Visual Circling Procedure in IMC? Surely not.

[A37575]

See the current AIP ENR 64.2 under the main heading of Landing Manoeuvres.

Among other things it states:

"..aircraft approaching a non-towered aerodrome for a landing should join the circuit in accordance with para 64.5 unless:

following an instrument approach procedure in IMC;
Or: "conducting a visual circling procedure in IMC after completion of an instrument approach"

I wonder if there is an error in the last paragraph as I would have thought a visual circling approach is always conducted in VMC - not IMC....?

[neville_nobody]

To circle visually you only need the minimum for the approach which is usually less than VMC. Read the bit about being in the circling area and runway environment in sight etc etc

[AerobaticArcher]

A37575, no misprint there.

When conducting a Visual Circling Procedure after an Instrument Approach, chances are that conditions will be below the VMC criteria ie 5km vis. Obviously one should be clear of cloud.

[Lasiorhinus]

VMC in the circuit means 5km visibility. If you have less than that, even if you have 4.9km visibility, you are actually in IMC.

IMC does not have to mean "in cloud".

[Tmbstory]

Visual Circling Procedures

A37575:

Part of the problem used to be the interepretation of the term "visual" in the Title. The term visual should be called " In Flight Visibilty" (IFV) and the definition of this " is the visiblity required to maintain sight of the airport in a rate 1 turn". This was assumed to be 3000 metres. To calcuate the required IFV, multiply the IAS of the aircraft by 20 and the result is in metres. EG. 180 KIAS x 20 = 3600 metres.

In the Operations Manual under the section " Aerodrome Operating Minima" that was in use at the time and the paragraph "Circling" ,I quote here as follows:

'Circling procedure must be employed if the final heading of the authorised letdown procedure diverges more than 30 degrees from the heading of the runway on which landing is intended.

An approach may not be continued down to the decision height or OCA/H published for the aid if this entails descending below the relevant circling height to the airport.

On descending to circling height it must be estabilished that actual in-flight visibilty (IFV) is of the required order and sufficient visual reference exists to fix the aircraft's position in relation to the airport continuosly and accurately.

Note : The Jeppesen and Australian guide for Australian Airports will state the visibilty required for circling.'

Hope this helps with the discussion.

Regards

Tmb

[AerocatS2A]

I guess it all comes back to airmanship and choosing a runway aligned approach in the first place (even though the awis says cloud was about 3000ft above the minima!) even though it will take another 10 mins for an approach! Comes down to experience spose? Not a nice environment to be learning lessons or gaining experience

I don't think most pilots would choose to do a circling approach, but if the runway doesn't have an aligned approach you might not have a choice. (Or it may have an approach but there's a nasty TS sitting over the IAF.)

Oh and if you do your checks in a simulator you get conditioned to expect and accept losing sight of the runway environment. On downwind as you pass the threshold the runway disappears beyond the limit of the sim's field of view and so you develop circling procedures based on timing as a work-around.

[43Inches]

Part of the problem used to be the interepretation of the term "visual" in the Title.

The word visual with regard to flying ops has always been in regard to the ability to navigate with reference to external features and/or maintain obstacle and traffic clearance.

Various governing bodies have then placed minimum requirements on this for safety purposes, ie; VMC for VFR ops and minimum visibility for IFR ops.

The term visual as used in IFR operations is no different, it just describes manuevres that require an external visual reference so some inflight visibility is required, most times below VMC requirements. A visual approach in CTA (IFR operations) by day may not be in VMC as it requires no minimum distance from cloud, only 5k vis.

During visual circling you are navigating visually as such to position the aircraft on final. However in minimum visibility day or night you may still be using mostly instruments for aircraft control.

There's gotta be a better way than circling approaches at night, if your track brings you to the runway at right angles, at some point on the downwind leg you will lose sight of the runway in a low wing aircraft.

Done about 5 night circles in a low wing twin in the last month and never lost sight of the runway during the manuevre.

Have to agree that runway aligned procedures are safer, especially if the weather is marginal. However runway aligned with no slope guidance or gradient chart it may be safer to circle at night.

[das Uber Soldat]

I thought the regs were pretty clear on this.

Within the circling area, visibility along the intended flight path greater than that specified by the IAL plate and able to maintain visual reference with the landing environment. Ie Threshold, threshold marker lighting or approach lighting. Obvious requirement at night to not descend below MDA until at position on d/w/base/final where a continuous descent to landing may be made using 'usual' rates of turn and descent for the aircraft.

If conditions are less than VMC then you can join the circuit however you like, no need to comply with the standard circuit join requirements of VMC flight.

[43Inches]

What technique do you use if you are doing a right circuit (you are in the left seat) when commencing the downwind turn to not lose sight of the runway?

Ask the guy in the right seat to keep an eye on it or let them fly the circuit.

You assume I was talking about a single pilot operation or that I sit in the left seat.

I only took point against the statement that you will lose sight of the runway. Whilst this is true for some aircraft it is not the case in all situations.

If you think the circling approach will be marginal (due weather, terrain or aircraft perculiarities) change to the runway aligned approach or wait for conditions to improve/divert.

As for GPS/RNAV replacing all ground aids I hope not. The GPS procedures are good but have seen GPS units fail or do strange things, especially in heavy overcast or rain and icing (when you need it to work). When they fix these issues fine, until then leave some ground aids scattered around the countryside.

[bushy]

Visibility??

Visibility is a nebulous thing in aviation. For night VMC it is not convenient for the law amkers to require visual navigation and obstacle clearance unless there is lighting. IE it seems that at night, visibility is measured by how far away LIGHTED objects can be seen. When you turn your back to the coast and fly inland where there are no lights and there is high cloud cover, what is the visibility then?
We still use the distance that we can see a lighted object, even though there are none.
Realists aren't we?

[compressor stall]

We've agreed to disagree about this before Bushy.

May I suggest your statement

We still use the distance that we can see a lighted object, even though there are none.

Read

"We ... use the distance that we could see a lighted object, if there were one."


If a tree falls in a forest, does it make a sound?

[Angle of Attack]

At the end of the day no one knows but the PIC and you just do what you have to do at the time. You judge the viz if you don't like it bug out, if its ok continue. Pretty simple really, I know I will not be going to the AIP while I am circling if I am not sure the conditions are right, common sense rings a bell... unfortunately the powers that be are trying to weed this out, in lieu of people making their own decisions. Rant over, now just get on with circling! ^^

[A37575]

requirement at night to not descend below MDA until at position on d/w/base/final where a continuous descent to landing may be made using 'usual' rates of turn and descent for the aircraft.

It should read that a pilot should not descend below the MDA at any time in the circuit unless they are assured of the legal obstacle (read terrain) clearance. It means that at night if you cannot clearly see the ground directly along your flight path and therefore are unable to judge terrain clearance, you should not descend below the published MDA until final approach and within the approach splay. Note the critical obstacle that dictates the MDA may not necessarily be shown on the chart.

[Tmbstory]

Visual Circling Procedures

Many years ago, in around the 1980's, the American system was that you made the approach to the opposite runway that you intended to land on , when visual, at the appropriate altitude, you flew to the far end of the runway and then did a 45 degree procedure turn and when on the inbound heading, intercepted final and completed the landing.

It was different to the Australian way of doing things

Tmb

[43Inches]

It should read that a pilot should not descend below the MDA at any time in the circuit unless they are assured of the legal obstacle (read terrain) clearance.

Not at all, the rules and diagram show that you maintain the circling MDA until intercepting the relevent part of the circuit. If the MDA is above circuit height descent will commence on downwind and a normal base and final is encouraged (using normal bank angles and rate of descent). If the MDA is less than circuit height then maintain the MDA until on base, intercept your normal circuit pattern and descend. The MDA for circling would rarely if ever be low enough that you would have to leave descent until final. Of course by daylight there is the allowance to descend prior to the circuit if visual obstacle clearance is maintained.

If it is dangerous to conduct a normal circuit with regard terrain and obstacles the area will be marked as a no circling area and circling prohibited.

I can not think of many IFR aircraft that have come to grief whilst circling recently that were following the rules. A few from the past at night have been due to operating below MDA prior to the circuit (in conditions close to or below minima) and operating in non-cirlcing areas.

[Counter-rotation]

Owen (post #11) -

What is stopping you flying an arc (outside the final fix, typically 5nm) and aligning with the runway, then proceding in and down? At most 90 degrees of arc, adding in the order of 4-6 minutes... Some of that would be spent in "traditional circling" anyway. This is a legitimate question - is that not what is meant by "no manoeuvering inside the final fix"? Or have I missed the point?

At worst, you could fly an arc outside the initial fix (typically 15nm) - adding more like 12-15 minutes at worst. But you'd still end up on a runway aligned approach. Small price to pay? Good practice? Up to the PIC I guess, and each case on it's merits. And yes, some DGAs are track specific - they would require a different plan of attack, but the majority that I see are the "all tracks to ......" variety.

It's worth a thought...

AHEM So the OP's question has been answered, but has anyone answered Mr Flappy's question (post #06)? It's an interesting one, and I'd like to know the answer myself...

Tmbstory - that description of the "old way" sounds like an excellent idea, no wonder it's been done away with!!

Bring on the RNAVs, runway aligned, with good GPS gear. But I guess we'll be stuck with distance predicated on the next waypoint, not distance to threshold...

CR.

[UnderneathTheRadar]

Manouvering outside the FAF

Counter-rotation

To do what you achieve is theoretically possible but causes some serious issues depending upon the location you're attempting to arrive at.

1. To achieve your aim, you are then limited to the sector MSAs that you are arcing through and at some airports this will require a much higher than optimum altitude that keeps you in the clag when you could be visual comfortably.

2. Manovering around to outside the FAF via an arc is only any good if the aligned approach you want to pick up an IAF that's somewhere near where you've manovered to. Not going to happen with the vast majority of NDBs and quite a few VOR approaches.

From some of the places I suspect Owen has experience of, issue 1 is a significant one....

UTR.

[43Inches]

AHEM So the OP's question has been answered, but has anyone answered Mr Flappy's question (post #06)? It's an interesting one, and I'd like to know the answer myself...

So, in the scenario that you conduct an instrument approach and get visual at a height of 800' AGL with a visability of more than 5km, you are in VMC.
My question is, how can you legally join the circuit?

You must follow the rules of CAR 166 (operations in the vicinity of non-controlled aerodromes). That is join on upwind, crosswind or downwind or conform with the straight in approach requirement. Only in IMC and if the approach will not facilitate joining the circuit appropriatly may you fly an alternative path.

800AGL is below normal circuit height but all circuit heights are recommended only.

Do you disregard the AWIS altogether and commence an instrument approach everytime? Do you only do the D/G arrival if it's 8/8ths black and no white fluffy stuff? (pretty dificult to work out most of the time) Do you only do the D/G arrival if it's closely runway aligned?

This is an exercise in local knowledge, example; if the area is non-coastal and fairly flat the cloud base and conditions near a field will be consistant (usually), AWS indications are generally reliable. If you have a coastal port with terrain then the cloud indicated may only be accurate within half a mile and subject to rapid change. An AWS only gives you a snapshot of the weather at the station and directly above, use it in conjunction with the forecasts and local knowledge, I would never disregard it.

[Tmbstory]

The old way!

Countre - rotation:

Re your post no: 20, thanks for the comment, it did work quite well.and kept you in a reasonably small area.

Regards

Tmb

[Tee Emm]

If the MDA is above circuit height descent will commence on downwind and a normal base and final is encouraged (using normal bank angles and rate of descent). If the MDA is less than circuit height then maintain the MDA until on base, intercept your

In each example in the discussion we are assuming night circling where you are unable to confirm the actual height of the aircraft above the terrain simply because it is hard to see the actual ground at night immediately below you.

That being so, how come it is considered perfectly safe to disregard the published circling MDA on downwind or base or both and so descend to suit the aircraft type profile but clearly not safe to descend below the circling MDA if it less than circuit height. Either way you have busted the published circling MDA before being established on final lined up with the runway.

The circling MDA has been determined by the chart designers taking into account local terrain. Day time no problem where you can see the ground around you - different thing altogether when you can't. The chart designers are not interested in the normal circuit height of your aircraft type whether it is a A380, 747 or Chieftain.
They are interested in your circling airspeed in order to survey for terrain that could affect the MDA. For example Canberra has a relatively high circling MDA due nearby terrain. The fact that MDA happens to be appreciably above a normal circuit height of 1000 ft for lighties to 1500 ft for jets matters not one iota to the chart designer. If the designer has calculated the MDA to allow safe legal obstacle clearance and it bothers the pilot because it is higher than suits his circuit - then stiff.

Of course, familiarity with the aerodrome area is needed as part of the preparation for a possible circle to land. But make sure at night the published MDA is burned into your brain and never descend below it until within the final approach splay. If that puts you too high on slope on final to ensure a stabilised approach then again - stiff. Divert somewhere else.