Circling area extravaganza!

[Hold_Short]

It's incredible just how these rules are made regulations.

Can someone high up somewhere tell me how they came up with the circling area limitations? For a CAT B aircraft, 2.66nm radii centred about each USABLE runway? Why don't they keep it simple stupid? I can't see how useful this random figure is and how to practically is.

Is a round number like 3 nm not practical? I'm all ears

[Jack Ranga]

I'm with ya. I found it very difficult to keep a Cheiftain in that area. Make the area bigger and it potentially has more terrain in it though I suppose. Individual cases might be yes, might be no?

In the end I wouldn't manoeuvre in circling areas at night, I'd fly an approach that wouldn't require it. Bit tough if there's no approach that didn't accommodate this though.

[Trent 972]

ICAO Doc 8168 2005 amendment 14 (http://www.icao.int/icaonet/dcs/8168/8168_v1_5ed_amend_14_advanced.pdf) (about 5 meg download!!!)
Chapter 7 contains the data you're looking for.

The visual manoeuvring (circling) area
The visual manoeuvring area for a circling approach is determined by drawing arcs centred on each runway threshold
and joining those arcs with tangent lines (see Figure I-4-7-1). The radius of the arcs is related to:

a)aircraft category;

b)speed: speed for each category in Chapter 1, 1.3.5;

c)wind speed: 46 km/h (25 kt) throughout the turn; and

d)bank angle: 20° average or 3° per second, whichever requires less bank.


Note.— See Tables I-4-7-1 and I-4-7-2, and Figure I-4-7-1.


All the tables and assumptions regarding application of default winds/spiral winds etc. are explained.
Good Luck with your reading.

[Trent 972]

Hold Short
Is a round number like 3 nm not practical? I'm all ears
Funnily enough, before we became all caught up in ICAO compliance the circling area was 3nm.
Flight Saferty Australia did a good article on circling about 10 years ago. You can find it here (http://www.casa.gov.au/wcmswr/_assets/main/fsa/2001/sep/34-39.pdf).

[Captain Nomad]

Is a round number like 3 nm not practical? I'm all ears

Funnily enough, before we became all caught up in ICAO compliance the circling area was 3nm.


It still is 3nm for aerodromes without an instrument approach procedure.

[FGD135]

As Trent 972 has pointed out, the dimensions of the circling areas are based on the amount of airspace that aircraft will use when making turns (at those standard speeds and rate of turn).


In the end I wouldn't manoeuvre in circling areas at night

If making a night visual approach, you can use the circling area of a higher category to give you more room. Instead of 2.66 NM, you can use the Cat D circling area, which is a more spacious 5.3 NM.

In which case, of course, you would need to observe the different obstacle clearance requirements of that larger area.

[Trent 972]

Apologies Nomad, of course you are correct in saying that the Night VFR circling area is 3nm. I however assumed that we were talking about the IFR seeing as HS mentioned 2.66nm.

[Captain Nomad]

Trent 972,

Jepp AU pg 601 1.4.2 "An aircraft operating under IFR by night having a MTOW not greater than 5700kg may be planned to a destination not served by a radio navigation aid or not having an approved instrument approach procedure, subject to the following requirements:

...c. Descent below LSALT for the route sector to be flown must not be commenced until the aircraft is positively fixed within 3 NM of the destination aerodrome and the aerodrome lighting has been visually identified. Subsequent maneuvering for descent and landing must be in VMC and confined within 3 NM of the destination aerodrome while operating below the LSALT;"

Point 'd' is also important - the pilot is responsible for ensuring that he/she is familiar with obstacles within that 3 NM and maneuvers appropriately (ie. no published 'no circling' areas - you have to figure that out yourself).

[Trent 972]

Nomad, I accept your Jepp references, but I don't have a copy with me atm. I do however have the Aus AIP and on this matter they say

Tracking Requirements. Tracking requirements for a visual approach include the following:
a. A pilot in command must maintain track/heading on the route progressively authorised by ATC until:
(1) by day, within 5NM of the aerodrome; or
(2) by night,
- for an IFR flight, within the prescribed circling area; or
- for a VFR flight, within 3NM of the aerodrome; and
- the aerodrome is in sight.
b. From this position the circuit must be joined as directed by ATC for an approach to the nominated runway.
12.8.5 Minimum Altitude Requirements. During the conduct of a visual approach, a pilot must descend as necessary to:
a. by day:
(1) for an IFR flight, remain not less than 500FT above the lower limit of the CTA; and
(2) for IFR and VFR flights, operate not below the lowest altitude permissible for VFR flight (CAR 157).

b. by night:
(1) for an IFR flight:
- maintain an altitude not less than the route segment LSALT/MSA or the appropriate step of the DME/‐ GPS Arrival procedure, or 500FT above the lower limit of the CTA, if this is higher; or
- if receiving an ATS surveillance service, operate not below the last assigned altitude;
until the aircraft is:
- within the prescribed circling area for the category of aircraft or a higher category, where the limitations of the higher category are complied with, and the aerodrome is in sight; or
- within 5NM (7NM for a runway equipped with an ILS) of the aerodrome, aligned with the runway centreline and established not below “on slope” on the T‐VASIS or PAPI; or
- within 10NM (14NM for Runways 16L and 34L at Sydney) of the aerodrome, established not below the ILS glide path with less than full scale azimuth deflection.
(2) for a VFR flight:
- maintain not less than the lowest altitude permissible for VFR flight (CAR 174B) until the aircraft is within 3NM of the aerodrome and the aerodrome is in sight.

I would contend that your Jepp reference requires VMC to be maintained ie. (at) night NVFR to be applied for aerodromes without an INST approach.
IFR circling, within the visual requirements, (not requiring VMC) can be applied (INST Approach required).
I know what you say is correct but the original poster HS was asking as to where the differing (IFR) circling areas originated from.
Your horse is running in a different race.

[Centaurus]

The night circling approach is where you need to keep your wits about you. The diagrams in Jepps and AIP can lead you into a trap especially where the circling MDA is higher than a normal circuit height. Canberra is an example.

The rules state you can descend below the circling MDA at night on downwind or base leg if that is necessary to maintain the normal aircraft descent profile. In other words it infers the circling MDA is breakable at your discretion simply to get in without a relatively high rate of descent for your aircraft type.

The small print says that if you choose to break the circling MDA then you must be confident of terrain clearance. In other words the pilot becomes entirely responsible for his own terrain clearance. The authorities have done their bit in providing you with a safe circling MDA. Below that it becomes your problem. That is sometimes difficult if you cannot judge your immediate height above terrain at night.

Unless familiar with the local terrain, it is safer to stay at the published circling MDA at night until within the approach splay. AIP warn that VASIS is designed to be available for glide slope guidance on base leg at night but that obstacle clearance is not guaranteed until inside the approach splay. If all this places you too high for a safe angle of approach then simply don't try to land on that runway.

[Captain Nomad]

Mate, I don't know about any horses or races but you are right (and so am I)! :} In reference to HS' original post, I was simply highlighting a case where 3 NM still applies as a circling area and it IS applicable to IFR (although essentially the same as NVFR). There are no variable circling area dimensions for IFR performance categories at an aerodrome without an instrument approach procedure.

Your original post very well explains the question of origins for aerodromes WITH an instrument approach procedure and the circling area distances derived from performance categories! :ok:

[aussie027]

Hold short,
If I remember correctly many years ago, in the 80s the circling minima obstacle clearance requirements and radii were different under the old ICAO charting criteria. They were simpler to remember being even figures etc. The current criteria came in with the newer ICAO PAN OPS 3 charting criteria.

The odd numbers for the radii of the arcs off runway ends do seem somewhat nonsensical and arbitary but are derived based on the criteria mentioned by Trent 972.
Yes the KISS principal has nothing to do with the experts charting criteria.
Going to 2 decimal points of a mile is in itself nonsensical. :rolleyes:
All distance readouts Ive ever seen go to 0.1 of a mile.

Totally impractical like saying based on some nav triangle calculation or 1 in 60 rule, fly a Hdg of 234.5 degrees when the instrument is only maybe accurate to +/- 3 degrees and the graduations aren't that small anyway.:ugh::rolleyes:

The main thing to remember is to stay within the distances given at the altitudes given to ensure your terrain clearance and fly smart too. If you dont think a day/night circling appch somewhere is safe under whatever conditions exist at the time then do not do it. Too many have died world wide getting this "high risk" manoeuvre wrong all in the name of "getting in".
At many places at night in particular a runway appch is the safest way to go.:ok:

[das Uber Soldat]

here we go again...

[Captain Nomad]

Another 'practical' one to add to the list: 10.3 degrees splay when calculating LSALT to/from an aid location. I don't know about you but it would take a pretty sharp pencil to get that .3 degree bit spot on! :suspect:

[Feather #3]

All will be revealed in terms of "practicality" if you convert the weird circling area radii into metres.

Don't shoot the messenger; I think they're stupid too!!

G'day ;)

[chimbu warrior]

As Feather says, I think the original calculations for this were done in metres, and 2.66 nm is approximately 5000 metres.

[Trent 972]

Unfortunately (close but) not the case, as shown in AIP ENR 1.3 -1.7.3

Note 3. The circling area is determined by drawing an arc centred
on the threshold of each usable runway and joining these arcs by
tangents. The radii are 1.68NM for Category A, 2.66NM for Category
B, 4.20NM for Category C, 5.28NM for Category D and
6.94NM for Category E. Runways less than 1,000M long are not
considered usable for Categories C,D and E.
1.68NM = 3,111M
2.66NM = 4,926M
4.20NM = 7,778M
5.28NM = 9,779M
6.94NM = 12,853M.

Stupidity still wins the day!

[Fission]

Typical outcome when rules are written by lawyers. I would guess that a lawyer with (real world) pilot experience would be a rare product, though I do know they exist.

Getting them to apply themselves to rewriting the CARs, CAOs, AIP, etc would be another thing.

In the meantime, sharpen the pencils lads and ladies :E

[Hold_Short]

Last time I flew, the only way to measure 2.66nm arc centred on each useable runway would be to walk it! GPS uses distance from the selected aid or from the aerdrome reference point, ie ypph, instead of ph.

I can't see how in the air we are able to measure this distance whilst in the air?

The reason for this is because Sydney airport is about 3nm in diameter at the greatest, with the VOR at the centre of this, and my GPS gives me distance from the VOR, so I should add 1.5nm, (approximately) onto the already 2.66nm which is 4.16nm is my approximate circling area?

Do you see how stupid this is? Every airport is different...

[Capn Bloggs]

I can't see how in the air we are able to measure this distance whilst in the air?
Some boxes have waypoints for each runway threshold. Makes it easy to 1/stay in circling area and 2/work out your desired profile as you fly around base below the MDA (Centaurus:}).

[Di_Vosh]

I can't see how in the air we are able to measure this distance whilst in the air?

Get the plate out and work it out when you're doing your flight planning. The ground distances on the plates aren't very accurate but you should be able to work out a conservative distance to add to your circling area.

At most airports it wont make much of a difference, generally only 0.1 or 0.2 Nm, but at somewhere like Avalon RWY18 the extra distance is considerable.

You should also write down your crosswind and downwind headings on the plate, also work out your descent point in the circuit (for anticipated cloud level and for circling minimum cloud level).

It's suprising how often an anticipated visual circuit can turn into a circling approach at the minimum. Anyone who's flown into Devonport (Tas) when there is a NE wind will agree. The stress levels experienced by the pilot will be influenced by how much prior planning has been done.

DIVOSH!

[Captain Sand Dune]

"Prior planning"? Radical concept, that!:rolleyes:

[Di_Vosh]

CSD, so true! :E

[Howard Hughes]

"Prior planning"? Radical concept, that!:D

I think it has something to do with the radical "Airmanship' sect...;)

[ForkTailedDrKiller]

After a decade of 3.0 nm circling area limits, it has taken me many years to become comfortable with judging that 0.34 nm difference, but I think I have it nailed now! :E

Dr :8