etrang .... Tactical Military .. only when absolutely necessary though! .... and IMHO
should only occur if the Mil Aircraft has functioning Air to Air Radar!
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.. other than that .... cannot think of any other 'legitimate' reason to turn it OFF
... on the surface, squat switches or air switch does the job!
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.. as I said previously, if the Alt encoder is inaccurate, ATC 'should' be instructing crews to select mode A only (no altitude)! ... at least they (ATC) will still see their radar return and can notify other traffic around them as appropriate! .... we do not verify levels (in radar CTA/R) on each flight for the fun of it!