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