ILS obstacle clearance
 

According to my Jepp ATC p215;

"The ILS obstacle clearance surfaces assume that the pilot does not deviate from the centreline more than half a scale deflection after established on track."

It then goes on to say thereafter to maintain the LLZ within half a course sector deflection once established.

Does this translate as "half a dot" or is it half the displayed scale.

I'd appreciate any input on this. rgds

Jepp Term states that a missed approach must be executed . . [quote]during the final segment of an instrument approach, the aircraft is not maintained within the applicable navigational tolerance for the aid in use<hr></blockquote>

The navigational tolerance is half scale for LLZ/ILS.

Here are some ILS cross sections (these are TERPS based)

http://www.terps.com/rnp/ILSX.jpg

http://www.terps.com/faaiap/terps.jpg

[ 18 February 2002: Message edited by: Zeke ]</p>

Thanks for the info and diags, Zeke; most appreciated.