controlling obstacles in IAPs

[chucky]

I've got a question about controlling obstacles and instrument approach procedures. The airport I'm doing my instrument training at, New Haven (KHVN) is served by one ILS approach - the ILS-02. The Cat-A straight-in minimums are 297/50. The TDZE is 6, so that's basically a DA of 300ft, and visibility 1m, which, since there is an approach lighting system (MASLF), is higher than the unrestricted Cat-I precision minimums. I'd like to know why.

There's no obstacle plotted on the ILS-2 approach chart, but there is one on the RNAV-02, which similarly has higher than standard LPV minimums. The obstacle is 99ft near the threshold, though exactly where is hard to tell. In the take-off minimums for runway 20, it says "Trees beginning 306' from DER, 399' left of centerline, up to 80' AGL/99' MSL", which must be the bugbear controlling the visual approach segment of the ILS and RNAV approaches, but I was wondering how I could tell for certain. My understanding is that all pertinent information in the creation of an ILS approach procedure is recorded on the FAA form 8260-3. Is there some way to get a copy of the one for this specific procedure?

 

[Steve]

The airport manager should have that information as well as the local ADO.

 

[chucky]

Ah, yes, thanks. Is that the sort of information just anyone can ask for, or is it like taking pictures?

 

[Steve]

Depends on the personalities you may have to deal with, but it should be available for the asking.

 

[John Collins]

Chucky,

I would not be surprised if you find that the controlling obstacle is on the departure side of the runway. The missed approach needs to be clear of obstacles below a plane that rises a 148 feet/NM so that the standard 200 feet/NM climb rate may be used. It may be that the obstacles in the missed approach path force the DA up so that the climb gradient can be met.

 

[chucky]

Oh, that might make sense, since there is a small ridge line off the departure end of 2. I hadn't considered that. I guess I'll try getting a copy of the 8260-3, then. I'll ask the flight school people who to ask at the airport, and if that doesn't work, I'll try the ADO. Thanks!

 

[chucky]

Turns out it's trees in the visual approach segment. I'm amazed they actually penetrate the slope, since there's nothing that looks particularly tall on the approach end, but there we are.