RMIT滄俴捄褶諺璃ㄜCompassesMassBrief

瑤諾楷桶衾 2010-8-21 01:39:42

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瑤諾楷桶衾 2010-8-21 01:39:55

Compasses Mass Brief Aim • To gain an understanding of the principles and limitations of using an aeroplane compass in flight. Application • To align the DG and compass in VFR flight • When the DG fails Overview • Definitions • Principles • Considerations • Airmanship Definitions • Simple Bar Magnet 每 A magnet freely suspended horizontally will swing so as its axis points roughly north/south. Definitions • Magnetic variation 每 The angular difference between the magnetic poles and true poles of the Earth. Definitions • Magnetic variation 每 Isogonal are lines that join places of same magnetic variation. 每 Agonic is the line that joins places of zero magnetic variation. Definitions • Easy way to remember when to add or subtract variation to get magnetic heading: ※Variation West, Magnetic Best Variation East, Magnetic Least§ Definitions • Deviation 每 Combined metal and electrical components of an aircraft create a magnetic field which interferes with the compass 每 Deviation cards are provided for correction Definitions • Lubber line 每 Is a line on the compass which shows the heading on the compass card Principles 每 A direct reading compass is filled with a liquid which; supports its weight, reduces friction and dampens oscillations Principles 000 180 270 090 N S N • The aircraft turns around a magnet which is aligned north/south Considerations • Magnetic Dip 每 At equator, lines of magnetic force are parallel to Earth＊s surface 每 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. N S S N Pivot Line Weight Considerations • Minimising Dip 每 By placing the pivot point above the CoG, it opposes the dip force 每 The greater the dip force, the greater distance of the CoG outwards, and the greater the restoring force 每 In the southern hemisphere, the compass CoG is north of the pivot line. Side View Considerations N S N S Pivot Line Weight N S • Acceleration errors 每 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. Side View Top View Considerations • In the southern hemisphere SAND • South Accelerate, North Decelerate West Apparent turn to the South Apparent turn to the North South None None East Apparent turn to the South Apparent turn to the North North None None HDG Acceleration Error Deceleration Error 000 180 270 090 N S Considerations • Turning Errors 每 The centripetal force of the turn pulls the pivot point of the compass into the turn, but the magnet is left behind again • In the southern hemisphere ONUS • Overshoot through North, Undershoot through South HDG 330 HDG 030 HDG 150 HDG 210 000 180 270 090 N S 030 000 180 270 090 N S 150 Considerations • DG failure 每 You can turn onto headings using a watch by timing the turn 每 Rate one turn is 360 degrees in 2 minutes (120 seconds) 每 This is 3 degrees per second 每 How many seconds would it then take to turn 90 degrees? Considerations • Turbulent weather 每 Compass may become unreadable in very bumpy weather since the compass is not stabilised in any way. 每 Use DG instead of compass 每 However aligning DG to compass could be difficult Airmanship 每 Always avoid placing ferrous/metallic/electronic materials near the compass 每 Apply SAND and ONUS rules where applicable 每 Always apply magnetic variation when flight planning ※What you see is true, what you hear is Magnetic§ 每 Always apply compass deviation 每 Check compass for fluid leaks 每 Never Align Compass to DG, in a climb, descent, turn, acceleration or deceleration 每 You can always use your watch in a timed rate one turn to turn onto a heading if you have a DG failure 每 Look at the compass from head on, otherwise you will get a small parallax error

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RMIT滄俴捄褶諺璃ㄜCompassesMassBrief