Go Around Procedures [Archive]

DFC

17th Apr 2010, 10:48

For non-precision approach it is very simple. The Missed Approach Point will always be specified and easily determined.

When flying a non-precision approach, no matter if using the CDFA or flying level at or above MDA, the missed approach point as published must be overflown during the missed approach.

The only possible exceptions to this could be where

a) The aircraft is at or above the minimum vectoring altitude and after being informed of the missed approach they issue an immediate vector.

b) The aircraft is above the applicable MSA and ATC approve a routing that doed not go via the MaPT.

c) The one OEI requirements make overflight of the MaPT impossible.

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In the case of the precision approach, the procedure is basically the same however, if you are flying an ILS you are left to determine at what point the glideslope intersects with the published DA - note I said published DA which could be lower that your personal or company minima.

If there is a DME then it is reasonably easy to determine where 200ft AAL is - about 2/3nm.

The rules in this case require that if a missed approach is started early, one still has to overfly the position where the glideslope intersects the DA.

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So let's look at ana example;

Sea level aerodrome

ILS procedure with DA 200ft

LOC (GS Out) procedure with MDA 400ft and MaPT at the on field NDB

Missed approach procedure is Straight ahead to 1000ft then left turn back to the LOM climbing to 2000ft

Your minima - DA500ft for ILS and MDA 600ft for LOC - using CDFA

In the case of the ILS the missed approach climb would be started at 500ft - (about 1.7nm) but even if the aircraft levels at 2000ft the left turn can not be made until 0.7 DME is passed because this is about where the published DA is.

For the LOC it is easy. Go arround at 600ft and start the turn at the NDB.

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The lesson to be learned is that when flying a precision approach one still needs to be aware of where the published DA lies despite using a higher value.

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Finally be aware. ATC may be expecting you to start the missefd approach at the published DA and may have based a non-standard missed approach instruction on this eg "straight ahead to 1000 then right turn heading 360" and might be a bit surprised if you manage to establish on heading 360 prior to passing the landing threshold!! - They shoulod not be but it can happen.

Pull what

3rd May 2010, 12:58

If one does a go-around from DA on a ILS approach and the Missed Approach Procedure involves a turn does one have to fly straight ahead to the MAPt before commencing the turn.

A precision approach does not have a MAPt-a MAPt is a function of a non precision approach only. If you see an MAPt on an ILS plate it is for the localiser approach only.

DFC

3rd May 2010, 15:03

A precision approach does not have a MAPt-a MAPt is a function of a non precision approach only

Partially correct.

On precision approach the missed approach point will where the nominal glide slope intersects the DA.

Similarly the final approach point is where the nominal glideslope intersects the intermediate altitude (platform altitude).

Since different operators may use different DA's then it is not possible to publish a common point.

Just because the missed approach point is not a fix doesn't mean that it does not exist.

Dan Winterland

3rd May 2010, 15:49

I think the answers to the questions are:

1. Generally yes.

2. Yes in nearly every case with probably a couple of exceptions. (I can actually think of one).

As mentioned, any MAP for a PA has to have a notional MAP because of variences in operators minima and type of precision approach. For example, a CAT3B approach may not have a DA. Also, there may be local variences, for example, TERPs or PANSOPs.

A good clue is to see what aircraft with Flight Management Systems do. The approach will always terminate in a waypoint. For a PA, this is invariably the runway threshold and initiating a GA will sequence the Missed Approach waypoint string from this. Some NPAs will terminate at the threshold and some at the MAP. The procedures are written assuming the GA will be made at minima. So in the case of higher level GA, it's very safe to say that you should overfly the MAP or the runway threshold. Which depends on the procedure - and the approach plates should tell you in the case of a GA.

If the MAP is an on airfield beacon, this will not generally be the last waypoint as it may be displaced, and in anycase, the approach will not be stabilised. Many published approaches now have an RNAV overlay and the Flight Management Computer sequence the waypoints along this path.

In any case, the autoflight aircraft will invariably go into a runway track or heading mode after a GA and it's up to the pilot to engage some form of lateral managed navigation to make it happen. Of course, once the realisation has dawned the aircraft can't land and the GA initated with subsequent flap and gear retractions, this won't happen immediately, so there is usually some lattitude, even with very low level turns.

DFC

3rd May 2010, 20:22

A good clue is to see what aircraft with Flight Management Systems do.

Dan,

While there are a variety of systems out there one common important thing is that one can never fly an ILS or LOC approach using the FMS.

This is critical.

To put it in GA terms - one can never use GPS to fly an ILS or LOC approach.

In most cases the ILS does not become an issue because even those in drastic need of help seem to remember to arm APP which couples the FD to the ILS (and not the fms).

The problem is when the GS is U/S and the "bright spark" thinks "I can do this in LNAV (FMS)" or "I can use the GPS".

This is dangerous.

The localiser gets more and more narrow as one gets closer to the threshold and therefore 1/2 scale deflection represents a smaller distance from the centreline at 1nm than at 5nm.

If one tries to use FMS LNAV / GPS then 1/2 scale deflection maintains a constant distance from the centreline and therefore one could leave the obstacle protected airspace.

As for the Missed approach. Generally, the missed approach becomes available for activation one one passes the FAF or FAP.

When one flies the approach one should set the heading bug appropriately. Therefore one initially has a heading to fly that will cause the aircraft to track straight ahead. Note I say straight ahead and not the runway centerline because the initial missed approach is a continuation of the final approach track and unless the tracking aid is on the runway centerline one will be flying across the centerline.

Having established the aircraft on the missed approach, if we arm LNAV then the FMS will cause the aircraft to track in accordance with the published missed approach procedure. The only time it will just leave you on a heading is when (just like on a SID or STAR) the procedure specifies that a heading is followed.

If the MAP is an on airfield beacon, this will not generally be the last waypoint as it may be displaced, and in anycase, the approach will not be stabilised.

I don't know what you are getting at here. The position of the MAPt has no relevance to stabilised approach criteria. We are now required to use CDFA (and I hope all schools are teaching it). No matter the type of straight in approach, the IMC stabilised criteria are normally determined at something like 1000ft AAL which will be a long way from the MApT (unless someone has mucked up the procedure!! ;)

Finally the last thing I would ever recomend is to base what one does on what the FMS has coded into it. Quite common to have coding errors and also find that (as some people did in Chambery recently) that the FMS can ask that a turn is made in the wrong direction is you get the missed approach speed wrong.

If we could trust the FMS / GPS we would not spend all that time every flight cross checking the waypoints etc!!

SNS3Guppy

3rd May 2010, 20:36

If one does a go-around from DA on a ILS approach and the Missed Approach Procedure involves a turn does one have to fly straight ahead to the MAPt before commencing the turn.

YES!!!

One may climb early, but not turn.

Dan Winterland

4th May 2010, 02:17

DFC, my illustrations were so that the questions raised could be answered and not for a discussion of how to manage a GA in an FMC equipped aircraft which is not really what this forum is for. But I will answer your points as I'm on standby and don't have much to do.

"While there are a variety of systems out there one common important thing is that one can never fly an ILS or LOC approach using the FMS."

You may be suprised to know that it is acceptable in at least one (and maybe some more) aviation authorities jurdisdiction to fly a LOC approach in NAV on certain aircraft types- as with any NPA. But if it doesn't have an RNAV overlay (as a LOC will not), raw data has to be displayed somewhere on the flightdeck.

"To put it in GA terms - one can never use GPS to fly an ILS or LOC approach".

Do you mean General Aviation or Go Around by your use of GA. If the first, no. The latter maybe. And FMS position derived from a mix of inertial, radio and GPS position and never from GPS alone.

"As for the Missed approach. Generally, the missed approach becomes available for activation one one passes the FAF or FAP".

Not on the aircraft from the airliner manufacturer who sold more than any other last year. It becomes active from the IAF, or when the approach is manully activated. If the MAP is an on airfield beacon, this will not generally be the last waypoint as it may be displaced, and in anycase, the approach will not be stabilised.

"When one flies the approach one should set the heading bug appropriately. Therefore one initially has a heading to fly that will cause the aircraft to track straight ahead. Note I say straight ahead and not the runway centerline because the initial missed approach is a continuation of the final approach track and unless the tracking aid is on the runway centerline one will be flying across the centerline".

You can't on an Airbus, well you can for 45 seconds, but there's no point. FMCs will specify which directional reference is active on a go around and apply it when the GA is initiated. They all do it differently and some even know which standard (TERPs or PANSOPs) the approach is using and apply the relevant technique.

"I don't know what you are getting at here. The position of the MAPt has no relevance to stabilised approach criteria."

The MAP in an FMS waypoint on a NPA with an RNAV overlay cannot be past the threshold, so there is another waypoint inserted before - either at the threshold or the MAP. It is relevant to stabilsed approaches as some types can fly NPAs fully managed, i.e in 3D. With both lateral and vertical navigation down to MDA.

I have used three very different FMCs in my career and they all do things differently. But one thing in common is that they all sequence waypoints when you get within certain parameters. It's crucial that the TO waypoint is relevant. If you are vectored on the approach and miss the TO waypoint without noticing it, your GA procedure may have you fly back to tthe waypoint you missed. If you activate the GA before you get to the MAP and there is another waypoint before the MAP, you need to make sure the GA track is flown from the MAP. Not a problem usually as the heading reference will usually be Runway Track or similar and you just need to make sure the NAV reference is activated with the MAP as the sart point for the GA procedure.

"Finally the last thing I would ever recomend is to base what one does on what the FMS has coded into it".

Well, I do. It's my company's SOPs and it will be the same with many others. The approach coded in the FMC is checked by each pilot from the approach plates. Every track, distance and constraint. And then we fly the approach with FMC guidance where relevant. However, usually, it's an ILS so from intercept, we are flying something other than FMC derived navigation. But we have a number of NPAs on our network, including a some GPS approaches (now referred to as RNAV) approaches, so we have no choice but to follow the FMC. An further to that, we can fly the approach fully managed. That is to say, we leave the autopilot in, when cleared for the procedure, we arm the approach and then watch the aircraft fly itself down to MDA just as if if were an ILS. All we have to do is click the autopilot out at the "Minimum" call and land it. And this isn't limited to RNAV approaches. We can do this on any NPA with an RNAV overlay. It's very safe, much safer than the pilots interpreting and chasing wobbling needle and we are encouraged to use this method rather than hand fly.

I don't know when you last flew an FMC, but things have changed.

DFC

4th May 2010, 09:12

DFC, my illustrations were so that the questions raised could be answered and not for a discussion of how to manage a GA in an FMC equipped aircraft which is not really what this forum is for.

Unfortunately, your "illustration" was rather confused wich does not help the reader and I think that this is the perfect forum for instructors and examiners and not limited to PPL level instruction.

Just some of the major points;

The MAP in an FMS waypoint on a NPA with an RNAV overlay cannot be past the threshold

1. There does not have to be an RNAV overlay for the NPA to be coded in the FMS.

2. The MAP can be past the threshold. However, if that is the case, then Virtual Glidepath or whatever your system calls it will not be available. i.e. you will get the normal LNAV indications but no VGP and will have to use some other vertical mode to follow the ideal profile as published for each mile on the chart.

3. GPS procedure - use GPS. RNAV - use any appropriate RNAV system. In most cases the FMS will use DME/DME and/or VOR/DME in addition to GPS so RNAV could be available when GPS is U/S ergo one could fly an RNav approach but not a GPS one.

As for the missed approach being available after the IAF - I again think that you are confusing being available rather than being available to be activated in accordance with normal procedures. Here is an important point related to the question posed - the missed approach must be started from the final approach track to ensure obstacle clearance.

If one starts a missed approach just after the IAF then unless one is cleared otherwise one follows the procedure to the MAPt. To do otherwise in many places could cuse one to fly into a mountain.

I am glad that you agree one should never use the FMS coded procedure without first checking that it is in accordance with the up to date chart and notams because we both agree that it is the chart that is what one follows be it by hand-flying raw data or sitting back and watching the aircraft do it for you.

Everyone needs to remember that no matter if you are flying a basic old PA34 on an instrument approach or the latest fly by wire FMS equipped aircraft it is the pilot that needs to know what is happening and about to happen because making an incorect decision eg early turn will put an Airbus into the mountain just the same as the PA34.

So to sum it up - do what the chart says. If there is any doubt then do not let the FMS database programmer become PIC!!

Pull what

4th May 2010, 11:12

Quote:
If one does a go-around from DA on a ILS approach and the Missed Approach Procedure involves a turn does one have to fly straight ahead to the MAPt before commencing the turn.
YES!!!

One may climb early, but not turn.

No-because there is not a chart MAPt on a precision approach as per PANS OPS
You follow the missed approach procedure (or ATC instructions) if an early turn is not allowed the missed approach procedure will make that statement

samusi01

4th May 2010, 20:52

I was taught not to turn until reaching the MAP or point at which DH/DA would normally be found. Consequently, my students have been taught the same. The FAA's guidance on the matter, per AIM 5-4-21:

Obstacle protection for missed approach is predicated on the missed approach being initiated at the decision altitude/height (DA/H) or at the missed approach point and not lower than minimum descent altitude (MDA).

Therefore, on an approach predicated on TERPS, an early turn below MSA/TAA or equivalent may result in loss of separation, as you are no longer operating at an altitude that has been surveyed.

Dan Winterland

5th May 2010, 04:00

DFC, Another standby day, so I'm going to answer. WRTo FMS overlays. It depends on the provider of your navigation database, but you will find these days that a RNAV overlay is generally required for a NPA to be included in the FMC as an available approach. Nearly every NPA in my company's route structure now has an overlay and suitably coded waypoints. You still find some which don't in the approach book, the older NDB A and B procedures which require timing outbound, but these are not in the FMC database. You can of course build these youself or fly them on raw data, but neither technique is recommended and has in fact been recently disallowed by my company's SOPs. The one exception of course is a LOC approach, but this uses the ILS as the selected approach in the FMC.

Ergo, any NPA with an RNAV overlay with a pulished MAP of a beacon past the threshold will have a termination waypoint at the runway threshold or another waypoint before the threshold to make it work. A managed approach with vertical guidance is not possible in this case.

GPS approaches are becoming known as RNAV approaches. I think this is to discourage pilots flying them with standalone or inappropriate GPS set which has caused a few accidents I gather. It depends on the equipment fitted, but in our operation we must have GPS navigation in High accuracy on all FMCs to commence the approach. If you haven't then you will almost certainly not have the RNP to commence the approach. (Our FMCs dispaly the RNP and ANP - Actual Nav Performance values). Flying a RNAV approach without GPS updating is not allowed within our SOPs

The Missed Approach procedure becomes active after the IAF, it is included in the waypoint string from the last waypoint on the approach. Initiating it depends on aircraft type, I can't remember how to do it on glass cockpit Boeings - it's been several years since I last flew them. But in the Airbus, you select TOGA (even if you don't want TOGA power - you just immediately bring the Thrust Levers back to the Climb detent before the engines respond) and the aircraft will go into a heading refrence mode. It's up to the pilot to reselect a NAV mode and ensure the TO waypoint is the one he wants and that the sequence follows the procedure. It will never fly you direct to the start of the Missed Approach Procedure unless it it the TO waypoint. In my experience, ATC will invariably give you a radar heading on a GA anyway, so being in a heading mode is probably best.

Apologies for the thread creep to all those of you who seek the answer to the original question.

I think it's been answered BTW!

DFC

5th May 2010, 11:24

You can of course build these youself

One must never build one's own procedure. If it is not in the database then it can not be used. If for no other reason than you have no way of ensuring that the sensitivity of the CDI changes appropriately for the various phases of the operation. Your company's SOPs are merely following what has been a requirement for a very long time.

Perhaps you (in common with many others) are confusing using the FMS to fly an RNAV approach and using the FMS to fly a series of tracks that you are using to fly an approach based on raw data i.e. the FMS is doing all the brain-work but the only reference for the approach is the raw data. You could do just the same by flying in Heading mode and working out the required headings yourself.

and the aircraft will go into a heading refrence mode

Ah we agree. As I said previously, the initial missed approach is in heading mode and provided one has set the heading bug to a figure that will maintain the final approach track then the initial missed approach will track straight ahead (an extension of the final approach track) as per the requirements.

The most important thing about GPS approaches is RAIM.

I think this is to discourage pilots flying them with standalone or inappropriate GPS set

It is entirely legal and common for aircraft to use a single (approved) GPS unit for GPS approaches.

It is also entirely legal and common for aircraft with no GPS to perform RNAV approach procedures (based on VOR/DME).

If I remember correctly the only time one needs an FMC (FMS) is when doing DME/DME procedures.

However, no matter what one is using to work out where to point the nose of the aircraft it remains the responsibility of the PIC to ensure the safety of the flight and this means following the relevant approach procedure correctly.

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Pull What,

No-because there is not a chart MAPt on a precision approach as per PANS OPS
You follow the missed approach procedure (or ATC instructions) if an early turn is not allowed the missed approach procedure will make that statement

6.1.4 It is expected that the pilot will fly the missed approach procedure as published. If a missed approach is initiated before arriving at the missed approach point (MAPt), the pilot will normally proceed to the MAPt (or to the middle marker fix or specified DME distance for precision approach procedures) and then follow the missed approach procedure in order to remain within the protected airspace.

Note 1.— This does not preclude flying over the MAPt at an altitude/height greater than that required by the
procedure.

Note 2.— In the case of a missed approach with a turn at an altitude/height, when an operational need exists, an
additional protection is provided for the safeguarding of early turns. When it is not possible, a note is published on the
profile view of the approach chart to specify that turns must not commence before the MAPt (or before an equivalent
point in the case of a precision approach).

The above is from PANS-OPS. In the second note I have highlighted the important words - when an operational need exists. You will not normally know when this is and there are many places where turning before the MApT would turn you into the side of a mountain. This also only applies to a turning missed approach where the turn is at an altitude.

To keep safe, unless you are sure of obstacle clearance and have ATC clearance then always overfly the MAPt.

Dan Winterland

6th May 2010, 03:34

"One must never build one's own procedure. If it is not in the database then it can not be used."

I'm not advocating building your own procedure! If it's published and not in the database, it's possible and legal withinin some authorites rules and regulations to build it from the approach plate. It should be checked independantly by both pilots and it has to be flown selected, not managed (if managed approaches are legal on your type/Authority/AOC).

''Perhaps you (in common with many others) are confusing using the FMS to fly an RNAV approach and using the FMS to fly a series of tracks that you are using to fly an approach based on raw data''

No, I'm not. The FMS flys a RNAV overlay NPA through a series of waypoints coded in the FMC. The raw data is there and has to be displayed, but we are essentially flying an RNAV approach (not to be consfused with a RNAV GPS approach) from the database. The raw data is now largely irrelevant. The old approach has been converted into a more mangeable and safer procedure. I've posted an example of an RNAV overlay NPA below.

http://i210.photobucket.com/albums/bb73/dbchippy/rnav-1.jpg

The faint references in the square brackets are the RNAV waypoints and are coded as such in the FMC. In this case, the approach can be flown fully managed in aircaft so certified. i.e - it can be flown with a 3D profile with vertical guidance in automatic flight just as an ILS would be

There is no confusing of anything. This is a certifed and authorised method and is now the primary technique for flying such approaches with many operators.

Incidently, this is an example of an approach which does not terminate at the threshold, but the MAP. So in this case, the missed approach should be initiated from the MAP, if the decision to go around is made before or at the MAP.

Pull what

6th May 2010, 07:38

DFC -- It doesnt matter how many times you quote PANS Ops or make other statemements, a precision approach does not contain an MAPt!

To keep safe, unless you are sure of obstacle clearance and have ATC clearance then always overfly the MAPt.You keep quoting an MAPt-it doesnt exist for a precision approach as your posted Pans Ops example shews. You proceed to the MKR or published DME distance, as you have quoted. So to recap again what I said, in the event of a missed approach on a precision approach you follow the published procedure, if an early turn is not allowed that will be written into the procedure by direct statement or DME distance.

If one does a go-around from DA on a ILS approach and the Missed Approach Procedure involves a turn does one have to fly straight ahead to the MAPt before commencing the turn.That was the original question, the answer is NO because there isnt a published MAPt on a precision approach and as your example shews, you fly to a stated DME distance or to a MKR. the only way the pilot knows this is by an associated statement with the GA procedure.

when an operational need exists. You will not normally know when this is
Not sure what you mean by that-how are you interpreting an operational need?

DFC

6th May 2010, 16:45

DFC -- It doesnt matter how many times you quote PANS Ops or make other statemements, a precision approach does not contain an MAPt!

Every instrument approach has a missed approach point.

Missed approach point (MAPt).
That point in an instrument approach procedure at or before which the prescribed

missed approach procedure must be initiated in order to ensure that the minimum obstacle clearance is not

infringed.

QUOTE=PANS OPS] 6.1.5 The MAPt in a procedure may be defined by:
a) the point of intersection of an electronic glide path with the applicable DA/H in APV or precision approaches;
or
b) a navigation facility, a fix, or a specified distance from the final approach fix (FAF) in non-precision

approaches.[/quote]

Just because it is not charted and/or is not a fix does not mean that the missed approach point does not exist.

Everyone needs to be aware of where the missed approach point is on every precision approach that they fly. The reason is that starting the missed approach later than the missed approach point can cause a loss of obstacle clearance. Note well that when you fly an ILS the missed approach point is the intersection of the nominal glide path and the decision altitude.

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Dan,

You could have picked an example outside the Former USSR / China countries!! :D

You could even have left people with some clue about where you are talking about if you wanted to discuss the matter. :D :D

Give us an example of an Authority that permitts a pilot to construct an approach procedure in their FMC or GPS and then fly that procedure. Perhaps you could explain to us how when flying such a procedure you ensure the automtaic changes in RAIM requirements and CDI scale.

Dan Winterland

6th May 2010, 17:48

I could have, but it doesn't matter where the procedure is. I used it as I happened to have the plate stored on my hard drive as this approach was the subject of a recent OPC. It exists and it's topical. This plate is one of my company's daily destinations in China - and I have flown there in the last week.

RAIM will not have any effect on the accuracy of the information displayed. If a lack of satellite coverage was an issue, then the degradation in Nav accuracy will be annunciated and an alternative method will have to be chosen. As for a CDI range, no aircaft equipped for such an approach will be fitted with a CDI these days. It will have an ND which will have it's range manually selected by the pilot according to personal preference or SOPs.

DFC, I don't know what your experience or background is, but either you are an ex-airline pilot who is out of date with the current techniques and equipment, or an instructor who thinks he knows it all. Either way it's clear that you don't fully understand what you profess to know.

BEagle

7th May 2010, 08:41

Huanghua (Changsha), pretty obviously, DFC.....:rolleyes:

Practising asymmetric NDB go-arounds from the MAP (overhead the beacon) at the Covert Oxonian Aerodrome was always good sport - because that meant (in those days) full power on 3 directly overhead the Stn Cdr's house.....:E

Came back once with another pilot at about 2230 local and we'd been given the 'hard word' to make sure that all Basic Training Requirements were completed before the end of the week.... 'Night rules' started at 2300 local, so we both flew asymmetric NDB go-arounds....in the full knowledge that the Stn Cdr (O***s) was on an early trip the next day in his desperate attempt to hog yet more hours. Perfectly within the rules - his wife later told my nav's wife that the noise had been unbelievable!!

The sound of freedom, courtesy of the mighty Vickers Whisperjet!

And now we return to the usual bickering, no doubt....:bored:

Dan Winterland

7th May 2010, 09:43

Indeed, Changsha (ZGHA). Another delightful :rolleyes: destination on our network. I had erased the navaid references but not the lat/long grid. Could be a cue for a new boring PPRuNe game - spot the airfield from the procedure. But then again, maybe not!

I remember those 3 engine NDB GAs. In the days when we used to do "dive and drive" NPAs before common sense and safety took over. I wonder whose idea it was to put the BZ beacon right next to the Station Commander's house? I take it your Nav was Snake!

Done bickering. Not on standby now. Don't bicker on my days off - except with Mrs W of course!

Pull what

8th May 2010, 10:58

or an instructor who thinks he knows it all.

Dan that comment has no value at all

BEagle

9th May 2010, 09:56

I had erased the navaid references

You missed one, Dan....;)

Those weren't 'dive and drive' NDBs. Flown as a normal NPA with 'height for range' passed by the navigator (to keep them occupied, I guess). But on reaching MDH, we levelled without busting it and then flew to the MAP which was at the other end of the RW.

Notional GP technique was only mandatory where published on the IAP chart. Otherwise the APATCC-1 design assumed a max RoD from the FAP which equated to 1000 ft/min at 150KIAS - so descending at that rate, then flying level to the MAP was often practised. Entirely safe provided that the crew knew what they were doing. Before we had the NDB/DME procs, the whole NDB was often flown based purely on timing without any navigator assistance whatsoever - apart from some drift values.

Flying notional GP NDB approaches using the published MDH 'the ba way' would guarantee an MDH bust if the pilot used it as a DH rather than a MDH.....:rolleyes:

No doubt DFC will be along with pages of dubious maths now.....:zzz:

dsw4ski

9th May 2010, 15:39

Good Example : In MANY ( most ) Mountain areas , DOWN in a flat valley is where the Runway and final Approach is.
If you make your turn too early OR too late.... you will hit the higher ridge that is on your left or on your right !! ( Cumulus Granite ! )
Fly to the MAP before making an turn. !!!

Chuck Ellsworth

9th May 2010, 19:19

DFC, I don't know what your experience or background is, but either you are an ex-airline pilot who is out of date with the current techniques and equipment, or an instructor who thinks he knows it all. Either way it's clear that you don't fully understand what you profess to know.

When I need to escape from reality I come here to reminisce about the past, these arguments remind me of some of the high time big iron drivers I used to give type ratings to on the PBY.

Every once in a while I ran into an expert who knew all the answers.......but behind the controls they were frightening in their lack of airplane handling skills.

Carry on kids this is fun reading. :ugh:

Pull what

10th May 2010, 10:09

If one does a go-around from DA on a ILS approach and the Missed Approach Procedure involves a turn does one have to fly straight ahead to the MAPt before commencing the turn.DFC ---that was the question

The answer (again) is no because on a precison approach there is not a published MAPt, the missed approach point is the decision altitude or height. A MAPt shewn on a chart is shewn for a non precision approach Where a runway has individual charts for the localiser and the ILS approach a MAPt will not be shewn on the ILS chart.

DFC

10th May 2010, 10:39

Let's try and cover one point at a time Dan;

As for a CDI range, no aircaft equipped for such an approach will be fitted with a CDI these days. It will have an ND which will have it's range manually selected by the pilot according to personal preference or SOPs.

CDI = Course Deviation Indicator

That is the pointer with the bar that moves left or right depending on which side you are moving away from the on course track.

It is what you use to fly the localiser during an ILS approach or the VOR track during a VOR approach etc.

Your EFIS aircraft will display it for you to use in such cases.

When using RNAV, the distance off track required for full scale deflection changes automatically - and most importantly in the case of Terminal and Approach are usually flagged on the flight display (usually a requirement to check the flag before starting the final approach or PRNAV procedure). The RAIM required accuracy will also automatically change at various stages. These are automatic and not pilot selectable. If you construct a procedure you may not get the required sequencing / accuracy of the CDI / RAIM checks. This is not something that you can play round with when there are obstacles about.

Just because you for example use ARC display and set the ARC range to 50nm or 10nm or 5nm during an approach does not change the sensitivity of the CDI when flying an ILS. At 1/2 scale deflection of the CDI it will still be the same distance from the nominal track.

As I said previously, the reason why one can not fly a LOC (Localiser) approach as an RNAV approach is that the RNAV provides a constant distance left or right of the nominal track as one proceeds along the approach. Now for a VOR or NDB approach then this is usually no problem because the RNAV accuracy is better than the smallest width of the protected area (at the beacon). It can not provide the same in the case of a LOC. In the (near) future With augmentation applied to GPS it will be possible but not safely yet.

------------

BEagle,

Flying notional GP NDB approaches using the published MDH 'the ba way' would guarantee an MDH bust if the pilot used it as a DH rather than a MDH

It is not 'the BA way' it is the ICAO and EU-OPS way. If you read EU-OPS you will see that if one intends to fly level at the MDA one will have to use higher RVR/Visibility minima because the approach is not stable.

The MDH is never used as a DH. An increment is added (usually 50ft) which accounts for the height lost during the initial missed approach.

Before we had the NDB/DME procs, the whole NDB was often flown based purely on timing without any navigator assistance whatsoever

There are still plenty of places that only use timing and many more that have timing as an option if the DME is u/s.

CDFA should be taught as the primary method of flying a stable non-precision approach with flying lefvel at the MDA reserved for approaches where it is not possible to calculate a descent profile or which lead to circling.

I don't think anyone is saying that the missed approach climb should be delayed until the MApT the doubt is over when one can turn is a turn at an altitude is specified in the procedure.

I hope that everyone flying the CDFA will go arround at the DA(H) without infringing the MDA(H) while anyone flying an approach with a level segement at DA(H) would start the go-arround climb at the point where a landing is no longer possible which may be before the MApT.

No point in becoming visual 1nm before the threshold at 900ft unless those are circling minima!!

Dan Winterland

10th May 2010, 17:22

Now let's try to answer one point at a time, shall we.

''CDI = Course Deviation Indicator

That is the pointer with the bar that moves left or right depending on which side you are moving away from the on course track.''

Thank you for explaining what a CDI is, but I think I may know as I used to use them - for many thousands of hours. However, It isn't what I use for flying an ILS or a LOC approach these days. I use the ND (Nav Display) for Navigation, but use the LOC and GS indications of the PFD (Primary flying display) for the required raw data. On the ND, I have the option of displaying raw data if I wish, and that display is called a Rose VOR or Rose ILS - and not a CDI - common both major airliner manufacturers. A CDI is an electro mechanical instrument which as you mention displays LOC deviation. For your information, some CDIs can display INS/IRS information as well. I used to fly Classic 747s which could switch the CDI to NAV track dispacement is so wished. And being fed with Litton 92 IRSs, they were very accurate. So accurate that the preferred method of flying a NPA was to use them as such with the raw data being displayed by the needles on outer ring of the CDI or the RMI.

Incidently, these aircraft had to have the CDIs ripped out and NDs installed for PRNAV requirements.

But I never wish to fly using the ND Rose modes as I can have a much better display if I use the ND in a Nav mode. The required raw data is either superimposed on the PFD as the LOC or on the ND as the VOR/NDB needle. I don't think you will find any pilot who would wish use his ND in Rose mode and in my years of flying glass cockpit aircraft, I have never done it myself, or found a pilot who another pilot who chose to it. The only one exception was one company (with slightly strange SOPs) which requird us to do some clever switching with the slectors so that raw data was displayed in Rose VOR on the lower EICAS display, but I can't ever remember referring to it even though it was there as we had NAV dispalys on our NDs.

''The RAIM required accuracy will also automatically change at various stages''

Maybe, but this is not indicated to the pilot on modern displays. If there is any issue with GPS accuarcy, it will be indicated, along with an indication of Naviagtion accuracy downgrade if applicable. RAIM is handled in different ways by different systems. On my current type the highest level of accuracy is assumed at all times. and we even have a system where we can deselect individual satelites which are NOTAMed as being unreliable. But it won't have any effect on the displays, unless we get to the level where there are not enough satelites being received to satisry RAIM requirements, when a downgrade of GPS and NAV accuracy will be annunciated.

"These are automatic and not pilot selectable. If you construct a procedure you may not get the required sequencing / accuracy of the CDI / RAIM checks".

on modern airliner types, RAIM tends not to be selectable for the reasons stated, but NAV accuracy parameters are. The Required Nav Performance (RNP for the phaes of approach sequences automaticly. If conducting a RNAV approach, we have to check it is the correct value. If not, we overwrite it. If the Actual Nav Perormance (ANP) exceeds this value, the pilots are warned.

''As I said previously, the reason why one can not fly a LOC (Localiser) approach as an RNAV approach is that the RNAV provides a constant distance left or right of the nominal track as one proceeds along the approach. Now for a VOR or NDB approach then this is usually no problem because the RNAV accuracy is better than the smallest width of the protected area (at the beacon). It can not provide the same in the case of a LOC. In the (near) future With augmentation applied to GPS it will be possible but not safely yet.''

You said it previously, but you were incorrect. A LOC can be flown as an RNAV approach. Any NPA with an RNAV overlay can be flown as a FMS managed approach. This includes the LOC, as even though an ILS is flown referenced only to external sources, there is still a RNAV sequenced approach for the procedure. The LOC is flown using the ILS RNAV waypoints. Don't get confused about GPS not being good enough - it is flown using RNAV position which in some aircraft is the IRS position updated by GPS and Radio Naviigation sources. If the ANP is within the RNP, you can do it.

Not all aircraft types or operators may have the authorisation from their authorities to conduct these, but I can assure you, mine does. In fact, our current OPC has the crew flying a LOC approach, and it is empahsised that the crew have the option of flying it in LOC or NAV modes.

It seems you are basing your assumptions on a specific aircraft type. There are more advanced systems out there, for which your statements are incorrect.

DFC

10th May 2010, 21:40

Dan,

I will leave the CDI issue as it it unimportant that you are unaware that the piece of graphics on your nav display which tells you your deviation from the chosen course is (funnily enough) a course deviation indicator.

You will next tell us that you flew an aircraft that had the attitude indicator as well as the HSI removed to be replaced with an all singing EFIS system so now there is no attitude indicator anywhere on board but only a PFD. :)

However, getting back to the critical aspects of what you are saying - the bits that could be dangerous.

It is a basic requirement that only approaches included in the database can be flown. It is a basic requirement that one can not construct one's own approach procedures and finally, obstacle clearance may not be guaranteed if one replaces a localiser procedure with an RNAV one.

It has taken some time but I have found a situation that many will be familiar with to illustrate this point. Have a look at Frankfurt runway 25R.

The charts are freely available at www.ead.eurocontrol.int (http://www.ead.eurocontrol.int)

It has the following non-precision procedures available;

(I have included cat C OCA just for you!!)

Localiser DME - 790

VOR DME - 820

NDB DME - 820

RNAV(GPS) - LNAV 830

Can you explain why the RNAV procedure using LNAV has a higher OCA than all the other 3? If your argument that it will fly the procedure just as accurately is relied upon then would it not have the same OCA? perhaps even a lower OCA?

Have a look at the Jeppesen database that you use. You will find that the VOR DME procedure is in there. Just because it is coded in the database of the FMC does not in any way approve it as an RNAV procedure. One can use the FMC to do the donkey work but one has to have raw data displayed and use the raw data as the primary reference. It is by doing this that one can use the VOR DME OCA of 820ft

But why do that when you have

RNAV APV OCA of 790.

Funny that - you can fly the Localiser approach with no vertical guidance over the same terrain as the RNAV(GPS) to OCA of 790 but the RNAV must have APV to fly to have the same OCA.

Perhaps all I can do is simply recomend some further reading - ICAO 8168 and the relevant FAA TSO paying particular attention to the requirements for database, automatic cdi sensitivity etc.

Now go on tell us all about those SRAs that you have flown in RNAV!! :D

bookworm

11th May 2010, 07:34

6.1.5 The MAPt in a procedure may be defined by:
a) the point of intersection of an electronic glide path with the applicable DA/H in APV or precision approaches;
...
Everyone needs to be aware of where the missed approach point is on every precision approach that they fly. The reason is that starting the missed approach later than the missed approach point can cause a loss of obstacle clearance.

Doesn't that raise a rather interesting issue with respect to the MAPt on a precision approach? How does the pilot reliably determine the MAPt if he goes around early and is therefore not flying the glidepath? There may be no DME (and that might be misleading anyway) and no markers.

Dan Winterland

12th May 2010, 15:27

Bookworm. An ILS has to have either DME or markers, otherwise a Glidepath height check cannot be carried out.

DFC. Your example of FRA 25R is interesting. I couln't access the link you gave, so I had a look at the Jeppessen charts. There are two CAT C/D minima published for the RNAV (GPS) approach. The first is the LNAV mnima of 830' (which you quote) and the LNAV/VNAV minima of 800'. Only 10' above the LOC minima and not 40'. Possibly the reason why you didn't see the lower minima is that not all operators are cleared for these '3D' RNAV approaches and they are not available to all. The Jepps my company use are specific to us and show these lower minima.

Why is it 800' and not 790'? I don't know, and I don't think you do either. Minima is based on both lateral and vertical constraints and perhaps the vertical profile is different. And why is it not lower if RNAV approaches are so accurate? Perhaps caution is the policy with the new technique. The minima will undoubtedly reduce as experience is gained and area augmentation improves - RNAV will probably replace ILS and MLS eventually - even down to LWMO minima.

I also had a look at the FRA VOR 25R as you suggested. I don't think this is a RNAV overlay approach due to the lack of final approach RNAV waypoint designators. I can't check it in the our FMC databse as you suggest, as FRA isn't in there. We have no destinations west of Mumbai.

I have spent enough time expaining the principles of these RNAV NPA approaches. Just because these new techniques are not in your experience, it doesn't mean they don't exist. The way NPAs can be flown on a suitably equipped aircraft and trained crews by authorised operators is changing fast. If you don't like it, I suggest you don't use these airlines. But you will find the airlines you can fly with reducing year by year.

And your flippant comment about SRAs and sarcastic smilies do not give your arguments any credibility. You seem to be arguing for the sake of it. There is no point in continuing this discussion - it's a waste of my time and way off topic.

We don't fly SRAs by the way. They are very rare in our area of operations, we don't train for them and we aren't authorised to fly them.

DFC

13th May 2010, 12:29

The bit about having to check the altitude of the glide at some stage is correct. However, that is a single point.

Having the middle marker U/S makes no difference to the minima (EU-OPS). Having the outer marker u/s makes no difference provided an equivalent position is defined that can be used to check the altitude of the glide.

Therefore it is entirely possible to fly an ILS to the published minima with both outer and middle markers u/s.

As for deciding when the nominal missed approach point is if you go-arround early and say the moddle marker is u/s, that is a good point. However, if you remember that the expected start of climb on the missed approach is some 900m after the point where the lowest DA is reached, and if you are climbing early, provided you delay the turn until you are over the start of the runway then you should be 100% safe.

Dan,

I have spent enough time expaining the principles of these RNAV NPA approaches.

Just for you I am posting what a French manufacturer of long range modern aircraft says about using FMS to fly approaches. Copied from a current long range version's ops manual (aircraft in current production);

Localizer-Based Approaches

The use of FMS guidance (lateral and vertical) on the final approach segment of a localizer based approach (LOC, LOC DME, LOC B/C, LDA, SDF, ILS, ILS-DME) is prohibited.

I think that "is prohibited" makes it very clear.

Again I say that you are confusing an RNAV approach with using the FMS to fly a nonprecision approach such as VOR/DME which is not an RNAV approach but which the database provider has coded into the FMS to assist you in flying the non-precision approach.

Anyone else allowed to fly the final approach segment of ILS based procedures using RNAV?

Anyone else allowed to constructo their own approach procedures on the fly / use procedures not included in the database?

I would be very interested to hear where it is allowed. Perhaps we could have the above piece removed from the manufacturer's ops manual.

Dan Winterland

16th May 2010, 04:35

I had a look at the ICAO DOC 8168 while flying yesterday - or the Jepp extract from it in the aircraft docs. It's not actually part of my own library. I can see where you get all your information now. The bit about constructing procedures relates only to RNAV approaches. And your comments about CDI sensitivity and RAIM switching are straight from the DOC. It seems they had a specific device in mind when they wrote that as it doesn't relate to modern equipment. You will not find CDIs on modern airliners for use in NAV mode - they use a nav display. And in fact, CDIs are not approved for PRNAV operations, so this document is behind the times. And as far as RAIM and sensitivity requirements are concerned, both are now included in the integrated position monitoring of the equipment. For example, RAIM is just one element of the ANP monitoring and not a standalone monitoring sytem in itself. And as for switching at the IAP, the system automaticly changes the RNP for various stages for the flight. This is not necessarily triggered by overflying the IAP. It uses a number of parameters to do this because if you are vectored for the approach there's a very good chance you will not overfly the IAP, or trigger point if not the IAP. And if it doesn't switch, we can adjust the RNP manually if a certain value is specified to conduct that approach.

And thank you for the Operating Manual reference. I fly the same manufacturer's aircraft and we don't have that paragraph in our manuals. I also have a set of a European operator's manuals for the same aircraft type and had a quick look but couldn't find it there either - but I'm not familiar with them so I would need a FCOM reference to check.

But Airbus, like Boeing provide manuals tailored for each operator and for each aircraft serial number in that fleet. And they can be very different. So the manual you have will not be relevant to every operation. For example - Is it amended to the latest Revision and OEB. Which operating authority. Which operator. Which MSN. Which FMGC - Thales or Honeywell. Is it FMC2 standard equipped. Which MMR standard is fitted. Is the database D0200A approved. And does this operator have SAAAR approval?

There is a lot more to this topic than just isolated quotes. And I'm not confusing what is or isn't a RNAV approach. I fly a variety of approaches in my job and to explain how we do each one would be very type and operation specific and will take more time than I'm willing to give. But be assured that I do have a current IR on my aircraft type!

And as for "Anyone else allowed to fly the final approach segment of ILS based procedures using RNAV?" That's daft. No one is. But RNAV approaches down to CAT III minima to replace ILS will be here one day. We are seeing the first vestiges of this transition now.

DFC

16th May 2010, 09:40

Dan,

ICAO 8168 is not written with any particular equipment in mind. It is the standard for all. You can look at the FAA guidance as well.

Let me try and help you a little bit.

You will not find CDIs on modern airliners for use in NAV mode - they use a nav display.

I think that you are having some sort of brain block here.

Your aircraft will probably allow you to set the HSI (portion of the) display to either rose or arc format. If you place the HSI in ARC format then in simple terms you are zoomin in to the top 120 degrees of the HSI and in this format it is common to be able to display a number of things;

Flightplan route

Weather

One or more RMI pointers

One or more CDI pointers

That pointer that points at the NDB is still an RMI pointer and it still works in the very same way and you can fly an NDB approach in the very same way that you would in a C172.

That CDI that you set to (or in some cases can be automatically set to) the ILS course works in the exact same way as the one in the PA28.

Just because it is delivered to you via a screen and some graphics rather than via a stand alone instrument does not change what it is or what it does or what it is used for.

You should still find that you are required to keep the CDI within 1/2 scale deflection when flying an ILS. Yes I know that following the flight director / letting the automatics do it will keep it well inside the limits but that does not remove the limits.

I really hope that you don't try an fly an ILS relying on the X-track error display!!!!!! :eek:

To bring it back to something that many more people will be familiar with, why not have a look at say the Garmin g 1000 integrated flight display. No doubt you will say that an aircraft with one of these modern integrated displays does not have a CDI but you will find that Garmin (in common with every other manufacturer) continue to refer to the CDI information displayed graphically on their displays as a CDI. Well what else would you call something that indicates your deviations from the required course!! :)

As for setting the RNP. Yes, we can within limits change the RNP settings. (SOPS should prevent messing with these so that some idiot does not cause the aircraft to apply RNP5 in terminal areas etc etc.) However, how do you propose to set the RNP so that the system applies the appropriate ramping and RNP for say the final approach of this procedure you have constructed when since the procedure is not in the database, the system has no way of knowing that it is making a final approach.

Perhaps you will have the PM (PNF) playing with the menu as you cross the FAF. :eek: :eek:

Remember that RAIM only applies when GPS is being used. With a multi sensor FMS system you may find that the system is using DME/DME to determine your position. You may find that when making a VOR/DME approach, the FMS uses RNAV based on VOR/DME using the primary navaid because it has decided that is the most accurate. You may even find that (within very tight time constraints) you can fly a procedure using just IRS.

Your procedures should have detailed information about checking the accuracy, notaming unuseable navaids and other important issues that I will not swamp your brain with here.

However, I recomend that you take some time to read-up on the whole subject.

And as for "Anyone else allowed to fly the final approach segment of ILS based procedures using RNAV?" That's daft. No one is. But RNAV approaches down to CAT III minima to replace ILS will be here one day. We are seeing the first vestiges of this transition now

I am glad that we have made some progress and we agree that at the moment you can not use RNAV to fly LOC approaches (just like the manufacturer I quoted says).

Dan Winterland

17th May 2010, 08:16

There is so much incorrect with what you have just written, I wouldn't know where to start - if I could be bothered. Which I can't.

But I will summarise by saying that you obviously don't know much about how modern integrated nav systems work or how they are used. One example I will give you is your comment about not changing RNP values. Actually, to conduct a RNAV SAAAR approach, we use an additional checklist which includes changing the RNP if necessary.

You like to sugggest reading. Well, I suggest you look at www.honeywellbusinessaviation.com/resources/dyn/files/223697/_fn/rnpsaarwhitepaper.pdf to actually learn something about what you profess to know before suggesting to others that they don't know their jobs!

No doubt you will reply as you always like to have the last word. But this is the end of the discussion as far as I'm concerend. It really has been a waste of time which could have been spent on something more useful,.

And if anyone else is still actually following this thread, I apologise on behalf of DFC and myself for taking it so far off topic.

mad_jock

17th May 2010, 08:37

Dan you could always just cut to the chase and and say.

DFC you are talking absolute bollocks as per usual (I might add he is on my ignore list so I am just presuming the standard bollocks he normally spouts)

DFC

17th May 2010, 09:46

Thanks Dan !!!! :ok:

You have posted a link to a document which coupled to the link provided in that document to FAA AC 90-101 provides 100% the same view as I have tried to explain to you.

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/821aca6a248d6aea862570ed00536340/$FILE/AC90-101.pdf

I particuluarly like the bits covering CDI and the fact that the procedures must be in the onboard database and not as you said constructed by the crew.

You are also now talking about stand alone RNAV approaches and not about using the FMS to fly a conventional NPA that is coded in the database.

Can you realy claim to have knowledge of the subject when you post information in support of your case that actually contradicts it?

:D :D

As for MadJock,

I just love the fact that you feel like you can comment while not reading any of the debate. Perhaps you don't know what a CDI is?

Did I give you a hard time in the sim?, fail your check ride? question your ability? If you don't know what the CDI is then it is highly likely!! :D

Assume - makes an ass of U in front of me (and everyone else!!)