Circling below circling MDA at night.

[cjam]

MANGO and Will,

I don't have those books available to me at the mo 'cause I am not flying in Ausi. It seems to me that you guys are trying to figure out what to do by reading the books and then doing exactly as it says. If I am off the mark and you guys have plenty of night approaches under your belt/s then I appologise. If I am right, then I reckon you should not so much read the book and only do as it says, you should look at all the different means of ensuring you don't run into a hill or a chimney etc while trying to get from LSALT to the runway......as well as read the book. Does it specifically say that you cant do it? Nah.
If you are not on an instrument approach then use everything available to you to keep you above obstacles and at the same time avoid high rates of descent when you're low.
If a plane going 160kts is clear of obstacles at 1900 ft within 4.2nm , then a plane doing 120kts will be too.
Keep an eye out for 'no circling ' areas on the maps.

Cheers

P.S.

I\'ll be in for the group hug but only if it is not rhythmic.

[Will Robinson]

Cjam

I do have a fair number of black night approaches under my belt(not sure i should say that around here) and I have to point out to people all the time exactly what you are saying, think about the best way to get to the runway before you get there, wether that is an instament approach even though it's VMC, a dme decent untill in the circling area or a visual approach into the circuit as all have their advantages and disadvatages. Their are some peculiareties to aus rules so some may be different to were you are, but most are there for a good reason. Reading your books and knowing these rules will lead hopefully you to the best decision under your current conditions. A good example is the question given about a visual aproach without having commenced an instument approach, you can only start your decent from msa/lsalt within 3 nm and then the aircraft must be flown to the vfr and that means not lower than 500ft above obstacles and 5000m vis on a vfr plan but if on an ifr plan it would be the circling area and it's obstacle clearance. That ifr chart you have with you is not so flash when it comes to obstacles and terrain so if you at least start an aproach it will be taking you on an initialy safe path untill you discontinue. If your flying in flat terrain and you are familiar with the airports then there is the temptation to cut a few corners and save a few dollars, but when you have the tea and bikies session with casa or th cp after you have been reported by your fo or another aircraft/person then it won't be worth it, that was if you missed that hill that wasn't marked as a spot height as the instrument approach chart you looked at to get your heights because the designers didnt consider it to be a main hazard to an aircraft that was doing an approach.

Having said all that I am certainly not having a go at you or anyone else, just putting my view out their.

Cheers

Will.

ps. In the aircraft I fly we can fly cat C. circling even though its cat B. just to get a bit more room and maintain more speed and this will on ocasions make a visual circling aproach a lot easier wile remaining within the rules.

[Howard Hughes]

you can only start your decent from msa/lsalt within 3 nm

Gidday Will, is this not 5nm?

Cheers, HH.

ok:

PS: DANGER, Will Robinson, DANGER....

[Will Robinson]

Hi Howard

I think you will find that 5nm is the size of the ctaf and 3nm is the NVFR circling area based on the aerodrome reference point. Our rules are complex and it's hard to find things at times and sometimes you may find somthing that semms contradictory, so there maybe something I have missed as I havn't flown to the VFR for years. A reference i can give is jep a.t.c. page au601 section 1.4.2 para c & d.

Cheers

Will.

ps. the last time someone said "DANGER Will Robinson " to me it was Woomera.

[Victor India]

Night Circling

It's been good to read all of the different ideas and understanding of the rules. I have what I consider a reasonable degree of experience flying night approaches under the VFR and the IFR in aircraft ranging from piston single to heavy multi-engine turboprop to twin engine jet.

The ideas I'm voicing here pertain particularly to the IFR Night Circling Approach (for example after becoming visual off an NDB or a DME arrival).

There have been various comments regarding the point at which descent below MDA is commenced, and the subsequent terrain clearance requirements. Without wanting to rub people's noses in it, I'll need to reiterate a couple of references from AIP...

ENR 1.5 para 1.7.2 states that the spot heights on IAL charts do not necessarily indicate all obstacles or the highest obstacles in the circling area. It also 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".

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" (deep breath!!!)

The main opinion which I'd like to voice is based on the red bits above. Just because you have circled on the correct side of the field (away from any published no-circling areas) does not mean you can assume a normal base turn point, base ground track and glidepath will keep you clear of obstacles. The rule says you must maintain at least the minimum obstacle clearance (300' Cat A/B or 400' Cat C) until on final. To do this, you MUST have studied a topo (as is clearly stated in para 1.7.2 above), imagined where your downwind/base flightpath lies and had a think about how you will maintain this clearance until on final. If it means flying a modified ground track or glide path until on final, then do that (within limitations of the aircraft type). A standard base turn will not ALWAYS work.

An example is a right hand circuit to runway 17 at Canberra (there is a "no circling" restriction outside 4nm west but many Cat C aircraft operate normal circuits inside 4nm). Trying to fly a standard profile in almost any aircraft without regard for Mt Ainslie and Mt Majura (both clearly marked on the VTC) would be suicidal. Clearly preferable to fly a left hand circuit but a right hand circuit is possible and requires particular awareness of the terrain even though not included in the "no-circling" area.

Lots of words I know but any more comments?

[cjam]

WILL:

Mate that sounds like a silly rule to me....you bloody ausi's I don't know.(jokes).....so let me get this straight, if I was in a barron on a nice clear (very black) night approaching an airport on a vfr plan I would have to wait until 3nm before descending....but I could do another approach exactly the same later that evening except that I am on an IFR plan and so now what? I can descend at 2.66nm or 3 or 4.2? It all sounds like poppy-cock to me, too confusing. If there are no 'no circling' areas I think I will start my descent at 4.2nm. Next thing you are going to try to tell me you cant join straight in and have to do three legs of the circuit or something equally crazy.....

[Howard Hughes]

Thanks Will,

I stand corrected, you are indeed right. It's amazing what you forget when you don't use it!

I think where I was getting confused is Jepp AU-706 1.9.9.5

until the aircraft is:

within 5nm (7nm for a runway equiped with an ILS) of the aerodrome, aligned with the runway centreline and established on the T-VASIS or PAPI.......etc, etc.

This is the procedure that I use if I have not conducted an instrument approach.

Cheers, HH.

[Will Robinson]

Victor India

Spot on and its good to have those AIP referances for people without jepps

cjam

Yep youv'e just about sumed it up and your gess was right. As Howard says in his next post, straight in approach will require the t-vasi or papi.. ect.

Howard

No worries mate. These questions realy had me thinking too and I have only just completed a renewal with a night sector to a strip that verry much reflects the strips in question (msa/lsalt above circuit alt with a visual approach, remote area) and I still had to really search.

Cheers again

Will.

[Mango]

Ok, I am interested to see what people say about the following.

Since Canberra is a good CFIT scenario lets use that. Sorry cjam cant include you in this

Say you are flying Sydney-Canberra via SHELLYS (V175) CAT B on a clear night landing on runway 35. LSALT=4900' MSA25nm=4500' but does change depending on your radial (check the plate) MSA10nm=5100nm. To be honest I would track from D20/CB to the IAF via the 13nm arc for an ILS just to be on the safe side every time.

But for the purpose of this topic lets say ATC has gone home, the noise abatement procedures were void and its visual. What would you do to get to runway 35? What hight would you fly at? When would you start descent in the circling area? keeping in mind this topic.

[cjam]

aarrggh MANGO!!!!
Thats simply not fair! I wanna play too. I'm guessing a radar derived dme sector arrival with a half double decaffinated haf caf....close?

[Victor India]

Mango,

I agree – an ILS would be my preference if there is no rush. A night circling approach increases your chances of having a CFIT accident hugely.

If for some reason the ILS is not an option, I would (since you set the scene as a visual night) plan a Night Visual Approach in accordance with those rules in AIP ENR 1.1 para 11.5.5. I have assumed that we’re flying under IFR and that accurate QNH is available from the AWIS. Once inside the circling area (which is pretty much where the visual approach rules leave us), I apply IFR circling rules in accordance with ENR 1.5 para 1.7.2 and 1.7.3.

Descent Profile:

I’d try to plan a continuous descent from the cruising level if possible, being aware of the following descent limitations:

Not below 4900’AMSL (V175 LSALT) until 25DME CB, then
Not below 4500’AMSL (CB 25NM MSA) until the Cat B cirlcing area, ie
2.66nm from the threshold of RW17, then
Not below 3250’AMSL (Cat B circling MDA) until that point on downwind, base or
final which a continuous descent can be made (see my previous post)…

Since the VOR/DME is 0.5 nm north of the RW17 threshold, fixing inside 2.66nm wouldn’t be too hard. 1.9 DME on the 031 radial (V175) would be safely inside Cat B circling. Refer to the airfield diagram if required.

Tracking:

I’d maintain V175 inbound until within the Cat B circling area, then turn left as required to join downwind then fly a right hand circling approach as required by ENR 1.5 para 1.7.3 d). Alternatively, keeping in mind that we should fly a left circuit when it’s MBZ, overfly for a left hand circling approach.

Not that you’d need it in this case, but if the 25nm MSA was a lot higher and/or the descent profile inside the Cat B circling area was too steep, I’d consider stepping down using the Cat C circling area and MDA at about 3.6DME (4.2nm RW17). I know it’s safe but you need to be happy the that the visual approach rule can be interpreted this way before you do it in a Cat B aircraft.

Hope this helps.

VI

[Will Robinson]

Mango

Exelent question.

the ILS would always be my prefered option followed by the next most accurate approach at night before considering a visual approach in such a high cfit situation, but for the purpose of your question i'll consider a visual approach, cat b, ifr plan.

decend on v175 from shellys to 5100' and go for a right downwind within the circling area of 2.66nm, probably around 2nm at aprox 1nm befor the threshhold of 35 start a decent around 600fpm and this should place me abeam disaster hill at aprox 2600' wich is above the sugested limit of 2400' from there it should still be a 600fpm rod to the threshold with a normal turn onto final.

I have no topo charts of this area and i am totaly unfamiliar with it so I have based my reasoning on the 2nm distance that the dme is from 35 threshholdand, the 4nm circling restriction to the west, the noted terrain and the circling area design based on 2.66nm limt from 35 threshold. If i did a left downwind there is high spotheights depicted as well but if you were at the limit of the circling area you would be at 4.66nm and in the no circling area so it dosn't seem as safe.

Ok thats me done but you seem to have some local knoledge Mango so you may want to fill us in later how it's done down there.

Will.

[Centaurus]

Question for the experts. Scenario No 1. Black night circling approach. Circling MDA 1200 ft agl. Position of critical obstacle unknown except by Air Services chart designer. AIP states you are authorised to commence descent in order to achieve typically a three degree profile from say downwind leg. You leave the MDA mid downwind to follow the three degree profile as per AIP ENR. AS you turn base on three degrees profile you are now 400 ft below the circling MDA but nicely on profile using visual judgement only.

Next scenario - same airport - same MDA - black night etc. You are in and out of cloud downwind and decide to descend below the circling MDA by 300 ft or more in order to maintain visual with runway. No vertical visibility in either case because it's dark. As you turn base you notice that your position is now exactly on the same profile as Scenario No 1. Handy coincidence which is nice.

Is Scenario No 2 safe and legal? If not, why not? Good instrument rating question, maybe?

[Will Robinson]

Centaurus

I would say case 2 is not ok as you will breach the requirement that by night you do no decend below mda unless you can maintain visability along the intended flight path as at the mda you are in and out of cloud and therefor cannot decend any further.

Will.

[OzExpat]

In and out of cloud while circling? According to Pans Ops, circling is called "visual manoeuvring". The MOC for circling by each aircraft category is intended to provide comfortable clearance above obstacles, especially during turns where - of course - one wing tip will be lower than the rest of the aeroplane and therefore potentially closer to the critical obstacle.

[Will Robinson]

Oz Expat

yes your right OZ, I neglected to ad to the end of my post that a missed approach would have to be carried out.

[cjam]

Scenario one sounds good although I don't agree with the
"nicely on profile using visual judgement only" bit. You said it was a black night circling approach, I would use visual judgement only to gauge where I am in the circuit, profile information would come soley from instruments. I would leave 1200ft agl at the end of the downwind and be fully established on finals by 600ft or nail the papis if they are there keeping a close eye on ROD the whole time ie dividing groundspeed by two method.
Scenario two I would take to warrent a missed approach climbing turn towards the runway. If you are in and out of cloud you are obviously losing sight of the runway and ground etc therefore MAP applies. Also with scenario two you are throwing your obs clearance out the window by descending lower than a normal profile....you should maintain MDA until intersection of the normal profile. In this case about three quarters of the way down downwind leg.
Good instrument rating question? Definately, I think discussing this sort of scenario with students will actually get them thinking about how they are going to stay in one piece instead of regurgitating rote learned bollacks.
I think this sort of thread is where pprune excells. I welcome as much constructive critisism of my posts on this as possible....hopefully might learn something. still waiting for that group hug HH....half way through a tray and it's starting to look good!

[Centaurus]

The flight paths as described in the question both coincided in a base leg turn at 400 ft below the circling MDA except that in the first scenario the aircraft left the MDA on the downwind leg in order to meet the desired visual profile for landing.

Scenario 2 also descended below the MDA downwind but for a different reason - and that was to maintain visual reference with the runway. Once the pilot left the MDA downwind (black night, runway in sight, but unable to positively maintain Cat C 400 ft terrain clearance due black night), he entered the danger zone where he became responsible for his own terrain clearance.

Both scenarios were equally dangerous in that both aircraft deliberately ignored the MDA by descending prematurely downwind, but for different reasons. Although the aircraft in Scenario No 1 was fully visual with the runway on the downwind leg, he still delberately elected to operate below the circling MDA downwind and on base. Remember the initial picture was that both aircraft were 400 ft below the MDA turning base and therefore unprotected by the Air Services published MDA of 1200 ft.

Of course, as someone quite rightly pointed out, No 2 aircraft should not have descended below the MDA downwind in order to maintain visual contact with the runway. Once it was clear he was in and out of cloud at the MDA he should make a missed approach.

Yet it seems it is quite OK for aircraft No 1 to do exactly the same descent below the MDA as No 2 aircraft, but in this case to meet a desired descent profile as authorised in AIP.

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.

During the conduct of a night circling approach where visual judgment of height above terrain immediately below the aircraft is not possible, then adherence to the circling MDA or above, is absolutely vital.

Only when the aircraft is aligned with the landing runway should descent below the MDA be contemplated. If this is not possible due to unacceptable excessive descent angle on final then an alternative approach procedure should be made. If that is not available then the pilot should not land.

Pilots should be aware that the wording in the AIP in regard to circling approach MDA and descent below the MDA to meet a desired aircraft profile can be misleading. What is not misleading, and in fact is crystal clear, is the published requirement at AIP ENR 1.5-3, to "maintain 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". And if you cannot see the terrain you are over, then you have no business descending below MDA downwind or base in order to set up a nice descent profile. All this is about circling approaches at night. Daytime is entirely different, where you can see the ground you are flying over.

[Will Robinson]

Centaurus

I would sugest that if you could not make an approach from the mda using the methodes setout in the regs then the designers would have put restrictions on the charts,ie- no circling ect.

I do agree although that when you go into a strip for the first time at night that it realy keeps you thinking and hoping you've got it right. The worst is probably a remote strip with no moon or background lights and kerro burners

Will.

[Centaurus]

I suppose the key to a safe circling approach at night is to accept that the chart designer has done all he can in this respect by publishing the circling MDA.

If the pilot in his wisdom(?) decides that the MDA is for wimps and the object of the exercise is to get the aircraft on the deck, then the next person in the equation is the ATSB to investigate the wreckage. The Chieftain accident in Young, NSW was a classic example. The pilot there steadily descended below the night circling MDA on downwind and base and ended up in a ball of flame. He thought he was safe.