures
Static BlockageAirspeed Indicator
Failure indicted by:• If static source blockage occurs
during flight the ASI is only correct at blockage altitude- If aircraft climbs above
blockage height ASI under-reads
- If aircraft descends below blockage height ASI over-reads
2. System failures
Static BlockageAltimeter
Failure indicted by:• Will continue to read blockage altitude
with an increase or decrease in altitude
Vertical Speed Indicator
Failure indicted by:
• Will continue to read zero with an increase or decrease in altitude
2. System failures
• G1000• Turn coordinator
Electrical FailureInstruments affected
Indicated by:
Troubleshooted by:
• Very high voltage reading• Very low voltage reading• Very high amp reading• Very low amp reading• Annunciator
• Depends on indication, refer to flight manual
2. System failures
Electrical FailureG1000
Failure indicted by:• Red X through affected instruments• If complete failure occurs the screens
may cease to function
Turn coordinator
• Red warning flag
Failure indicted by:
Note: The balance ball will still be functional
2. System failures
Questions?