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I'm very confused of the actual radius of the "protected area" in a circling approach for a PAN-OPS approach plate. The ICAO doc 8168 contains information for circling approach at 1 000 ft. But what about airports that are sea level? How do you calculate the radius?

P.s. Not TERPS :)

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The 300 m and 1 000 m tables you found are examples. For the actual radius for any aerodrome elevation you need to apply the formulae.

The radius is determined using the formulas in Section 2, Chapter 3, Turn area construction (...) The TAS is based on:

a) altitude: aerodrome elevation + 300 m (1 000 ft); and
b) temperature: ISA + 15°.

First is $R$ (rate of turn) using $V$ (TAS in km/h) and $\alpha$ (bank angle of 20° for circling per Table I-2-3-1). Then plug $R$ in $r$ for the radius.

$$R = (6\;355 \tan \alpha) / \pi V $$

$$r = V / (20 \pi R) $$

Now, the $V$ (TAS) depends on the category and altitude (which is already aerodrome + 1 000 ft).

First get the IAS from Table I-4-1-1, then convert the IAS to TAS using the conversion factor in Section 2, Appendix to Chapter 1 (I-2-1-App-1).

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