Circling below circling MDA at night.

[Victor India]

This thread seems to spark up enormous debate and the variation in opinion probably is evidence that the current AIP rules still lack enough guidance for some readers. Nonetheless – I have no gripes with the rules as they stand and believe I am safely conducting night circling approaches (when absolutely necessary) including descent below MDA prior to reaching final.

I posted a reply on page 2 of this thread (21st Apr 01:10). I think a couple of points from that reply could do with reiteration…


Centaurus:

Re: Your reply on this thread on 20th Apr 18:47 (page 2 of this thread). You asked:

Once you leave the protected altitude which is the published circling MDA, am I right in saying you become responsible for your own terrain clearance?

Absolutely.

AIP ENR 1.5 para 1.7.2 states "Before commencing an instrument approach, pilots should familiarise themselves with the location and altitude of obstacles in the circling area by studying an appropriate topographic map".

Based on this rule, your comments immediately following your question concern me a little:

Have you got time to drag out a WAC or Military Survey chart to plot the position of the critical obstacle? Of course not.

In a later reply (22nd Apr 23:48, page 3 of this thread), you state:

Notwithstanding the provisions of the AIP with regard to intercepting a "normal" profile for the type of aircraft, in order to make a continuous descent to land from downwind, it should be clear that if this involves deliberately ignoring the MDA, the pilot does this at his (and his passengers), peril.

Well – I would tend to agree if you are going to ignore the AIP rule of making reference to a topographic map as required by para 1.7.2 above. THIS RULE IS CRITICAL TO THE SAFE CONDUCT OF NIGHT CIRCLING APPROACHES.

If a topographic map of the airfield is available, the obstacles surrounding the airfield should never be known only to the approach designer.

The approach plate is an INSTRUMENT APPROACH plate designed to safely get you to the minima (hopefully) before the MAPT. From there, the pilot needs to have done some solid homework with a topo regarding the terrain before flying a night circling approach. No – I would not expect someone to do this airborne – this is a preflight preparation task. During the approach brief, the topo can be revisited briefly to refamiliarise oneself with the orientation gained during preflight preparation. Your method of maintaining MDA until on final, whilst seeming to be on the safe and conservative side of the rules, may in some cases lead you to require a high rate of descent on final after just flying over possibly flat and featureless terrain on downwind and base. Seems a bit silly and a less safe approach overall.

Then again – if during your preflight study of the topo you had identified an obstacle under the base turn flight path which would infringe your expected glidepath by more than 300’/400’, you might choose to modify your base turn position and/or your vertical profile (rate of descent) to maintain your 300’/400’ clearance until on final when you could then use a slightly increased rate of descent early on final. I have needed to plan and fly such a modified profile on several occasions, although granted I did have the help of obstruction lighting to help me identify the obstacles.

Sorry to harp on but I feel that the need to consult a topographic map has been largely neglected by you and others on this thread.


DirectAnywhere:

Re : Your reply on this thread on the 23rd Apr at 10:36

You mention that the 300’/400’ terrain clearance requirement is inapplicable to the night case.

ENR 1.5 para 1.7.3 d) "by night or day ...intercepts a position on the downwind, base or final leg of the landing traffic pattern, and, from this position, can complete a continuous descent to the landing threshold using rates of descent and flight manoeuvres which are normal for the aircraft type and, during this descent, maintains an obstacle clearance along the flight path not less than the minimum for the aircraft performance category until the aircraft is aligned with the landing runway "

I think that the second part of Note 1 specifically mentions the obstacle clearance requirement because this is an absolute minimum anywhere in the circuit by day only. Since early descent below MDA is not allowed at night, the first part of Note 1 doesn't specifically mention the terrain clearance. I reckon both cases are still covered by para 1.7.3 d) above.

CJAM:

You requested responses from anyone regarding airfields at which a standard circuit will not work due to terrain.

Canberra is a classic. Have a look at the VTC and the RW17 VOR plate. Although there is a no-circling restriction beyond 4nm west of Canberra (I think this may be based on Black Mountain Tower), a standard circuit can be flown in almost any aircraft type inside 4nm. Inside 4nm, however, there is some very significant terrain (Mount Ainslie and Mount Majura which is probably the limiting obstacle). The circling MDA for a Cat C aircraft to RW17 is 3530’AMSL on accurate QNH (about 140’ above a 1500’AGL circuit altitude for a jet). If a standard jet circuit is flown with descent just before the base turn point (MDA 1640’AGL), not only will the 400’ obstacle clearance requirement until on final be breached, but the aircraft will probably hit Mount Majura (highest marked elevation 3036’AMSL). Modifying the base turn ground track and glidepath (within circling area and aircraft limits) is required and results in an acceptable circuit. With some local knowledge and good obstruction lighting, this can be done this at night but I would strongly discourage it without adequate obstruction lighting. Obviously, a left hand circuit is preferable. Interesting though that even if all obstruction lighting is out of service, AIP in no way removes our option to do a night circling approach. Maybe because we've all looked at a topo...

(Here's a link to the RW17 VOR for those without the plate)

www.airservices.gov.au/publications/current/dap/SCBVO01-101.PDF

CJAM : Is this what you’re after?


I am really interested to know if people think this topographic map awareness stuff is all hot air.

VI

[DirectAnywhere]

Oops, meant to delete that bit, VI. Bodgy cut and paste job from the net by me followed by putting mouth into action before brain.

As far as I'm concerned, the first part of your post hits the nail on the head.

BTW, try this link, broken link in VIs post.

CB VOR RWY 17

[cjam]

VI,

That is exactly what I am after and I don't mind admitting I am surprised that it exists. I have no charts etc for Aus but it sounds to me like there is a hill at 1100ft above aerodrome level half way along base and within a circling area. Scarey. Is it well promulgated on the approach plates ? Is a modified circuit depicted that would make you think twice before you launched into it? The last thing I brief on my approach briefs is 'terrain' and I generally look at the plate to see any spot heights etc where I am headed, would that pick it up?

That is exactly what I was asking for examples of. Thankyou.
I will take on board your advise with respect topo's and have a wee look at my circling theories.( I normally look at the toppo's for the places I go but not specifically for obs clearance within the circuit)

SWH, yeah my question was not constructed perfectly was it...what I was getting at was, are there any airports where descending WITHIN a deignated circling area, and within a normal circuit pattern, at a normal profile, will bust your obs clearance. I wasn't talking about doing a circuit in an area that isn't designated for circling. The answer is yes by the looks of things.

I can't see why the planners deignate it as a circling area to tell you the truth but I am sure there are reasons. Has anyone been caught out at Canberra?

Are there any other circling areas that have terrain within the circuit area higher than say 500ft aal?....when answering that question I think heights and MDA's etc are needed because some people get confused and list airports that have high terrain that is not in circling areas. It would be good to get them listed on here even if it is just to get an idea how common it is.

This is a good thread that a lot of people may learn from, Cheers, cjam

[Victor India]

CJAM,

I edited my earlier post today to include a link to the Canberra VOR17 on the Airservices Australia site.

As I mentioned earlier, the spot height of Mount Majura is 3036'AMSL. You can see this spot height a couple of runway lengths (approx 2.5-3nm) north of the field and just west of the extended centreline - under a normal mid base turn position (and well inside the allowable circling area).

You can also see a 3311' spot height (Black Mountain Tower) about 5nm west of the field which I believe drives the circling restriction outside 4nm.

I have checked all documents and none make mention of any special circuit procedure to be followed for right circuits onto RW17.

Another such case which comes to mind is at Townsville (YBTL). Here's the ILS RW01 plate:

http://www.airservices.gov.au/public...TLII01-102.PDF

On this plate, there is a 671'AMSL hill (Mt Louisa) on a left base for RW01 which is within the allowable circling area. Most aircraft will turn base outside or inside but not directly over this hill. There is a note in the Enroute Supplement Australia which states:

RWY01 T-VASIS use during night hours - Pilots are advised that MT Louisa can infringe approach path for left base RWY01 if aircraft is below on slope indication of the VASIS.

Interesting since we're not meant to use the VASIS for guidance during the base turn...

Also, at Wollongong (YWOL) there are multiple masts up to approx 600'AGL within the allowable circling area which can require a slightly modified base turn profile. Here's a link to the NDB plate:

http://www.airservices.gov.au/public...OLNB01-101.PDF

The Enroute Supp entry for Wollongong states that RPT or >5700kg need approval from CASA to operate there at night. There is a fair amount of terrain around (to the west), quite poor airfield lighting and dodgy PAL but I'm not sure exactly why this restriction exists.

It seems in some cases, there are notes in the Enroute Supp directly (or indirectly) indicating terrain problems in the circling area, but Canberra - the most severe in my opinion - escapes any comment. Curious.

I'll let you know if I come across others.

VI

[Centaurus]

Victor India. Funny thing about studying a topgraphical map as preparation for the possibility of a night circling approach. You are dead right it says so in the AIP. Here is the puzzling part, though. I have never ever seen pilots undergoing an instrument rating test in the simulator drag out a topo from their briefcase and pre-plot a circling approach even though the test is conducted by an airline CASA FOI.

For some reason they rely almost exclusively on the instrument approach chart circling MDA. The CASA FOI's seem happy about that.

Guess it must be too hard to read all the terrain hachures, contours and coloured tints on the topo and almost impossible to remember all that vital info off by heart. In any case I doubt if too many airline pilots with their glass cockpit whizz-bang FMC's bother about carrying a set of topos in their nav bags.

[swh]

Centaurus,

Its the operators responsibility (An operator must not permit a pilot to act in the capacity of pilot in command of an aircraft engaged in) under CAR 218/219 to esure that the PIC has " an adequate knowledge of the route to be flown, the aerodromes which are to be used and the designated alternate aerodromes, including a knowledge of:

(i) the terrain;
(ii) the seasonal meteorological conditions;
(iii) the meteorological, communication and air traffic facilities, services and procedures;
(iv)the search and rescue procedures; and
(v)the navigational facilities;
associated with the route to be flown;"

For RPT CASA approves and directs how this is done. While a PIC may not pull out a topo in flight, they might have a part of the airline which does look into this, may produce special procedures, and produce manuals for flight crews.

This brings a standard approach to looking at risks associated with each port. Any organisation that is smart would do a risk assessment to any port they go to, terrain would be just one risk factor. To suggest they dont is false.

And a common way I have seen this done is to have a policy that circling approaches should not be done where runway aligned approaches are available, i.e. have an approach allowance at dispatch time so that a runway aligned approach can be made.

[Victor India]

CAAP 178-1(1) “Non-Precision Approaches” contains some more information. It is a 20 page document which has the following blurb regarding night circling:

Why are the rules different for day and night?

At night it may not be possible to maintain visual clearance from obstacles even if those obstacles are lit or shown on instrument approach charts. For this reason the rules for circling at night require that the MDA is maintained until in a position where a normal descent can be conducted, and the aerodrome Obstacle Limitation Surfaces (OLS) are intended to enable a safe approach to be conducted in those circumstances. (Refer AIP ENR 1.5 para 1.7.2). However the responsibility for maintaining adequate obstacle clearance still remains with the pilot and caution should be exercised. Descent should not be commenced or continued until obstacles that may affect a safe visual approach from the MDA are identified or passed.

CJAM : It does state that the OLS are intended to enable a safe approach by an aircraft using a normal descent, but then covers itself by leaving the final responsibility for safe obstacle clearance with the pilot.

Centaurus : In your last reply, you said:

Here is the puzzling part, though. I have never ever seen pilots undergoing an instrument rating test in the simulator drag out a topo from their briefcase and pre-plot a circling approach even though the test is conducted by an airline CASA FOI.

I agree with you entirely in never having seen a topo in a sim or a sim briefing. I reckon the reason for this is that there is so much to get through in most of these sims that the preparation is assumed to have been done by the individual pilot, or (since we’re talking about simulators here) by the airline/operator as SWH mentioned above. In all of the circling approaches I’ve done in simulators, the emphasis in the brief has been the appropriate use of automation and flying a stabilised descent, and in most cases the aerodrome used has been on substantially flat terrain.

Given the increased reliability of engines and systems these days and the comparitavely increasing likelihood of CFIT accidents, perhaps sim training could include more focus on the operational application of these circling rules. Then again, with the world push towards straight in GNSS/RNAV style approaches with ILS glideslope style vertical guidance, hopefully these circling approaches will soon become a thing of the past.

You also stated:

Guess it must be too hard to read all the terrain hachures, contours and coloured tints on the topo and almost impossible to remember all that vital info off by heart.

Assuming that your company hasn’t looked at this (maybe you fly a corporate jet without airline style support) and you need to take responsibility, the amount of detail to be recalled in the cockpit isn’t really that great. I generally just have a look at where my intended circuit pattern will take me on the topo (VTC works OK if available), and look for any obstacles which are likely to infringe 400’ (Cat C) during my descent from MDA before I’m aligned with final. I’ll give you an example which I needed to use one night at Wollongong doing a left circuit onto RW16. Have a look at the (Sydney) VTC if you can.

Normally, I’d be rolling out on final at about 700-800’AGL. Just before that, late in the left base turn to RW16 at Wollongong, there is a 436’ mast. That’s reasonably close to breaching the 400’ clearance before I’m on final, so I look to make a simple plan to avoid this. The circling MDA is 1930’ (assuming no accurate QNH) which is 430’ above a standard jet circuit, so I’ll need to commence descent from MDA about the time I pass abeam the landing threshold of RW16. Also, I’ll extend the downwind leg just a little so that, using normal rates of descent, I can limit my descent to not below 836’ (mast height plus 400’) until on final without being left steep on final. Once on centerline (and therefore clear of the mast), I allow descent to continue. If done properly, I would not need to level off at all.

This is all done within the circling rules in AIP and guidance in the CAAP, and results in normal rates of descent and profiles being flown. It only took a couple of minutes to devise.

In reality, flying an accurate standard circuit over the 436’ mast would not infringe the 400’ clearance, but what if I got distracted? (like the Chieftain pilot at Young probably did).

Much nicer to have an awareness of the obstacles and a simple plan to avoid them than leave it to chance!

VI

[cjam]

A fair bit of time and effort gone into answering some of these questions, thanks.
I've thought about it a bit and come to the conclusion that I know all the airports that I regularly go into pretty well and am happy with the obs clearance on night circling approaches at these. The area of greatest risk for me would be a divert to an unfamiliar field. It would have to be pretty serious (ie fire) to go to an unfamiliar field, if we are doing that it will be unlucky if we have to do a circling approach ( a bit of tailwind would be preferable to time in the air), and if we do circle, again, it will be unlucky if we strike one of these fields where the OLS doesn't provide obstacle clearance. I will keep it in mind that this is a possibility though and I think that just being aware of these things is half the battle won. I've learnt a bit, cheers. cjam

[CaptainToBe]

I havent read any of the previous posts, but my memory has served me well and this should clarify it for you.

Night
you cannot descent unless youre in the circling area (dependant upon your category af aircraft). this can be extended to 5 miles if the runway has a papi or tvasi and youre not below glide slope. this can be extended to 7 miles if the tvasi or papi is on a runway that also has an ILS, this can be extended to 10 miles if you are on the ILS (visual) and not below glide slope. this can be extended to 14 miles if youre on runway 34L or 16L at YSSY. At all times you must be able to maintain sight of the ground or water (so you cant be between layers), you have to have 5km vis, and you must follow height restrictions (ie, 1000 above populated areas, 500 above non-populated areas). you must also be able to maintain the above conditions.

Day
within 30 miles of airport, be in constant sight of ground or water, follow height restrictions, 5km vis, and be able to maintain the above conditions.

Hope that helps, and i hope i didnt misread the question and look foolish by giving that answer, but if i did, then there a fun fact for you anyway.

[Centaurus]

Captain 2B. I think you are getting confused with the requirements of a visual approach at night, and a circling approach at night from an instrument approach. Two very different things.

The subject of night circling approaches is extremely well covered in Pprune Rumours and News under the heading "Air China 767 crashes in South Korea". Although the crash happened in April 2002, it evoked some very interesting discussions and has been resurrected in a couple of posts this month (May 2005).