Interesting Approach - MSO

drhunt

Pre-takeoff checklist
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Mar 8, 2005
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Moose Air
http://download.aopa.org/iap/20050929/NW-1/mso_ils_rwy_11.pdf

The ILS 11 approach into Missoula, MT (MSO) is a little different in that it requires you to fly the glideslope down to 1350 AGL and then fly 4.1 miles to the runway. This results in a fairly high ceiling minumum for an ILS and quite often, a no-go. Yesterday, while inbound the latest ATIS (50 minutes old) reported overcast 400 ft and 6 miles, not looking good for an approach and I hoped that the update would show the forecasted improvement to allow me to get in. The updated ATIS reported broken 600 ft, overcast 8000 and 6 miles...not looking good. I was below the higher overcast and when I got a look at the broken layer, I requested and was granted a SVFR clearance which worked out OK to get in. Maybe that's typical elsewhere but it struck me as odd that I could get in SVFR but not IFR on an ILS approach.
 
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I'm curious why you don't/can't fly this down to a traditional 200 to 300 foot minimum. My calculations (admittedly I failed out of engineering school) suggest that the glideslope would take you all the way down ok.

No obstructions on the final path that seem to cause a problem.

The only reason that I can see not to take you that low is that it might be impossible to go that low and successfully make the missed? There are some obstructions looming very soon on runway centerline, as well as in either direction on a turn. I certainly wouldn't want to have to make a climbout after a missed down to 200 agl, in actual, with all those pointy items sticking up. Particularly at these altitudes. I know how the trusty skyhawk responds that 5K feet. Sluggish is the word I would use.

It certainly is an interesting approach.

Jim G
 
Probably because of the climb gradient requirements for the missed.
 
I'm pretty sure that the approach minimums are based upon the missed approach climb requirements.
 
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