RMIT飞行训练课件－Compasses 罗盘指南针

航空

游客，如果您要查看本帖隐藏内容请回复

航空

RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 1
COMPASSES
Aim: To understand the principles and considerations of compass operations.
Application:
- Navigation flying
- When DG fails
Definitions:
 Simple Bar Magnet
- a magnet freely suspended horizontally will swing so as its axis points roughly
north/ south.
 Magnetic Field
- Earth acts like a large weak magnet
 Magnetic Variation
- the angular difference between the magnetic poles and true poles of the
Earth.
- Isogonal are lines that join places of same magnetic variation.
- Agonic is the line that joins places of zero magnetic variation.
Easy way to remember relationship:
VARIATION WEST, MAGNETIC BEST
VARIATION EAST, MAGNETIC LEAST
Brief 27
RMIT Flight Training Compasses
RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 2
 Deviation
- combined metal and electrical components of an aircraft create a
magnetic field which interferes with the compass
- deviation cards are provided for correction
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
- aircraft turns around magnet which is aligned north / south
Brief 27
RMIT Flight Training Compasses
RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 3
Considerations:
 Magnetic Dip
- at equator, lines of magnetic force are parallel to Earth’s surface
- approaching magnetic poles, lines of magnetic force dip toward them and
the compass aligns to these lines
 Magnetic dip is zero at equator and maximum at the poles.
 Minimising Dip
- by placing the pivot point above the CoG, it opposes the dip force
- the greater the dip force, the greater distance of the CoG outwards, and
the greater the restoring force
 In the southern hemisphere, the compass CoG is north of the pivot
line.
 Acceleration Errors
- due to CoG displacement, acceleration errors occur. As aircraft
accelerates, pivot point moves with the aircraft, but the magnet is left
behind causing errors, until it is realigned.
Brief 27
RMIT Flight Training Compasses
RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 4
- this error is not apparent when flying north or south, due to pivot point and
CoG of compass being aligned in the direction of
acceleration/deceleration.
In southern hemisphere: SAND
HDG Acceleration Error Deceleration Error
Northerly None None
Easterly Apparent turn to S Apparent turn to N
Southerly None None
Westerly Apparent turn to S Apparent turn to N
 Turning Errors
- the centripetal force of the turn pulls the pivot point of the compass into
the turn, but the magnet is left behind again
In southern hemisphere: ONUS
Brief 27
RMIT Flight Training Compasses
RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 5
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
Brief 27
RMIT Flight Training Compasses