T/O perf : Runway DRY, Braking Action GOOD
Thread Starter
Joined: Feb 2012
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From: belgium
T/O perf : Runway DRY, Braking Action GOOD
Hello,
What to do with T/O perf if the ATIS says : Runway DRY, braking action is GOOD.
For 737, when calculating T/O perf with the computer, we have to choose between DRY, WET, CONTAMINATED or SLIPPERY.
If we choose slippery, then we are asked to choose the braking action (from POOR to GOOD).
Do we have to consider SLIPPERY runway, with braking action good , or DRY runway? That make a big difference in calculation.
Thanks guys !
What to do with T/O perf if the ATIS says : Runway DRY, braking action is GOOD.
For 737, when calculating T/O perf with the computer, we have to choose between DRY, WET, CONTAMINATED or SLIPPERY.
If we choose slippery, then we are asked to choose the braking action (from POOR to GOOD).
Do we have to consider SLIPPERY runway, with braking action good , or DRY runway? That make a big difference in calculation.
Thanks guys !
Thread Starter
Joined: Feb 2012
Posts: 8
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From: belgium
Thanks for your answers guys !
By the company said : if there is two information in the Atis; ALWAYS take the most restrictive (= more safety). So, when it's DRY and there is a braking action mentionned, we have to take the braking action into consideration.
Reason is that we, as stupid pilots, are not able to determine if a dry runway has a perfect , good, medium or poor braking action, so we have to rely on the professionnal people who mesure the BA.
That's a bit strange, but who can complain that our company decide to go on the safe side ?
By the company said : if there is two information in the Atis; ALWAYS take the most restrictive (= more safety). So, when it's DRY and there is a braking action mentionned, we have to take the braking action into consideration.
Reason is that we, as stupid pilots, are not able to determine if a dry runway has a perfect , good, medium or poor braking action, so we have to rely on the professionnal people who mesure the BA.
That's a bit strange, but who can complain that our company decide to go on the safe side ?
Joined: Feb 2005
Aviation Qualifications: ATPL
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From: Correr es mi destino por no llevar papel
This beggars belief.... why would clear, dry and paved runway had anything except "good" as BA?
There can't be two information in ATIS, it is just this one is probably fully automated and programmed to always report braking action even when it is really not necessary. BA good means .4 and above, if one is to use tester on dry runway results would be probably out of scale and chances are good your slippery+BA good calculation uses 0.40 as the friction coefficient. Safe you would be but performance penalty might hurt you economically and quite unnecessarily at that.
if there is two information in the Atis
Thread Starter
Joined: Feb 2012
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From: belgium
"There can't be two information in ATIS"
Go to Liege airport in Belgium, and anytime it's reported DRY, they say also: BA GOOD.
But i agree it's a big cost penality for the airline ... (fuel, engines... and, delays, because it's not allowed to T/O with tailwind if runway is slippery ... )
Go to Liege airport in Belgium, and anytime it's reported DRY, they say also: BA GOOD.
But i agree it's a big cost penality for the airline ... (fuel, engines... and, delays, because it's not allowed to T/O with tailwind if runway is slippery ... )
Joined: Dec 2002
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From: UK
A possible problem is that the runway surface description and estimated braking action are being intermixed.
Dry describes the runway surface, as would wet or contaminated (with sub descriptions).
Good is the estimated braking action for the description and is relative to the description; i.e. wet – good implies ‘good’ braking action for wet conditions, similarly dry snow – good, is ‘good’ for snow contamination, but is not the same as wet. The combination of dry – good is usually self-evident as it represents the best condition.
The background for this is in ICAO Annex 14 Chapt 6, Att A.
“If the surface is affected by snow or ice and the braking action is reported as “good”, pilots should not expect to find conditions as good as on a clean dry runway (where the available friction may well be greater than that needed in any case). The value “good” is a comparative value and is intended to mean that aeroplanes should not experience directional control or braking difficulties, especially when landing”.
The choice of which parameter to use when determining the takeoff data may depend on the basis of the aircraft’s certificated data.
Thus any confusion in the takeoff calculation might arise from the performance computer, which presumably for the dispatch case, should be based on AFM; thus check which terms the AFM uses for determining takeoff performance.
Note that ‘slippery’ is a generic term (Boeing) covering wet, and snow and ice descriptions, which may add to the confusion.
For landing distance (advisory), Airbus tends to use a descriptor with type and depth of contamination, whereas Boeing (QRH) use the estimated braking action either from the tower or with greater variability from pilot reports.
Dry describes the runway surface, as would wet or contaminated (with sub descriptions).
Good is the estimated braking action for the description and is relative to the description; i.e. wet – good implies ‘good’ braking action for wet conditions, similarly dry snow – good, is ‘good’ for snow contamination, but is not the same as wet. The combination of dry – good is usually self-evident as it represents the best condition.
The background for this is in ICAO Annex 14 Chapt 6, Att A.
“If the surface is affected by snow or ice and the braking action is reported as “good”, pilots should not expect to find conditions as good as on a clean dry runway (where the available friction may well be greater than that needed in any case). The value “good” is a comparative value and is intended to mean that aeroplanes should not experience directional control or braking difficulties, especially when landing”.
The choice of which parameter to use when determining the takeoff data may depend on the basis of the aircraft’s certificated data.
Thus any confusion in the takeoff calculation might arise from the performance computer, which presumably for the dispatch case, should be based on AFM; thus check which terms the AFM uses for determining takeoff performance.
Note that ‘slippery’ is a generic term (Boeing) covering wet, and snow and ice descriptions, which may add to the confusion.
For landing distance (advisory), Airbus tends to use a descriptor with type and depth of contamination, whereas Boeing (QRH) use the estimated braking action either from the tower or with greater variability from pilot reports.
Joined: Jan 2012
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From: Not far from the edge of the Milky Way Galaxy in the Orion Arm.
thats nothing, it took Lon Volmet Main 24 hrs to catch up to the fact that their 10 km or more was in fact totally 
hazy all over western europe = including Paris CGD, Stan, Gat, EGLL, MAN, AMS, BRUX - some bright spark cottoned on to the fact a day later . . . even EGLL corrected, was way out with the viz, pretty bang on with the wind though.
hazy all over western europe = including Paris CGD, Stan, Gat, EGLL, MAN, AMS, BRUX - some bright spark cottoned on to the fact a day later . . . even EGLL corrected, was way out with the viz, pretty bang on with the wind though.
Joined: Mar 2010
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From: in a dirty cockpit
Even if your company says to take the worst condition given by the ATIS, in this case just think that the penalty is from a "SLIPPERY" braking action GOOD.
But if the braking action GOOD is from a DRY runway, this is just something added automatically by the ATIS as a standard set up.
In even more simple terms, the condition "SLIPPERY GOOD" of your computer based performance or paper performance tables doesn't apply because....basically the Runway is not Slippery!
But if the braking action GOOD is from a DRY runway, this is just something added automatically by the ATIS as a standard set up.
In even more simple terms, the condition "SLIPPERY GOOD" of your computer based performance or paper performance tables doesn't apply because....basically the Runway is not Slippery!
Last edited by Breakthesilence; 13th April 2013 at 20:44.
