Straight in Minimums

midlifeflyer

midlifeflyer

Touchdown! Greaser!
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I'm looking for an example of an approach where the straight in minimums for category A and B are different.
 
For this to be the case, it generally would require a turning missed approach. Due to the increased turning radius as the Cats increase, that can bring in more terrain.

A straight-out missed won't have the turning radius as a factor.
 
Of course, there is SEA ILS OR LOC RWY 16L, ILS minimums, but that's a highly unusual special case which would require its own discussion (perhaps over a beer at Sun N Fun?) and likely isn't what you're asking.
 
RussR said:
Of course, there is SEA ILS OR LOC RWY 16L, ILS minimums, but that's a highly unusual special case which would require its own discussion (perhaps over a beer at Sun N Fun?) and likely isn't what you're asking.
Click to expand...

That's extortion. Can't make Sun N Fun, but if I mail you an unmarked beer in a plain brown wrapper, will you give it up? A higher than B, C, or D? That's a head scratcher.
 
RussR said:
Of course, there is SEA ILS OR LOC RWY 16L, ILS minimums, but that's a highly unusual special case which would require its own discussion (perhaps over a beer at Sun N Fun?) and likely isn't what you're asking.
Click to expand...
Not this year, Russ. We'll, not SnF. If we''re in the same place at the same time, definitely a beer :)

Besides, when I see stuff like that (lower LNAV/VNAV mins than LPV is another) I just accept it as part of the deeper mysteries of TERPS which are well beyond my desire, and perhaps my ability, to comprehend :D

It was really just the existence of them I was interested in.
 
I'm going to rain on Russ's parade. :)

The reason the CAT A DA is higher on the KSEA ILS 16L, is to protect the control tower from being hit by a CAT A airplane missing in a strong west crosswind component.
 
aterpster said:
I'm going to rain on Russ's parade. :)

The reason the CAT A DA is higher on the KSEA ILS 16L, is to protect the control tower from being hit by a CAT A airplane missing in a strong west crosswind component.
Click to expand...

Hmm. Is that actually calculated when the Approach is being built? Or did it come up during Flight Check? Or was there an incident? Given the reason I wouldn’t think it would be that rare. And it brings up the question of which Category you should use if you are flying outside the speed range of your airplanes ‘listed’ Category. You are supposed to your airplanes Category even if you are actually flying slower than it’s speed range. And you are supposed to use the higher Category if you’re flying faster than that airplanes range. Staying with you’re airplanes ‘Category’ doesn’t seem wise if you’re actually flying at ‘A’ speeds on this Approach.
 
luvflyin said:
Hmm. Is that actually calculated when the Approach is being built? Or did it come up during Flight Check? Or was there an incident? Given the reason I wouldn’t think it would be that rare. And it brings up the question of which Category you should use if you are flying outside the speed range of your airplanes ‘listed’ Category. You are supposed to your airplanes Category even if you are actually flying slower than it’s speed range. And you are supposed to use the higher Category if you’re flying faster than that airplanes range. Staying with you’re airplanes ‘Category’ doesn’t seem wise if you’re actually flying at ‘A’ speeds on this Approach.
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Not sure. I believe it became an issue when they sited the new tower.
 
aterpster said:
I'm going to rain on Russ's parade. :)

The reason the CAT A DA is higher on the KSEA ILS 16L, is to protect the control tower from being hit by a CAT A airplane missing in a strong west crosswind component.
Click to expand...

Dang Wally, how am I going to get free beer now?

Wally is correct. This issue was identified during design. The control tower actually penetrates the missed approach surfaces for all categories, but a study was performed to determine that the only real impact was to Cat A.
 
RussR said:
Dang Wally, how am I going to get free beer now?

Wally is correct. This issue was identified during design. The control tower actually penetrates the missed approach surfaces for all categories, but a study was performed to determine that the only real impact was to Cat A.
Click to expand...
...and since velocity is a square in the formula, slower airplanes would be a smaller impact? :eek:
 
RussR said:
Dang Wally, how am I going to get free beer now?

Wally is correct. This issue was identified during design. The control tower actually penetrates the missed approach surfaces for all categories, but a study was performed to determine that the only real impact was to Cat A.
Click to expand...
For Runway 16L only? I don't recall.
 
RussR said:
Dang Wally, how am I going to get free beer now?

Wally is correct. This issue was identified during design. The control tower actually penetrates the missed approach surfaces for all categories, but a study was performed to determine that the only real impact was to Cat A.
Click to expand...

Ah! So A mins weren't raised, the rest were lowered. Betcha there was some 'industry' input on this.
 
Last edited:
RussR said:
Dang Wally, how am I going to get free beer now?

Wally is correct. This issue was identified during design. The control tower actually penetrates the missed approach surfaces for all categories, but a study was performed to determine that the only real impact was to Cat A.
Click to expand...

Free?? I was gonna send it postage due.
 
luvflyin said:
Ah! So A mins weren't raised, the rest were lowered.
Click to expand...
Not really. The U.S. changed from it's own ILS criteria to the ICAO criteria in the 1970s or 1980s. That brought about the "trough" which resulted from the ICAO collision risk model (CRM). CRM can be used to mitigate a few obstacles on any given ILS except those in the "W" Surface. The CRM assessment validated an acceptable level of risk for the new control tower, except for Category A. Hey, I am a cynic but I agreed and still agree with the assessment at KSEA.
 
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