ILS question

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photofly
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Re: ILS question

Post by photofly »

Gannet167 wrote: Mon Nov 11, 2019 8:51 pm Fair enough, I didn't realize that flying an ILS won't keep you legal on the minimums on some loc only approaches. If I were flying a loc only, I'd still fly it CDA.
Sometimes CDA data isn't shown on the plate it's typically because a CDA approach would be steeper than 3 degrees; would you calculate your own data in advance (or in your head) or ...?

For example, the CYHM ILS RWY 12 - the 3 degree approach (which is the ILS) descends below the LOC minimums prior to the FAF, and there is no CDA data on the plate for use with the LOC approach. What would be your approach there (no pun intended)?
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goingnowherefast
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Re: ILS question

Post by goingnowherefast »

Big Pistons Forever wrote: Mon Nov 11, 2019 6:47 pm
goingnowherefast wrote: Mon Nov 11, 2019 6:43 pm

The only reason I could ever imagine doing the LOC over the ILS would be for glideslope issues. The glideslope transmitter might be broken for example.
If the GS is broken I would fly the LPV because virtually all runways with an ILS also now have an LPV approach. In any case if you are flying an ILS with the GS out, which incidentally is almost impossible with the new style ILS units, all of the numbers to fly the LOC only including all required crossing heights will be on the plate, so again why would you fly the ILS numbers and not the LOC numbers ?
Yeah, I'd fly the GPS approach too. Minimums are likely better than the LOC only. This thread is largely semantics. Nobody circles anymore. Besides PPC rides, the last time I legitimately circled was 2 years ago and that airport now has approaches to both runways.
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digits_
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Re: ILS question

Post by digits_ »

How do you circle illegitimately?

Seriously though, there are plenty of places, mainly in mountains, where circling approaches are the only approach available, depending on your airplane equipment.
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goingnowherefast
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Re: ILS question

Post by goingnowherefast »

The training environment, haha.
Fly the approach with the tailwind just so you have the opportunity to circle. That's not a legitimate reason to circle.

Don't most of the mountain circling approaches have minimums over 2000' above the airport? That's hardly circling anymore, more like a cloud breaking procedure through a valley that allows a VFR approach and landing.

Castlegar is a great example. Can't tell me that you're staying within the 1.7 miles from the runway at 2754' then divebombing the threshold on final. That's roughly a 15° slope.
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Gannet167
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Re: ILS question

Post by Gannet167 »

photofly wrote: Tue Nov 12, 2019 5:39 am
Gannet167 wrote: Mon Nov 11, 2019 8:51 pm Fair enough, I didn't realize that flying an ILS won't keep you legal on the minimums on some loc only approaches. If I were flying a loc only, I'd still fly it CDA.
Sometimes CDA data isn't shown on the plate it's typically because a CDA approach would be steeper than 3 degrees; would you calculate your own data in advance (or in your head) or ...?

For example, the CYHM ILS RWY 12 - the 3 degree approach (which is the ILS) descends below the LOC minimums prior to the FAF, and there is no CDA data on the plate for use with the LOC approach. What would be your approach there (no pun intended)?
Getting off topic, but depending on the aircraft and specific circumstances, yes I would. It's fairly easy to do. Even without published CDA, I'd set a descent rate that approximates the glide path I want based on ground speed and cross check altitudes on the way down, adjusting as required.

Steeper than 3 degrees does not necessarily prohibit a CDA. There are some published with above 3 degree CDA. Jeppesen CYHM has 3.53 degrees as the published CDA for the LOC only and the NDB. I'm fortunate to fly an aircraft that has most non precision approaches coded in the box and it magically does this for me.

If I had to fly the LOC only in CYHM, I'd be level at 2200, then passing the FAF I'd fly 3.53 degrees to MDA. Some planes allow a flight path angle set in the flight director, some display it on the HUD, the handy chart on the approach plate says at 140 kts gnd speed that's 875'/min.

To answer the OP question, you could do this to circling MDA, or fly the ILS to circling MDA, then circle to land.
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Curiousflyer
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Re: ILS question

Post by Curiousflyer »

kevenv wrote: Tue Nov 12, 2019 5:34 am
Curiousflyer wrote: Mon Nov 11, 2019 8:41 pm First of all, you will not be cleared a “localizer” approach if there is an ILS on the chart. You are cleared for the approach based on the name of the chart. “Cleared the ILS Runway XX, Glideslope unserviceable” is the appropriate approach clearance given by ATC if the glideslope is out and you have to fly the localizer only.
This is not correct. As stated in the CapGen on page 45 under multiple procedures, ILS and LOC are considered one approach and not separately identified. If the glide path is unserviceable I will clear an a/c for a LOC approach. There is no need for me to say "ILS Rwy XX, glide path unserviceable". What if the glide path is not unserviceable and one of our training a/c asks to do a LOC approach? Again, "cleared LOC Rwy XX approach".

Untitled.jpg
Then you are using slang and doing it wrong.
It clearly states they are one approach and not separately identified, so why would you?
According to the AIM
“When an approach clearance is issued, the published name
of the approach is used to designate the type of approach “
You should never clear someone a localizer approach if it is not the published name. You should clear them the ILS and advise if the Glideslope is unserviceable, if it is.
If you have a training aircraft wanting to do the loc, you should clear them the ILS as that is the name of the approach.
Now it’s become common practice to hear cleared the loc, or requesting the loc, and in that situation personally clearly an ILS is just going to create confusion.

As a side note, plenty of RNAV approaches have different minimums, including ones without vertical guidance. No one is asking for the LNAV approach, because it doesn’t exist. It’s the name on that chart, RNAV XX.
This is old slang that continues to be used for localizers.
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co-joe
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Re: ILS question

Post by co-joe »

I'm not sure ILS approaches are optimized for circling. It all depends where you are on the approach when you reach MDA, and commence circling. For some reason in my mind, an ILS would put you too close to the threshold but I may be visualizing it wrong. As long as you break off the approach once you reach circling MDA have the required visual reference, stay within the proper arc for your category of aircraft, and have a clearance to circle you should be G2G.
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iflyforpie
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Re: ILS question

Post by iflyforpie »

goingnowherefast wrote: Tue Nov 12, 2019 9:42 am The training environment, haha.
Fly the approach with the tailwind just so you have the opportunity to circle. That's not a legitimate reason to circle.

Don't most of the mountain circling approaches have minimums over 2000' above the airport? That's hardly circling anymore, more like a cloud breaking procedure through a valley that allows a VFR approach and landing.

Castlegar is a great example. Can't tell me that you're staying within the 1.7 miles from the runway at 2754' then divebombing the threshold on final. That's roughly a 15° slope.
Try Terrace.

ILS 33. Circling minimums are 507 feet above the runway.

Am I going to go 30 miles past the airport to pick up an LNAV that’s only going to get me to the same minimums when it’s 1000 OVC? Not a chance.

So yeah.. to answer the OP.. I’m cleared for the ILS Y 33 circling 15. I arm the approach in LOC and GS to follow the 20 mile approach. Approaching MDA and with required visual reference I’ll disarm the approach, select heading mode and vertical speed mode to capture the MDA.. or use VS and ALT to gradually transition to a higher altitude.. and fly a downwind circling approach.

I’ve never heard about any law saying that you can’t be coupled in an NPA. And what does that even mean, anyways? Flying in LNAV mode or approach mode doesn’t really make much of a difference until you’re past the FAF and heading to minimums.

The biggest difference will be in GPS approaches which will make the sensitivity increase as you get closer (like a LOC does in a precision or non precision approach) and it will either create a GPS glidepath or capture an ILS glidepath with will also get more sensitive and ignore selected altitudes. As long as your aware that it will do this, I don’t see the problem.

The other mistake most people make on a circling approach is staying within that 1.7 or whatever it is for their category when visual. Once you’re visual and leaving MDA... you’re visual. The MDA is 300 feet above the highest obstacle in that area. This is why lots of circling approaches end in disaster, people trying to keep inside this area until final. Forget it... even in a flat land airport. Either you have visual and can keep it.. or if it looks like you’re going to lose it, go missed.
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