How To Judge The Braking Action During Landing (Question)
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How To Judge The Braking Action During Landing (Question)
Hello....
As we are approaching the winter season ... and in preparation ...i came across this question...
When The ATC request from the pilot during the final approach ..to report the braking action after landing (wet runway)...how would you judge this braking action...is it by:
-feeling the aircraft decelaration.
-watching how fast the speed trend droping.
Or
-(for Airbus Pilot) selecting auto brake low..in case of a long runway...and monitoring the brake release signal .
any idea's ...suggestions ?
thanks in advance.
As we are approaching the winter season ... and in preparation ...i came across this question...
When The ATC request from the pilot during the final approach ..to report the braking action after landing (wet runway)...how would you judge this braking action...is it by:
-feeling the aircraft decelaration.
-watching how fast the speed trend droping.
Or
-(for Airbus Pilot) selecting auto brake low..in case of a long runway...and monitoring the brake release signal .
any idea's ...suggestions ?
thanks in advance.
Last edited by kuwait340; 6th Oct 2007 at 18:54.
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It's very difficult. It's not much more than a very rough estimation of 'do you think much slipping has taken place, and vaguely estimate how much?'. The answer can only be Good/Medium/Poor. Most estimations seem to be rubbish, and always exaggerated. It is an estimation of runway slipperiness, not taxiway.
We were in a Classic 747 following a domestic DC9 into JFK when ATC asked the DC9 that question- plenty of snow and ice about. After landing, he said 'Poor!'. We looked at each other in horror, with 30 seconds to go, and selected Full Autobrake. As soon as we touched down, braking was so effective our arms were thrown forward, galleys were crashing and banging, and our noses were almost pressed into the windscreen! I realised then not to listen to such daft reports again- a pilot report is a waste of time!
We were in a Classic 747 following a domestic DC9 into JFK when ATC asked the DC9 that question- plenty of snow and ice about. After landing, he said 'Poor!'. We looked at each other in horror, with 30 seconds to go, and selected Full Autobrake. As soon as we touched down, braking was so effective our arms were thrown forward, galleys were crashing and banging, and our noses were almost pressed into the windscreen! I realised then not to listen to such daft reports again- a pilot report is a waste of time!
Must have been quite spectacular 
- but I bet you'd have been even more upset if you hadn't selected FULL and then slid up to the end 
Taxying (sp?) out in a VC8 at EDI one day we slid around the taxiway on freezing rain and advised ATC accordingly.
We then held at the runway for a BAC111 to land. BAC111 arrived and disappeared off towards far end where he advised ATC that braking action was poor. Poor chap hadn't been advised of our report.
- but I bet you'd have been even more upset if you hadn't selected FULL and then slid up to the end Taxying (sp?) out in a VC8 at EDI one day we slid around the taxiway on freezing rain and advised ATC accordingly.
We then held at the runway for a BAC111 to land. BAC111 arrived and disappeared off towards far end where he advised ATC that braking action was poor. Poor chap hadn't been advised of our report.
Last edited by Basil; 7th Oct 2007 at 23:53. Reason: To say posted in reply to now deleted post.
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On the 747 you can feel the brakes releasing and grabbing as the anti-skid works on a slippery runway. If I feel no antiskid releases, I call it good. If I feel any releases, I call it fair. If the antiskid is working hard, I call it poor.
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K340 - pilot braking action reports are like turbulence reports - very subjective. I use Intruder's method, plus the reaction to nosewheel steering inputs.
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is it recommended to use the max auto brake in boeing...
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is it recommended to use the max auto brake in boeing...
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kuwait,
not sure about the airbuses but on the boeings, there are landing distance tables for different runway braking conditions and autobrake selections. select a conservative autobrake setting then compare the actual landing distance with the tabulated figures to 'guestimate' the braking action. i think this is a more academic method. however, braking action are just advisory and varies constantly. there's still no conclusive method of determining braking action to date. therefore, personally i always try to err on the cautious side
SR
not sure about the airbuses but on the boeings, there are landing distance tables for different runway braking conditions and autobrake selections. select a conservative autobrake setting then compare the actual landing distance with the tabulated figures to 'guestimate' the braking action. i think this is a more academic method. however, braking action are just advisory and varies constantly. there's still no conclusive method of determining braking action to date. therefore, personally i always try to err on the cautious side
SR
For accurate reporting you need to relate the actual stopping distance with the expected distance (ICAO definitions below), but as both depend on max brake this is generally impracticable.
Thus, most pilot reports are subjective (and very variable). The sensed deceleration relates to the amount of brake applied and the friction of the surface; again quantities which are hard to define. Also, remember that deceleration (braking effectiveness) may vary along the runway, particularly where there are rubber deposits.
IMHO pilots only report when they have been surprised by the conditions not meeting with their expectations, this usually results in a ‘medium’ call, whereas in reality it probably is ‘poor’.
If asked to report, the ICAO guidance can help if ‘expected distance’ (a norm based on experience) is substituted for the scheduled distance; this provides some correlation with the conditions when landing on non limiting runways where max braking is not used. The more limiting the runway length is then the closer ‘expected’ and ‘scheduled’ become, and also more braking is used.
When deciding to land based on a pilot report of braking conditions, don’t forget that “you are betting the safety of your ‘butt’ of the feeling in some other pilots ‘butt’.”
ICAO reporting:
Good:- Aircraft can expect to land comfortably within the scheduled distance, where this is “wet” distance, without undue directional control problems.
Medium:- Aircraft are likely to use all the “wet” scheduled distance including the safety factor part of the distance, and may run even further. Directional control might be impaired.
Poor:- Aircraft can expect to run for up to the full “very wet” or aquaplaning distance where this too is scheduled. Directional control will also be poor.
Thus, most pilot reports are subjective (and very variable). The sensed deceleration relates to the amount of brake applied and the friction of the surface; again quantities which are hard to define. Also, remember that deceleration (braking effectiveness) may vary along the runway, particularly where there are rubber deposits.
IMHO pilots only report when they have been surprised by the conditions not meeting with their expectations, this usually results in a ‘medium’ call, whereas in reality it probably is ‘poor’.
If asked to report, the ICAO guidance can help if ‘expected distance’ (a norm based on experience) is substituted for the scheduled distance; this provides some correlation with the conditions when landing on non limiting runways where max braking is not used. The more limiting the runway length is then the closer ‘expected’ and ‘scheduled’ become, and also more braking is used.
When deciding to land based on a pilot report of braking conditions, don’t forget that “you are betting the safety of your ‘butt’ of the feeling in some other pilots ‘butt’.”
ICAO reporting:
Good:- Aircraft can expect to land comfortably within the scheduled distance, where this is “wet” distance, without undue directional control problems.
Medium:- Aircraft are likely to use all the “wet” scheduled distance including the safety factor part of the distance, and may run even further. Directional control might be impaired.
Poor:- Aircraft can expect to run for up to the full “very wet” or aquaplaning distance where this too is scheduled. Directional control will also be poor.
BOAC I assume that you do not mean to dissuade pilots from using Max Auto Brake - “I would urge caution as it really does stop!” (#9) as in limiting conditions this system is a critical safety item.
Less experience pilots might be put off by a description of harsh deceleration. High decelerations might be encountered on a dry or damp runway, but in wet and particularly slippery conditions max braking may only produce decelerations similar to normal landings, just when all of the deceleration is required.
The industry had a torrid time with pilots / braking problems during RTOs, - failure to apply or maintain maximum braking; auto brake was part of the solution. Now days landing accidents appear to dominate the statistics thus there must not be any suggestion which detracts from the use of brakes i.e. using max brake when the conditions require.
Brake for safety not for comfort.
A point of interest; as I understand, a PIREP is not used for reporting braking action, although it appears to be (mis)used in this way.
See the last FAA conference on Runway Condition Determination, Reporting, and Report Dissemination Workshop. The summary suggests that the N. American operators are planning to rewrite the definitions used in reporting, or is it that the ICAO terms are not that well understood in the US?
Useful links Safety aspects of aircraft performance on wet and contaminated runways.
Braking Action Measurement.
Braking action; NBAA
Less experience pilots might be put off by a description of harsh deceleration. High decelerations might be encountered on a dry or damp runway, but in wet and particularly slippery conditions max braking may only produce decelerations similar to normal landings, just when all of the deceleration is required.
The industry had a torrid time with pilots / braking problems during RTOs, - failure to apply or maintain maximum braking; auto brake was part of the solution. Now days landing accidents appear to dominate the statistics thus there must not be any suggestion which detracts from the use of brakes i.e. using max brake when the conditions require.
Brake for safety not for comfort.
A point of interest; as I understand, a PIREP is not used for reporting braking action, although it appears to be (mis)used in this way.
See the last FAA conference on Runway Condition Determination, Reporting, and Report Dissemination Workshop. The summary suggests that the N. American operators are planning to rewrite the definitions used in reporting, or is it that the ICAO terms are not that well understood in the US?
Useful links Safety aspects of aircraft performance on wet and contaminated runways.
Braking Action Measurement.
Braking action; NBAA
