A321 Aeroflot from Moscow overrun in Kaliningrad
Thanks lemme,
The left hand side of the table you have posted is particularly interesting, but IIRC acceptable depths of contaminant, and their implications to performance, vary according to aircraft type. In this case the double-slash in the runway state (the suffix to the METARS) indicates that the depth was either not measured or insignificant, so I guess we can only speculate as to the possible depth when the aircraft landed?
The left hand side of the table you have posted is particularly interesting, but IIRC acceptable depths of contaminant, and their implications to performance, vary according to aircraft type. In this case the double-slash in the runway state (the suffix to the METARS) indicates that the depth was either not measured or insignificant, so I guess we can only speculate as to the possible depth when the aircraft landed?
Hi Anvaldra,
I agree that the crew would not have been in receipt of the 2100Z METAR, with its associated braking coefficient of 0.32. If ATC did not have time to inform them of the deterioration, they would have had the figure of 0.37 from the 2030Z METAR.
But I find your interpretation of the braking coefficient figures puzzling. Crews of western airlines landing a European aircraft at a European aerodrome would interpret 0.37 as equating to medium-good, and 0.32 as medium. This is confirmed by the table provided above by lemme.
As I pointed out in post #37, however, the heavy sleet at 2100Z suggests that the braking action is likely to have been deteriorating rapidly, so the figure of 0.32 quoted later on the 2130Z METAR should be viewed with caution.
Quote from andrasz:
"All this talk about braking action is quite irrelevant, AVH presented pretty good evidence that final stop was a litte over half way down and to the right of the runway, just short of taxiway C. This was NOT an overrun, it was a runway excursion, some gear malfunction with loss of directional control would be consistent with this."
Thanks for answering the question I posed here 36 hours ago (post #31). This was originally described as a runway overrun and - as I write this - two paragraphs in the report by The Aviation Herald still refer to it as such. Quotes:
"The airline reported the aircraft landed in strong crosswind and poor braking action causing the runway overrun, which resulted in the nose gear collapse."
"Kaliningrad's Ministry of Emergency Situations (MCHS) reported the aircraft overran the runway."
Presumably, the following paragraph is more recent, and confirms what you now write:
"Video evidence received on Jan 5th 2017 shows the aircraft did not run beyond the end of the runway, but veered right off the runway and came to a stop just short of taxiway C (in direction of runway 24 first taxiway towards the apron)."
That does not necessarily mean that the braking action is irrelevant, particularly in view of the light-to-moderate crosswind. Admittedly, reports in the Russian media do seem to have suggested a landing-gear malfunction. Correct me if you have better information, but it seems unclear if the alleged malfunction was apparent to the crew before the approach and landing, or if it was unexpected.
Gear problems causing a sudden veering off the runway at high speed could include brake failure or seizure, or a nosewheel assembly that is offset and unable to castor. The latter would be less likely on a relatively new aircraft.
I agree that the crew would not have been in receipt of the 2100Z METAR, with its associated braking coefficient of 0.32. If ATC did not have time to inform them of the deterioration, they would have had the figure of 0.37 from the 2030Z METAR.
But I find your interpretation of the braking coefficient figures puzzling. Crews of western airlines landing a European aircraft at a European aerodrome would interpret 0.37 as equating to medium-good, and 0.32 as medium. This is confirmed by the table provided above by lemme.
As I pointed out in post #37, however, the heavy sleet at 2100Z suggests that the braking action is likely to have been deteriorating rapidly, so the figure of 0.32 quoted later on the 2130Z METAR should be viewed with caution.
Quote from andrasz:
"All this talk about braking action is quite irrelevant, AVH presented pretty good evidence that final stop was a litte over half way down and to the right of the runway, just short of taxiway C. This was NOT an overrun, it was a runway excursion, some gear malfunction with loss of directional control would be consistent with this."
Thanks for answering the question I posed here 36 hours ago (post #31). This was originally described as a runway overrun and - as I write this - two paragraphs in the report by The Aviation Herald still refer to it as such. Quotes:
"The airline reported the aircraft landed in strong crosswind and poor braking action causing the runway overrun, which resulted in the nose gear collapse."
"Kaliningrad's Ministry of Emergency Situations (MCHS) reported the aircraft overran the runway."
Presumably, the following paragraph is more recent, and confirms what you now write:
"Video evidence received on Jan 5th 2017 shows the aircraft did not run beyond the end of the runway, but veered right off the runway and came to a stop just short of taxiway C (in direction of runway 24 first taxiway towards the apron)."
That does not necessarily mean that the braking action is irrelevant, particularly in view of the light-to-moderate crosswind. Admittedly, reports in the Russian media do seem to have suggested a landing-gear malfunction. Correct me if you have better information, but it seems unclear if the alleged malfunction was apparent to the crew before the approach and landing, or if it was unexpected.
Gear problems causing a sudden veering off the runway at high speed could include brake failure or seizure, or a nosewheel assembly that is offset and unable to castor. The latter would be less likely on a relatively new aircraft.
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Landing on a slippery runway with strong crosswinds could easily give results that could be confused with gear faults, namely a lack of directional control and rapidly modulating braking from the ABS kicking in and out. Measuring of braking action of contaminated runways is very unreliable and pilot reports highly subjective, hence the introduction in many companies of the US TALPA system, but I doubt Aeroflot are one of those companies. So, it could be that the pilots were lead to believe they would have better traction than they got. For all that, perhaps there was a gear fault. Time will tell.
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Hi Anvaldra,
I agree that the crew would not have been in receipt of the 2100Z METAR, with its associated braking coefficient of 0.32. If ATC did not have time to inform them of the deterioration, they would have had the figure of 0.37 from the 2030Z METAR.
But I find your interpretation of the braking coefficient figures puzzling. Crews of western airlines landing a European aircraft at a European aerodrome would interpret 0.37 as equating to medium-good, and 0.32 as medium. This is confirmed by the table provided above by lemme.
As I pointed out in post #37, however, the heavy sleet at 2100Z suggests that the braking action is likely to have been deteriorating rapidly, so the figure of 0.32 quoted later on the 2130Z METAR should be viewed with caution.
I agree that the crew would not have been in receipt of the 2100Z METAR, with its associated braking coefficient of 0.32. If ATC did not have time to inform them of the deterioration, they would have had the figure of 0.37 from the 2030Z METAR.
But I find your interpretation of the braking coefficient figures puzzling. Crews of western airlines landing a European aircraft at a European aerodrome would interpret 0.37 as equating to medium-good, and 0.32 as medium. This is confirmed by the table provided above by lemme.
As I pointed out in post #37, however, the heavy sleet at 2100Z suggests that the braking action is likely to have been deteriorating rapidly, so the figure of 0.32 quoted later on the 2130Z METAR should be viewed with caution.
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Braking coefficient within the CIS is measured differently and has a completely different table and values than the standard Western ones in use in the USA and EASA.
This should be of no surprise obviously to the SU crew.
I also presume any Airline flying to these regions has notified and trained its crews of this difference and supply appropriate tables within easy access. ( checklist...)
This should be of no surprise obviously to the SU crew.
I also presume any Airline flying to these regions has notified and trained its crews of this difference and supply appropriate tables within easy access. ( checklist...)
Hi Anvaldra,
Thanks for correcting my misinterpretation of the runway-state information on the relevant Kaliningrad METARS that I posted here a few hours after the accident (post #5), and for the two explanatory tables.
Of course we know that, despite the existence of ICAO, there remains no single, worldwide standard for the codes used in METARS. I was not aware (or had perhaps forgotten in retirement), however, that the countries of the CIS (Commonwealth of Independent states, comprising Armenia, Azerbaijan, Belarus, Kazakhstan, Kyrgyzstan, Moldova, Russia, Tajikistan and Uzbekistan) promulgate braking-coefficient data on a different scale from the rest of the world. This seems unnecessary, as I imagine the conversion could be made easily by the agency that transmits the CIS METARS into the system.
It is also surprising, particularly as the values are similar but higher than ours, that this potentially-misleading difference is not indicated in the METAR format. In the case of wind speeds, for example, the use of metres-per-second instead of knots is clearly indicated by the addition of "MPS". In the case of North America, where the values of QNH are quoted in inches of mercury instead of hectopascals, the figures are so different that there is no confusion.
Returning to this Kaliningrad accident, however, I entirely agree with you and Icelanta that there is unlikely to have been any confusion by the Aeroflot crew. However, if a non-CIS crew with no experience of ops into CIS airports ever had to divert to Kaliningrad suddenly in an emergency, they might find the runway considerably more slippery than expected.
Thanks for correcting my misinterpretation of the runway-state information on the relevant Kaliningrad METARS that I posted here a few hours after the accident (post #5), and for the two explanatory tables.
Of course we know that, despite the existence of ICAO, there remains no single, worldwide standard for the codes used in METARS. I was not aware (or had perhaps forgotten in retirement), however, that the countries of the CIS (Commonwealth of Independent states, comprising Armenia, Azerbaijan, Belarus, Kazakhstan, Kyrgyzstan, Moldova, Russia, Tajikistan and Uzbekistan) promulgate braking-coefficient data on a different scale from the rest of the world. This seems unnecessary, as I imagine the conversion could be made easily by the agency that transmits the CIS METARS into the system.
It is also surprising, particularly as the values are similar but higher than ours, that this potentially-misleading difference is not indicated in the METAR format. In the case of wind speeds, for example, the use of metres-per-second instead of knots is clearly indicated by the addition of "MPS". In the case of North America, where the values of QNH are quoted in inches of mercury instead of hectopascals, the figures are so different that there is no confusion.
Returning to this Kaliningrad accident, however, I entirely agree with you and Icelanta that there is unlikely to have been any confusion by the Aeroflot crew. However, if a non-CIS crew with no experience of ops into CIS airports ever had to divert to Kaliningrad suddenly in an emergency, they might find the runway considerably more slippery than expected.
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Just to add to the confusion re: breaking coefficient, the scale (normative vs. measured) may be different based on how the info is disseminated:
1. Spoken in Russian (e.g., ATC or ATIS): normative scale
2. Spoken in English: measured scale
3. METAR: measured scale
And the practice may differ depending on the airport as well...
1. Spoken in Russian (e.g., ATC or ATIS): normative scale
2. Spoken in English: measured scale
3. METAR: measured scale
And the practice may differ depending on the airport as well...
Not that it is necessarily relevant to the accident, peekay4, but does that mean that my earlier interpretation of the METAR runway state was correct?
If so, one wonders if an Aeroflot crew would be using the METAR figures, or if they get their weather actual reports from a different source.
Anvaldra, can you comment?
If so, one wonders if an Aeroflot crew would be using the METAR figures, or if they get their weather actual reports from a different source.
Anvaldra, can you comment?
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peekay4, you are right. Information depends on the airport. To complete the picture:
1.METAR (UUEE only) - measured
2.METAR (other apts) - normative
3.METAR (UUDD,UUDL,UIUU,URFF and some CIS apts) - braking action
4.ATIS in Russian - normative
5.ATIS in English - measured and braking action (but not everywhere, mainly for apts with international trafic)
Concerning UMKK refer to item 2
1.METAR (UUEE only) - measured
2.METAR (other apts) - normative
3.METAR (UUDD,UUDL,UIUU,URFF and some CIS apts) - braking action
4.ATIS in Russian - normative
5.ATIS in English - measured and braking action (but not everywhere, mainly for apts with international trafic)
Concerning UMKK refer to item 2
Only half a speed-brake
Anvaldra: we'd discussed this before, and you've proven me wrong as I believed the normatives were extinct altogether. The offical advice I had at that time turned out to be SVO-specific, with a dose of confirmation bias from my side listening to ENG-atis as we went there quite a lot.
Please do not feel too hard pushed for it, yet could I have a reference to your table? Something I plan to keep in my flightbag afterwards. Until now I actually believed the same as posted by peekay4 above - if disseminated beyond domestic use (e.g. METAR) = measured.
Notwithstanding the practice-du-jour/nuit.
Please do not feel too hard pushed for it, yet could I have a reference to your table? Something I plan to keep in my flightbag afterwards. Until now I actually believed the same as posted by peekay4 above - if disseminated beyond domestic use (e.g. METAR) = measured.
Notwithstanding the practice-du-jour/nuit.
Only half a speed-brake
Braking coefficient expressed in different numerical values compared to ICAO ones. There is a conversion table in AIP, provided by Anvaldra above.
The trap is reading normative (Russian domestic) b.coeff. such as 0,3 and using it unknowingly as measured cf. The real braking action is much less, equivalent to 0,15 !
The trap is reading normative (Russian domestic) b.coeff. such as 0,3 and using it unknowingly as measured cf. The real braking action is much less, equivalent to 0,15 !
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To expand a little bit, there are many ways (and equipment) which can be used to measure braking coefficients, and they all return slightly different numbers.
E.g., a particular runway surface might measure 0.45 when tested with a surface friction tester (SFT), but just 0.37 when measured with a Brakemeter-Dynometer (BRD). There are about 8 different types of equipment in common use.
The ICAO approach is simply to report the measured value along with the equipment type used since the differences are usually "close enough" and the tables are conservative. So you might see 45/42/39 BRD in a Snowtam.
Another approach is to convert these equipment-specific values to some "normative" standard, and report that instead. Unfortunately the Russian normative values are different enough from the above, that a different table is required for interpretation.
Then there's also "braking action" reports, with a completely different qualitative scale (1 to 5, 5 being the best).
Per Anvaldra's post above, it appears that three three international airports in Moscow alone use three different scales in METAR (measured, normative, breaking action)... may be recipe for an accident.
E.g., a particular runway surface might measure 0.45 when tested with a surface friction tester (SFT), but just 0.37 when measured with a Brakemeter-Dynometer (BRD). There are about 8 different types of equipment in common use.
The ICAO approach is simply to report the measured value along with the equipment type used since the differences are usually "close enough" and the tables are conservative. So you might see 45/42/39 BRD in a Snowtam.
Another approach is to convert these equipment-specific values to some "normative" standard, and report that instead. Unfortunately the Russian normative values are different enough from the above, that a different table is required for interpretation.
Then there's also "braking action" reports, with a completely different qualitative scale (1 to 5, 5 being the best).
Per Anvaldra's post above, it appears that three three international airports in Moscow alone use three different scales in METAR (measured, normative, breaking action)... may be recipe for an accident.
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SU1008 SVO-KGD / Airbus A320 VP-BME
UMKK 132100Z 31001MPS 0900 0800SW R24/2000D +SHSN VV002 M00/M00 Q0990 R24/690531 NOSIG RMK QBB080 OBST OBSC QFE741/0989
UMKK 132100Z 31001MPS 0900 0800SW R24/2000D +SHSN VV002 M00/M00 Q0990 R24/690531 NOSIG RMK QBB080 OBST OBSC QFE741/0989
