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Circling Approach From An ILS?  
User currently offlinesmartt1982 From United Kingdom, joined Nov 2007, 225 posts, RR: 0
Posted (1 year 11 months 4 weeks 1 day 9 hours ago) and read 6028 times:

In our company if we were required to perform a circling manoeuvre we would have to perform either a Localiser only approach or some other form of non-precision approach on the instrument runway, this would be the case even if the ILS was fully operational, we would still carry out a LOC only approach so that we could set the circling minima and would get ALT HOLD upon reaching that minima (either through VNAV or VS). I was asked recently about why we never use the full ILS (so with GS) on the instrument runway. I could not give an adequate reason other than for the aircraft we fly which is the 737 NG the autopilot would go straight through whatever minima we would set without getting ALT ACQ/HLD. Of course I realise that you could always fly this manually but using the automation, is there any way to perform this?, perhaps just press ALT HOLD upon reaching the circling minima?.

Also on side note, whilst performing a circling I notice that the auto throttle system always seems to struggle with keeping the bugged speed as we level off at the minima and began the breaking off action. I have been told that this is because the A/T cant cope with that amount of change, any ideas?

Any info would be greatly appreciated.

Many Thanks

18 replies: All unread, jump to last
 
User currently offlinewilco737 From Greenland, joined Jun 2004, 9029 posts, RR: 75
Reply 1, posted (1 year 11 months 4 weeks 1 day 6 hours ago) and read 5983 times:
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Quoting smartt1982 (Thread starter):

It is quite some time ago since I flew the 737, but IIRC you cannot simply push ALT HLD while the AP is engage and LOC G/S is active. You need to switch off AP and FD and then you can put in new modes.
That's why you use the LOC mode only and V/S or VNAV, then you can push ALT HLD and the AP levels off.

wilco737
  



It it's not Boeing, I am not going.
User currently offlinetb727 From United States of America, joined Jun 2005, 1596 posts, RR: 9
Reply 2, posted (1 year 11 months 4 weeks 1 day 5 hours ago) and read 5939 times:

Too much automation!! That's just my opinion.  


Too lazy to work, too scared to steal!
User currently offlineGlobalMoose From United States of America, joined Aug 2012, 30 posts, RR: 0
Reply 3, posted (1 year 11 months 4 weeks 1 day 2 hours ago) and read 5871 times:

I don’t fly the 737 but I was always taught that pilots should plan to circle from a non-precision approach (note the ‘should,’ not will or must).
This is from our instrument flight manual and helps to explain procedurally why it is best to plan to circle from a non-precision approach:

“The circling MDA and weather minima to be used are those for the runway to which the instrument approach is flown (this is not always the landing runway). The circling minima listed on IAPs apply to all approach types on the IAP (RNAV (GPS), ILS, LOC, VOR, TACAN, etc.). However, 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 are cautioned to ensure the aircraft is within the appropriate circling radius before abandoning the precision glideslope, if planning to circle from a precision final approach.”

For technique, our guidance discourages the ‘dive and drive’ method of once you hit the FAF to descend as quickly as possible to the MDA and drive on in to the MAP. They like us to calculate a good VSI to try and hit the VDP right at the MDA. I personally like to get down prior to the VDP/MAP to get my bearings in the area and hopefully breakout below any clouds.

Using the autopilot, I set the altitude window to the next 100 feet rounded up. Once I get to that altitude, I’ll spin 200 or so feet down on the VSI and hit ALT HOLD once I reach the MDA. Once visual I engage split axis and let the automation take care of speed and altitude.

Hope this helps.



When it absolutely positively has to be there ... at some point.
User currently offlinezeke From Hong Kong, joined Dec 2006, 9097 posts, RR: 75
Reply 4, posted (1 year 11 months 4 weeks 22 hours ago) and read 5824 times:

Quoting smartt1982 (Thread starter):

That seems to be a specific issue with the aircraft, I do not think it is an issue on newer Boeing's, or on Airbus aircraft. There is no legal reason why you cannot circle off an ILS, and we used to do it in practice at a number of airports like Fukuoka ILS on 16 circle to 34. However our manages have recently banned all circling approaches, and we no longer do NDBs either, newer aircraft do not even come with an ADF installed.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 5, posted (1 year 11 months 4 weeks 19 hours ago) and read 5788 times:

Wilco737 is correct and we would just hand fly the circle at mins. I think using the a/p for a circling app would be more difficult. You must be visual at mins so why not hand fly it?

User currently offlinesmartt1982 From United Kingdom, joined Nov 2007, 225 posts, RR: 0
Reply 6, posted (1 year 11 months 4 weeks 3 hours ago) and read 5665 times:

Quoting CosmicCruiser (Reply 5):
Wilco737 is correct and we would just hand fly the circle at mins. I think using the a/p for a circling app would be more difficult. You must be visual at mins so why not hand fly it?

Trust me I would love to hand fly it, other than in one of our recurrent sims were we were required to hand fly it, our SOPS dictate that we use ALT HOLD and fly using heading select. I can understand the reason as it reduces the workload and increases capacity in concentrating on keeping tracks and the timing required before turning onto the landing runway before eventually disconnecting.
I think it would be a bit more awkward though using a full ILS (with GS) to then hand fly as the level off could be more abrupt unless of course you were hand flying the ILS before hand.
I think I was born 30 years too late sometimes with regards to the aircraft I could have flown i.e. 707/747/DC 10. I would love to hand fly all the time.


User currently offlineXFSUgimpLB41X From United States of America, joined Aug 2000, 4200 posts, RR: 37
Reply 7, posted (1 year 11 months 3 weeks 6 days 21 hours ago) and read 5628 times:

Just follow the GS by using V/S. Then when you hit circling minimums select ALT HOLD.

Don't make it more difficult than it is.  

Am I correct in remember that once LOC/GS are captured you cannot get out of that mode except via GA or turning off the automation and clearing the FDs?

The airbus you don't get an inhibit until 400 feet..way better!



Chicks dig winglets.
User currently offlinePihero From France, joined Jan 2005, 4445 posts, RR: 76
Reply 8, posted (1 year 11 months 3 weeks 6 days 16 hours ago) and read 5586 times:
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Quoting GlobalMoose (Reply 3):
I was always taught that pilots should plan to circle from a non-precision approach
Quoting GlobalMoose (Reply 3):
However, 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.

I am probably missing something but your two sentences above are a bit of a paradox :
- Descending on an ILS glide slope, the circling altitude determines a very accurate position at which you start your circling manoeuvre, as the intersection of the glide and that altitude.

Quoting zeke (Reply 4):
That seems to be a specific issue with the aircraf

On the 320/30/40, as XFSU wrote, one has five or six ways to get out of the G/S mode.The procedures vary from airline to airline but just let's say that
- One can deselect the ILS approach by pushing the APPR button
- By pressing the LOC button, one reverts to VS - or FPA - for the pitch axis.
- Pulling HDG/TRK or the VS/FPA selector, the system reverts to HDG/TRK and LOC + VS or FPA respectively.

The preferred manipulation is, approaching the MDA - on the ILS - to pull the HDG /TRK button so that the system reverts to the basic modes, then press the FPA selector ( called then " Push to level-off" ), and set the initial circling track.
That at a height above 400 ft.



Contrail designer
User currently offlinewilco737 From Greenland, joined Jun 2004, 9029 posts, RR: 75
Reply 9, posted (1 year 11 months 3 weeks 6 days 7 hours ago) and read 5518 times:
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Quoting XFSUgimpLB41X (Reply 7):

Read my reply further up, I explained it. Once in LOC and G/S you cannot get back. Only go around buttons or AP and FD off will let you out of these modes...

wilco737
  



It it's not Boeing, I am not going.
User currently offlineXFSUgimpLB41X From United States of America, joined Aug 2000, 4200 posts, RR: 37
Reply 10, posted (1 year 11 months 3 weeks 5 days 22 hours ago) and read 5457 times:

Quoting wilco737 (Reply 9):

Quoting XFSUgimpLB41X (Reply 7):

Read my reply further up, I explained it. Once in LOC and G/S you cannot get back. Only go around buttons or AP and FD off will let you out of these modes...

That's what I thought.   I remember it for a fact on the 75/76, but I try to suppress the dark memories of flying that cramped wind noise machine around.  



Chicks dig winglets.
User currently offlineMir From United States of America, joined Jan 2004, 21620 posts, RR: 55
Reply 11, posted (1 year 11 months 3 weeks 5 days 19 hours ago) and read 5440 times:

Quoting CosmicCruiser (Reply 5):
I think using the a/p for a circling app would be more difficult. You must be visual at mins so why not hand fly it?

Using the AP allows the PF to maintain better altitude control (which is useful if circling at MDA) while keeping eyes outside to maintain visual contact with the airport. I'll click the AP off in order to start my descent from MDA to the runway, or if the wind conditions are such that I want more direct control.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlinewilco737 From Greenland, joined Jun 2004, 9029 posts, RR: 75
Reply 12, posted (1 year 11 months 3 weeks 5 days 8 hours ago) and read 5363 times:
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XFSUgimpLB41X,

I know what you mean. I haven't flown the 737 since April 2007. But the 747 I am flying acts the same way. But here you can use LNAV and VNAV to the MDA, push ALT HLD and then fly the breakout with AP still engaged.

wilco737
  



It it's not Boeing, I am not going.
User currently offlineXFSUgimpLB41X From United States of America, joined Aug 2000, 4200 posts, RR: 37
Reply 13, posted (1 year 11 months 3 weeks 5 days 7 hours ago) and read 5353 times:

Quoting wilco737 (Reply 12):

XFSUgimpLB41X,

I know what you mean. I haven't flown the 737 since April 2007. But the 747 I am flying acts the same way. But here you can use LNAV and VNAV to the MDA, push ALT HLD and then fly the breakout with AP still engaged.

Must be universal for the Boeings, then. At my carrier we had the option of doing LOC and V/S or LNAV/VNAV in such a situation...It really didn't make much of a difference.

Kudos on getting on the whale! Hopefully I'll be able to jump on her in a few years.



Chicks dig winglets.
User currently offlineGlobalMoose From United States of America, joined Aug 2012, 30 posts, RR: 0
Reply 14, posted (1 year 11 months 3 weeks 5 days 1 hour ago) and read 5312 times:

Quoting Pihero (Reply 8):
I am probably missing something but your two sentences above are a bit of a paradox :
- Descending on an ILS glide slope, the circling altitude determines a very accurate position at which you start your circling manoeuvre, as the intersection of the glide and that altitude.

On second glance, you're right, that is a bit confusing. I’ve never flown a circle from an ILS so this is a great thinking exercise. In response to your quote, I’d be very careful to begin circling at the point where you intercept the circling MDA on the glideslope. Remember to take circling radii into consideration; I circle at CAT D or E depending on weight (that’s a 2.2 NM difference!).

So let’s assume that you are circling at CAT D mins, a 2.3 NM radius. If the HAT for the approach is 700 ft or less, you could use that as a guide that it would be safe to start your circle (always using DME or other methods to determine your distance from the airfield). (700 ft / 300 ft per NM for a 3 degree glide slope results in 2.3 NM from where the glideslope intercepts the runway, usually 1000 feet from the threshold, providing an extra .16 NM of safety).

After further thought, the real question is if you are flying an ILS to a circle, are you flying a precision or non-precision approach? I don’t have a good answer right now, but I’ll find an evaluator pilot the next time I go back to work and see if they have a definitive answer. Going over the obvious, but for the benefit for all:

Precision approach procedure (P/C Glossary) – a standard instrument approach procedure in which an electronic glideslope/glidepath is provided.

Non-precision approach procedure (P/C Glossary) – a standard instrument approach procedure in which no electronic glideslope is provided.

The missed approach point for a precision approach is when the aircraft is at the DA/DH. The missed approach point for a non-precision approach is determined either by distance to, from, or at a NAVAID or via timing.

So if you are circling from an ILS, is it half precision, half non-precision? When do you go missed? When circling from the ILS you are not going down to ILS minimums but the circling MDA (which is an MDA, not a DA). Do you immediately execute the missed approach when you hit the circling MDA while on glideslope or do you drive into the MAP for the LOC approach?

If anyone has a good answer (with references), it would be much appreciated!

This is why I don't circle from a precision approach  



When it absolutely positively has to be there ... at some point.
User currently offlinewilco737 From Greenland, joined Jun 2004, 9029 posts, RR: 75
Reply 15, posted (1 year 11 months 3 weeks 4 days 16 hours ago) and read 5248 times:
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Quoting GlobalMoose (Reply 14):
Precision approach procedure (P/C Glossary) – a standard instrument approach procedure in which an electronic glideslope/glidepath is provided.

Correct  
Quoting GlobalMoose (Reply 14):
Non-precision approach procedure (P/C Glossary) – a standard instrument approach procedure in which no electronic glideslope is provided.

Correct, but the modern FMC's have a virtual glideslope which you can easily fly with VNAV (or in the new B748 you only hit APP and it flies a proper 3 ° glideslope, just like an ILS)

Quoting GlobalMoose (Reply 14):
So if you are circling from an ILS, is it half precision, half non-precision?

Basically it is a non precision approach, as you do select the circling minimum and not the ILS minimum.

Quoting GlobalMoose (Reply 14):
When do you go missed?

Whenever you do not have the runway in sight anymore. If you don't have the runway insight at circling minimum: go around.

Quoting GlobalMoose (Reply 14):
When circling from the ILS you are not going down to ILS minimums but the circling MDA (which is an MDA, not a DA). Do you immediately execute the missed approach when you hit the circling MDA while on glideslope or do you drive into the MAP for the LOC approach?

You use the circling minimum (which is stated on every ILS IAC) and this will be an MDA. So you follow the GS until MDA and if you have the runway insight you can follow the circling approach. If you lose the runway: go missed.

Quoting GlobalMoose (Reply 14):
If anyone has a good answer (with references), it would be much appreciated!

Cannot give you any specific reference, but this is how I learnt it at flight school. And during my 9 years of flying I did 3 real life circling approaches and all of them were out of an ILS.

Quoting GlobalMoose (Reply 14):
This is why I don't circle from a precision approach

I prefer the precision approach for a circling apprach. Then I don't have to observe the vertical profile for the non precision approach, I don't have an offset (which happens at times for VOR or NDB approaches).

My 2 cents  

wilco737
  



It it's not Boeing, I am not going.
User currently offlinePihero From France, joined Jan 2005, 4445 posts, RR: 76
Reply 16, posted (1 year 11 months 3 weeks 4 days 15 hours ago) and read 5235 times:
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Quoting GlobalMoose (Reply 14):
I'd be very careful to begin circling at the point where you intercept the circling MDA on the glideslope. Remember to take circling radii into consideration;

Why is it so different from starting your circling manoeuvre from a VOR ? I posit the start of your procedure is more accurate.

Quoting GlobalMoose (Reply 14):
if you are flying an ILS to a circle, are you flying a precision or non-precision approach?

Put simply, you are flying a non-precision approach with a very accurate point of origin.

Quoting GlobalMoose (Reply 14):
Do you immediately execute the missed approach when you hit the circling MDA while on glideslope or do you drive into the MAP for the LOC approach?

No, of course not. An MDA is just the lowest allowed altitude you have until you can insure a visual trajectory to your landing.
Nothing prevents you from initiating your break-away,; on the glide, as soon as you have the field in sighht ( not recommended) , as people would prefer staying on the glide until MDA and then open the trajectory.

Quoting wilco737 (Reply 15):
I prefer the precision approach for a circling apprach. Then I don't have to observe the vertical profile for the non precision approach

So do I. And on the 'Bus, the procedure is sooo easy : ( On ILS ), gear down, flaps config 3, spoiler armed... (Approaching MDA ) :Pull HDG / TRK selector (ILS disconnects leaving me with TRK /FPA )... at MDA, "Push top level off" and turn the TRK selector to the BKaway track... count ~ 30 seconds depending on wind... I'm nicely positioned for the downwind leg...set the altitude for an eventual go around, ( turning ionto final ), full flaps, complete the landing checklist.
Can be done with or without A/P.



Contrail designer
User currently offlinezeke From Hong Kong, joined Dec 2006, 9097 posts, RR: 75
Reply 17, posted (1 year 11 months 3 weeks 4 days 14 hours ago) and read 5228 times:

Quoting GlobalMoose (Reply 14):
Remember to take circling radii into consideration; I circle at CAT D or E depending on weight (that’s a 2.2 NM difference!).

I have not seen an approach chart with a CAT E minimum for a long time, where are you flying to that publishes CAT E ? What are you flying ? Concorde ? Jepp do not even publish CAT E charts.

Quoting GlobalMoose (Reply 14):
So let’s assume that you are circling at CAT D mins, a 2.3 NM radius. If the HAT for the approach is 700 ft or less, you could use that as a guide that it would be safe to start your circle (always using DME or other methods to determine your distance from the airfield).

Those are TERPS numbers, there is another world out there that use standard ICAO numbers. Nothing stopping operators specifying a higher minima than what is published on the chart ( a lot do ). We never circled below 1000' AGL as per company SOP. If conditions were below that, we would have to use another approach with a lower minima, or divert.

Quoting GlobalMoose (Reply 14):
After further thought, the real question is if you are flying an ILS to a circle, are you flying a precision or non-precision approach?

Precision approach to a circling minima. One needs the precision aid to get to the circling MDA (i.e you cannot fly an ILS approach to any minima without a glideslope and LLZ, you might be able to revert to LLZ NPA which if often overlaid on the same chart), and needs to have the equipment on-board required by the chart in order not only to fly the approach, also the missed approach.

Quoting GlobalMoose (Reply 14):
Precision approach procedure (P/C Glossary) – a standard instrument approach procedure in which an electronic glideslope/glidepath is provided.

That is no longer the case, precision approaches also include PAR, GLS, TLS, and SCAT-I DGPS.

Quoting GlobalMoose (Reply 14):

The missed approach point for a precision approach is when the aircraft is at the DA/DH.

I do precision approaches with no DA or DH.

Quoting GlobalMoose (Reply 14):
The missed approach point for a non-precision approach is determined either by distance to, from, or at a NAVAID or via timing.

RNAV ? WAAS GPS ? Baro-VNAV, LDA with glidepath, LNAV/VNAV and LPV, i.e. Approach with Vertical Guidance (APV).

Quoting GlobalMoose (Reply 14):
When do you go missed?

When the criteria to continue is not met, they could be criteria in the AIP/AIM, or company specific criteria. The criteria is extensive, viability, lights, navaid monitoring, aircraft limits (specifically crosswind and tailwind tend to be most limiting), approach speed, bank angles, unstable approach, SOPs etc.

Quoting GlobalMoose (Reply 14):
When circling from the ILS you are not going down to ILS minimums but the circling MDA (which is an MDA, not a DA).

The plan is to go below the circling MDA and the DH at some point in order to land the aircraft. If while circling, one has a loss of visual reference, or become unstable etc and needs to execute a missed approach, turn towards the airport while climbing and join the published missed approach procedure for which you were cleared (e.g. the ILS), this may require a 270 degree turn if commenced on base. ATC may even give you an amended missed instructions. When cleared for the approach, that is a clearance to conduct the specific approach and the associated missed missed approach, that is what they will expect you to do if comms fail. To keep yourself safe, turn toward the airport and get above the MSA asap.

From the FAA AIM

"If visual reference is lost while circling-to-land from an instrument approach, the missed approach specified for that particular procedure must be followed (unless an alternate missed approach procedure is specified by ATC). To become established on the prescribed missed approach course, the pilot should make an initial climbing turn toward the landing runway and continue the turn until established on the missed approach course. Inasmuch as the circling maneuver may be accomplished in more than one direction, different patterns will be required to become established on the prescribed missed approach course, depending on the aircraft position at the time visual reference is lost. Adherence to the procedure will help assure that an aircraft will remain laterally within the circling and missed approach obstruction clearance areas. Refer to paragraph h concerning vertical obstruction clearance when starting a missed approach at other than the MAP."

Note circling, is a visual maneuver, assumes either 20 or 25 deg AoB depending on what rules are being followed.

Quoting GlobalMoose (Reply 14):
Do you immediately execute the missed approach when you hit the circling MDA while on glideslope or do you drive into the MAP for the LOC approach?

Are you serious ? have a think about that one again.

Quoting GlobalMoose (Reply 14):

This is why I don't circle from a precision approach

In practice it is one done a few airports, most airports are setup for straight in approaches either end.

Quoting wilco737 (Reply 15):
Correct, but the modern FMC's have a virtual glideslope which you can easily fly with VNAV (or in the new B748 you only hit APP and it flies a proper 3 ° glideslope, just like an ILS)

That is nothing new in industry, been standard on FBW Airbus now for 25 years, and you find it on most business jets. Only just taken 40 years for the 747 to catch up.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlinePihero From France, joined Jan 2005, 4445 posts, RR: 76
Reply 18, posted (1 year 11 months 3 weeks 4 days 7 hours ago) and read 5183 times:
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As an illustration of this thread, here is Ajaccio. See plates 12 and more importantly , 13, titled VPT b RWY 22 .
Having done it quite a few times in marginal weather, I know it's rather sporty.
Of course, the pattern is mandatory.
Ajaccio Napoleon Bonaparte

[Edited 2012-09-25 10:52:56]


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