PDA

View Full Version : Circling Minima


Eurotraveller
5th Oct 2009, 21:00
I'm sure there's a very simple explanation for this but I can't immediately think what it might be!

I've noticed that at a few airfields, circling minima for the same runway seems to vary depending on the instrument procedure you circle off.

Here's an example: at GCTS RW08, a CAT C aircraft can circle off an ILS/DME approach down to 1350ft, but off a VOR/DME approach the minima increases to 1720ft.

Most other airfields seem to have the same minima for circling regardless of the instrument procedure you fly. Is this specific to GCTS or is it something to do with the way the minima are constructed?

Intruder
5th Oct 2009, 21:44
It has to do with very complex terrain and obstacle clearance criteria. If an approached is missed from a particular place, more obstacles and/or different terrain may come into play.

Spooky 2
5th Oct 2009, 23:12
Okay, I'm going to go out on a limb and say you cannot transition from an ILS to a circling approach here in the US.:= That is unless you are using minima of 1000/3 or better for the circle. Go ahead I'm taking cover as I write this.

Capn Bloggs
6th Oct 2009, 00:46
Sounds like a load of bollocks! :) If you're visually circling in the circling area, it doesn't matter how you got there or from what angle. Obstacle clearance in it is obstacle clearance. As for missed approaches, you'd always be doing those off the end of a straight segment, not operating inside the circling area, off the approach track, in IMC, surely? if you then do go IMC, well that's a different matter.

We use PANS OPS 4, and all our circling MDAs (and vis) are the same regardless of the approach used to get into the CA. Cat C: 4.2nm radius from the runway ends, 400ft above all obstacles anywhere in the CA.

reynoldsno1
6th Oct 2009, 03:23
Circling minima are not calculated with reference to a radio navigation aid - they are based on radii from landing thresholds. They can never be less than the straight-in minima for any approach.

It sounds as though the calculated circling minima at GCTS is 1350ft, but the VOR/DME straight-in minima is 1720ft - the circling minima must therefore be raised for that approach.

galaxy flyer
6th Oct 2009, 04:13
Spooky2

That might be correct on the 1000/3 for airlines, not so much for everyone else. Technically, an circling approach ends at the MDA, so one cannot use the ILS, but must circle from the LOC approach.

GF

Capn Bloggs
6th Oct 2009, 04:45
GF,
Technically, an circling approach ends at the MDA, so one cannot use the ILS, but must circle from the LOC approach.
What's your reference for this? Our country rules certainly have no such requirement, and practically, it doesn't make sense. Why does it matter how you get to the circling area (it may even be via a radar vector)? An ILS to a circle would be safer than a LLZ as you have vertical guidance down to the MDA.

Actually, a circling approach starts at the MDA (or DA). You cannot circle in IMC. A "circling approach" is in reality a visual manoeuvre after you have completed the instrument approach.

411A
6th Oct 2009, 04:45
That might be correct on the 1000/3 for airlines....
Only some airlines.
We regularly circle with 600-2 (or charted minima, whichever is higher) with a heavy jet.

galaxy flyer
6th Oct 2009, 04:49
Cap Bloggs

Well, yes, I agree, the instrument portion of a circling approach ends at the MDA, then it is a visual maneuver. Well, I'll have to do some research, as it was an USAF technicality that was more pedantic than real. The AF Instrument Manual also stated the FAF for an ILS was GP intercept, not the charted FAF that was used for timing on the LOC.

Let me see what I can find

GF

galaxy flyer
6th Oct 2009, 05:13
Here's the quote from AF Manual 11-217 Instrument Flight Procedures, for what it is worth:

Circling procedures and techniques are not compatible with precision approach criteria, and under normal circumstances, should not be attempted. Since the MAP associated with the precision approach is determined by the pilot in terms of a DH and not a specific point along the final approach course, it becomes difficult to ascertain when to discontinue the approach if visual conditions are not encountered. Therefore, pilots should not plan to circle froma precision approach.

GF

Eurotraveller
6th Oct 2009, 08:44
reynoldsno1:

It sounds as though the calculated circling minima at GCTS is 1350ft, but the VOR/DME straight-in minima is 1720ft - the circling minima must therefore be raised for that approach.

I thought the same thing, but the straight-in minima for the VOR/DME on 08 is 950ft (3.5% missed approach gradient) or 1060ft (2.5% missed approach gradient) :confused:

9.G
6th Oct 2009, 09:19
Technically, an circling approach ends at the MDA, so one cannot use the ILS, but must circle from the LOC approach. Absolutely not dear G.F. all you have to do is to insert MDA for circling. Once on the ILS the decision to commence circle to land will be take on the MDA for C. to L. procedure.
Eurotraveller, you'll do the same for any IAP. the very much valid MDA is the one for circling approach not for VOR, ILS etc.
Cheerio. :ok:

Spooky 2
6th Oct 2009, 15:11
Take a look at this and I think it will answer most of our questions or at least mine. http://www.jeppesen.com/download/aopa/jan00aopa.pdf

I quite familair with the airlines that use the 1000/3 restriction in their ops. Saves training time and eliminates the circle from their ops, thus eliminating just one more hazard from the daily scheme of things. Not a big deal to have the restriction removed from your certificate and some airlines that use expats want to see that removed prior to getting hired.

Capn Bloggs
6th Oct 2009, 15:29
Slightly off topic but it is interesting to note the stark contrast between PANS OPS circling areas and TERPS. For cat C, they are 4.2nm and 1.7nm (from that article) respectively.

Trying to remain within 1.7nm of a runway threshold in a medium jet and do a stabilised approach from 4-500ft AGL would be very difficult with 30° AOB or less. No wonder Americans don't like doing circling approaches.:ouch:

Port Strobe
6th Oct 2009, 17:52
GF
Since the MAP associated with the precision approach is determined by the pilot in terms of a DH and not a specific point along the final approach course, it becomes difficult to ascertain when to discontinue the approach if visual conditions are not encountered

This doesn't really ring true to me. If you've not acquired suitable visual reference to continue the approach upon reaching circling minima then you go around no? Given a LPC (civvy I know but I can't think it'd be wildly different in the mil) expects the handling pilot to be able to maintain profile to not more than half scale deflection on the glide slope, and make account for a hotter than ISA day, then that pretty much defines the farthest out from the runway you could be upon reaching circling MDA. It's reasonably likely this will leave you more certain of position that any NPA, or am I missing something?

Spooky 2
6th Oct 2009, 18:04
One more factor to consider on the B777 is that once below 1500' and coupled to the ILS you need to disconnect the AP to break off or deselect the approach. Someone mentioned that the cirlce is a visual maneuver and I agree but in the case of getting down to circling mins via the ILS, you want to be sure that the missed approach for the ILS runway is compatable with the missed approach for your circle runway.

galaxy flyer
6th Oct 2009, 18:08
While I presented what about 10,000 current and unknown, to me, USAF pilots have been taught for, at least, the last 40 years, I do not have the technical understanding of the guidance. BUT, let me ask this: At point on the approach will the MA be started, assuming one never broke cloud? Upon reaching the MDA, perhaps?

GF

9.G
6th Oct 2009, 19:18
galaxy flyer, one would discontinue the IAP at the minimum for circle to land (MDA) in case the visual cues aren't acquired as much as circle to land will be discontinued and MA for the IAP in use executed should the visual reference become insufficient. To picture it, let's say ILS 27 is IAP and the conditions aren't suitable to land on 27 but for 09. 09 doesn't have a IAP thus you will fly ILS 27 to circling minima MDA and circle to land on the 09. In case you decided to discontinue the circle to land you'll have to fly MA for the ILS 27.
Cheers.:ok:

Spooky 2
6th Oct 2009, 19:22
I will quote from the B777 FCTM and I think it will answer your question at the same time.

"If a missed approach is required at any time while circling, make a climbing turn in the shortest distance toward the landing runway. This may result in a turn greater than 180 degrees to intercept the missed approach course. Continue the turn until established on a intercept heading to the missed approach course corressponding to the instrument approach that was just flown. Maintain the missed approach flap setting until close in maneuvering speed is completed".

So I believe the answer is that you would do the MAP procedure for the approach that took you to the MDA in the first place unless instructed otherwise by ATC.:ok:

411A
6th Oct 2009, 21:26
Trying to remain within 1.7nm of a runway threshold in a medium jet and do a stabilised approach from 4-500ft AGL would be very difficult with 30° AOB or less. No wonder Americans don't like doing circling approaches
Speak for yourself, Bub...:rolleyes:
On my heavy jet (category D...I don't fly medium jets, and have no desire to do so, either) we regularly circle at 600/2, without any difficulties.
IF you simply cannot do so in a category C jet...you don't belong at the pointy end.
IE: leave the flying to those that know how...even my 2000 hour First Officer can do this circling maneuver, with good results, every time.
Howsomever...IF you have a 200 hour wonder in the RHS, the Commander is supposed to know how to do these circling approaches...yes, even using TERPS.

Anyone else...baloney.
Harry Truman said it best...
'Can't stand the heat, stay out of the kitchen'.

NB.
Circling with a heavy jet during a type rating with the FAA, requires the maneuver to be completed under TERPS (read, FAA) to 600/2.
Can't do so...a pink slip is issued, forthwith...unless, your airline requires 1000/3, in which case, a circling limitation is placed on the license...VFR only.

We don't hire the latter types...and will not do so in the future.
Ever.

NB2.
We don't hire 'FMS operators/button pushers', without basic flying abilities, to do so would absolutely affect the bottom line...negatively.
And yes, we have an FMS (dual installation) the first on a wide body jet to incorporate complete LNAV/VNAV/engine thrust management, in one neat package.
It is called...a Lockheed L1011.
Thank you.

9.G
6th Oct 2009, 21:38
gotta agree with ya 411 having done it myself don't see any problems there.
If my memory serves me right one is required to complete circle to land on a clean wing as well as per TERPS for the initial type. The circle to land becomes more intriguing matter when a prescribed track comes into a play like in LIRA. :eek:

galaxy flyer
6th Oct 2009, 21:39
9.G

While we are stealing the thread, if an ILS missed approach point is the DH (A) on the course and on glide path, what would be the defined missed approach point on the ILS 27, circle to land 9, in your example? As I understand it, you would miss upon reaching MDA, on course, on glide path. I am just trying to explain the reasoning behind flying the LOC procedure to the circling MDA, rather than an ILS which does not have a MDA associated with it.

GF

Yes, I know the answer, use the MAP as defined in the LOC procedure, timing or DME, and descend on glide path to circling MDA, level off and wait for the MAP to accomplish the missed approach procedure. But, that is a rather made-up procedure, IMHO. All that is gained is a rather ineffective path to the MDA.

411A

Giving deference to the superior skills at your operation, do they have to circle OEI or with partial flap and TERPS?

9.G
6th Oct 2009, 21:50
galaxy flyer, the MAP is as per design of the IAP (you just gotta find it on the approach plate) however you if don't deem to have acquired required visual reference at the MDA for circle to land regardless of the IAP flown, you ought to go around. Hope that helps.

galaxy flyer
6th Oct 2009, 21:57
9.G

The MAP on an ILS is the DH(A), it is defined as a point in space where the DH and the 'on course,on glide path' intersect. If you fly the GS to a MDA, there will be not defined point at which to execute the missed approach procedure--you would have to make one up by combining the LOC procedure with the ILS procedure. Yes, I agree, if you cannot see the runway/airport environment, one would have to go missed, but where abouts?

GF

Spooky 2
6th Oct 2009, 22:03
GF

I must be missing something in you question? You should fly the MAP for the approach you have just used to get to the Missed Approach Point. Doesn't matter if your planning to circle when you get there or not. It's all over if you cannot see the runway environment to circle. Simply exceute the MAP for the ILS, LOC, or VOR, NDB or?

9.G
6th Oct 2009, 22:06
galaxy flyer, m looking at the very chart of the GSTC for VOR ILS/DME RWY 08 and the MA point for this approach is defined as MM. Thus you fly the VOR ILS/DME to the minima of 1350 for circling and if you go around your MAP is MM in this case. The way I see it, you hit the minimum and proceed to MM and follow the published MA. The best way is always to have a peep at the chart.
Cheers:ok:

BizJetJock
6th Oct 2009, 22:08
Slightly off topic but it is interesting to note the stark contrast between PANS OPS circling areas and TERPS. For cat C, they are 4.2nm and 1.7nm (from that article) respectively.

You need to compare like with like. The categories are different. My (fairly small) medium jet is Cat C under PANS-OPS; under TERPS we are Cat C for a straight-in but Cat D for circling. Max speed for circling Cat C is 135 knots, which makes it not too hard to stay within 1.7 miles.
If my memory serves me right one is required to complete circle to land on a clean wing as well as per TERPS for the initial type.
I think your memory is failing you. This would require circling at around 200 knots for many aircraft....:eek: And I certainly did all my initial types circling in the appropriate configuration.

9.G
6th Oct 2009, 22:21
BizJetJock, yeah that's about it around 200 Kts. Maybe it was a visual can't really remember but for sure I did land clean wing. It's been a while though. We're talking bout FAA type, don't we?

Spooky 2
6th Oct 2009, 22:42
Hey 411,

Just where do you train regarding circling approaches? Not to many if any L1011 level C sims out there with an FAA approved circling approach. I assume you are Part 125. I will say that you can train just about anyone to do a cirling approach if it's done time after time in the sim but out on the line it can be a very different story IMO. :}

AirRabbit
7th Oct 2009, 00:01
:hmm:
A couple of things to ponder … first, there isn’t anything, at least in the US, called a “circling approach” … there is only the “circle to land” maneuver. Of course, there are several “instrument approaches” for which you can receive clearance to fly, and then, tagged on the end of the “cleared for VOR approach…” clearance (for example), you can get “…circle to land runway XX.” The actual circling “maneuver” is a visually referenced maneuver to get you from the end of the instrument approach to a different runway on which you are to land. If you do not have the airport in sight, including the runway to which you are to circle to land, when get to the point that you need to break off for the circle, you are obligated to execute a missed approach. If you have the appropriate visual references, you can break off from the instrument approach and maneuver (not below the circling minima, however) to align with the other runway. You must be able to keep the runway of intended landing in continuous sight throughout the maneuver (unless you’re flying a high wing airplane and the airplane geometry is the only reason for not being able to “continuously” see the landing runway), because if you do lose sight of that runway, for any reason besides the one I’ve mentioned here you are obligated to execute a missed approach. Now … in that case, you are expected to continue to turn in the direction of the runway to which you were circling to land until you can intercept the missed approach for the instrument approach you originally flew – and fly that missed approach procedure.

Next, at least in the US, I think you’ll find that the regulator doesn’t qualify any simulator for the “circle to land” maneuver unless all of what I’ve described above can be accomplished with the simulator set to maximum gross weight for landing of the simulated airplane, the weather set to the minimums for the approach, and the landing runway must be at least 90 degrees from the approach course for the instrument approach to be flown. That means the visual system capability in the simulator has to be good enough for the pilot to be able to perform the tasks described. There is no corner cutting in getting the simulator qualified … now, how the simulator is actually used may be an entirely different circumstance – but, if that is true, it’s not because of a limitation of the simulator. The regulator cannot afford someone learning a procedure in a simulator, that, if conducted in the real world, would lead to an accident or incident.

411A
7th Oct 2009, 00:17
Giving deference to the superior skills at your operation, do they have to circle OEI or with partial flap and TERPS?
One engine inop, flap 22....just the way the Lockheed AFM says, TERPS included.
It can be done, just follow the plot.

Just where do you train regarding circling approaches?
In the actual airplane.
Gosh, what a surprise.:rolleyes:
We spend the bucks, crews trained...profits flow in.

Yes, I know...old fashioned, but it works.:ok:

BizJetJock
7th Oct 2009, 10:33
9.g Yep, talking FAA. I've put below the relevant section of the Practical Test Standard, which clearly says "appropriate configuration".
I'm not sure what purpose is served by doing circuits at 200 knots, other than being a fun way of getting used to the handling of the type and learning how hard it is to slow down to landing configuration!:ok:
Air Rabbit, you'll notice the title of the manoevre is "Landing from a circling approach".


D. TASK: LANDING FROM A CIRCLING APPROACH

REFERENCES: FAR Part 61; AC 61-27; Pilot's Operating Handbook, AFM, AIM.

Objective. To determine that the applicant:

1. Exhibits adequate knowledge of a landing from a circling approach.
2. Selects, and complies with, a circling approach procedure to a specified runway.
3. Considers the environmental, operational, and meteorological factors which affect a landing from a circling approach.
4. Confirms the direction of traffic and adheres to all restrictions and instructions issued by ATC.
5. Descends at a rate that ensures arrival at the MDA at, or prior to, a point from which a normal circle-to-land maneuver can be accomplished.
6. Avoids descent below the appropriate circling MDA or exceeding the visibility criteria until in a position from which a descent to a normal landing can be made.
7. Accomplishes the appropriate checklist items.
8. Maneuvers the airplane, after reaching the authorized circling approach altitude, by visual references, to maintain a flightpath that permits a normal landing on a runway at least 90° from the final approach course.
9. Performs the maneuver without excessive maneuvering and without exceeding the normal operating limits of the airplane. The angle of bank should not exceed 30°.
10. Maintains the desired altitude within +100, –0 feet (+30, –0 meters), heading within ±5°, and approach airspeed/V-speed within ±5.
11. Uses the appropriate airplane configuration for normal and abnormal situations and procedures.
12. Performs all procedures required for the circling approach and airplane control in a timely, smooth, and positive manner.
13. Accomplishes a smooth, positively controlled transition to final approach and touchdown.
14. Maintains positive directional control and crosswind correction during the after-landing roll.
15. Uses spoilers, prop reverse, thrust reverse, wheel brakes, and other drag/braking devices, as appropriate, in such a manner to bring the airplane to a safe stop.
16. Completes the after-landing checklist items, after clearing the runway, in a timely manner and as recommended by the manufacturer.

9.G
7th Oct 2009, 11:13
BizJetJock, what bout a visual? I remember there was something on clean wing that's for sure. Thanx for info anyways.:ok:

Kirks gusset
7th Oct 2009, 11:48
What a load of thread creep! The answer is simple, circling minima is determined under PAN OPS for the specific runway and approach and provides protection both vertical and lateral. The VOR may be offset for instance, this could determine a different minima based on the approach track. No additives to circling minima and you have to keep the "aerodrome environment" in sight, and circle within the prescribed radius. As correctly stated, the missed approach from a circle to land is based on the instrument approach carried out. Individual aircraft configs are left up to SOPs

OzExpat
7th Oct 2009, 13:20
This is somewhat interesting and some of the comments are truly frightening. From the perspective of a Pans Ops procedure designer, here's the basic criteria (very basic!) for an aerodrome at 1,000 feet AMSL.

Cat A IAS 100 Circling Radius 1.68 NM
Cat B IAS 135 Circling Radius 2.66 NM
Cat C IAS 180 Circling Radius 4.20 NM
Cat D IAS 205 Circling Radius 5.28 NM
Cat E IAS 240 Circling Radius 6.94 NM

Little wonder that the FAA is jittery about circling in a jet within 1.7 NM! I'm given to understand that the FAA has admitted the problems associated with their TERPs circling criteria but, after all these years, despite prangs off circling approaches, they're reluctant to change! So all they do is discourage circling... interesting.

As to the difference that was initially discussed between circling MDA for a ILS/DME and a VOR/DME approach, I can't imagine it unless the VOR is offset toward terrain AND the MAPt for the VOR/DME procedure is in a position that is far removed from the final approach course for the ILS/DME. Without seeing the procedure and the way it was designed - including whether Pans Ops or TERPs - it's not possible for me to comment further.

For those who are heroic enough to be able to circle at 200 knots, or thereabouts, within 1.7 NM, I say more power to your elbow! For my own part, I would much prefer the greater safety afforded by Pans Ops procedures.

As to the way to go missed approach off a circling manoeuvre - no matter what nomenclature is applied to it under the FAA system - I don't see a major problem in turning back over the runway at the outset. The only proviso I would add is that, if you've already descended below circling altitude, or you can't turn pretty sharply, you better be able to pray to some sort of God.

And, of course, all bets are off if you lose sight of the runway during the turn toward it. Still, it's better than nothing.

Spooky 2
7th Oct 2009, 14:32
Wow 411A. You must be the only profitable L1011 operation going these days:rolleyes:. Training in the airplane is damn expensive as well but what ever works.

9.G
7th Oct 2009, 21:17
For those who are heroic enough to be able to circle at 200 knots, or thereabouts, within 1.7 NM, I say more power to your elbow! For my own part, I would much prefer the greater safety afforded by Pans Ops procedures. Speaking of safety what safety does a circle to land as per PANS OPS offer you while flying one with prescribed tracks? Shall we open up a can of worms? :eek:

Capn Bloggs
8th Oct 2009, 00:47
9G and 411A,
Could you describe that actual technique you TERPS guys use to do a circling approach? For example, when do you roll out on final ie distance from threshold and altitude, what is your downwind spacing and at what point/time do you commence the base turn and bank angle during the turn?

It seems to me that a TERPS Cat C or Cat D cannot remain in the circling area and get stabilised by even 400ft AGL without exceeding 30° AOB around the base turn, but I'm always learning.

On the other hand, PANS OPS' 4.2nm circling area is quite comfortable to stay "in". Maintaining the threshold environment in sight with 4km vis is another matter...

Back to the thread topic, for the 717:
When flying an ILS approach and circling to land, set both BARO minimums to the CIRCLE-TO-LAND MDA. After established on the ILS localizer and prior to AUTOLAND/DUAL/SINGLE LAND annunciation, preselect the FCP altitude to the same MDA value. After glidepath capture, the airplane will descend to the MDA and the FMA will read APPR ONLY. At the MDA, the FMA and flight guidance will change to HEADING HOLD and ALTITUDE HOLD. Maneuvering can then be accomplished with heading or track mode.
Auto leveloff at the MDA on the ILS. Nice.

411A
8th Oct 2009, 01:45
It seems to me that a TERPS Cat C or Cat D cannot remain in the circling area and get stabilised by even 400ft AGL without exceeding 30° AOB around the base turn, but I'm always learning
Can't comment about category C airplanes (don't fly those) however, I do fly a Category D heavy jet, and the TERPs circling requirement is 2 miles, normally flown at 160 knots, with (in our case) flaps 22, gear down.
The lowest circling minima (under TERPs) is 600 feet for a category D airplane, so...at 160 knots, it is quite manageable.
Note: for the FAA type rating, circling as I have described is required, otherwise a VFR circling limitation is placed on the license.
...when do you roll out on final ie distance from threshold and altitude...

600 feet, no more than two miles, select landing flaps at this point, and...land.
Is this a demanding maneuver?
Yes, it certainly can be, especially with significant crosswinds, so...I expect many airlines have simply eliminated the circling maneuver, for their own ops.
IE: different strokes for different folks.

Capn Bloggs
8th Oct 2009, 01:59
600 feet, no more than two miles, select landing flaps at this point, and...land.
600ft is 2nm on a 300ft/nm path. If you're rolling out on final then, there is no way you can stay inside the 2nm circling area. You have gone way outside it whilst on base. If you roll out at 2nm, you have to be outside that beforehand. :confused:

411A
8th Oct 2009, 02:34
You have gone way outside it whilst on base
Negative, one must remain within two miles during the circling maneuver.
You will note that I mentioned...no more than two miles on final...normally it is about 1.8 miles, with the possibility of landing flaps selected whilst in base, and the descent begun at that point.
Is this allowed?
Yes.
The FAA requires very accurate flying, and it certainly can be done.
Is TERPs limiting?
Yup, sure is.

zon3
8th Oct 2009, 07:13
So, if I get this right 411a, on base you remained within 2 nm of threshold and you were wings level on finals at about 1.8 nm...? :D

411A
8th Oct 2009, 07:49
on base you remained within 2 nm of threshold and you were wings level on finals at about 1.8 nm...?
Not necessarliy wing level, and there is not a requirement to do so.
Early descent from MDA is not allowed, nor are high rates of decent.
A demanding maneuver, to be sure.
I expect this is the reason many airlines have eliminated (or severely restricted) circling from their normal operations.

9.G
8th Oct 2009, 07:54
same story for cat C airplane with associated speeds and turn radius. Nothing else to add. No big drama all in all. :ok:

Spooky 2
8th Oct 2009, 12:35
The reason that most airlines have removed the circle is driven by one, safety and two economics. The circle takes up a lot of sim time that can better be used for other maneuvers and in the case of our Capt. 411A, it uses up a lot of fuel as well.

Not so sure about 411 comment regarding going to full flaps on base to final (if that's what I understood), as a best practice is to go to final flaps before you turn base, thus keeping the turn radius to a minimum.

What ever works:hmm:

captjns
8th Oct 2009, 13:04
Not so sure about 411 comment regarding going to full flaps on base to final (if that's what I understood), as a best practice is to go to final flaps before you turn base, thus keeping the turn radius to a minimum.

Full flaps before turning base to reduce ground speed, and helps to ensure the 2 mile boundry. At least that's how I've done it for the past 30+ years. Works good, and lasts a good time.:ok:

Tee Emm
8th Oct 2009, 13:40
as a best practice is to go to final flaps before you turn base, thus keeping the turn radius to a minimum

Accepting that final flaps before turning base causes significant thrust increase to offset extra drag caused by flaps extending - in turn significant triiming to offset the thrust increase, then significant thrust decrease as descent commences with more trimming etc etc. And with landing flap before base imagine the consternation if an engine failed at that point with full flap down in level flight and high power holding level flight.

One aspect of the circling approach often unheeded, is the tendency to commence descent on base in order to fit the landing profile. You should ask yourself - where is the controlling obstacle? You probably wouldn't have a clue because it isn't shown on the chart. Maybe it is on late downwind - maybe on base leg. The aerodrome chart will not necessarily display this spot height. That means once you opt to descend below the published circling MDA for whatever reason, the captain is entirely responsible for his own obstacle clearance. Easy enough by day - but by night where you cannot see the ground directly below you, a different thing altogether.

9.G
8th Oct 2009, 14:27
Tee Emm, to appease your critics, those aerodromes with critical terrain profile usually impose restrictions for circle to land at night or require additional training.
Other than that as it's been said different strokes for different folks, don't do it if not comfortable. In the end that's what it is a VISUAL flight maneuver. You're fully accountable and responsible for the successful outcome of the mission "impossible" :ok:

DFC
8th Oct 2009, 23:34
The first thing that comes to mind regarding GCTS is that the VOR is SW of the aerodrome.

It is possible to reduce the circling area (exclude a portion of the total area) in order the acheive lower minima. This has been done at GCTS.

However, when this is done the area in which obstacle clearance is provided has to include those parts of the final approach and missed approach that are in the total circling area.

With the VOR a distance from the runway, the final approach area and missed approach area will splay outward i.e. get bigger as one moves from the VOR towards the runway.

The ILS however, will have the area reducing in width as one gets closer to the runway.

Thus it is possible that the circling area in which obstacles have to be considdered is different for the VOR and the ILS.

However, for me the biggest clue could lie in the fact that the ILS charts refered to are some years older then the other approach charts.

Therefore, until I had the situation clarified, I would use the higher minima as published on the later charts.

FullWings
9th Oct 2009, 09:44
Thus it is possible that the circling area in which obstacles have to be considered is different for the VOR and the ILS.
But as the circling area is defined as distances from the airfield (a sort of convex hull around radii projected from the respective thresholds), either you're inside the area or not... :confused: The charts show the same circling limitations (066-->264deg) for all approaches.

At GCTS, the ILS & VOR approaches are both aligned with the runway and at a MDA of 1,350' on 08 you're only about 2.5nm outbound from the VOR - 5deg track error is c.0.2nm laterally at this range. As pointed out, the dates on the charts range from 2001-->2008...

For those who are heroic enough to be able to circle at 200 knots, or thereabouts, within 1.7 NM, I say more power to your elbow!
Quite. 200kts, 30deg AOB gives a turn diameter of > 2 miles, so staying within 1.7 to land on, say, a reciprocal runway would be interesting manoeuvre, to say the least... :eek:

My airline still authorises circling approaches but fairly recently raised the minima to at least 1,000'AAL. We do train for this type of approach but to be frank, most sims are crap in this regard as you don't have a proper visual reference for a lot of the "visual" segment so are reduced to watching the map - not exactly good practice.

It does cross my mind that the most likely time (for us) to have to do one of these approaches would be into some hick airfield on an ETOPS diversion in the middle of winter. Personally it would have to be one hell of a cross/tail wind to persuade me not to use the instrument runway! BGSF comes to mind here...

DFC
9th Oct 2009, 10:11
But as the circling area is defined as distances from the airfield (a sort of convex hull around radii projected from the respective thresholds), either you're inside the area or not... http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/confused.gif The charts show the same circling limitations (066-->264deg) for all approaches.



From memory so please check;

The area to be excluded is clearly defined as you say. However, if the final approach area and missed approach area for the VOR overlies part of this area, then obstacles in this overlap will still have to be taken into account despite the fact that overflight is not permitted by the restriction.

Even if the restriction was simply no circling north of 08/26, obstacles north of the centerlines of each runway contained within the annex 14 approach areas and the final approach and missed approach areas for the procedure which are north of the centerline and within the total circling area have to be included.

In simple terms you have to be safe in terms of obstacles flying just inside the most northerly boundary of the final approach area and missed approach area which are contained within the circling area.

While pilots are thinking in terms of being 5 degrees off to the north from overhead the VOR, the final approach area will be a certain width at the VOR and diverge at 8 degrees. Thus really being only 5 degrees off after passing exactly over the VOR would not be at the northern boundary of the approach area in which obstacles are considdered.

There is the posibility of a pilot at the circling MDA being well north of the final approach track but still being contained within the final approach area for the VOR.

Remember that the VOR final approach area is expanding as one moves away from the VOR but the LOC final approach area is getting smaller.

Sit back and do a few simple math calculations based on the following principles for CAT C (ICAO);

1. Circling minimum obstacle clearance is 394ft with a lower limit of 591ft above the aerodrome elevation

2. The final approach obstacle clearance for the VOR final approach area is 246ft as it is for LOC

Missed approach obstacle clearance is a minimum of 98ft and then 164ft

You can play with the figures and come up with a best guess as to what the obstacle is causing and then look at the chart.

My guess is that the slopes of the hill NW of the airport are the dominant obstacle.

However, all that is simply guess work and I would be more inclined to err on the side of safety and use the more recent higher minima for all circling operations.

--------

As for TERPS, circling area is defined in "miles" and is much smaller than icao but the speeds are different and the minimum obstacle clearance is less. So not really the same thing at all.

----------

ICAO circling is based on 20 deg aver age bank or rate 1 whichever requries less bank and for cat C a TAS of 180Kt and wind of 25Kt giving an overall speed of 215 Kt combined with 20 degrees AOB for calculation of turn radius.

9.G
9th Oct 2009, 11:16
Personally it would have to be one hell of a cross/tail wind to persuade me not to use the instrument runway! I guess you haven't flown many time to CIA or BEG. Not every day business there but certainly the opportunities to shoot one of those do present themselves periodically. :ok:

FullWings
9th Oct 2009, 15:20
DFC,

Thanks for the info. I can see why you might have to raise the circling minima because of obstacle/missed approach requirements pertinent to the approach you actually use to get to circling MDA and will also use in the event of a missed approach. What I don't understand in this case is that the original approach minima are not as restrictive, e.g. 1,060' for the VOR... :confused:
There is the posibility of a pilot at the circling MDA being well north of the final approach track but still being contained within the final approach area for the VOR.
Yes, but in that case he'd be OK* for terrain etc. down to the VOR limit: 1,060'. If he didn't get the required visual references at circling MDA, some 300-600' above the VOR MDA then he'd have to fly a missed approach. Even the lower of the two possible circling MDAs more than compensates for the increase in required clearances between circling & NPA?

* Not trying to imply he could mix'n'match with the two approaches: below the circling minimum he can only complete a VOR approach or go-around.

I would be more inclined to err on the side of safety and use the more recent higher minima for all circling operations.
You and me both!

I guess you haven't flown many time to CIA or BEG.
No, but there does seem to be a VOR onto RW33 @ CIA - it's classed as circling although as it's <30deg off the RW and <400'/nm it could technically be called a straight-in...:p And why would you want to circle at BEG when there's an ILS at both ends? ;)

FullWings
9th Oct 2009, 17:34
My opinion on circling approaches is that if I was down to one engine on a dark night, they would be the absolute last thing I'd want to do, especially at a terrain-constrained airfield. I would consider an out-of-wind but better served runway as a lower risk endeavour, as long as performance criteria were met. Autoland first choice, RNAV second & circling last.

Kirks gusset
9th Oct 2009, 18:50
What was the original question? !!! so presumably if I post about tyre pressure by the end of the thread I will know how to build an undercarriage!

captjns
9th Oct 2009, 18:51
A circling approach, when properly briefed, and executed as briefed, is a non-event. It does not take “Maverick” or “Chuck Yeager” to perform circling maneuvers. Personally, I along with competent airmen have performed the maneuver in actual conditions, to published minima without any squawks. As for myself, I have be performing circling maneuvers all over the world since the mid ‘70s in all types of aircraft from singles up to and including the wide bodies.

Is the circling maneuver the choice procedure to perform under adverse situations??? no… at least not mine. But if you have to do it, you do it. It’s no big deal. If during the maneuver you don’t like what you see… well… execute the published missed approach.

Circling maneuvers come with the job. Proficiency is demonstrated in the simulator 2 times a year, and sometimes during an actual line check. At the end of the day, if one has trepidations about performing such a maneuver, which is approved under their carrier’s Ops Specs, then perhaps another airline that prohibits such maneuvers is the carrier of choice to be employed. There are carriers that do prohibit such procedures if weather is less than 1,000’ ceiling, and 3 miles of visibility, unless category D minima are greater.

Perhaps performing circling maneuvers in actual IFR in a twin, with an instructor in the right seat may help allay one’s fears too.

9.G
9th Oct 2009, 18:59
OK FW sorry my apologies it's BGY not BEG.
To tackle the 200 Kts issue once and for all. As I said the requirement to perform a landing on a clean wing for the initial type check ride is as per FAR. Who is the world lands on a clean wing on daily basis? The answer is those having troubles getting out the flaps, isn't it? Hence the situation is abnormal not to say resembling kinda emergency, certainly the case if only circling is left as an option, all the norms are down the drain. Mayday and the sky is yours or do you wanna maintain that in case of a dual engine failure you care bout boundaries or obstacle clearance? Specially if the weather is CAVOK and you can see miles away. Well so much to Malevich loving brothers who love to paint it all black regardless of the forms or contents.

Back to CIA. Your have chosen your words wisely my friend it only SEEMS indeed. Nothing even close to a straight in it's circling VOR 33 thus it's a circling approach using a prescribed track. Remember we were talking bout circling so forget the once coming from LAT or FRS. as you can see only ROM DME is required to shoot it, isn't it? So you're coming over ROM for a circling VOR 33, aren't you? Do you still have 4,2 NM obstacle clearance in this case? What is your primary means of navigation? Finally what's he applicable weather minimum?

Have fun :ok:

BOAC
9th Oct 2009, 19:31
I didn’t realize you were the appointed spokes person for the posters on PPRuNe. - certainly for that one - and I volunteered, not appointed. Your 'comments' about FW were totally misplaced. There there.:{

FullWings
9th Oct 2009, 23:34
I'm getting a warm, fuzzy feeling... http://www.mysmiley.net/imgs/smile/love/love0080.gif (http://www.mysiley.net)

Thanks, BOAC ;)

9.G, I totally agree about emergencies and rulebooks, etc. However, if you're stuck in clean config, you're not dead yet and it would be a shame to risk piling in short (not implying you would, of course!) when good manners dictate that you should crash on the runway, or at least the airfield. CAVOK means do what you think's best - after all, they're minima not maxima: an appropriately sized visual circuit would seem to fit the bill?

Back to CIA. Your have chosen your words wisely my friend it only SEEMS indeed. Nothing even close to a straight in it's circling VOR 33 thus it's a circling approach using a prescribed track. Remember we were talking bout circling so forget the once coming from LAT or FRS. as you can see only ROM DME is required to shoot it, isn't it? So you're coming over ROM for a circling VOR 33, aren't you? Do you still have 4,2 NM obstacle clearance in this case? What is your primary means of navigation? Finally what's he applicable weather minimum?
I've never been there so I was just looking at the approach plates (pdf, 3.6MB: Googled from an Italian sim. site but look like genuine ENAV ones) (http://www.vatita.net/download/planning/files/lira_iap.pdf) with RW33 being the last in the sequence. It looks like you can go ROM outbound, complete the base turn, join the FAT inbound to ROM, breaking off at 4d to align with the runway if you are visual. The limits appear to be lower for this approach than circling from the other end, so I'd have thought it would be better if the wx was poo? I know it's called a circling approach on the plate but to me it reads more like an offset VOR, albeit with a few more criteria to fulfil when visual... Anyway, I'm not trying to start an argument (that's room 12a) as I readily admit I don't get much practice at circling, apart from the odd bit in the Caribbean and it's rare to be near the minima, so any advice is gratefully received!

Sorry to bore everyone - please feel free not to read this post if you don't want to.

Pugachev Cobra
10th Oct 2009, 00:13
This thread reminds me of an interesting discussion I heard about circling procedures.

Imagine a circling approach for a random aerodrome with a MDA of 650' AGL, and minimum ceiling 700'.

Now, this means that if the pilot has visual conditions and constant visual contact with the runway at 700', he can make a visual landing.

Isn't a circling approach a pseudo standard traffic pattern?

But wait, why is the standard visual traffic pattern at 1000' then?

And why is the minimum ceiling for a visual operation on an aerodrome 1500', or 1000' Special VFR?

If there is a published procedure for visually circling, approaching and landing at 700' AGL or less, why can't VFR aircrafts use this ceiling as well?

Just interested in what you have to say.

Cheers.

Pugilistic Animus
10th Oct 2009, 20:51
Pugachev Cobra:

not necessarily for safety
VFR minimums are not published to help VFR pilots at all that's why you can fly 'VFR' on moonless nights or in heavy haze with no horizon and still be VFR ---they are published simply to protect IFR traffic so that the two don't mix operationally when things get iffy---to see and avoid and see and be seen

one myth is you need a natural horizon to be VFR [ maybe hard nosed joe does not] you don't really need a horzon to fly VFR just ceiling and visibilty to help cut down on aluminum shower forecasts:}

remember they don't care too much about your safety or abilty just that of others

PA

captjns
10th Oct 2009, 21:24
one myth is you need a natural horizon to be VFR [ maybe hard nosed joe does not] you don't really need a horzon to fly VFR just ceiling and visibilty to help cut down on aluminum shower forecastshttp://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/badteeth.gif

Splain that one Lucy?

Pugilistic Animus
10th Oct 2009, 21:33
They don't care if you can or can not actaully control the plane by reference the/a natural horizon only that you don't interfere with IFR traffic; actual sky conditions don't matter [legally] the FAA can't be there to know that
if you go up on a hazy day find yourself in IMC on the guages due to haze or night but you can see the other aircraft [legal reported vis] and you meet the cloud clearance requirements then feel free to spiral into the ground as you wish:)

same goes for rain on the wind shield

captjns
10th Oct 2009, 21:41
And BOAC says.... There there.http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/boohoo.gif

And captjns says... Ooooooooooooookay:rolleyes:.

411A
10th Oct 2009, 21:59
In the end, captjns, it is the pilots that were never taught how, nor never practiced a circling maneuver in a jet transport airplane are nearly always the ones who profoundly shout....can't be done, safely'.
Of course they are truly misinformed, nevertheless...
Best to ignore these folks, as they have their minds made up, never mind the facts.:rolleyes:

captjns
10th Oct 2009, 22:07
In the end, captjns, it is the pilots that were never taught how, nor never practiced a circling maneuver in a jet transport airplane are nearly always the ones who profoundly shout....can't be done, safely'.
Of course they are truly misinformed, nevertheless...
Best to ignore these folks, as they have their minds made up, never mind the facts.:rolleyes:

Cheers 411A. Ergo the good old axiom... airplane pilot versus simulator pilot.

captjns
10th Oct 2009, 22:10
They don't care if you can or can not actaully control the plane by reference the/a natural horizon only that you don't interfere with IFR traffic

I'm sorry Pugal... but who doesn't care? Can you cite the regulation approprate to your assertion?

DFC
10th Oct 2009, 23:21
And why is the minimum ceiling for a visual operation on an aerodrome 1500', or 1000' Special VFR?



You are confusing an IFR flight manoeuvring with visual refernce to the runway / environs and a VFR flight which is something totally different.

The ceiling of 1500ft for a VFR flight in a control zone come about as a result of two other ICAO rules;

1. minimum cruise height of 500ft AGL and

2. requirement for a VFR flight in such a case to be 1000ft vertically from cloud.

i.e. if the ceiling is 1400ft you are not going to be able to comply with the above ICAO rules.

If I make an ILS approach with a DH of 200ft and an RVR of 550m, the bit from 200ft to touchdown will be a visual manoeuvre. With circling there is simply a lot more manoeuvring before touchdown.

Pugilistic Animus
14th Oct 2009, 22:54
Hey Captjns,

There's no regulation that states that you specifically can not.
however the explanation is a little circuituous

but the reason that in controlled airspace we have basic VFR weather minima is NOT to protect pilots from themselves but rather to protect those operating in controlled airspace so that when a certain amount of cloud cover or visibilty prevails everone is under positive ATC control; also, in the US visual contact with the ground is not required[except for some limited licences i.e sport pilot, ultralights]

furthermore visibilty as reported is slant range visibility and the refractive effects of haze, lack of good sky ground contrast etc.. can cause a legal visibilty and it can be cloudless, for example, yet the natural horizon is non-existent requiring Instrument flying techniques-so the basic reason for VFR mins are
1. to allow IFR and VFR traffic the ability to see and avoid one another without being unduly restrictive
2. to set a final minima where all traffic operating within the specific class of controlled airspace must be positively controlled

Historically, basic US basic flight rules come from the Avigation Act of 1926?
written in blood-of course:)

going back to the old axiom of "what is legal is not always safe and vice versa]" there is not regulation that stops a newly minted PPL with no IR to take off over-water on a moonless night with little backgound lighting as long as he wont hit anybody--the burden of flying is on the PIC---there's no reference in the FARS about horizon just cloud clearance and visibilty

lastly the reason we have VFR mins for uncontolled airspace is becuase it is legal for an IR pilot to fly IFR in class G airspace WITHOUT even a flight plan or clearance --- dumb in most cases IMHO,...but at least he wont be contending with some fool scud running:\

I hope I've clarified myself a bit:)

PA

galaxy flyer
15th Oct 2009, 03:17
PA

it is legal for an IR pilot to fly IFR in class G airspace WITHOUT even a flight plan or clearance --- dumb in most cases IMHO

Indeed, it is legal and frequently done in many remote areas--Africa, Canada, Australia, South Atlantic Ocean, parts of the Indian Ocean, all of it in jet planes at FLs.

GF

dubfan
15th Oct 2009, 10:38
Hi Guys.

Just did a circling app in my last sim. I fly a cat B a/c which is limited to 135 kts on these approaches. We configure as normal on the circling app but delay landing flap till 90 degrees in the turn on final

In icing conditions, we are required to fly at a speed plus 10kts which, at certain weights, will take the speed above 135. In such cases, I assumed that we simply couldnt fly the circling approach.

Not so say our wise TRI - you simply go to the next category that the new speed takes you into, in our case, B to C

Is that legal. How can we simply re categorise our a/c. I am aware that the speeds associated with each category is based on the turn radius required to maintain a rate one and be wings level on final with sufficient distance to go, but I didnt think I could simply cherry pick the category I wished based on my airspeed.

Cheers

DFC
15th Oct 2009, 10:53
Yes you can use a higher category during the circling. You have to use the higher MDA and need the increased visibility.

There is noting stopping a Cat A aircraft using Cat C minima for a circling approach since all that happens by raising the minima to the CAT C ones is that the area within which the aircraft must remain gets bigger.

So if as you found that due icing or due configuration limitations etc you have to use a speed higher than 135 for your CAT B aircraft all you have to do is use the higher minima for a CAT C so as to increase the size of the circling area to accomodate your higher speed.

What you must not do is fly a CAT C aircraft and say that "today we are so light that we can fly at 135 knots during the circle so we will use the CAT B minima". That is totally against the rules.

dubfan
15th Oct 2009, 11:06
Thank you DFC

As always, I live 'n learn

Pugilistic Animus
15th Oct 2009, 22:34
GF I always cover my butt; notice, I carefully wrote 'in most cases':}

as one very deeply missed [on our pages] aviator writes

Happy Contrails:(