When can I start to circle? (VMC)

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Ryan B
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When can I start to circle? (VMC)

Post by Ryan B »

I heard someone fail their I-something exam today while I was slingshotting around Burbank for some practice approaches. I think I heard the controller say the pilot was too high on the ILS - in other words, he circled pretty early. I believe he was flying a cherokee or something likely approach category A or B. I was always under the impression you could start your circle when basically at any time after the FAF inbound (assuming clear in a million here, otherwise you'd need the airport env in sight). But maybe not - I note the circling radii in the AIM, but am I really supposed to wait till I'm so close to the runway to circle? There's no way I'd want to circle at 200 ft agl coming in for an ILS... that sounds most unwise.

As a rw controller I've seen pilots start their circle at various times on the descent... frankly I don't know what the legal requirements are for the pilots.

So what do the instrument pilots say on this matter?
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Peter Grey
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Re: When can I start to circle? (VMC)

Post by Peter Grey »

Hello Ryan,

Here are the legal requirements from a pilot point of view:

Remain at or above the circling minimums (which will always be at least 300' AGL {but normally much higher}) until you are in the normal position to land. This will require you to level off at some point prior to the ILS DA and ignore the glideslope. Note that circling approaches don't have DA's, but MDA's (like a non precision approach) (91.175 c 1)

Have the airport in sight with the minimum required visibility. (91.175 c 2 and c 3)

There's actually no guidance on when to start the circle that's a "legal requirement". You'll find the following "non legal guidance" however:

From the Practical Test Standards:
Maneuvers the aircraft, after reaching the authorized MDA
and maintains that altitude within +100 feet, −0 feet and a
flightpath that permits a normal landing on a runway. The
runway selected must be such that it requires at least a 90°
change of direction, from the final approach course, to align
the aircraft for landing.
Note that the "after reaching the authorized MDA" is a by product of how the checkride has to be conducted and shouldn't result in an unneeded descent below the clouds to a lower altitude then would be used for a traffic pattern. Or as put from the instrument flying handbook:
It is
important to remember that circling minimums are only
minimums. If the ceiling allows it, fly at an altitude that more
nearly approximates VFR traffic pattern altitude. This makes
any maneuvering safer and brings the view of the landing
runway into a more normal perspective
And from the AIM
Maneuver the shortest path to the base or
downwind leg, as appropriate, considering existing
weather conditions. There is no restriction from
passing over the airport or other runways.
From a TERPS point of view you are protected at the circling MDA along the final approach course until it intercepts the "circling radii" around the airport. If you want to 100% guarantee you won't hit terrain you must remain on the final approach course until you are within the radii. However, there is no "direct" rule requiring so. Failure to do so is unlikely to result in a deviation, but could result in a crash.

I suppose you could argue a violation of 91.175 a:
Unless otherwise authorized by the FAA, when it is necessary to use an instrument approach to a civil airport, each person operating an aircraft must use a standard instrument approach procedure prescribed in part 97 of this chapter for that airport. This paragraph does not apply to United States military aircraft.
Part 97 incorporates the TERPS and to be within the approach zone you'd have to fly the way I describe above. So you would argue that leaving the protected airspace prior to the circling radii means you aren't on the approach per the TERPS which means you aren't using a SIAP per part 97. That's a bit of a stretch honestly.

There's no NTSBs records on point for this one so I can't point to precedent at all.

That's the best I can give you.
Peter Grey
PilotEdge Director of Quality Assurance and Operations
peter@pilotedge.net
RyanK
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Re: When can I start to circle? (VMC)

Post by RyanK »

I'm guessing you overheard what's described in this thread: viewtopic.php?f=26&t=6156

You should wait until within the appropriate circling radius to start the circle. Leaving the approach path while you're beyond that distance puts you outside of where obstacle clearance would be assured. You'll be using circling minimums, which won't be as low as 200' AGL. The circling minimums on the ILS at KBUR are at 462' AGL for category A aircraft. Those are minimums, you could fly the circle higher if conditions allow, or use the minimums for a higher category. For example, use the category D minimums of 1440-2 (662' AGL), and you're protected as long as you remain within 2.3 NM of a runway threshold. Circling can be perfectly safe and simple in some situations, but your instinct that it might be sketchy in others is correct. At minimums, at night, and/or in unfamiliar areas can make it a pretty demanding maneuver.

Edit: Peter beat me to it with a more complete, better referenced answer.
Ryan B
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Re: When can I start to circle? (VMC)

Post by Ryan B »

Actually this happened today the 23rd -

So I'm not sure why the pilot failed after reading through your and Peter's posts... Maybe he was far too high on the circle.
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rtataryn
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Re: When can I start to circle? (VMC)

Post by rtataryn »

Remember too that unless the ILS approach plate has circling minima listed, circling is not authorized. I was on an instrument (PilotEdge) flight into KSBP last week. The ATIS reported ceilings at 700 and ILS RWY 11 in use with winds 310 at 6. The approach controller told me to expect the ILS Runway 11 circling to 29. After I reviewed the approach plate and saw no minima for circling for that approach I made a call back to approach and informed them that it doesn't appear authorized without the published altitude. He took a look and thanked me for catching it. I also told said that a six knot tailwind was not an issue for me on this runway and straight in for runway 11 would be fine. Remember, you're the PIC. If things don't look or feel right, speak up.
Rod
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Keith Smith
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Re: When can I start to circle? (VMC)

Post by Keith Smith »

Rod,

Absolutely. The reason for this, I suspect, is because the LOC version of the approach is published as a separate plate, and it does contain circling minimums. In cases where the ILS and LOC plates are separate, my guess is that they don't include circling minima on the precision version of the approach because it's already covered by the LOC plate.
Ryan B
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Re: When can I start to circle? (VMC)

Post by Ryan B »

I know I've done a circle in that very setup at SBP - I guess that's a no no. Next time I'll ask for a contact approach I guess.
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RyanK
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Re: When can I start to circle? (VMC)

Post by RyanK »

Another case is where LPV minimums are on a separate plate. Note no circling minimums on the GPS Z approach:

KCMA RNAV (GPS) Y RWY 26: https://skyvector.com/files/tpp/1603/pdf/00680RY26.PDF
KCMA RNAV (GPS) Z RWY 26: https://skyvector.com/files/tpp/1603/pdf/00680RZ26.PDF
Ryan B
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Re: When can I start to circle? (VMC)

Post by Ryan B »

Why does one have circling mins and the other not? Can you circle on both?
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RyanK
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Re: When can I start to circle? (VMC)

Post by RyanK »

Ryan B wrote:Why does one have circling mins and the other not? Can you circle on both?

It's basically the same situation as the ILS vs. LOC approach which are usually on the same plate. LPV is flown like a precision approach, with a decision altitude instead of a minimum descent altitude. Usually LPV, LNAV, and Circling minumums would be listed on the same plate, but in this case the LPV approach is slightly different so it gets its own plate, without circling minimums. If you want to circle to a different runway you'd use the GPS Y 26 approach and the circling minimums.
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