Good - Fair - Poor - Nil
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Good - Fair - Poor - Nil
In the NTSB special investigation report NTSB/SIR-83/02 we find following definitions of pilots terms: (These definitions are from the 1980 edition of the Air Transport Association's Snow Removal Handbbook.)
GOOD
More braking is available than will be used in an average airline type deceleration. If a max energy stop were attempted, some distance in excess of certified stopping distance would be expected.
FAIR
Sufficient braking and cornering force is available for a well flown approach and landing using light braking. However, excess speed or long touchdown would result in an extremely low safety factor depending on runway length and crosswind component. Careful planning and good judgement are required.
POOR
Very careful planning, judgement and execution are absolutely essential. Crosswind becomes a "priority one" consideration. While a safe and successful approach, landing and stop can be accomplished if all factors are favorable, there is little room for error. Care must be exercised in every facet of the operation and a very careful evaluation of all existing conditions is necessary.
NIL
Extremey slippery with poor directional control even while taxiing. This is the kind of report we would envision during a freezing rain condition if nothing were done to the runways or taxiways.
Are these definitions still valid?
Are there other definitions for GOOD - FAIR - POOR - NIL in operational use?
GOOD
More braking is available than will be used in an average airline type deceleration. If a max energy stop were attempted, some distance in excess of certified stopping distance would be expected.
FAIR
Sufficient braking and cornering force is available for a well flown approach and landing using light braking. However, excess speed or long touchdown would result in an extremely low safety factor depending on runway length and crosswind component. Careful planning and good judgement are required.
POOR
Very careful planning, judgement and execution are absolutely essential. Crosswind becomes a "priority one" consideration. While a safe and successful approach, landing and stop can be accomplished if all factors are favorable, there is little room for error. Care must be exercised in every facet of the operation and a very careful evaluation of all existing conditions is necessary.
NIL
Extremey slippery with poor directional control even while taxiing. This is the kind of report we would envision during a freezing rain condition if nothing were done to the runways or taxiways.
Are these definitions still valid?
Are there other definitions for GOOD - FAIR - POOR - NIL in operational use?
tribo ---
ICAO Annex 14 (Aerodromes), Attachment A gives an explanation on what "good" means:
> 6.6 The table below with associated descriptive terms was developed from friction data collected only in compacted snow and ice and should not therefor be taken to be absolute values applicable in all conditions. If the surface is affected by snow or ice and the braking action is reported as "good", pilots should not expect to find conditions asgood 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 comperative value and is intended to mean that aeroplanes should not experience directional control or braking difficulties, especially when landing.
>
>Measured coefficient / Estimated braking action / Code
0.40 and above -- Good -- 5
0.09 to 0.36 -- Medium to good -- 4
0.35 to 0.30 -- Medium -- 3
0.29 to 0.26 -- Medium to poor -- 2
0.25 and below -- Poor -- 1
That doesn't really answer your question, but anyway....
ICAO Annex 14 (Aerodromes), Attachment A gives an explanation on what "good" means:
> 6.6 The table below with associated descriptive terms was developed from friction data collected only in compacted snow and ice and should not therefor be taken to be absolute values applicable in all conditions. If the surface is affected by snow or ice and the braking action is reported as "good", pilots should not expect to find conditions asgood 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 comperative value and is intended to mean that aeroplanes should not experience directional control or braking difficulties, especially when landing.
>
>Measured coefficient / Estimated braking action / Code
0.40 and above -- Good -- 5
0.09 to 0.36 -- Medium to good -- 4
0.35 to 0.30 -- Medium -- 3
0.29 to 0.26 -- Medium to poor -- 2
0.25 and below -- Poor -- 1
That doesn't really answer your question, but anyway....
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I don't have any empirical data on this, but i do recall reading an article a long time ago on the effects of various types of runway contaminants on the landing performance. It was catered toward bizjet airplanes, but the numbers should be pretty close to the mark for commercial airplane types too. With wet ice - or anything with braking action poor (or worse, nil), landing distance required (LDR) increases in the order of 3 times (if memory serves correctly). That pretty much precludes most runways in normal line operations. Even if that number is overly conservative, i don't have any qualms about diverting off somewhere where it's nicer... Don't need to be a hero here, esp for ppl who don't operate in this kind of condition day in & day out. Nobody's gonna give you a pat on the shoulder for sliding off the r/w!
My last 2 airlines both had company policies prohibiting landing in POOR braking action anyway.
My last 2 airlines both had company policies prohibiting landing in POOR braking action anyway.
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Flugholm
You are correct, it does not really answer my questions. But we have a (ICAO) definition for
GOOD
Aeroplanes should not experience directional control or braking difficulties, especially when landing.
With respect to the braking action table some information can be found at http://www.asft.se/history.html
From this you will se that the table was developed from about 3000 pilot reports. These were most probably piston driven aircrafts like Convair 440, DC-6, DC-7C and Saab 90 Scandia.
The actual braking action table was agreed upon in an meeting i Stockholm, Sweden 13 - 14 October 1959 and later found its way into the ICAO SNOWTAM-format. (Amendment 10 of Annex 15 - 1967/68)
gengis
Did your last two airliners distinguish between
- Poor as reported estimated surface friction/braking action or
- Poor as a measured or calculated coefficient (friction number)?
You are correct, it does not really answer my questions. But we have a (ICAO) definition for
GOOD
Aeroplanes should not experience directional control or braking difficulties, especially when landing.
With respect to the braking action table some information can be found at http://www.asft.se/history.html
From this you will se that the table was developed from about 3000 pilot reports. These were most probably piston driven aircrafts like Convair 440, DC-6, DC-7C and Saab 90 Scandia.
The actual braking action table was agreed upon in an meeting i Stockholm, Sweden 13 - 14 October 1959 and later found its way into the ICAO SNOWTAM-format. (Amendment 10 of Annex 15 - 1967/68)
gengis
Did your last two airliners distinguish between
- Poor as reported estimated surface friction/braking action or
- Poor as a measured or calculated coefficient (friction number)?
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Tribo, you wrote:
"Did your last two airliners distinguish between
- Poor as reported estimated surface friction/braking action or
- Poor as a measured or calculated coefficient (friction number)?"
1 expressly prohibited landing anytime reported braking action was poor - either by runway coefficient or by braking action.
The other specifies that landings will not be made on runways with more than one half inch of standing water, slush, or wet snow. It further goes on to provide a table regulating the maximum landing crosswind based on Reported Braking Action (Good, Good-Medium, Medium, Medium-Poor, Poor), Reported Runway Coefficient & Equivalent Runway Condition (Dry/damp/wet, slush/dry snow or wet snow/standing water/hydroplaning risk).
I would add, however, that neither of these two airlines operate routinely in severe icing conditions.
Hope this helps.
"Did your last two airliners distinguish between
- Poor as reported estimated surface friction/braking action or
- Poor as a measured or calculated coefficient (friction number)?"
1 expressly prohibited landing anytime reported braking action was poor - either by runway coefficient or by braking action.
The other specifies that landings will not be made on runways with more than one half inch of standing water, slush, or wet snow. It further goes on to provide a table regulating the maximum landing crosswind based on Reported Braking Action (Good, Good-Medium, Medium, Medium-Poor, Poor), Reported Runway Coefficient & Equivalent Runway Condition (Dry/damp/wet, slush/dry snow or wet snow/standing water/hydroplaning risk).
I would add, however, that neither of these two airlines operate routinely in severe icing conditions.
Hope this helps.
The following text is taken from the presentation and speaker notes in Managing Threats and Errors During Approach and Landing.
Note that the friction reports are relative to the wet stopping performance. Slide 27 shows this diagrammatically i.e. the reports don’t commence until the friction has already decreased to the wet value. Thus good on a wet runway is not ‘good’ when compared with dry performance and the certificated distances unless a max energy stop is performed.
The ICAO ‘ATC’ runway friction report codes relate to the surface conditions i.e ‘good’ on a wet runway relates wet stopping performance which is already degraded with respect to dry runway operations.
NORMAL - Maximum energy stops possible with little deterioration in certified (dry) stopping distance.
GOOD - More braking is available than will be used in an average airline type deceleration. If a maximum energy stop were attempted (wet), some distance in excess of certified stopping distance would be expected.
FAIR - Sufficient braking and cornering force is available for a well-flown approach and landing using light braking. However, excess speed or long touchdown would result in an extremely low safety factor depending on runway length and crosswind component. Careful planning and good judgment are required.
POOR - Very careful planning, judgment, and execution are absolutely essential. Crosswind becomes a "priority one" consideration. While a safe and successful approach, landing, and stop can be accomplished if all factors are favorable, there is little room for error. [/b] Care must be exercised in every aspect of the operation and a very careful evaluation of all conditions is necessary.
Note: "Unreliable" will be reported when surface conditions do not permit a meaningful action value to be determined (i.e., standing water, slush, wet snow [potential hydroplaning]).
“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 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.” JAA WP061
Refs: (Most can be found via Google)
FAA NASA B 737 Aircraft test results from 1996 joint winter runway friction measurement program. T Yeager, NASA Langley
DoT Canada Procedures for Accounting for Runway Friction on Landing TC 14082E
DoT Canada Falcon 20 Aircraft Braking Performance on Wet Concrete Runway Surfaces No. TP 14273E
Re questions:
Are these definitions still valid? Yes
Are there other definitions for GOOD - FAIR - POOR - NIL in operational use?
Unfortunately yes, but these are unofficial, non ICAO standard, and only add confusion. Either non conforming ATC or both ATC and pilots make up their own interpretations of the definitions in an attempt to help others. Thus, the friction reports are also relative to the reporter’s aircraft type, his/her interpretation and the variability in the measuring device which can be significant.
Note that the friction reports are relative to the wet stopping performance. Slide 27 shows this diagrammatically i.e. the reports don’t commence until the friction has already decreased to the wet value. Thus good on a wet runway is not ‘good’ when compared with dry performance and the certificated distances unless a max energy stop is performed.
The ICAO ‘ATC’ runway friction report codes relate to the surface conditions i.e ‘good’ on a wet runway relates wet stopping performance which is already degraded with respect to dry runway operations.
NORMAL - Maximum energy stops possible with little deterioration in certified (dry) stopping distance.
GOOD - More braking is available than will be used in an average airline type deceleration. If a maximum energy stop were attempted (wet), some distance in excess of certified stopping distance would be expected.
FAIR - Sufficient braking and cornering force is available for a well-flown approach and landing using light braking. However, excess speed or long touchdown would result in an extremely low safety factor depending on runway length and crosswind component. Careful planning and good judgment are required.
POOR - Very careful planning, judgment, and execution are absolutely essential. Crosswind becomes a "priority one" consideration. While a safe and successful approach, landing, and stop can be accomplished if all factors are favorable, there is little room for error. [/b] Care must be exercised in every aspect of the operation and a very careful evaluation of all conditions is necessary.
Note: "Unreliable" will be reported when surface conditions do not permit a meaningful action value to be determined (i.e., standing water, slush, wet snow [potential hydroplaning]).
“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 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.” JAA WP061
Refs: (Most can be found via Google)
FAA NASA B 737 Aircraft test results from 1996 joint winter runway friction measurement program. T Yeager, NASA Langley
DoT Canada Procedures for Accounting for Runway Friction on Landing TC 14082E
DoT Canada Falcon 20 Aircraft Braking Performance on Wet Concrete Runway Surfaces No. TP 14273E
Re questions:
Are these definitions still valid? Yes
Are there other definitions for GOOD - FAIR - POOR - NIL in operational use?
Unfortunately yes, but these are unofficial, non ICAO standard, and only add confusion. Either non conforming ATC or both ATC and pilots make up their own interpretations of the definitions in an attempt to help others. Thus, the friction reports are also relative to the reporter’s aircraft type, his/her interpretation and the variability in the measuring device which can be significant.
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alf5071h
Agree with you, adds to confusion.
I am trying to find the "most offical" definitions. According to responses so far we have the following scale:
Normal
Good
Medium/Fair
Poor
Unreliable
With definitions:
Normal - Maximum energy stops possible with little deterioration in certified (dry) stopping distance.
Good - More braking is available than will be used in an average airline type deceleration. If a maximum energy stop were attempted (wet), some distance in excess of certified stopping
distance would be expected.
Medium/Fair - Sufficient braking and cornering force is available for a well-flown approach and landing using light braking. However, excess speed or long touchdown would result in an extremely low safety factor depending on runway length and crosswind component. Careful planning and good judgment are required.
Poor - Very careful planning, judgment, and execution are absolutely essential. Crosswind becomes a "priority one" consideration. While a safe and successful approach, landing, and stop can be accomplished if all factors are favorable, there is little room for error. Care must be exercised in every aspect of the operation and a very careful evaluation of all conditions is necessary.
Unreliable - "Unreliable" will be reported when surface conditions do not permit a meaningful action value to be determined (i.e., standing water, slush, wet snow [potential hydroplaning]).
Are these definitions sufficient?
Do they give the pilot the info needed for "situational awareness"?
Any experience telling otherwise?
Agree with you, adds to confusion.
I am trying to find the "most offical" definitions. According to responses so far we have the following scale:
Normal
Good
Medium/Fair
Poor
Unreliable
With definitions:
Normal - Maximum energy stops possible with little deterioration in certified (dry) stopping distance.
Good - More braking is available than will be used in an average airline type deceleration. If a maximum energy stop were attempted (wet), some distance in excess of certified stopping
distance would be expected.
Medium/Fair - Sufficient braking and cornering force is available for a well-flown approach and landing using light braking. However, excess speed or long touchdown would result in an extremely low safety factor depending on runway length and crosswind component. Careful planning and good judgment are required.
Poor - Very careful planning, judgment, and execution are absolutely essential. Crosswind becomes a "priority one" consideration. While a safe and successful approach, landing, and stop can be accomplished if all factors are favorable, there is little room for error. Care must be exercised in every aspect of the operation and a very careful evaluation of all conditions is necessary.
Unreliable - "Unreliable" will be reported when surface conditions do not permit a meaningful action value to be determined (i.e., standing water, slush, wet snow [potential hydroplaning]).
Are these definitions sufficient?
Do they give the pilot the info needed for "situational awareness"?
Any experience telling otherwise?
tribo Sorry I have nothing more official, but to add to the confusion:-
From: European Regions Airline Association - Icing Workshop 21st Nov 02, EUROCONTROL, Luxembourg
“Braking Action Measurement” by Alistair Scott, BAE SYSTEMS - Regional Aircraft
Runway Condition and Braking Definitions -
ICAO: Damp, Wet, Water Patches, Flooded
JAR Ops 1.480: Dry, Damp, Wet, Contaminated
JAA Certification: Water, Slush, Wet Snow, Dry Snow, Compacted Snow, Specially prepared Winter Runway, Ice
Manufacturer: Slippery, contaminant depth
ATC: Good, Medium, Poor, nil
From: UK CAA AIC 61 99 “Risks and factors associated with operations on runways affected by snow, slush or water”.
DRY : The surface is not affected by water, slush, snow or ice. NOTE: Reports that the runway is dry are not normally passed to pilots. If no runway surface report is passed, the runway can be assumed to be dry.
DAMP: The surface shows a change of colour due to moisture. NOTE: If there is sufficient moisture to produce a surface film or the surface appears reflective, the runway will be reported as WET.
WET:The surface is soaked but no significant patches of standing water are visible. NOTE: Standing water is considered to exist when water on the runway surface is deeper than 3 mm. Patches of standing water covering more than 25% of the assessed area will be reported as WATER PATCHES. For JAR-OPS performance purposes, runways reported as WATER PATCHES or FLOODED should be considered as CONTAMINATED.
WATER PATCHES: Significant patches of standing water are visible. NOTE: Water patches will be reported when more than 25% of the assessed area is covered by water more than 3 mm deep.
FLOODED: Extensive patches of standing water are visible. NOTE: Flooded will be reported when more than 50% of the assessed area covered by water more than 3 mm deep.
From: “An Evaluation of Winter Operational Runway Friction Measurement Equipment, Procedures, and Research” submitted by the Winter runway friction measurement and reporting working group January 25, 1995
The following definitions of braking action were agreed upon by the ATA Flight Operations Committee for use with the Mu-Meter and James Brake Decelerometer friction values and were added to the Runway Friction-measuring Program:
NORMAL - Maximum energy stops possible with little deterioration in certified stopping distance.
GOOD (Mu 0.6) - More braking is available than will be used in an average airline type deceleration. If a maximum energy stop were attempted, some distance in excess of certified stopping distance would be expected.
FAIR - Sufficient braking and cornering force is available for a well-flown approach and landing using light braking. However, excess speed or long touchdown would result in an extremely low safety factor depending on runway length and crosswind component. Careful planning and good judgment are required.
POOR (Mu 0.3) - Very careful planning, judgment, and execution are absolutely essential. Crosswind becomes a "priority one" consideration. While a safe and successful approach, landing, and stop can be accomplished if all factors are favorable, there is little room for error. Care must be exercised in every facet of the operation and a very careful evaluation of all existing conditions is necessary.
James Brake Indicator Excellent, Good, Fair, Poor, Nil
For convenience, the various conditions of airport surfaces during winter are grouped into the following categories in determining the surface friction characteristics:
Dry surface (bare) and free from winter contaminants,
Wet surface but free from winter contaminants,
Dry ice present on surface,
Wet ice present on surface,
Loose snow present on surface,
Compacted, dry snow present on surface,
Wet snow present on surface, and
Slush present on surface.
????
From: European Regions Airline Association - Icing Workshop 21st Nov 02, EUROCONTROL, Luxembourg
“Braking Action Measurement” by Alistair Scott, BAE SYSTEMS - Regional Aircraft
Runway Condition and Braking Definitions -
ICAO: Damp, Wet, Water Patches, Flooded
JAR Ops 1.480: Dry, Damp, Wet, Contaminated
JAA Certification: Water, Slush, Wet Snow, Dry Snow, Compacted Snow, Specially prepared Winter Runway, Ice
Manufacturer: Slippery, contaminant depth
ATC: Good, Medium, Poor, nil
From: UK CAA AIC 61 99 “Risks and factors associated with operations on runways affected by snow, slush or water”.
DRY : The surface is not affected by water, slush, snow or ice. NOTE: Reports that the runway is dry are not normally passed to pilots. If no runway surface report is passed, the runway can be assumed to be dry.
DAMP: The surface shows a change of colour due to moisture. NOTE: If there is sufficient moisture to produce a surface film or the surface appears reflective, the runway will be reported as WET.
WET:The surface is soaked but no significant patches of standing water are visible. NOTE: Standing water is considered to exist when water on the runway surface is deeper than 3 mm. Patches of standing water covering more than 25% of the assessed area will be reported as WATER PATCHES. For JAR-OPS performance purposes, runways reported as WATER PATCHES or FLOODED should be considered as CONTAMINATED.
WATER PATCHES: Significant patches of standing water are visible. NOTE: Water patches will be reported when more than 25% of the assessed area is covered by water more than 3 mm deep.
FLOODED: Extensive patches of standing water are visible. NOTE: Flooded will be reported when more than 50% of the assessed area covered by water more than 3 mm deep.
From: “An Evaluation of Winter Operational Runway Friction Measurement Equipment, Procedures, and Research” submitted by the Winter runway friction measurement and reporting working group January 25, 1995
The following definitions of braking action were agreed upon by the ATA Flight Operations Committee for use with the Mu-Meter and James Brake Decelerometer friction values and were added to the Runway Friction-measuring Program:
NORMAL - Maximum energy stops possible with little deterioration in certified stopping distance.
GOOD (Mu 0.6) - More braking is available than will be used in an average airline type deceleration. If a maximum energy stop were attempted, some distance in excess of certified stopping distance would be expected.
FAIR - Sufficient braking and cornering force is available for a well-flown approach and landing using light braking. However, excess speed or long touchdown would result in an extremely low safety factor depending on runway length and crosswind component. Careful planning and good judgment are required.
POOR (Mu 0.3) - Very careful planning, judgment, and execution are absolutely essential. Crosswind becomes a "priority one" consideration. While a safe and successful approach, landing, and stop can be accomplished if all factors are favorable, there is little room for error. Care must be exercised in every facet of the operation and a very careful evaluation of all existing conditions is necessary.
James Brake Indicator Excellent, Good, Fair, Poor, Nil
For convenience, the various conditions of airport surfaces during winter are grouped into the following categories in determining the surface friction characteristics:
Dry surface (bare) and free from winter contaminants,
Wet surface but free from winter contaminants,
Dry ice present on surface,
Wet ice present on surface,
Loose snow present on surface,
Compacted, dry snow present on surface,
Wet snow present on surface, and
Slush present on surface.
????
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alf5071h
Thanks for the input. May look a bit confusing to start with, but sorting out your input I think we can handle it.
First we have to distinguish between description of braking action and description of surface conditions
Braking action
Normal
Good
Medium/Fair
Poor
Unreliable
Surface conditions
Dry
(Damp - no longer in use according to latest harmonisation - http://www.easa.eu.int/home/easa NPA 14/2004, CRD 14/2004)
Wet
Slush
Wet snow
etc.
+ combinations of these
Surface conditions (for reporting purposes) is a topic of its own, and I will stop here for not loosing track of the braking action terms with assosiated definitions.
You make reference to the 1995 evaluation - http://ntl.bts.gov/lib/1000/1100/1106/wrfmrwg1.pdf . I know this document and there are several statements in this document which are not stricktly correct. When you start to combine the definitions with measured friction coefficients you start to get into trouble. The first mistake is that one mix operational measurements (snow and ice) and measurements for maintenance purposes (wetted surface). And once you start talking about friction measurements you have to distinguish between different friction measurement devices. So let us address these things under an other heading and concentrate on the braking action terms. Otherwise your quote from the document are in line with earlier mentioned definitions for braking action.
With respect to the James Brake Index. Today it is named Canadian Runway Friction Index. Info found at http://www.tc.gc.ca/CivilAviation/co.../CRFI/menu.htm The CRFI has been updated to current knowledge through the Joint Winter Runway Friction Measurement Program (JWRFMP).
The term Excellent would have to be compared to normal, and we have (with assosiated descriptive terms):
Normal/Excellent - Maximum energy stops possible with little deterioration in certified (dry) stopping distance.
Good - More braking is available than will be used in an average airline type deceleration. If a maximum energy stop were attempted (wet), some distance in excess of certified stopping
distance would be expected.
Medium/Fair - Sufficient braking and cornering force is available for a well-flown approach and landing using light braking. However, excess speed or long touchdown would result in an extremely low safety factor depending on runway length and crosswind component. Careful planning and good judgment are required.
Poor - Very careful planning, judgment, and execution are absolutely essential. Crosswind becomes a "priority one" consideration. While a safe and successful approach, landing, and stop can be accomplished if all factors are favorable, there is little room for error. Care must be exercised in every aspect of the operation and a very careful evaluation of all conditions is necessary.
Unreliable - "Unreliable" will be reported when surface conditions do not permit a meaningful action value to be determined (i.e., standing water, slush, wet snow [potential hydroplaning]).
We have also sorted out following items to be treated seperatly:
1. Surface conditions (for reporting purposes)
2. Type of friction measurements - operational vs. maintenance
3. Harmonisation of friction measurement devices.
Thanks for the input. May look a bit confusing to start with, but sorting out your input I think we can handle it.
First we have to distinguish between description of braking action and description of surface conditions
Braking action
Normal
Good
Medium/Fair
Poor
Unreliable
Surface conditions
Dry
(Damp - no longer in use according to latest harmonisation - http://www.easa.eu.int/home/easa NPA 14/2004, CRD 14/2004)
Wet
Slush
Wet snow
etc.
+ combinations of these
Surface conditions (for reporting purposes) is a topic of its own, and I will stop here for not loosing track of the braking action terms with assosiated definitions.
You make reference to the 1995 evaluation - http://ntl.bts.gov/lib/1000/1100/1106/wrfmrwg1.pdf . I know this document and there are several statements in this document which are not stricktly correct. When you start to combine the definitions with measured friction coefficients you start to get into trouble. The first mistake is that one mix operational measurements (snow and ice) and measurements for maintenance purposes (wetted surface). And once you start talking about friction measurements you have to distinguish between different friction measurement devices. So let us address these things under an other heading and concentrate on the braking action terms. Otherwise your quote from the document are in line with earlier mentioned definitions for braking action.
With respect to the James Brake Index. Today it is named Canadian Runway Friction Index. Info found at http://www.tc.gc.ca/CivilAviation/co.../CRFI/menu.htm The CRFI has been updated to current knowledge through the Joint Winter Runway Friction Measurement Program (JWRFMP).
The term Excellent would have to be compared to normal, and we have (with assosiated descriptive terms):
Normal/Excellent - Maximum energy stops possible with little deterioration in certified (dry) stopping distance.
Good - More braking is available than will be used in an average airline type deceleration. If a maximum energy stop were attempted (wet), some distance in excess of certified stopping
distance would be expected.
Medium/Fair - Sufficient braking and cornering force is available for a well-flown approach and landing using light braking. However, excess speed or long touchdown would result in an extremely low safety factor depending on runway length and crosswind component. Careful planning and good judgment are required.
Poor - Very careful planning, judgment, and execution are absolutely essential. Crosswind becomes a "priority one" consideration. While a safe and successful approach, landing, and stop can be accomplished if all factors are favorable, there is little room for error. Care must be exercised in every aspect of the operation and a very careful evaluation of all conditions is necessary.
Unreliable - "Unreliable" will be reported when surface conditions do not permit a meaningful action value to be determined (i.e., standing water, slush, wet snow [potential hydroplaning]).
We have also sorted out following items to be treated seperatly:
1. Surface conditions (for reporting purposes)
2. Type of friction measurements - operational vs. maintenance
3. Harmonisation of friction measurement devices.
tribo Thanks for the update, I am getting out of date in retirement.
However back to the questions:
Are these definitions still valid?
Are there other definitions . . . in operational use?
Or even more important;
What are pilots taught about the definitions of runway conditions? And what do they understand about them and aircraft performance so as not to be confused?
What and how will ATC communicate the runway conditions to pilots?
Is this what you are seeking; if so then probably most of the industry is looking with you.
Is the comment “There is no overall accepted certification / operational correlation between mu meters and airplanes” still valid? I have mislaid the source reference.
However back to the questions:
Are these definitions still valid?
Are there other definitions . . . in operational use?
Or even more important;
What are pilots taught about the definitions of runway conditions? And what do they understand about them and aircraft performance so as not to be confused?
What and how will ATC communicate the runway conditions to pilots?
Is this what you are seeking; if so then probably most of the industry is looking with you.
Is the comment “There is no overall accepted certification / operational correlation between mu meters and airplanes” still valid? I have mislaid the source reference.
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alf5071h
Your questions are absolutely to the point.
The most important thing is that we "speak the same language".
The information gathered by the "ground staff" must be understood by both parties and transmitted to the pilot as speedily and accurately as possible.
I am involved in a couple of projects dealing with these questions, and yes I want the industry to look with me. There is a lot of experience out there - good experience. One difficulty is that the focus on the measured friction coefficient have "masked" the knowledge and use of the descriptive terms, therefore my questions and search.
The comment: There is no overall accepted ...... is still valid. And that it is not only for the my-meter. The outcome from the JWRFMP found a better correlation between aircraft performance and decelerometer type of measuring instrument then for those of fixed or variable slip type.
New friction measurement devices enter the marked every year - they claim to be better than the previous - but they add to the complexity and confusion and frustration - and the result is that there is even a bigger need for harmonisation - timeless. In the early 60's ICAO was told that the accuracy of the measurements was 0.01. Today we know that not to be true. It is more close to 0.1. (repeatability and reproducibility). ICAO (study groups) also had difficulties with harmonisation between two types of instruments in the early 60's. There were an ICAO harmonisation project in the 70's with several instruments. NASA have looked into the subject. The last major project was the JWRFMP administrated by Transport Canada. One outcome was the update of the Canadian Runway Friction Index - CRFI. Finnair has also made use of results from JWRFMP for their operations. One thing in common for both Canada and Finland - they have standardised on one single type of friction measurement device. Canada a decelerometer, Finland av fixed slip device.
Your questions are absolutely to the point.
The most important thing is that we "speak the same language".
The information gathered by the "ground staff" must be understood by both parties and transmitted to the pilot as speedily and accurately as possible.
I am involved in a couple of projects dealing with these questions, and yes I want the industry to look with me. There is a lot of experience out there - good experience. One difficulty is that the focus on the measured friction coefficient have "masked" the knowledge and use of the descriptive terms, therefore my questions and search.
The comment: There is no overall accepted ...... is still valid. And that it is not only for the my-meter. The outcome from the JWRFMP found a better correlation between aircraft performance and decelerometer type of measuring instrument then for those of fixed or variable slip type.
New friction measurement devices enter the marked every year - they claim to be better than the previous - but they add to the complexity and confusion and frustration - and the result is that there is even a bigger need for harmonisation - timeless. In the early 60's ICAO was told that the accuracy of the measurements was 0.01. Today we know that not to be true. It is more close to 0.1. (repeatability and reproducibility). ICAO (study groups) also had difficulties with harmonisation between two types of instruments in the early 60's. There were an ICAO harmonisation project in the 70's with several instruments. NASA have looked into the subject. The last major project was the JWRFMP administrated by Transport Canada. One outcome was the update of the Canadian Runway Friction Index - CRFI. Finnair has also made use of results from JWRFMP for their operations. One thing in common for both Canada and Finland - they have standardised on one single type of friction measurement device. Canada a decelerometer, Finland av fixed slip device.
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With respect to the use of Ground Fricxtion Measurement Devices:
Quote from EASA NPA 14/2004 found at http://www.easa.eu.int/doc/Rulemakin...PA_14_2004.pdf
With respect to the use of Ground Fricxtion Measurement Devices:
Quote from EASA NPA 14/2004 found at http://www.easa.eu.int/doc/Rulemakin...PA_14_2004.pdf
Ideally it would be preferable to relate aeroplane braking performance to a friction index measured by a ground friction device that would be reported as part of a Surface Condition Report. However, there is not, at present, a common friction index for all ground friction measuring devices. Hence it is not practicable at the present time to determine aeroplane performance on the basis of an internationally accepted friction index measured by ground friction devices. Notwithstanding this lack of a common index, the applicant may optionally choose to present take-off and landing performance data as a function of an aeroplane braking coefficient or wheel braking coefficient constant with ground speed. The responsibility for relating this data to a friction index measured by a ground friction device will fall on the operator and the operating authority.
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I will now link the definitions for Good - Medium - ... with info from Boeing.
At the 2003 Boeing Performance and Flight Operations Engineer Confereence, Boeing presented:
Airplane Braking Coefficient - Pilot Reported Braking Action - Runway Description
0.4 - Approximates dry runway - Friction limited certification values
0.2 - Good - Wet Runway, Jar certification for compact snow
0.1 - Medium/Fair - Ice, Compacted Snow
0.05 - Poor/Nil - Wet Ice, Slush, Melting Compacted Snow, Standing Water
On a runway covered with wet ice, slush, melting compacted snow, or standing water the possibility of hydroplaning exists, which can result in nil braking capability. For that reason we recommend that the flight crew use the operational landing distance for POOR Braking Action in such conditions to determine the acceptability of landing on such a runway.
If we combine this with the definitions from ATA we get:
NORMAL/EXCELLENT - Friction limited certification values. Maximum energy stops possible with little deterioration in certified stopping distance.
Runway Description - Dry runway
Aircraft Braking Coefficient 0.4
GOOD - More braking is available than will be used in an average airline type deceleration. If a maximum energy stop were attempted, some distance in excess of certified stopping distance would be expected.
Runway Description - Wet runway. CS (JAR) certification for compact snow.
Aircraft Braking Coefficient 0.2
MEDIUM/FAIR - Sufficient braking and cornering force is available for a well-flown approach and landing using light braking. However, excess speed or long touchdown would result in an extremely low safety factor depending on runway length and crosswind component. Careful planning and good judgment are required.
Runway Description - Ice, Compacted Snow
Aircraft Braking Coefficient 0.1
POOR - Very careful planning, judgment, and execution are absolutely essential. Crosswind becomes a "priority one" consideration. While a safe and successful approach, landing, and stop can be accomplished if all factors are favorable, there is little room for error. Care must be exercised in every facet of the operation and a very careful evaluation of all existing conditions is necessary. Possibility of hydroplaning/aquaplaning exists.
Runway Description - Wet Ice, Melting Compacted Snow, Slush, Standing Water
Aircraft Braking Coefficient 0.05
NIL - Extremely slippery with poor directional control even while taxiing.
Runway Description - Freezing rain condition if nothing were done to the runways or taxiways.
Aircraft Braking Coefficient 0.05
-------------------------------------------------------------------------------
Please give comments/feedback on the "suitabilty" of the above terms and relationships in an operational pilot's world.
(I will later bring in other documented relationships.)
At the 2003 Boeing Performance and Flight Operations Engineer Confereence, Boeing presented:
Airplane Braking Coefficient - Pilot Reported Braking Action - Runway Description
0.4 - Approximates dry runway - Friction limited certification values
0.2 - Good - Wet Runway, Jar certification for compact snow
0.1 - Medium/Fair - Ice, Compacted Snow
0.05 - Poor/Nil - Wet Ice, Slush, Melting Compacted Snow, Standing Water
On a runway covered with wet ice, slush, melting compacted snow, or standing water the possibility of hydroplaning exists, which can result in nil braking capability. For that reason we recommend that the flight crew use the operational landing distance for POOR Braking Action in such conditions to determine the acceptability of landing on such a runway.
If we combine this with the definitions from ATA we get:
NORMAL/EXCELLENT - Friction limited certification values. Maximum energy stops possible with little deterioration in certified stopping distance.
Runway Description - Dry runway
Aircraft Braking Coefficient 0.4
GOOD - More braking is available than will be used in an average airline type deceleration. If a maximum energy stop were attempted, some distance in excess of certified stopping distance would be expected.
Runway Description - Wet runway. CS (JAR) certification for compact snow.
Aircraft Braking Coefficient 0.2
MEDIUM/FAIR - Sufficient braking and cornering force is available for a well-flown approach and landing using light braking. However, excess speed or long touchdown would result in an extremely low safety factor depending on runway length and crosswind component. Careful planning and good judgment are required.
Runway Description - Ice, Compacted Snow
Aircraft Braking Coefficient 0.1
POOR - Very careful planning, judgment, and execution are absolutely essential. Crosswind becomes a "priority one" consideration. While a safe and successful approach, landing, and stop can be accomplished if all factors are favorable, there is little room for error. Care must be exercised in every facet of the operation and a very careful evaluation of all existing conditions is necessary. Possibility of hydroplaning/aquaplaning exists.
Runway Description - Wet Ice, Melting Compacted Snow, Slush, Standing Water
Aircraft Braking Coefficient 0.05
NIL - Extremely slippery with poor directional control even while taxiing.
Runway Description - Freezing rain condition if nothing were done to the runways or taxiways.
Aircraft Braking Coefficient 0.05
-------------------------------------------------------------------------------
Please give comments/feedback on the "suitabilty" of the above terms and relationships in an operational pilot's world.
(I will later bring in other documented relationships.)
tribo
The definitions are a reasonable certification/regulation summary, but they need to be associated with the operating situation, harmonized with ATC descriptions, and as far as possible ‘error proofed’.
Normal / excellent would (could?) only be associated with a dry runway, thus an ATC statement such as “Runway dry, braking normal” conveys both the description of the runway conditions and the braking action that provides a link to the data that the crew could use (dry landing data).
Similarly, “Runway wet, braking good” provides the description and the link to wet landing data, which should be used. However this is complicated where operators are allowed to use dry data on a wet grooved runway; here the actual stopping distance may lie between “normal” and “good”. Furthermore this might have to accommodate additional descriptors i.e. Damp, Water patches (AIC 61 / 99), and there could be further complications with “Runway wet with water patches” as the braking action could be good, medium/fair, or even poor.
From this discussion and the SW 737 at Midway thread – Boeing data (statement above), we might conclude that there should not be any ‘medium / fair’ operation, instead as soon as a runway is ‘contaminated’ the braking action should only be stated as ‘poor’ (use of most conservative data) so as to guard against aquaplaning. Operations should be prohibited in ‘nil’.
The ‘error proofing’ has to cope with helpful ATC who might use non standard or enhanced descriptions (human nature), and crew’s who misinterpret information in their choice of landing data (risk assessment).
The choice in the data is between every day operations using factored data that has well proven margins (the norm in memory), and a contaminated operation with relatively lower safety factors or none at all (rarely encountered or practiced).
Factored data is normally used on runways that have a narrow range of braking conditions, normal / excellent (wet/dry), good (wet), that appear easy to assess accurately both by ATC and pilots.
The ‘lesser’ factored (contaminated) data covers a wider range of conditions, which are more difficult to assess (requirement for Mu meter); thus, there is opportunity for error in assessing the runway conditions that may contribute to the pilot using inappropriate data.
An associated issue may be that pilots do not understand the differing levels of risk associated with ‘factored’ contaminated data, and that regulators may have assumed too much about the pilots knowledge/judgment of risk and of the validity of the data. Hence the Boeing / Airbus documents, and the Flight Safety Foundation’s presentation raising the industry’s awareness to these problems.
Overall, I would simplify the definitions by removing ‘excellent’ and ‘fair’ and link the remainder with descriptions of the runway surface. Further simplifications where there could be a range or potentially ambiguous combinations of descriptors, would limit the operation by the use of more reliably factored data or the most conservative data, i.e. only use ‘poor’ landing data on a ‘wet with water patches’ or ‘contaminated’ runway. Delete medium from practical operations.
The definitions are a reasonable certification/regulation summary, but they need to be associated with the operating situation, harmonized with ATC descriptions, and as far as possible ‘error proofed’.
Normal / excellent would (could?) only be associated with a dry runway, thus an ATC statement such as “Runway dry, braking normal” conveys both the description of the runway conditions and the braking action that provides a link to the data that the crew could use (dry landing data).
Similarly, “Runway wet, braking good” provides the description and the link to wet landing data, which should be used. However this is complicated where operators are allowed to use dry data on a wet grooved runway; here the actual stopping distance may lie between “normal” and “good”. Furthermore this might have to accommodate additional descriptors i.e. Damp, Water patches (AIC 61 / 99), and there could be further complications with “Runway wet with water patches” as the braking action could be good, medium/fair, or even poor.
From this discussion and the SW 737 at Midway thread – Boeing data (statement above), we might conclude that there should not be any ‘medium / fair’ operation, instead as soon as a runway is ‘contaminated’ the braking action should only be stated as ‘poor’ (use of most conservative data) so as to guard against aquaplaning. Operations should be prohibited in ‘nil’.
The ‘error proofing’ has to cope with helpful ATC who might use non standard or enhanced descriptions (human nature), and crew’s who misinterpret information in their choice of landing data (risk assessment).
The choice in the data is between every day operations using factored data that has well proven margins (the norm in memory), and a contaminated operation with relatively lower safety factors or none at all (rarely encountered or practiced).
Factored data is normally used on runways that have a narrow range of braking conditions, normal / excellent (wet/dry), good (wet), that appear easy to assess accurately both by ATC and pilots.
The ‘lesser’ factored (contaminated) data covers a wider range of conditions, which are more difficult to assess (requirement for Mu meter); thus, there is opportunity for error in assessing the runway conditions that may contribute to the pilot using inappropriate data.
An associated issue may be that pilots do not understand the differing levels of risk associated with ‘factored’ contaminated data, and that regulators may have assumed too much about the pilots knowledge/judgment of risk and of the validity of the data. Hence the Boeing / Airbus documents, and the Flight Safety Foundation’s presentation raising the industry’s awareness to these problems.
Overall, I would simplify the definitions by removing ‘excellent’ and ‘fair’ and link the remainder with descriptions of the runway surface. Further simplifications where there could be a range or potentially ambiguous combinations of descriptors, would limit the operation by the use of more reliably factored data or the most conservative data, i.e. only use ‘poor’ landing data on a ‘wet with water patches’ or ‘contaminated’ runway. Delete medium from practical operations.
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The definitons needs to be harmonized with those used by the ground staff who gather the information and describe the operative surface. ATC, when transmitting the information must use harmonized and standardised terms. 'error proofed'
Dry
Ground/ATC - Runway dry
Crew - Use dry landing data
Default Aircraft Braking Coefficient = 0.4
Wet
Ground/ATC - Runway wet
Crew - Use wet landing data
Default Aircraft Braking Coefficient from 'equations'
Don Stimson, FAA at the 2003 Boeing Performance and Flight Operations Engineering Conference
The harmonized regulation 25.109 (c) and (d) has two sets of 'equations'. One set applies to grooved runways.
In the hormonizing prosess the term 'Damp' are no longer in use as damp is considered wet. (A damp runway is a wet runway)
I do not agree. The terms Good, Medium, ..... applies to runway contaminated with snow, slush and ice. They have been used for decades. The aircraft operators need a 'scale' for relating operations on contaminated/slippery runways. There are documents bridging this need. Now we have to look at the work done by EASA. At these links,
http://www.easa.eu.int/doc/Rulemakin...PA_14_2004.pdf
http://www.easa.eu.int/doc/Rulemakin...RD_14_2004.pdf
you will find documents related to operations on contaminated runways. These documents identify surface conditions and combine them with default friction values (Aircraft Braking coefficient).
'Error proofing'
Using terms and definitions from the EASA documents we speak the same language as used in certification. For many surface conditions we can link to and refine the Good, Medium, ..... scale. Thus harmonize between the operational terms and the certification/regulation terms. There are however difficulties related to the term ' Specially prepared winter runway' which we have to handle. More on that later.
Please have a look at the EASA documents.
The definitions are a reasonable certification/regulation summary, but they need to be associated with the operating situation, harmonized with ATC descriptions, and as far as possible ‘error proofed’.
Normal / excellent would (could?) only be associated with a dry runway, thus an ATC statement such as “Runway dry, braking normal” conveys both the description of the runway conditions and the braking action that provides a link to the data that the crew could use (dry landing data).
Ground/ATC - Runway dry
Crew - Use dry landing data
Default Aircraft Braking Coefficient = 0.4
Similarly, “Runway wet, braking good” provides the description and the link to wet landing data, which should be used. However this is complicated where operators are allowed to use dry data on a wet grooved runway; here the actual stopping distance may lie between “normal” and “good”. Furthermore this might have to accommodate additional descriptors i.e. Damp, Water patches (AIC 61 / 99), and there could be further complications with “Runway wet with water patches” as the braking action could be good, medium/fair, or even poor.
Ground/ATC - Runway wet
Crew - Use wet landing data
Default Aircraft Braking Coefficient from 'equations'
Airplanes certified to Amendment 25-92 of Part 25 (effective March 20, 1998) or Change 15 of JAR-25 (effective October 1, 2000) must have wet runway takeoff performance data provided in their Airplane Flight Manuals (AFM). These data are considered to be normal operating limitations for the airplane in the same manner that dry runway data are. The FAA and JAA certfication requirements for how these performance data are developed are the same. Thus, the airplane type certification regulations for wet runway takeoff performance are harmonized.
The harmonized regulation 25.109 (c) and (d) has two sets of 'equations'. One set applies to grooved runways.
In the hormonizing prosess the term 'Damp' are no longer in use as damp is considered wet. (A damp runway is a wet runway)
From this discussion and the SW 737 at Midway thread – Boeing data (statement above), we might conclude that there should not be any ‘medium / fair’ operation, instead as soon as a runway is ‘contaminated’ the braking action should only be stated as ‘poor’ (use of most conservative data) so as to guard against aquaplaning. Operations should be prohibited in ‘nil’.
http://www.easa.eu.int/doc/Rulemakin...PA_14_2004.pdf
http://www.easa.eu.int/doc/Rulemakin...RD_14_2004.pdf
you will find documents related to operations on contaminated runways. These documents identify surface conditions and combine them with default friction values (Aircraft Braking coefficient).
The ‘error proofing’ has to cope with helpful ATC who might use non standard or enhanced descriptions (human nature), and crew’s who misinterpret information in their choice of landing data (risk assessment). The choice in the data is between every day operations using factored data that has well proven margins (the norm in memory), and a contaminated operation with relatively lower safety factors or none at all (rarely encountered or practiced). Factored data is normally used on runways that have a narrow range of braking conditions, normal / excellent (wet/dry), good (wet), that appear easy to assess accurately both by ATC and pilots. The ‘lesser’ factored (contaminated) data covers a wider range of conditions, which are more difficult to assess (requirement for Mu meter); thus, there is opportunity for error in assessing the runway conditions that may contribute to the pilot using inappropriate data.
An associated issue may be that pilots do not understand the differing levels of risk associated with ‘factored’ contaminated data, and that regulators may have assumed too much about the pilots knowledge/judgment of risk and of the validity of the data. Hence the Boeing / Airbus documents, and the Flight Safety Foundation’s presentation raising the industry’s awareness to these problems.
Overall, I would simplify the definitions by removing ‘excellent’ and ‘fair’ and link the remainder with descriptions of the runway surface. Further simplifications where there could be a range or potentially ambiguous combinations of descriptors, would limit the operation by the use of more reliably factored data or the most conservative data, i.e. only use ‘poor’ landing data on a ‘wet with water patches’ or ‘contaminated’ runway. Delete medium from practical operations.
An associated issue may be that pilots do not understand the differing levels of risk associated with ‘factored’ contaminated data, and that regulators may have assumed too much about the pilots knowledge/judgment of risk and of the validity of the data. Hence the Boeing / Airbus documents, and the Flight Safety Foundation’s presentation raising the industry’s awareness to these problems.
Overall, I would simplify the definitions by removing ‘excellent’ and ‘fair’ and link the remainder with descriptions of the runway surface. Further simplifications where there could be a range or potentially ambiguous combinations of descriptors, would limit the operation by the use of more reliably factored data or the most conservative data, i.e. only use ‘poor’ landing data on a ‘wet with water patches’ or ‘contaminated’ runway. Delete medium from practical operations.
Using terms and definitions from the EASA documents we speak the same language as used in certification. For many surface conditions we can link to and refine the Good, Medium, ..... scale. Thus harmonize between the operational terms and the certification/regulation terms. There are however difficulties related to the term ' Specially prepared winter runway' which we have to handle. More on that later.
Please have a look at the EASA documents.
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Took a brief look at the material in this thread, nearly fell asleep in the seat, felt like the end of an INTL duty day
Seriously, we all get complacent landing on long, dry runways when conditions at VMC. Landing data, as provided to the pilot, from the manufacturer, through the airline and (when operating in anything other than the above conditions) interpreted by both dispatch and the PIC is more art than science. When someone reports that on a cluttered runway, in IMC, with a tailwind (reported when and how much really X vis tail) the landing distance allows only (pick a number) 800 feet runway remaining ; you gotta take that with a grain of salt.
Any braking action report, either "official" or pilot report less than fair should be considered with great doubt. Unless the runway is very long and conditions are good to see before landing no landing with a tailwind should be considered.
Its easy in hindsight to say this but, only though others tragedies can we all re praise our future decisions.
Seriously, we all get complacent landing on long, dry runways when conditions at VMC. Landing data, as provided to the pilot, from the manufacturer, through the airline and (when operating in anything other than the above conditions) interpreted by both dispatch and the PIC is more art than science. When someone reports that on a cluttered runway, in IMC, with a tailwind (reported when and how much really X vis tail) the landing distance allows only (pick a number) 800 feet runway remaining ; you gotta take that with a grain of salt.
Any braking action report, either "official" or pilot report less than fair should be considered with great doubt. Unless the runway is very long and conditions are good to see before landing no landing with a tailwind should be considered.
Its easy in hindsight to say this but, only though others tragedies can we all re praise our future decisions.
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Night Mission,
"Landing data, as provided to the pilot, from the manufacturer, through the airline and (when operating in anything other than the above conditions) interpreted by both dispatch and the PIC is more art than science. When someone reports that on a cluttered runway, in IMC, with a tailwind (reported when and how much really X vis tail) the landing distance allows only (pick a number) 800 feet runway remaining ; you gotta take that with a grain of salt.
Any braking action report, either "official" or pilot report less than fair should be considered with great doubt. Unless the runway is very long and conditions are good to see before landing no landing with a tailwind should be considered.
Its easy in hindsight to say this but, only though others tragedies can we all re praise our future decisions."
I concur fully.
"Landing data, as provided to the pilot, from the manufacturer, through the airline and (when operating in anything other than the above conditions) interpreted by both dispatch and the PIC is more art than science. When someone reports that on a cluttered runway, in IMC, with a tailwind (reported when and how much really X vis tail) the landing distance allows only (pick a number) 800 feet runway remaining ; you gotta take that with a grain of salt.
Any braking action report, either "official" or pilot report less than fair should be considered with great doubt. Unless the runway is very long and conditions are good to see before landing no landing with a tailwind should be considered.
Its easy in hindsight to say this but, only though others tragedies can we all re praise our future decisions."
I concur fully.
tribo, et al, I have read the JAA documents. Both refer to Part 25 certification rulemaking and deal with ‘ideal’ conditions and ‘theoretical’ performance.
Many of the respondent’s comments relate to the disparity between certification proposals and actual operations; this follows many well established, but erroneous traditions in certification, which in this instance could yet again widen the gap between regulation and operations.
The proposals appear to be enabling operations beyond reasonable safety whilst attempting to provide data that are more accurate. The assumptions that the operator / pilots will have, and will use, guidance material falls short of reality, whilst guidance might be noted in part 25, no proposals appear to be planned for JAR-OPS etc, and also why hide information away in another ‘approved document’. Unless the guidance is spelt out in unequivocal terms then pilots will continue to be unaware of the assumptions made in certification. Similarly, those replies that state that ‘the issue is beyond the scope of the NPA’ show the weakness of the proposal and the processes that should improves safety.
I reinforce the point that it extremely disappointing that the FAA is not considering rulemaking, yet are party to JAR comment procedures. The FAA’s position does little to reduce the problems of differing standards and alternate terminology in use around the world.
As I interpret the comments, whilst normal landings have a safety margin of 1.67 /1.92 for jet aircraft on a dry/wet runway, on top of the measured landing distance, the contaminated data will only have a 1.15 factor above a theoretical distance (plus an arbitrary allowance by local authority or operator). The conditions on a contaminated runway are unlikely to match the assumed certification standard. A runway covered in dry snow may soon become rutted and slushy, or even ‘contaminated’ by de-icing fluid from aircraft taking off.
Thus, neither the theoretical distances nor the safety factor may provide a realistic stopping distance. Who can believe that a landing distance not less than the factored wet distance has the same safety margin on a contaminated runway? The responsibility for safety is yet again to be placed on the pilot by regulators who at this time have the opportunity in new regulation to help pilots, and maintain the highest levels of safety.
The rules and regulations are ever increasing in complexity, requiring pilots to have greater and deeper knowledge of a range of specialist subjects. Where is the department for clarifying regulations, even removing them, what efforts are being made to simplifying operations and thus improve safety? Where is the book of all of the certification assumptions made about pilot’s knowledge and performance … there are many draft sections in the accident and incident reports around the world.
Re the point, “I do not agree. The terms Good, Medium, ..... applies to runway contaminated with snow, slush and ice. They have been used for decades. The aircraft operators need a 'scale' for relating operations on contaminated/slippery runways.”
In the decades of using potentially ambiguous terms, alternatives, and those open to misinterpretation, the hull-loss accident statistics show that overruns are top of the list. If the industry is to improve safety in this area, then more rigid safety barriers are required. Many of the contributory causes involve human error; in order to reduce this, the threats to the operation have to be removed or their effect minimized, e.g. by providing adequate safety margins or prohibiting tailwind landings on contaminants, and the error provoking circumstances such as interpreting third party runway reports and choosing between ‘less than ideal’ data sets should be eliminated.
Many of the respondent’s comments relate to the disparity between certification proposals and actual operations; this follows many well established, but erroneous traditions in certification, which in this instance could yet again widen the gap between regulation and operations.
The proposals appear to be enabling operations beyond reasonable safety whilst attempting to provide data that are more accurate. The assumptions that the operator / pilots will have, and will use, guidance material falls short of reality, whilst guidance might be noted in part 25, no proposals appear to be planned for JAR-OPS etc, and also why hide information away in another ‘approved document’. Unless the guidance is spelt out in unequivocal terms then pilots will continue to be unaware of the assumptions made in certification. Similarly, those replies that state that ‘the issue is beyond the scope of the NPA’ show the weakness of the proposal and the processes that should improves safety.
I reinforce the point that it extremely disappointing that the FAA is not considering rulemaking, yet are party to JAR comment procedures. The FAA’s position does little to reduce the problems of differing standards and alternate terminology in use around the world.
As I interpret the comments, whilst normal landings have a safety margin of 1.67 /1.92 for jet aircraft on a dry/wet runway, on top of the measured landing distance, the contaminated data will only have a 1.15 factor above a theoretical distance (plus an arbitrary allowance by local authority or operator). The conditions on a contaminated runway are unlikely to match the assumed certification standard. A runway covered in dry snow may soon become rutted and slushy, or even ‘contaminated’ by de-icing fluid from aircraft taking off.
Thus, neither the theoretical distances nor the safety factor may provide a realistic stopping distance. Who can believe that a landing distance not less than the factored wet distance has the same safety margin on a contaminated runway? The responsibility for safety is yet again to be placed on the pilot by regulators who at this time have the opportunity in new regulation to help pilots, and maintain the highest levels of safety.
The rules and regulations are ever increasing in complexity, requiring pilots to have greater and deeper knowledge of a range of specialist subjects. Where is the department for clarifying regulations, even removing them, what efforts are being made to simplifying operations and thus improve safety? Where is the book of all of the certification assumptions made about pilot’s knowledge and performance … there are many draft sections in the accident and incident reports around the world.
Re the point, “I do not agree. The terms Good, Medium, ..... applies to runway contaminated with snow, slush and ice. They have been used for decades. The aircraft operators need a 'scale' for relating operations on contaminated/slippery runways.”
In the decades of using potentially ambiguous terms, alternatives, and those open to misinterpretation, the hull-loss accident statistics show that overruns are top of the list. If the industry is to improve safety in this area, then more rigid safety barriers are required. Many of the contributory causes involve human error; in order to reduce this, the threats to the operation have to be removed or their effect minimized, e.g. by providing adequate safety margins or prohibiting tailwind landings on contaminants, and the error provoking circumstances such as interpreting third party runway reports and choosing between ‘less than ideal’ data sets should be eliminated.
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alf5071h, et al
Some FAA history on the subject - contaminated runway.
At the Aeronautical Information Services and Aeronautical Charts Division Meeting 1966, specification for Snowplan; definition and pro forma for SNOWTAM was on the agenda. Statement by the delegation of the USA:
“The Delegation of the United States of America wishes to record a reservation to Recommendation 2/1 – Amendment to Annex 15, (Snow Plans), Recommendation 2/2 – Snowtam Reports, and Recommendation 2/3 – Amendments to Annex 15 (Snowtam proforma). This reservation is based on the fact that without having looked at the substance of EUM V Recommendation 4/9, 4/10 and 4/11, the Air Navigation Commission referred these recommendation to AIS/MAP Meeting only insofar as the reporting and dissemination procedures are concerned. This was done less than 14 days before this Meeting convened. Consequently, the Delegation of the United States and perhaps many other delegations were not prepared to consider all the various aspects of the problems raised by these recommendations from the Fith EUM Meeting. In formulating its recommendations, this Meeting clearly exceeded the terms reference given it by the Air Navigation Commission. Nevertheless, it is hoped that action by this Meeting will not be considered to have prejudged the importance and continuing work of the ICAO Study Group on Snow, Slush, Ice and Water on Aerodromes, which may in due course produce more mature and considered recommendations for world-wide standards, practices and procedures.”
With reference to the 1966 meeting, the Snow Plan and SNOWTAM-format was part of Amendment 10 of ICAO Annex 15 (Adopted/Effective/Applicable – 13 Jun 67/8 Oct 67/8 Feb 68)
There exists a draft FAA AC 91-6B – Performance information for operation with water, slush, snow, or ice on the runway”. It is dated JUN 18 1986.
ALPA commented the AC in a letter OCT 7 1986:
“We are pleased the FAA is issuing an AC on this subject. For many years the U.S. military services and many foreign regulatory agencies and carriers have had procedures and correction charts for dealing with decreased friction on runways. We have long advocated more precise air carrier procedures for dealing with contaminated runways.”
8 comments
“Again, we want to congratulate the FAA for taking the initiative in developing such a comprehensive document. The use of this AC should go a long way toward improving safety while operating on contaminated runways”
There exist another updated version of the draft AC dated 8-16-89.
JAA - JAR 25. In Change 13, 18 Oct 1988 - Performance Information for Operations with Contaminated Runway Surface Conditions – became part of JAR 25. The rule and associated advisory material addressed the development of performance information on both wet and contaminated runways. In this you will find definitions for contaminated runway in principle as used in the draft FAA AC 91-6B.
EASA NPA 14/2004 – Operation on Contaminated Runways:
“FAR 25 does not address performance on contaminated runways so harmonisation is not currently a consideration”. …. “However, harmonisation of this will be addressed in the future.”
Don Stimson. FAA, Transport Standards Staff.
From the Proceedings of the 3rd International Meeting on Aircraft Performance on Contaminated Runways, IMAPCR 2004, Montreal November 2004.
“Abstract:
Currently, the FAA’s certification and operating rules do not contain specific requirements for operating on runways contaminated by snow,slush, standing water, or ice. Guidance for contaminated runway operations is provided in FAA Advisory Circular (AC) 91-6A, “Water, Slush, and Snow on the Runway,” dated May 24, 1978. FAA Order 8400.10, “Air Transportation Inspector’s Handbook,” provides guidance to FAA inspectors for contaminated runway operations.
In 2002, the Aviation Rulemaking Advisory Committee (ARAC)recommended that the FAA revise the operating rules to take intoaccount the effects of contaminated runways on takeoff performance anddevelop harmonized airplane certification requirements for contaminatedrunway performance. Because of concerns about economic impact, the ARAC did not reach a consensus on whether consideration for an engine failure (as in the current dry and wet runway takeoff requirements)should be included.
Due to resource constraints and higher priority safety and security issues,the FAA has not yet taken action on the ARAC’s recommendations. Even without specific Federal Aviation Regulations requirements, however,many U.S. operators account for contaminated runways for dispatch.”
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Well, as harmonization will take place in the future (some time) it is a good thing that FAA comments on the EASA regulations. At least there is a "dialogue". But like you I am disappointed with respect to the progress to
"...in due course produce more mature and considered recommendations for world-wide standards, practices and procedures.”
as the US delegation expressed themselves in 1966.
I reinforce the point that it extremely disappointing that the FAA is not considering rulemaking, yet are party to JAR comment procedures. The FAA’s position does little to reduce the problems of differing standards and alternate terminology in use around the world.
At the Aeronautical Information Services and Aeronautical Charts Division Meeting 1966, specification for Snowplan; definition and pro forma for SNOWTAM was on the agenda. Statement by the delegation of the USA:
“The Delegation of the United States of America wishes to record a reservation to Recommendation 2/1 – Amendment to Annex 15, (Snow Plans), Recommendation 2/2 – Snowtam Reports, and Recommendation 2/3 – Amendments to Annex 15 (Snowtam proforma). This reservation is based on the fact that without having looked at the substance of EUM V Recommendation 4/9, 4/10 and 4/11, the Air Navigation Commission referred these recommendation to AIS/MAP Meeting only insofar as the reporting and dissemination procedures are concerned. This was done less than 14 days before this Meeting convened. Consequently, the Delegation of the United States and perhaps many other delegations were not prepared to consider all the various aspects of the problems raised by these recommendations from the Fith EUM Meeting. In formulating its recommendations, this Meeting clearly exceeded the terms reference given it by the Air Navigation Commission. Nevertheless, it is hoped that action by this Meeting will not be considered to have prejudged the importance and continuing work of the ICAO Study Group on Snow, Slush, Ice and Water on Aerodromes, which may in due course produce more mature and considered recommendations for world-wide standards, practices and procedures.”
With reference to the 1966 meeting, the Snow Plan and SNOWTAM-format was part of Amendment 10 of ICAO Annex 15 (Adopted/Effective/Applicable – 13 Jun 67/8 Oct 67/8 Feb 68)
There exists a draft FAA AC 91-6B – Performance information for operation with water, slush, snow, or ice on the runway”. It is dated JUN 18 1986.
ALPA commented the AC in a letter OCT 7 1986:
“We are pleased the FAA is issuing an AC on this subject. For many years the U.S. military services and many foreign regulatory agencies and carriers have had procedures and correction charts for dealing with decreased friction on runways. We have long advocated more precise air carrier procedures for dealing with contaminated runways.”
8 comments
“Again, we want to congratulate the FAA for taking the initiative in developing such a comprehensive document. The use of this AC should go a long way toward improving safety while operating on contaminated runways”
There exist another updated version of the draft AC dated 8-16-89.
JAA - JAR 25. In Change 13, 18 Oct 1988 - Performance Information for Operations with Contaminated Runway Surface Conditions – became part of JAR 25. The rule and associated advisory material addressed the development of performance information on both wet and contaminated runways. In this you will find definitions for contaminated runway in principle as used in the draft FAA AC 91-6B.
EASA NPA 14/2004 – Operation on Contaminated Runways:
“FAR 25 does not address performance on contaminated runways so harmonisation is not currently a consideration”. …. “However, harmonisation of this will be addressed in the future.”
Don Stimson. FAA, Transport Standards Staff.
From the Proceedings of the 3rd International Meeting on Aircraft Performance on Contaminated Runways, IMAPCR 2004, Montreal November 2004.
“Abstract:
Currently, the FAA’s certification and operating rules do not contain specific requirements for operating on runways contaminated by snow,slush, standing water, or ice. Guidance for contaminated runway operations is provided in FAA Advisory Circular (AC) 91-6A, “Water, Slush, and Snow on the Runway,” dated May 24, 1978. FAA Order 8400.10, “Air Transportation Inspector’s Handbook,” provides guidance to FAA inspectors for contaminated runway operations.
In 2002, the Aviation Rulemaking Advisory Committee (ARAC)recommended that the FAA revise the operating rules to take intoaccount the effects of contaminated runways on takeoff performance anddevelop harmonized airplane certification requirements for contaminatedrunway performance. Because of concerns about economic impact, the ARAC did not reach a consensus on whether consideration for an engine failure (as in the current dry and wet runway takeoff requirements)should be included.
Due to resource constraints and higher priority safety and security issues,the FAA has not yet taken action on the ARAC’s recommendations. Even without specific Federal Aviation Regulations requirements, however,many U.S. operators account for contaminated runways for dispatch.”
-----------------------------------------------
Well, as harmonization will take place in the future (some time) it is a good thing that FAA comments on the EASA regulations. At least there is a "dialogue". But like you I am disappointed with respect to the progress to
"...in due course produce more mature and considered recommendations for world-wide standards, practices and procedures.”
as the US delegation expressed themselves in 1966.
