Turn as soon as practicable

25.02.2005

Submission:

I have an ILS CAT I approach with a turning missed approach as soon as
possible and my question is about the obstacle evaluation.

In the figure you can see an example. I have a soc ( start of climb) and a soc tolerance.

(Missed approach climb gradient called Z)

- The obstacle O1 is evaluated as HO1 < OCA-HL + D1. Z - MOC

However, how to evaluate obstacle O2? Is it that HO2 < OCA-HL - MOC ?, or is the obstacle O2 protected by the OAS?

Must I consider the turning at the soc like a turning point at an altitude OCA-HL?

Is it possible for the airplane to start the turn before the soc? (I think that if the airplane is following the glide path this is not possible to be at the OCA/H altitude before the soc, so the first possible point of turning is the soc, is it not?)

Raquel Monje - Spain

Answer or Commentary:

(I.W.

Firstly attachment J in the green pages has some useful information for dealing with this type of problem.

Secondly, aircraft can carry out a missed approach at any time after the final approach fix. So personally, when I have a "turn as soon as practicable" situation I usually add a statement to the missed approach text "no turns before ??". You could create an OM fix as your not before position. This would then eliminate the possibility of an early turn and consequently eliminate O2 from the missed approach assessment.

As a further point, I normally do not have a turn as soon as practicable greater than 15 degrees because then I have to use a MOC of 50m for all aircraft categories from the earliest turning point. This would have the effect of raising the OCA/H as 50m is greater than the height loss.)