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Old 24th Sep 2009, 13:31
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BOAC
Per Ardua ad Astraeus
 
Join Date: Mar 2000
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As JT says
Coriolis considerations tends to get lost in the scatter
The effect is all due to the rotation of the earth in space and your motion around an object. The black magic' involved in constraining the space-frame references to the earth-frame are wondrous..(refer Newton's First Law).

If you were able to 'hover' over a point on the equator for 12 hours, starting facing east and making NO changes to your 'space' attitude, you would finish up inverted and pointing west.

Similarly, if you started 'hovering' at 60 North, facing north and made no changes, you would arrive inverted and severely 'nose-up' after 12 hours but still 'pointing' north.

Setting off from the UK, pointing east (with a space referenced attitude) and aiming to fly to a point 'due east' you would see that point gradually move to the left of your nose as the earth rotates until it arrives behind you after 12 hours. This is the dilemma the poor old shell faces since its motion vector is 'in space'. Since your aircraft's motion is also a vector 'in space', you are a little like the shell. However, unless we are planning a long period of 'DR', as JT says, the Coriolis effect is lost in the constant corrections you make to stay 'on track' with wind changes, heading deviations and the like, not to mention using 'magnetic' directions with varying variation............. To stay pointing 'east' (magnetic) requires constant changes in some or all of pitch, roll and yaw to maintain - again fixed changes due to earth's rotation and variable according to your speed. Once you start following a 'line on the map' or tracking a radial or following an INS track, the 'corrections' required just 'happen'. The line on the map and the radial are all based on an earth reference and thus correct automatically. The INS has built in corrections to its space reference for earth rotation (earth rate) and your movement across the surface (profile rate) so it 'knows' the corrections it needs to apply to your space attitude to 'allow' for earth rotation and your motion across it. If I were Sir Francis Chichester in 'Gypsy Moth' aiming for that little island in the Pacific 10 hours away, yes, I would allow for it. For 'modern' flying, as I said, just relax

Phew!
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