Braking action Poor - Can A/C land?
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BA in Sand Pit
H Dicktator: from one or two on my arrivals in sandy bottom, after a rain shower, you know the ones 3 in in 3 mins...... the float planes ruled for several hours.
What is the Policy in UAE re wet/wet/wet.
Glf
What is the Policy in UAE re wet/wet/wet.
Glf
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HeathrowDictator, I think that the Bristol situation was rather different. If I recall correctly, the problem there occurred during runway resurfacing and resulted from oil leeching from the new tarmac creating a very slippery surface when it was wet. This was exacerbated (for parts of the runway, at least) because the new tarmac had not been grooved to enable the water to run off as quickly as possible - this, no doubt, would also have added some degree of friction to the surface. On the face of it, the Bristol situation appears to have been an almost total failure of safety management for a problem that, perhaps, could have been foreseen and certainly had been identified soon after the first incident. I don't recall the way that CFME was used but I don't think it was designed for this situation.
And whilst I have huge respect for many of the AAIB Inspectors, they don't always get it right. This is particularly true when a recommendation is made about ATC or other ground operations; understandable when you consider that their staff are drawn primarily from aircraft operations and engineering specialisations.
But they have come up with some blinders! The one which immediately comes to mind resulted in the 'absolute minima' procedure in the UK - another blanket procedure introduced because one crew broke the rules. It may well be that such blanket procedures are good safety nets but maybe they are being used to mitigate poor training or adherence to existing procedures and so on.
It's a bit like saying that IRVR information should not be passed to pilots because the information might not truly reflect the conditions on the runway. I can quite see that someone looking at where transmissometers are located and variations in atmospheric conditions might believe that the information could be misleading. Is it really better to withhold potentially valuable information that to ensure that it is used in an informed manner? Things in our business are rarely black and white, but we seem to be moving toward a regulatory environment where we will have a rule for every eventuality...and if we can't find a rule to be followed we put our heads in the sand (and that's not intended to relate to your location!).
And whilst I have huge respect for many of the AAIB Inspectors, they don't always get it right. This is particularly true when a recommendation is made about ATC or other ground operations; understandable when you consider that their staff are drawn primarily from aircraft operations and engineering specialisations.
But they have come up with some blinders! The one which immediately comes to mind resulted in the 'absolute minima' procedure in the UK - another blanket procedure introduced because one crew broke the rules. It may well be that such blanket procedures are good safety nets but maybe they are being used to mitigate poor training or adherence to existing procedures and so on.
It's a bit like saying that IRVR information should not be passed to pilots because the information might not truly reflect the conditions on the runway. I can quite see that someone looking at where transmissometers are located and variations in atmospheric conditions might believe that the information could be misleading. Is it really better to withhold potentially valuable information that to ensure that it is used in an informed manner? Things in our business are rarely black and white, but we seem to be moving toward a regulatory environment where we will have a rule for every eventuality...and if we can't find a rule to be followed we put our heads in the sand (and that's not intended to relate to your location!).
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Fair and valid points Spitoon, and yes regarding Bristol - I think you are correct with that!
However, whilst the current methods of assessing braking action remain unreliable how else are you supposed to provide the information? It certainly provokes interesting discussion. Does anyone know if a device is being researched which would allow accurate assessments on wet runways?
I do not feel I have enough experience in the field to comment on the why's and wherefore's - other than to say I can see both sides of the argument.
-HD-
However, whilst the current methods of assessing braking action remain unreliable how else are you supposed to provide the information? It certainly provokes interesting discussion. Does anyone know if a device is being researched which would allow accurate assessments on wet runways?
I do not feel I have enough experience in the field to comment on the why's and wherefore's - other than to say I can see both sides of the argument.
-HD-
'Absolute minima'. Introduced actually after a second incident, the first being the Citation which blocked the M27 at Southampton by touching down on the 02 numbers (it was landing on 20 at the time!)
The second was the '125 at Farnborough on a non public transport flight. Landed successfully off a PAR, and straddled what he thought was the centreline lighting. Unfortunately Farnborough doesn't have centreline lights and he actually straddled the edge lights to the left of the runway touching down on the grass!
The second was the '125 at Farnborough on a non public transport flight. Landed successfully off a PAR, and straddled what he thought was the centreline lighting. Unfortunately Farnborough doesn't have centreline lights and he actually straddled the edge lights to the left of the runway touching down on the grass!
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Thank you all of you about nice discussion. However one more quesiotn do you think that there is a need to declare local/full emergency alert at the airport when an aircraft is landing with BA poor?
Thanks.
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However one more quesiotn do you think that there is a need to declare local/full emergency alert at the airport when an aircraft is landing with BA poor?
(i.e. manning the tenders outside the fire station, but no alert outside airfield fire service)
From the Norwegian CAP, rough translation
Increased preparedness undertaken when an aircraft is / are believed to be in difficulties, however, is of such nature that the aircraft can normally make a safe start and landing. Examples of factors that indicate increased readiness:
- Strong crosswind
- Slippery contaminated runway or other deterioration of rwy conditions.
- Reduced visibility that makes ATC unable to see the maneuvering area.
- Strong crosswind
- Slippery contaminated runway or other deterioration of rwy conditions.
- Reduced visibility that makes ATC unable to see the maneuvering area.
SAS 737 landing on 2500m runway in dry snow with breaking action est poor in NIL wind -> No action taken
Pegasus 737 landing on same runway in wet/slush conditions with 15 knots crosswind and breaking action est poor?
....well that might.....
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Spitoon, sorry to say you are wrong with esters rising to the surface and when combined with water reduce friction. Not only did the AAIB not point at this the area called the 'patch' was filled with a regulating course not Marshall Asphalt which does suffer from this in the first months of operations.
The fact that there was a crosswind of biblical proportions and the rainfall rate would have caused standing water on any runway didn't figure very high in their report.
The fact that the runway wasn't grooved is irrelevant. Look at Bournemouth, Manchester, Humberside, Farnborough and CDG none of these runways are grooved.
Lastly, if you look at CAP 683 quoted previously you'll see that the certified friction carts have different figures. So if you need and can make use of a BA then surely you would need to ascertain the type of unit that was used to produce the unreliable figures?
SGC
The fact that there was a crosswind of biblical proportions and the rainfall rate would have caused standing water on any runway didn't figure very high in their report.
The fact that the runway wasn't grooved is irrelevant. Look at Bournemouth, Manchester, Humberside, Farnborough and CDG none of these runways are grooved.
Lastly, if you look at CAP 683 quoted previously you'll see that the certified friction carts have different figures. So if you need and can make use of a BA then surely you would need to ascertain the type of unit that was used to produce the unreliable figures?
SGC
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I bow to your greater expertise on the subject, Sir George.
But if I understand you correctly, you are saying that Marshall Asphalt (the top 'coat') does leech materials that when combined with water result in a slippery surface. The runway was being progressively resurfaced and so, although there was an area with exposed regulating course, as the project progressed there was an increasing length of the newly surface runway that was finished with Marshall Asphalt along with the associated potentially slippery surface. This, I understood to be a principal cause of the problems. Strong crosswinds are nothing out of the ordinary art Lulsgate Bottom but the amount of standing water may have been increased because the 'drainage' mechanism was not complete. Whatever, these two points will have contributed elements to the incidents - holes in the cheese as Jim Reason would have it - perhaps if the resurfacing work had been handled in some other way one more hole wouldn't have lined up.
I'm not sure that the runway not being grooved is completely irrelevant. If the runway was designed to have a grooved surface (as I believe it was), I presume it would have been profiled to enable the surface water to run off through the grooves. As I suggested a moment ago, if the grooves were not there the drainage properties would not have met the design criteria. It's interesting that you mention a selection of other runways that are not grooved - it does surprise me because I was pretty sure that Manchester and Bournemouth were both grooved but, again, you're probably far more up to date than I. But are you saying that grooving a runway makes no difference to its friction characteristics?
As to CAP 683, whilst I haven't looked at the latest re-write in any detail I fully understand that it's essential to know what CFMD was used to make the measurements. But if I recall correctly (and they haven't changed it) CAP683 is about measuring friction with a self-wetting device (i.e. a known volume/depth of water) for the purposes of planning when and where maintenance work is required rather than environmental measurements for operational purposes. Whether this is the case or not, it is true that one needed to know about the CFMD used to generate braking action values - and I think this was an essential part of the information that used to be provided when the data were provided. I think the old way of providing the data on request was intended to enable operators' Ops Depts to investigate the runway conditions and CFMD used at specific airports in good time and to be able to make informed judgements (and perhaps via guidance in the Ops Manual) regarding the use of the runway in adverse conditions. But I wonder if this ever happened....
But if I understand you correctly, you are saying that Marshall Asphalt (the top 'coat') does leech materials that when combined with water result in a slippery surface. The runway was being progressively resurfaced and so, although there was an area with exposed regulating course, as the project progressed there was an increasing length of the newly surface runway that was finished with Marshall Asphalt along with the associated potentially slippery surface. This, I understood to be a principal cause of the problems. Strong crosswinds are nothing out of the ordinary art Lulsgate Bottom but the amount of standing water may have been increased because the 'drainage' mechanism was not complete. Whatever, these two points will have contributed elements to the incidents - holes in the cheese as Jim Reason would have it - perhaps if the resurfacing work had been handled in some other way one more hole wouldn't have lined up.
I'm not sure that the runway not being grooved is completely irrelevant. If the runway was designed to have a grooved surface (as I believe it was), I presume it would have been profiled to enable the surface water to run off through the grooves. As I suggested a moment ago, if the grooves were not there the drainage properties would not have met the design criteria. It's interesting that you mention a selection of other runways that are not grooved - it does surprise me because I was pretty sure that Manchester and Bournemouth were both grooved but, again, you're probably far more up to date than I. But are you saying that grooving a runway makes no difference to its friction characteristics?
As to CAP 683, whilst I haven't looked at the latest re-write in any detail I fully understand that it's essential to know what CFMD was used to make the measurements. But if I recall correctly (and they haven't changed it) CAP683 is about measuring friction with a self-wetting device (i.e. a known volume/depth of water) for the purposes of planning when and where maintenance work is required rather than environmental measurements for operational purposes. Whether this is the case or not, it is true that one needed to know about the CFMD used to generate braking action values - and I think this was an essential part of the information that used to be provided when the data were provided. I think the old way of providing the data on request was intended to enable operators' Ops Depts to investigate the runway conditions and CFMD used at specific airports in good time and to be able to make informed judgements (and perhaps via guidance in the Ops Manual) regarding the use of the runway in adverse conditions. But I wonder if this ever happened....
