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Old 14th Nov 2013, 10:12
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Trim Stab
 
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As Shotone implies, if you couple an autopilot to an ILS and don't disconnect it at minimums, the aircraft will continue on its trajectory until it's nose wheel hits the runway piano-keys. The minimums on ILS are low (0-200ft depending on various factors) because the pilot does not need to make any configuration changes or alter the trajectory of the aircraft (except to flare) in order to complete the landing. This is why it is called an Instrument Landing System. The maximum runway non-alignment of an ILS is normally 3 degrees.

If the aircraft has to be manoeuvred visually by the pilot at minimums because the radio-beams are not aligned with the runway, then the approach is an IGS (such as Lugano which I mentioned, and the old Hong Kong approach). IGS means Instrument Guidance System. It uses the same ground and aircraft equipment as ILS, and the pilot flies it in exactly the same way as an ILS, except that at minimums he will have to visually manoeuvre the aircraft to land, and sometimes make configuration changes too (e.g. at Lugano the approach is so steep that I preferred to only select full flap once I was below minimums, aligned with centreline and on a 3 degree glidesope, even though this meant taking full flap much later than is normally sensible). The minimums of IGS are much higher to give the pilot altitude and time to correct the trajectory of the aircraft and make any configuration changes needed.

I haven't been to Lydd, but if the misalignment is 5 degrees, then possibly it should be classified as an IGS, as that would immediately flag up to the pilot the misalignment.
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