"JPH" wrote in message news:NkZDe.26717$mC.16233@okepread07...
wrote:

The origin of the timing table was not specifically referenced to ground
speed. In fact, the KISS concept in pre-GPS days favored simply applying IAS
on final, as in managing human factors and keeping the priority tasks at the
top of the list, so to speak. So, the discussion is not silly at all.


That may have been a simple way some pilots were taught to use it, but the time/distance table is based on
true speed, not indicated speed. If the FAF to MAP distance is 5NM, the time shown under 60 kts will be 5:00
minutes. This requires 60 kts TAS to cover that 5 NM distance in 5 minutes. If you have a IAS of 60 and a TAS
of only 30 based on headwinds, then it will take you 10 minutes to get to the MAP. Of course, using IAS,
you're unlikely to overshoot the MAP as long as you have a headwind, so you're safe in that respect, but then
you might start a missed approach turn too early, and fly into an area not protected by TERPS obstacle
assessment.

JPH

I don't think you really meant TAS in that paragraph...