ILS question

[mmm..bacon]

Having a discussion at work: are you allowed, legally, to fly an ILS down to circling minimums, using an autopilot? That is, can you engage the A/P in approach mode, have it fly a coupled approach, and then hit altitude hold or disconnect at the MDA, and (assuming that you have the ceiling/vis) break off the loc, and circle?

Pros: Yes, otherwise they wouldn't put circling minima on the plates. Yes, it's the same as flying an ILS to higher than minimums, and continuing once you're visual.

Cons: Your clearance is for the ILS Rwy whatever at wherever, which is a precision approach down to defined minima; a circling approach is not a precision approach, and therefore you can't be coupled. You can still mimic the glideslope using a vertical speed (respecting stepdown limitations, of course.)

Lots of discussion in our workplace this AM - I'm not taking a position, just trying to articulate both sides of the discussion clearly.

[ahramin]

Legally allowed? Of course. Anyone that thinks there is a regulation requiring a certain autopilot mode at a certain time should go find the regulation. Please let me know if they do, I've done it a dozen times this year. Using VS to follow a glideslope is not best practice if you can couple it instead.

Just a note though, you have to transition to ALT hold mode high enough that you level off at or above the MDA. If you wait until you get to the circling MDA before engaging ALT, you'll end up below it which is not acceptable.

[Gannet167]

Your clearance would be for approach X, circling to rwy Y. If you were only cleared the ILS 24, then you're supposed to land on that runway. You can fly any approach with published circling minimums and circle to another runway, as long as you get that clearance and follow any circling restrictions such as no circling to one side of the airport. Precision approach or non precision, it makes no difference.

As the pilot, you fly the approach and keep the plane within the tolerances. How you do it is up to you. Autopilot, hand flown, flight director only, raw data, whatever you want, just fly it accurately. Other than aircraft specific limitations on the use of automation, or a specific restriction published on the approach plate (LaGuardia ILS 04 “Autopilot coupled approach not authorized” for example) it's up to you.

[indieadventurer]

No, I don't think you can. As of April this year the circling approaches remaining are based off of LOC not ILS approaches (and in the absence of a LOC then VOR and then NDB). Often LOC approaches fly a different profile than ILS approaches, a different FAF crossing altitude for example.

Maybe a controller from NavCan can chime in here but would you still clear someone for the ILS X circling Y anymore?

Source: https://www.navcanada.ca/EN/products-an ... oke-EN.pdf

[photofly]

Not withstanding the communique from NavCanada, as of today, CYHM is still showing circling minima on the joint ILS or NDB RWY 12 (GNSS) approach plate, and CYKF is still showing circling minima on the ILS RWY 26 plate.

[nbinont]

indieadventurer: I understand your link indicates that a number of circling minima are being removed from approaches. I would agree that you can't circle to land for an approach that doesn't include circling minima. (Unless, of course, you break out in VFR conditions, cancel IFR, and join the VFR circuit - but that's not really circle to land anymore.)

But if the approach includes circling minima and you get the appropriate clearance, regardless of the approach type, you can circle to land at any point above the circling minima.

[indieadventurer]

The circling minima are based off of the LOC approaches so you’d have to fly the LOC approach to the circling minima not the ILS approach to circling minima. That’s how I read it at least.

[goingnowherefast]

The AP approach mode is certified to and capable of flying an ILS to 200', correct?

Then why can't it fly an ILS approach to ~500'?

If you're cleared for ILS 18 circle 36, the autopilot approach mode is allowed to track the loc and gs, so why not use it. Then disconnect approach mode at the appropriate minimums and begin the circling maneuver. Whether it's a precision approach or a non-precision approach doesn't really matter. It's about what data is feeding the autopilot and what it's certified to be used for.

FWIW, I've done PPC rides in the past that needed a precision approach and a circling approach. The ACP had me fly the ILS xx circle yy. Got both requirements taken care of in one shot. There was even a balked landing that lead to the missed approach off the circle and covered that requirement too. Oh, and I used approach mode while on the ILS.


If your clearance is localizer 18 circle 36, that's very different than ILS 18 circle 36. Likely has different step-down attitudes making it a pain in the ass.

[Big Pistons Forever]

Personally I think the OP is overthinking this. You fly the approach you are cleared to the appropriate minimums straight in or circling. At the published minimums you either go around or manoeuvre visually to the landing again either by flying straight ahead, or making a turn to align the aircraft with the runway for approaches with an offset approach track, or maneuver for a full or partial circuit to get you to the landing runway

As others have said what level of automation you use is only governed by the limitations section of the AFM for the technology or by company policy in the COM/FOM

[photofly]

If your clearance is localizer 18 circle 36, that's very different than ILS 18 circle 36. Likely has different step-down attitudes making it a pain in the ass.

Can you find any approach where flying the ILS glideslope down to LOC minimums would violate the LOC approach to the same runway? It's hard to imagine why that might be the case, particularly given TC's hard-on for non-precision approaches to be flown via a constant descent angle.

[Gannet167]

Even if I could only fly a circling approach using the LOC, I'd still use the glide slope and make it a constant descent "LOC only". Rule #1: don't hit anything. If you're following something published on an approach, that's been assessed for obstacle clearance, you're good.flying an ILS won't violate any minimums on the loc.

[indieadventurer]

Flying an ILS can violate minimums on a LOC approach. ILS 12 in CYHM and ILS 07 in CYOW (since they were mentioned earlier by somebody) both have glideslope FAF crossing altitudes on the ILS that are below the LOC approach altitude at the FAF. If you're flying the GS when cleared the LOC you're below a published altitude for that approach.

[photofly]

True... no CDA data published, for that approach either.

[Big Pistons Forever]

I am having difficulty understanding the issue here. You fly the approach you are assigned. If it is the ILS you fly the ILS numbers if it is a LOC only you fly those numbers. Why would anybody fly a LOC approach using the ILS numbers ?

[photofly]

Because you want to fly a CDA approach when cleared for a LOC. For instance at CYKF, the LOC RWY 26 has CDA data that matches the ILS RWY 26.

[goingnowherefast]

The obstacle clearance is calculated differently for step down approaches than it is for approaches with vertical guidance, ILS and LPV. As mentioned earlier, there's many ILS approaches that take you below the LOC step down altitudes.

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.

[Big Pistons Forever]

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 ?

[Curiousflyer]

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.
Secondly,
“Cleared ILS Runway XX” - this allow you to either fly the ILS to multiple minima (based on available lighting) OR the localizer MDA
“Cleared ILS Runway XX, circle runway YY”- this allows you to either fly the ILS GS to circling MDA OR the localizer to circling MDA.
Both are completely legal and acceptable and can be hand flown or on autopilot as long as aircraft limitations are not broken.

[Gannet167]

We've gone down a rabbit hole. The OP asked about circling, I think the answer is clear above. My point was, if you have a working glide slope, why wouldn't you use it while tracking the localizer (fly an ILS)?

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. If the glide slope was working, I'd just fly an ILS. And to answer the OP's question, you can even if you're going to circling MDA and going to circle.

No one is suggesting flying a LOC only using ILS numbers.

[kevenv]

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".

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