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When/Where you could descend below IFR circling height?

For actual landing, specifically on IFR circling (MVL/VPT/MVI), there is a hard min height that one can stay above but when one can start the descent to land?
My understand one base leg to final as one lands but is there a specific place?

For inbound leg, I guess one can still ask to fly straight-in to MDH height minima then to MAPt, to closely inspect runway and windsock and get comfortable with weather then go missed, then come back to fly 2nd approach to MVL height minima for circling? does this need an extra clearance? view it as dry run, if you can’t pull a straight-in down to 200ft and go missed, don’t expect you can circle at 400ft, let alone go missed from it !

AFAIK, the UK used to allow one do exactly this but on single approach, you descend on straight-in MDH on IAP down to MDH height before climbing to MVL height at MAPt, then circling

The question for IFR only, let’s put aside how low and tight one can make "VFR circuit”, this has been debated and the answer depends if you are doing precautionary landing on unprepared strips in Botswana (50ft agl?) or circuits around some calm village in some valley Switzerland (1500ft agl?), obviously, one can cancel IFR CTL and fly as tight & low VFR/SVFR circuit but they lose missed approach, alternate and obstacles protections…and in controlled class D aerodrome, they will get sucked into a “black-hole” if ceiling is less than 1500ft/600ft due to compilation errors !

Paris/Essex, France/UK, United Kingdom

Before ASOS/AWOS was ubiquitous in the US, I would sometimes use the circling MDA to overfly the airport, look at the wind sock, and chose which runway to use for landing. Circling did not restrict me to only go around the pattern once, but if I missed the approach, I would need a new approach clearance.

KUZA, United States

A circling approach (which is a procedure under IFR) is supposed to be flown at the published circling height, or higher, and any descent below that is obviously legal under the takeoff or landing exemption.

Whether you can descend below the circling height if you are not landing, is a question like this French law? That then led to this thread which is not necessarily in the IFR context, again due to the takeoff/landing exemption.

Administrator
Shoreham EGKA, United Kingdom

NCYankee wrote:

Before ASOS/AWOS was ubiquitous in the US, I would sometimes use the circling MDA to overfly the airport

Thanks, I was referring to doing a descent on instrument runway axis to the straight-in MDA1 (say 200ft on ILS runway) bellow the circling MDA2 (say 400ft on non-LOC runway), say you are visual at both MDA1 & MD2, then you have a closer look before going back to MAPt at MDA2 to fly over the axis, circle or go missed (I guess after this needs 2nd approach clearance)

That should always stay in the “protected areas”? does it need an explicit clearance?

Last Edited by Ibra at 16 Nov 14:20
Paris/Essex, France/UK, United Kingdom

Peter wrote:

Whether you can descend below the circling height if you are not landing,

More where does circling height apply after MAPt? or before MAPt? on runway axis?

I am sure,
- You can’t go bellow circling height minima away from runway axis after MAPt
- You can go bellow circling minima to straigh-in minima before MAPt (say flying ILS down to 200ft with tailwind followed by missed)
- You gotta land on opposite runway at some point?

Paris/Essex, France/UK, United Kingdom

For the last point, I looked online, it seems even heavy metal don’t have a single criteria for descent to touchdown from MDA(H)

I would love to know what you declare visual – in the latter case the crew become fully responsible for terrain avoidance means in B747 IFR CTL context? seems naughty

https://www.ukfsc.co.uk/files/External%20Meetings/EAC%20Discussion%20Paper%20Circling%20approach%20March%202011.pdf

Based on the received responses it may be concluded that there is no common understanding on when the crew can commence descent to touchdown from MDA(H). Here are some of the interpretations:

•Only when visual contact can be maintained and on the middle of the base leg, never earlier.

•Within 30 degrees from the final approach track

•This depends on whether visual or have achieved circling criteria. This is interpreted that you cannot descend below Circling Minima until you intercept the nominal approach angle, or you declare visual – in the latter case the crew become fully responsible for terrain avoidance.

•If the Circling minima are high (above 1500ft AAL – normal basic training circuit altitude) some operators ask crews to ensure that the aircraft remain within the protected area at all times. To achieve this it may mean descending before the base turn is commenced to ensure a normal descent angle to landing. Before leaving MDA certain criteria must be met. Ideally the RWY environment should be visual at every stage of the descent but practically this may not always be the case, particularly if the MDA is high or there is a prescribed track associated with the circling manoeuvre. The really important point is that we must assure ourselves that the predicted flight path of the aircraft will remain in a clear area at all times with regard to both weather and obstacles before a descent is commenced.

•The crew must maintain the MDA until the runway threshold has been positively identified by the PF and that a normal FPA can be achieved to land in the TDZ, a steep or a flat descent should not be attempted, if at any stage the visual cues of the runway are lost, a missed approach should be initiated

•Generally, crew should stay at circling MDA/ H until necessary for approach and landing; this is often on base leg. This is based on the height of MDA and the interception of a normal glide path.

•Fly at circling minima (AP and AT engaged) all the way to the end of the downwind leg and commence descent when turning bas.•Landing threshold acquired by PF and the aircraft is in a position to carry out a landing.

•It is important that the descent is to be made in a way to allow for a stabilized approach.

•Some operators require that the MDA be maintained until the aircraft has manoeuvred to within a 300-degree angle of the extended runway centreline

Last Edited by Ibra at 16 Nov 15:15
Paris/Essex, France/UK, United Kingdom

In FAA land, this is the requirement:

(c) Operation below DA/DH or MDA. Except as provided in § 91.176 of this chapter, where a DA/DH or MDA is applicable, no pilot may operate an aircraft, except a military aircraft of the United States, below the authorized MDA or continue an approach below the authorized DA/DH unless –
(1) The aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers, and for operations conducted under part 121 or part 135 unless that descent rate will allow touchdown to occur within the touchdown zone of the runway of intended landing;
(2) The flight visibility is not less than the visibility prescribed in the standard instrument approach being used; and
(3) Except for a Category II or Category III approach where any necessary visual reference requirements are specified by the Administrator, at least one of the following visual references for the intended runway is distinctly visible and identifiable to the pilot:
(i) The approach light system, except that the pilot may not descend below 100 feet above the touchdown zone elevation using the approach lights as a reference unless the red terminating bars or the red side row bars are also distinctly visible and identifiable.
(ii) The threshold.
(iii) The threshold markings.
(iv) The threshold lights.
(v) The runway end identifier lights.
(vi) The visual glideslope indicator.
(vii) The touchdown zone or touchdown zone markings.
(viii) The touchdown zone lights.
(ix) The runway or runway markings.
(x) The runway lights.

You can’t descend below the circling MDA down to a lower MDA/DA and then climb back up to circle. There is no specific point required to make the descent to the runway on the circle maneuver except that “The aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers, and for operations conducted under part 121 or part 135 unless that descent rate will allow touchdown to occur within the touchdown zone of the runway of intended landing”. A circling maneuver can be made at a circling altitude at or above the applicable MDA, so if one is circling at pattern altitude, the point that one would initiate the descent to the runway would be different than if circling at the MDA was half the normal pattern altitude. In the first instance, one might begin descent abeam the numbers and in the second case, it might be after established on a base or final leg. There is no one size fits all.

KUZA, United States

Also, at a towered airport, ATC must authorize the CTL, whereas at a non towered airport, it is pilot discretion.

KUZA, United States

I’m not sure I totally understand the question but I think what NCYankee describes is similar in France
Runway 07 is in use let’s say. Runway 25 has an ILS approach. 07 has no IAP or has a GNSS procedure but RAIM is not available.
You fly the ILS approach and at the MDA for the circling approach or above you assess visual on field you break for the circling approach maintaining MDA or above. If its an MVL there is protection for what would be considered a normal Visual circuit. If its an MVI/VPT then you follow a designated visual circuit.
Descending to land is as you would do VFR eg if the circle to land is 500ft AAL you might delay your descent until you turn final. If circle to land is above 500’ AAL you might descend in base so that you turn final as you would normally do, around 500ft AAL.
A circle to land is different to a VFR circuit in that the VFR circuit is normally left handed or right handed and marked as such on the VAC chart whereas unless it says something else on IAC chart or is a VPT the circle to land can be left or right, pilot’s choice.
The difference comes when you need circling to land to meet the requirements of a non towered non ATS field and the runway in use is the same as that for a straight in approach.
Here again you follow the procedure for the straight in approach but you need to fly down the runway to determine wind direction, possible obstacles, wild boar on runway, or a bull (as at Propriano a few years ago, I assume that the spirit of the law would say that you overfly the runway at circle to land minima or above. However, I have seen military officer and VIP carrying aircraft flying down the runway following an ILS approach to minima 200ft AAL and then pulling up to circle to land altitude for the circuit and landing. Whether this is legal or not I do not know, but then there’s no-one in the tower to report them anyway. Of there was they would have made a straight in landing.:)

France

Ibra wrote:

For actual landing, specifically on IFR circling (MVL/VPT/MVI), there is a hard min height that one can stay above but when one can start the descent to land?
My understand one base leg to final as one lands but is there a specific place?

PANS-OPS doesn’t specify a particular place for circling. This is what it says:

Descent below MDA/H should not be made until:
a) required visual reference has been established and can be maintained throughout the manoeuvre;
b) the pilot has the landing threshold in sight; and
c) the required obstacle clearance can be maintained and the aircraft is in a position to carry out a landing using normal rates of descent and angles of bank

Last Edited by Airborne_Again at 16 Nov 15:56
ESKC (Uppsala/Sundbro), Sweden
55 Posts
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