We did this before [ threads merged ]
Maybe the design is done for a 2.5% achievable climb gradient?
Is there an additional factor if the LOC is offset?
Peter wrote:
Is there an additional factor if the LOC is offset?
Yes. According to PANS-OPS the minimum approach category A OCH is 340’ (rather than 200’ for a regular ILS) if the final approach course is offset more than 5°. The increase is even higher for other approach categories.
This is quite funny because it is not difficult to turn an aircraft by 5 degrees (or even a lot more) at 200ft 
But it makes the ILS worth a lot less. 340ft is probably what you can get with an NDB…
Peter wrote:
340ft is probably what you can get with an NDB…
Almost. The system minimum for an NDB approach is 350’.
300’ for NDB/DME.
I think the issue of higher minima for offset approach is rather where to expect to see the runway? although anyone crabbing in slow GA aircraft will tell you +/-20deg is very common, the Archer Century AP used to disconnect on those scenarios
Probably the system design starts with Cat C and D types, where there is several seconds of inertia, and where the main landing gear is expected to straddle the centre line at minima and one dot deviation. Also the PF might not be able to see the runway from his side on an offset.
The IGS Runway 13 Kai-Tak was on the chequerboard hill, so presumably minima was 200 feet or 250 feet above the hill elevation. If as customary on a difficult approach the PF was FO am wondering how the Captain as PM might have taken over the landing? The FO having a betview of the threshold.
