Ils Minimums @ Kcxy

[LineBoy]

Question:

Why are the minimums published for the ILS RWY 8 at CXY (capital City- Harrisburg) as follows?

S-ILS 8 940-2 (600-2)
S-LOC 8 1160-1 (900-1)

The altitudes get you lower with the full ILS, but the visibility is higher then just the localizer.....why?

Also note this ILS only gets you down to 600 ft. AGL.....The glideslope is unusable below 940 MSL.

I only showed the CAT-A mininmums....it is similar for the rest of the categories...

 

[Andy Neill]

Just taking a quick look at it, note that the 2 mile minimum for the ILS is for all approach categories whereas the 1 mile min for the LOC is for Cat A only. Cat C and D mimima for the LOC are > 2 miles with the same MDA.

 

[Flyerjosh]

I don't have the plate in front of me, but it's possible that there is an obstruction/terrain during the ILS missed approach that requires the higher vis minimums for the lower descent. Take a look at the departure requirements (takeoff mins) that might provide some insight.

 

[A Squared]

Question:

Why are the minimums published for the ILS RWY 8 at CXY (capital City- Harrisburg) as follows?

S-ILS 8 940-2 (600-2)
S-LOC 8 1160-1 (900-1)

The altitudes get you lower with the full ILS, but the visibility is higher then just the localizer.....why?

Also note this ILS only gets you down to 600 ft. AGL.....The glideslope is unusable below 940 MSL.

I only showed the CAT-A mininmums....it is similar for the rest of the categories...

I think that it is because of the high DA. On the ILS, you go missed when you reach DA. On a 600' AGL DA you reach DA about 2 miles from the airport. On the LOC only approach, you may track inbound at MDA until you are over the end of the runway before going missed. You might have difficulty meeting some other requirements for landing, especially under 135 or 121, but, the point is that the LOC approach, while higher, allows you to get closer before going missed.

 

[Flysher]

Yea i know, our ILS sucks

Im an instructor at CXY btw.

We are supposed to be getting a new ALS soon that will lower our minimums to 200 agl. Right now our GPS and ILS app. pretty much are the same as far as HAT at DA/MDA

Outta curiousity, Do you fly into CXY??

 

[Flyerjosh]

I think that it is because of the high DA. On the ILS, you go missed when you reach DA. On a 600' AGL DA you reach DA about 2 miles from the airport. On the LOC only approach, you may track inbound at MDA until you are over the end of the runway before going missed. You might have difficulty meeting some other requirements for landing, especially under 135 or 121, but, the point is that the LOC approach, while higher, allows you to get closer before going missed.

Good catch. I'd concur with that statement.

 

[LineBoy]

A squared...You are correct. I checked with ACY FAA flight inspection. They stated that because DH is at 600', 600' is reached approx. 2 miles from the end of the runway. Thus visibility minimums are 2 miles for all categories...The localizer visibility is lower because the MDA is higher which allows for tracking all the way to the runway.....So, the question is, why is the DH on the ILS 600'? The answer was approach obstructions. Not missed approach obstructions or inadequate lighting. I was also told there are only a handful of ILS approaches in the country that are like this...

 

[A Squared]

A squared...You are correct. I checked with ACY FAA flight inspection. They stated that because DH is at 600', 600' is reached approx. 2 miles from the end of the runway. Thus visibility minimums are 2 miles for all categories...The localizer visibility is lower because the MDA is higher which allows for tracking all the way to the runway.....So, the question is, why is the DH on the ILS 600'? The answer was approach obstructions. Not missed approach obstructions or inadequate lighting. I was also told there are only a handful of ILS approaches in the country that are like this...

Hey, thanks for the follow up, and good work going to the source and getting the real answer. My response was just speculation, just like the others, it's good to see somone keep digging until they get an authoritative answer. If more people did that, there would be a lot less misinformation and old wives tales floating around aviation.

 

[LineBoy]

Thanks.....

 

[FlyinTim]

I'm goin with A-Squared.... why have a mile vis if you reach DA farther out?...as useless as 'tats' on a bull