Definitions
• VARIATION WEST, MAGNETIC BEST
• VARIATION EAST, MAGNETIC LEAST
Principles
• Aircraft turns around magnet which is
aligned north / south
090
270
360
180
Principles
A direct reading magnetic compass is filled
with a liquid which
• supports its weight,
• reduces friction, and
• dampens oscillations
Lubber line shows heading on compass
card
Principles
Definitions
• Deviation
Considerations
• Magnetic Dip
Considerations
• Minimising Dip
Acceleration Errors
• due to CoG displacement,
• As aircraft accelerates, pivot point moves
with the aircraft, but the magnet is left
behind.
Considerations
South
Accelerate
North
Decelerate
090
270
360
180
Considerations
Westerly Apparent turn to S Apparent turn to N
Southerly None None
Easterly Apparent turn to S Apparent turn to N
Northerly None None
HDG Acceleration Error Deceleration Error
Considerations
• Turning Errors
340
040
340
060
040
030
330
030
310
330
Considerations
• Turning Errors
200
160
200
170
160
150
210
150
190
210
Considerations
Overshoot
North
Undershoot
South
Airmanship
• Always avoid placing ferrous materials
near the compass
• Apply SAND and ONUS rules where
applicable
• Always apply magnetic variation when
flight planning
• Always apply compass deviation
Review
• What is an Isogonal?
• What is Magnetic Dip and How do we
overcome it?
• Acceleration Errors
• Turning Errors
Constant Speed Unit
Aim
• To gain an understanding behind the
operation and use of a variable-pitch
propeller (CSU)
Application
• When flying a CSU aircraft
• C182 or PA44
Overview
• Revision
• Definitions
• Principles
• Considerations
• Air Exercise
• Airmanship
Revision
• Fixed-Pitch Propeller
– Same rotational velocity (RPM), different
forward speed
Low Speed
Higher AoA
High
Speed
Lower AoA
Revision
• Fixed-Pitch Propeller
– Same forward speed, different rotational
velocity (RPM)
High rotational velocity
Higher AoA
Low rotational velocity
Lower AoA
Revision
• With a fixed pitch propeller
– If the aircraft is put into a climb, what will
happen to the RPM with a fixed power setting?
– If the aircraft is put into a descent, what will
happen to the RPM with a fixed power setting?
Definitions
• CSU
– Constant Speed (propeller) Unit, is a type of
propeller that has a variable blade angle
– It is called constant speed unit because the
propeller can be set to a certain RPM and
stay there with an increase or decrease of
power.
• Governor
– A mechanical device that keeps the propeller
at a set RPM, by means of springs and
flywheels
Definitions
• Propeller Governor Cut-away
Definitions
• Fine pitch
– Small blade angles, used at
low airspeeds
• Coarse Pitch
– Large blade angles, used at
high airspeeds
• Feather
– When the blade chordline is
parallel with the aircraft’s
relative airflow
• Pitch Stops
– Variable pitch propellers are
typically limited to angles
between 15 and 25.
Between these stops
(fine/coarse pitch stops) the
propeller acts as a CSU. At
the stops it becomes a fixedpitch
propeller.Governor
Blade
Angle
Definitions
• CTM
– Centrifugal twisting moment is the force acting on the blade,
trying to turn the blade towards a fine pitch
• ATM
– Aerodynamic twisting moment is the force acting on the blade,
trying to turn the blade towards a course pitch
Definitions
• Manifold Pressure (MAP)
– Is an indication of engine power, measured in
inches of Mercury (“Hg)
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