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Thai Air B777 Melbourne NDB approach

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Thai Air B777 Melbourne NDB approach

Old 9th Feb 2008, 16:47
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Nice comments and some real practical advice about V/S over VNAV. I think V/S is better myself, as you are much more in control and 'in the loop', but you need to get configured and all checks out the way as you say, to concentrate on the profile.

When I fly an non-precision approach I write out check altitudes for every DME mile on a bit of paper (someone mentioned that a couple were omitted on this approach chart, which indeed they are), especially when all I am offered is a platform and a marker crossing altitude. I get the other pilot to check these in the cruise to look for errors. I then brief the PM that I want a call at every DME mile plus half (i.e, at 8.5d, 7.5d, 6.5d) with the NEXT crossing altitude, i.e. passing 8.5d - "8d - 2890ft", then as I pass 8d a call such as "50ft high".

The other benefit of getting fully configured before descent is you can cross check groundspeed and aim for an appropriate V/S (shown in the box to the right of the vertical profile on this LIDO chart.) If you aren't fully configured and are going to try to slow down and go down the final approach what V/S are you picking at the descent point? Invariably things are starting to get a little rushed, a V/S is selected (usually too much) and then with config and speed reduction the attention is lost from the V/S and the approach is already getting unstable with a high rate of descent (100fpm+) which is not checked until (usually at least) 2nm further on, when it is realised that you are going low.

However, regarding
it is often easier said than done, especially with regard to the "fully configured" bit, when ATC vectors you in tight, there is a tailwind, or finger trouble with MCP selections, all resulting in not being at the correct platform ht
Well, I would argue that is the airmanship element. Brief it FULLY and PROPERLY, get ahead of the game and stay ahead. Think about the tailwind and slow earlier. Tell ATC what you require, don't necessarily just accept being turned in too early. NEVER forget about that fantastic speed reducer that is the landing gear. So many pilots seem reluctant to use gear really early when it will regain the upper hand easily. Forget slick, min fuel burn approaches when doing non-precision approaches; get down and get dirty!!! How many pilots consider taking the landing gear on a radar vectored base leg to a non-precision final approach when you can see they are only just going to make the platform altitude at the descent point? They only have a couple of stages of flap and need to configure fully and slow down still, but many try to fly it just like it is an ILS. Never ceases to amaze me. ATC invariably vector you tight as they think that is efficient and what you want (which it is for an ILS!!!) Brief this and then it is no surprise, drop the gear and stay ahead of the game!

I have flown 75/76 and now fly both genres of 73 in charter ops, so probably get much more exposure to non-precision approaches than the average 777/747 pilot, but that says to me that longhaul pilots need to give it even more thought and get slowed down and configured EARLY!!

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Old 9th Feb 2008, 16:53
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As for FLCH on finals, don't think so somehow!
Sums it all up for me as well! V/S, FPA but not FLCH.
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Old 9th Feb 2008, 19:28
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When I fly an non-precision approach I write out check altitudes for every DME mile on a bit of paper (someone mentioned that a couple were omitted on this approach chart, which indeed they are), especially when all I am offered is a platform and a marker crossing altitude. I get the other pilot to check these in the cruise to look for errors.

Agree entirely; into critical places like KTM, used to write the numbers on my crib in extra large font, especially at night, eyes/glasses not being what they used to be. I wonder how many people know/remember what happened to PIA A 310 landing there some years back; one step adrift on the profile calls and flew into the hill on finals.

Re: Tailwinds on finals; love to brief it in the cruise, and usually do as a "contingency", but to quote erstwhile defence secretary Rumsfeld, it is one of those "unknowables" that are thrown at you, usually as you are turned from base onto finals just outside the outer marker. AMS are just as guilty as the guys at MAA! But can we blame them? Surface winds reported as light and variable can be a moveable feast when compared to winds at platform height.
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Old 10th Feb 2008, 22:28
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Some more interesting reading. Watch out with those NPAs! Brief, check, and double check!



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Old 10th Feb 2008, 23:42
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Very interesting links, Pilot Pete, and should be required reading.

From Birmingham,
Safety Recommendation 2007-111: It is recommended that Mahan Air should expand its FMS database to include all approaches relevant to their route structure.
I hope the ATSB (or whoever investigates this) comes to the same conclusion with Thai.

From Khartoum,
The investigation was unable to identify any formal CAA policy, in place prior to the incident, regarding the implementation of MNPA operations. Instead, agreement was reached between individual operators and their respective CAA Flight Operations Inspector on how they might implement such operations.
That was the point I was making before. I'm as good as anyone at "build-your-own-approaches", but are they legal, even if you are only ceating and using a lateral path and monitoring it with raw data?

I also noted the old "MDA on the ALT SEL" chestnut; at Khartoum the MDA didn't appear to be set on the ALT SEL as the aircraft went straight thru it, with the autopilot still engaged in V/S?
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Old 11th Feb 2008, 05:37
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Some great advice seen here re sound flying procedures for NPAs.

The self built vs database appch consids are important, as Airbus at least does not endorse any changes to a database appch after the FAF, thus to fly a managed self- built rwy appch would be a definite no-no.

The idea of using an ILS overlay to fly an NPA is certainly creative, but I doubt if the acft or FMS manufacturer would support such an activity. Those who trust their airline SOPs to support them in the event of an incident/accident during such an appch may find themselves out in the cold. Is it actually written in balck and smudge somewhere? I would certainly doubt that CASA would go out on a limb and endorse such a procedure. Perhaps a creative Airline Trng manager is writing cheques that his position can't actually cash.

In any case a database appch will not guarantee a correctly flown managed appch as per the plate, as they are often riddled with mistakes, do not align with the raw data all that closely and are sometimes unable to fly steep vert profiles with changing descent gradients and thus undercut the steps on final. Additionally, you may suffer a 'map shift' or loss of GPS primary & thus sufficient nav accuracy, thus the green/magenta line is no longer accurate. It is human nature to follow the neat fltpln Nav Display line, so very few pilots will manually select lat navigation in such cases, even with the raw data out of tolerance (automation complacency). Those who don't believe me simply haven't seen enough examples in the sim. All the above instances are commonplace in the area of the world where I commit aviation. I am yet to see a managed database appch here that flies with reasonable accuracy according to the IAP plate and raw data upon which it is predicated. Infact, due to the above safety consids, many of the pilots in my company will only fly an NPA in selected modes vertically and laterally. I think more emphasis needs to be placed on these types of simple real world problems during airline sim training.

The bottom line is, some NPAs are too tricky (read poorly designed) to be coded correctly thus the automation won't handle it effectively, that's why we pilots still have jobs! When PF on an NPA, I would say knowing your vertical profile is paramount and don't expect the other guy to feed you all the info as his mind might be elsewhere, as seen in the Thai incident.

I suppose the real bottom line is for regulators to hurry up and approve GPS NPAs at all airports.
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Old 11th Feb 2008, 09:32
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The idea of using an ILS overlay to fly an NPA is certainly creative
I would certainly doubt that CASA would go out on a limb and endorse such a procedure
It would appear that CASA have approved exactly that!

Using the aircraft's GPS capability to fly a NDB approach. How novel!

If only the USAF Boeing 737-200 at Dubrovnik had a GPS/FMS or a 2nd ADF!
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Old 11th Feb 2008, 15:51
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This incident has many similarities with those described in the link below.
For those who believe that this was a minor incident, then consider if your biased perception might lead to a more hazardous position – “I know better, it’s not a real warning, no need to pull up etc, etc”. Of course you could share with us the secret of not suffering error in this type of operation.

Use of VNAV etc would overcome many of the problems (and open new opportunities for error), but this is not always an available solution – timescale and in some countries cost or ability to produce the procedure.
The crew can use defences; the use of the basic crosschecks, an altitude-range table, the required vertical speed, timing. All of these are on the chart – were they briefed, were they used? An NPA requires a good plan, a good briefing, and then an error tolerant operation involving crosschecking / monitoring. … are Captains good monitors?

The NPA and chart have opportunities for error. The use of overlapping range scales – the hazard of the DME displaced from the threshold. If GPS is used which range datum should be used? Will the threshold be visible at MDA in minimum visibility? Thus in addition to error in operating modern technology, crews are exposed to further opportunities for error during the procedure.

One critical issue is that MDA is not a safe altitude; it’s only a minimum altitude during the latter part of a correctly executed procedure; this strengthens the necessity to pull up even with an amber alert.
Although an operator’s procedure for an EGPWS ‘amber’ alert might only require ‘an adjustment to the flight path’ (certification terms to differentiate from a red pull up warning) the adjustment can and should be a climb. EGPWS alerts a situation where there an error has occurred (crew, ATC, procedure, etc), which has led to a reduced safety margin; the crew are unlikely to know why this has occurred, so climb and start again. Being visual with the runway does not guarantee safety particularly if you don’t start for a safe position – note the hazards of poorly defined obstacles or an illusion.

Ref EPGWS events and analysis.
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Old 11th Feb 2008, 17:12
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alf - I have not been into this chart/approach in detail, but I have to query some of your comments:
One critical issue is that MDA is not a safe altitude; it’s only a minimum altitude during the latter part of a correctly executed procedure;
- surely once established on the i/b track, and past FAF, you can (should you wish - not my way!) SAFELY 'dive and drive' down to MDA in the absence of stepdown limits? Would this not have been a technically 'safe' option if correctly flown here? Terrain does not look like a serious issue. Indeed, our friend 411A would probably have been steaming in at MDA for miles
the adjustment can and should be a climb.
- 'can', indeed, but need not be 'should', surely? Not if it is simply high terrain closure rate? I would hazard a guess that was the 'warning' here, and I guess they half expected it too!

NB I do not defend the crew who appear to have grossly mishandled this particular approach
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Old 11th Feb 2008, 20:18
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CDAP Approaches

The ATSB report was an interesting read...

I can't speak for the B777, but at our company the use of VNAV on a CDAP approach is not allowed on the B763/752. If the non-precision approach is not in the FMC, we can overlay a precision approach (such as ILS for NDB if the tracks coincide with each other) to fly the approach in LAV. One pilot must, however, monitor the appropriate raw data from no later than the FAF to the MAP , and step-down fixes in the final approach segment must be verified with raw data.

Our procedure is to be in landing configuration by 2 NM prior to FAF; DA is MDA + 50'; after ALT CAP at FAF altitude, set TDZE in the MCP (rounded up to the next even 100'), at .2 NM to the FAF, selected the pre-briefed descent rate with V/S (we are allowed to bracket the pre-briefed descent rate by +/- 300 fpm, but a rate greater than 1200 fpm is not allowed) and use all available info to monitor the descent rate. Our techniques for monitoring involves: 1) the green arc should be approximately on the runway threshold (once TDZE is set in the MCP); 2) VDI on the HSI showing on profile; and 3) monitor Vertical Track Error on PROG page 2/2.

Admittedly NDB approaches are being removed from most airports in the US so the chance of flying one domestically is almost nil, but we still practice it during PC/PT just in case we encounter one internationally. We do fly other non-precision approaches occasionally (SAN LOC 27 comes into mind) and we usually brief it to death during cruise just because we don't fly one very often. Let's hope that we can learn from this incident and avoid a potential CFIT event in the future.

BTW, if I did the math correctly, the relief pilot started his B777 course with 594 hrs total flight experience! During the last hiring spree by our company, there were probationary pilots getting B744 and B777 F/O bids but even then our new-hires would have thousands of hours of flight time with at least 1000 hrs PIC. Now that our company is hiring again, I understand the new-hires are being restricted to B737 and A320 F/O assignments (even when the B763/752 fleet is very short of pilots) because management does not want "inexperienced" pilots flying internationally. I'm not saying that experienced pilots do not make mistakes (and of course there have been lots of screw ups by experienced crews in our company), but perhaps more flight time as actual pilot flying (as opposed to a relief pilot not touching the controls during T/O and landing) before being assigned as a large jet F/O would reduce the number of incidents/accidents.

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Old 11th Feb 2008, 23:26
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Irrespective of whether or not it's legal/sensible to use an ILS overlay to fly a non-precision approach, it seems to me the problem here was an inappropriate choice of autopilot vertical mode to carry out the approach.

Having missed the descent point for the NDB approach, the FO selected FLCH to commence the descent. Having done so, the only terrain protection available was the 1,190 ft (MDA+50ft) set on the MCP. If they'd stayed in VNAV and simply pressed the Altitude Selector button on the MCP, the aircraft would have commenced the descent in VNAV SPD, captured VNAV PTH when the correct descent profile was eventually intercepted, and respected any intermediate altitude constraints entered in the FMC.

VNAV is a great tool, but there are plenty of traps.

Last edited by BuzzBox; 12th Feb 2008 at 03:14.
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Old 12th Feb 2008, 02:06
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BOAC, in principle, (as I understand PANS OPS) the terrain / obstacle clearances for NPAs are divided into three segments; IAF - IF, IF – FAF, and FAF – MAP. These segments have clearances of 1000ft, 500ft, and 250ft respectively. Thus, your assumption would be correct (but still bad practice). However, the chart shown in the ASTB report shows two ‘minimum’ altitudes after ‘F’ (6 DME), 1250ft and the MDA of 1140ft. If ‘F’ is the FAF as indicated by the chart, then there is some ambiguity between PANS OPS and the chart being used (another chart hazard?). It would appear more logical that the FAF was at ‘ROC’ (4.2 DME) beyond which MDA applies. Perhaps someone with access to the originating Australian procedure chart could comment.

Re ‘can / should’ be a climb. The history of the certification wording for EGPWS will show a valid, but exceptional, reason why a turn vs climb maneuver is allowed at the amber level. However, the industry’s experience and continued improvements to the EGPWS alerting algorithms might now show that a climb is always a suitable maneuver, hence IMHO, the same simple procedure for an alert and warning – pull up, can be taught and practiced. This also avoids any crew deliberation on what to do after and amber alert, perhaps minimizing the risk of debating the reason for the alert – it doesn’t matter, the aircraft should not be where it is. Furthermore, if a turn was to be flown, it implies the use of the terrain map, which may not be as accurate as the basic navigation aid (including ADF in remote areas) unless the EGPWS uses an internal GPS receiver – i.e. beware map shift (we get complacent when using high quality technology in areas well equipped with navigation aids).

I think that the industry is too harsh in attributing connotations of blame on the crew, i.e. ‘mishandled the situation’, etc. Lets see what the investigation discovers; several issues have already been identified that can lead to an error, and the use of VS might have been a simple mistake, or slip (cf Strasbourg). This is not to excuse the crew / operator; a professional operation should have detected one or more the errors (and briefed the hazards). Crews are accountable for a safe operation (before the event) and on the evidence so far this operation appears not to have achieved the required level of safety, but we only believe that due to ‘an error’ (identifiable after the event).

Edit; I note that there are procedure differences between PANS OPS and TERPS. TERPS uses 250 ft, whereas PANS OPS minimum are 295 ft without a FAF and 246 ft with a FAF. This might answer the ambiguity in minimum altitudes before / after ‘ROC’, but it is still not clear to me where the FAF is.
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Old 12th Feb 2008, 02:11
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This is the Australian Chart. I have no idea how to read it - its to hard compared to Jepps!

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Old 12th Feb 2008, 02:45
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Airservices Australia have forgotten more about approach charts than Jepp will ever know...
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Old 12th Feb 2008, 02:46
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The final fix for that approach is at 6DME, on the Jeppe chart, near 6D on the plan is a note 'FF16' and on the profile is a maltese cross at 6D which I believe is standard depiction for an approach final fix.


I agree that the AUS AIP charts are a little more difficult to read than the Jeppes, but that's only because I've been using Jeppes for over twenty years and rarely use the AUS AIP charts. All depends what you're used to I suppose.

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Old 12th Feb 2008, 13:50
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blueloo, thanks for the chart, it appears to originate from Airservices Australia, which I believe is the originating legal reference. Note that the currency date (22 Nov 07) is after the date of the incident.
At least this chart only uses one range scale and defines the GPS range reference, thus avoiding any ambiguity in the use of altitude-range checks. I would prefer that the check table be formatted as ‘altitude over range’ as the former is far more important in achieving safe terrain clearance. Also adding (ML) next to ‘DME’ would further help to avoid misinterpretation.
The FAF is depicted – highlighting the weaknesses of the incident chart (but it’s their symbology – so much for world standardisation). The minimum approach altitudes appear to support the notion that the higher PANS-OPS value is used before the final nav aid (ROC), and that MDA applies thereafter. Both BOL and ROC ADFs are required.
Thus BOAC’s belief in this instance, is incorrect – beware those who think that dive and drive is safer! MDA is not a safe altitude inside the FAF.

"… are Captains good monitors?" No takers … of course there were three crew members, were they all looking outside?
This incident is a good example where investigations conclude ‘CRM failure’ without actually identifying which aspects or what the underlying causes for the human failures were. I have more confidence in ASTB, who show a keen interest in the HF aspects of events than do most investigators. We have much to learn from what initially appeared to be a 'minor incident'.
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Old 13th Feb 2008, 18:42
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Its interesting to see how many people propose ‘high tech’ solutions to the problems identified by this incident, but the use of LNAV / VNAV, Vert profile, GPS, etc, has many ‘gotch yers’ which start with a simple mistake or poor system knowledge. These systems represent increasing complexity in the modern world, which is often linked with higher workload, the need for wider knowledge, and much more crosschecking to avoid error and complacency.

The NDB 16 approach is a simple procedure; a 3 deg slope starting at 11.5 nm; in most respects just like a visual straight in. In IMC the visual cues have to be replaced with an electronic track – clearly depicted on an EFIS, and altitude checkpoints combined with vertical speed to confirm the required glidepath. Altitude checks can be made approximately every 30 sec (every nm @ 120kt GS). Thus the crew task is to use a scan pattern to include these aspects, together with airspeed etc to maintain safe flight. Crosschecks can be provided with timing, beacon crossing, comparison with the briefing (the plan), and the approach chart.
What could be easier; the modern jet transport has the latest display aids, further safety crosschecks provided by RNAV / GPS distance / position, and EGPWS terrain display, yet many of these aircraft get dangerously close to the ground short of the runway – see the link at #69.

Procedures remain simple (charts may need improvement) and aircraft are better equipped (safer), so why are these incidents still occurring? (The prevalence of events might be due to the identification and reporting from EGPWS data, another positive safety function of the system).
Some people cite that modern aircraft are more complex to operate (still simple to fly), but this complexity might be by choice where operators (management, even regulators) elect to use the high tech equipment without thinking about likely situations and consequences of error. In some circumstances it might be safer not to use the 'high tech' solution as the first choice (easier to fly, less opportunity for error), but still use it as a crosscheck.
Another variable involving people is the crew, the standards of training, professionalism, experience all appear to be changing and not necessarily for the better. These are the people who decide on the tactical use of the ‘high tech’ systems. They rely on a technical solution whereas some simple thought and preparation would provide a less complex and safer solution.
Perhaps its time to put people back into the flying loop (thinking and doing), which might improve airmanship and experience.
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Old 16th Feb 2008, 12:22
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How difficult is it for PM to sing out the required ht against DME range and for the PF to adjust accordingly
The PF should already have the chart in front of him and he should be referring to it. The support call by the PNF is a back-up to what the PF should already know. To rely on just one pilot calling the chart details is poor airmanship as PNF's have been known to call erroneous heights versus DME distances. The PIA A310 crash at Kathmandu, the Air Manila (?) 707 crash 20 miles from Manila and many other similar CFIT accidents attest to that.
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Old 16th Feb 2008, 12:41
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Perhaps its time to put people back into the flying loop (thinking and doing), which might improve airmanship and experience
It will never happen. With the major manufacturer's pushing for full use of automation and major airlines blindly accepting this advice to a often foolish degree, you will rarely see a return to basic instrument flying skills. The Twin NDB approach into Melbourne runway 16 is dead straight simple but it took a bunch of automatic monkeys to cock it up. No doubt it will happen again while pilots blindly twiddle the knobs and gaze with awe at the beautiful picture on MAP. Would you conduct a instrument approach in a light twin with a WAC series map on your lap to see where you are going? I doubt it - but in effect that is what MAP is - a sophisticated WAC chart.
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Old 16th Feb 2008, 13:06
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As I said at the start, the Lido chart has two missing profile heights, 7DME and 6DME. While the 6DME alt is below, in the heat of the moment...

How about the system gives people a fighting chance?!
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