Wet Runway Factors
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Wet Runway Factors
Folks,
In the old days, Australia applied a 15% factor to dry runway LDR to give wet LDR.
I have a feeling that the FAA ignored "wet" but would love someone with the current information to tell me how it works now.
Similarly, if anyone has a copy of BCAR "D" I would be interested in how those rules dealt with "wet" and equally how JAR 25 now covers it.
------------------
Stay Alive,
[email protected]
In the old days, Australia applied a 15% factor to dry runway LDR to give wet LDR.
I have a feeling that the FAA ignored "wet" but would love someone with the current information to tell me how it works now.
Similarly, if anyone has a copy of BCAR "D" I would be interested in how those rules dealt with "wet" and equally how JAR 25 now covers it.
------------------
Stay Alive,
[email protected]
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http://www.srg.caa.co.uk/includes/ga/07bleafl.pdf
Is the published CAA advice for light aircraft.
If nobody beats me to it, I'll dig out my copy of Section D at the weekend and see what that says. I'm afraid that I'm not a JAR-25 man however.
G
Is the published CAA advice for light aircraft.
If nobody beats me to it, I'll dig out my copy of Section D at the weekend and see what that says. I'm afraid that I'm not a JAR-25 man however.
G
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The FAA FAR121 always required the 15% if the 'dest'was below 300/1/2(WX) or the runway was wet!! not required for the alt',for dispatch requirements.
The CAA always accounted for wet since the 50/60's???..
With the advent of the JAr's 'wet' is still definitely there,with very definite explanations(3mm moisture constitutes wet)
320 fcom(02 04 10p3),and the 'new'FAA requirements cover wet distance req'(but it's not retroactive to cover a/c developed before 78)
The European situ' is covered by PJ Swatton's Aircraft Perf' theory
Cheers
The CAA always accounted for wet since the 50/60's???..
With the advent of the JAr's 'wet' is still definitely there,with very definite explanations(3mm moisture constitutes wet)
320 fcom(02 04 10p3),and the 'new'FAA requirements cover wet distance req'(but it's not retroactive to cover a/c developed before 78)
The European situ' is covered by PJ Swatton's Aircraft Perf' theory
Cheers
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m&v,
I see now why I had a feeling FAA ignored wet - it was not a certification limit but rather an operating limit.
The old Oz rule applied to Transport Category aeroplanes and I do not believe that it changed as a function of the class of operations. I am fairly certain it did not distinguish between destination and alternate aerodromes.
I understand that CAAUK has long accounted for wet - my question was "how".
Is the new JAA coverage applicable to the certification or operating rules? How does it account for wet?
------------------
Stay Alive,
[email protected]
I see now why I had a feeling FAA ignored wet - it was not a certification limit but rather an operating limit.
The old Oz rule applied to Transport Category aeroplanes and I do not believe that it changed as a function of the class of operations. I am fairly certain it did not distinguish between destination and alternate aerodromes.
I understand that CAAUK has long accounted for wet - my question was "how".
Is the new JAA coverage applicable to the certification or operating rules? How does it account for wet?
------------------
Stay Alive,
[email protected]
Moderator
Likewise, the old Australian rules distinguished the two aspects in a similar manner. The certification bits (which largely piggybacked on the US (ANO 101.6) and UK (ANO 101.5) rules were then supplemented by the operational rules in ANO 20.7.1b - it was just a pity that the two had the odd discrepancy but the intention was honourable.
This led to a few problems for a while in the early stages of harmonising with the OS rules when ANO bits and pieces were tossed out in a somewhat undisciplined manner.
The use of a 15 percent fudge factor was used for considerations such as gravel runways as well
In respect of category, the usual application was that all heavy aircraft were certificated in Transport Category. For the lighties, the old and well-loved P-charts (and I had an involvement with more than a few of those) covered a range of surface conditions allowing the pilot to hazard a guess as to what might be appropriate for the particular day.
I find it more than amusing that, having thrown out the baby with the bathwater, the System in a recent crash comic is now advocating an informal return to the protocols of the P-chart algorithms... quite amazing.
Unlike the UK system at the time, I am not aware that the Australian regulator ever permitted a distinction between destination and alternate for performance matters.
The real problem is measurement of surface frictional characteristics and the general one of repeatability. Whichever way you go, be cautious when conducting contaminated surface operations if you don't have greatly excess distance and width, especially with crosswind conditions.
This led to a few problems for a while in the early stages of harmonising with the OS rules when ANO bits and pieces were tossed out in a somewhat undisciplined manner.
The use of a 15 percent fudge factor was used for considerations such as gravel runways as well
In respect of category, the usual application was that all heavy aircraft were certificated in Transport Category. For the lighties, the old and well-loved P-charts (and I had an involvement with more than a few of those) covered a range of surface conditions allowing the pilot to hazard a guess as to what might be appropriate for the particular day.
I find it more than amusing that, having thrown out the baby with the bathwater, the System in a recent crash comic is now advocating an informal return to the protocols of the P-chart algorithms... quite amazing.
Unlike the UK system at the time, I am not aware that the Australian regulator ever permitted a distinction between destination and alternate for performance matters.
The real problem is measurement of surface frictional characteristics and the general one of repeatability. Whichever way you go, be cautious when conducting contaminated surface operations if you don't have greatly excess distance and width, especially with crosswind conditions.
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A copy of the JAR's is available on the internet at http://www.jaa.nl/jar/jar/toc00000536.htm
this will give some info on performance criteria.
this will give some info on performance criteria.
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JT,
As usual, I lacked the necessary precision. CAO 101.5/6 set out the certification data requirements and were quite precisely coupled with CAO 20.7.1B - importantly, neither rule differentiates by class of operation, ie RPT/CHTR/AWK/PVT. In the US, FAR 121 applies only the equivalent of our HICAP RPT. The "wet" rules in Oz were established by letter to Ansett and TAA only, not by legislation (as should have been done!)
As I now understand it, in OZ there are no "wet" runway rules per se, since the abandonment of Oz Flight Manuals - you just sort of apply what you think the rules of the foreign certification authority are, if any. Should be very interesting for good old CASA to regulate - I wonder what regulation they would quote?
The reason I started the thread was to try to unearth some expert advice. As we all know, reading a rule is one thing, knowing how it is applied and what other rules come into play is very much a local experience thing!!!
As usual, I lacked the necessary precision. CAO 101.5/6 set out the certification data requirements and were quite precisely coupled with CAO 20.7.1B - importantly, neither rule differentiates by class of operation, ie RPT/CHTR/AWK/PVT. In the US, FAR 121 applies only the equivalent of our HICAP RPT. The "wet" rules in Oz were established by letter to Ansett and TAA only, not by legislation (as should have been done!)
As I now understand it, in OZ there are no "wet" runway rules per se, since the abandonment of Oz Flight Manuals - you just sort of apply what you think the rules of the foreign certification authority are, if any. Should be very interesting for good old CASA to regulate - I wonder what regulation they would quote?
The reason I started the thread was to try to unearth some expert advice. As we all know, reading a rule is one thing, knowing how it is applied and what other rules come into play is very much a local experience thing!!!
Moderator
The category of operation bit was addressed by a circuitous route in the ANOs. I don't have my archive copies with me so I won't try to recall the exact spot to avoid getting egg on my face when someone jumps up and tells me I quoted an incorrect reference. If you need to know, I can dig it out for you in due course. Or else you could give Nev Probert in Canberra a call as he would recall the reference at the blink of an eye.
There was a single note in one ANO which required that the heavies were certificated in Transport Category, so the question of RPT throught PVT was irrelevant. In addition, CAA, DOT, DOT-ATG, DofA, CASA (or whatever letterhead you might choose from day to day) would not, in reality, let you fly a serious heavy in other than a manner equivalent to RPT, eg recall the Associated Airlines operation.
The contaminated runway requirement was imposed by 20.7.1b in which a clause required the operator to do some unspecified thing to address the problem. The usual mechanism was to go into written dialogue with the regulator and arrive at an understanding. The same sort of thing applied with runway lineup allowances - the original letter was to QF in respect of their big bird operations. I have that somewhere in the filing cabinet. I suspect that that reference still binds the operators to doing something useful in respect of contaminated runway operations.
Do keep in mind that the tech people in airworthiness and operations weren't the originators of many of the changes in recent years.... they often were vigorous opponents but were drowned out in the cacophony.
I have a reasonably pertinent background in the area in Australian operations and there are a few others in the ops engineering area who can throw some historical light on these matters.
There was a single note in one ANO which required that the heavies were certificated in Transport Category, so the question of RPT throught PVT was irrelevant. In addition, CAA, DOT, DOT-ATG, DofA, CASA (or whatever letterhead you might choose from day to day) would not, in reality, let you fly a serious heavy in other than a manner equivalent to RPT, eg recall the Associated Airlines operation.
The contaminated runway requirement was imposed by 20.7.1b in which a clause required the operator to do some unspecified thing to address the problem. The usual mechanism was to go into written dialogue with the regulator and arrive at an understanding. The same sort of thing applied with runway lineup allowances - the original letter was to QF in respect of their big bird operations. I have that somewhere in the filing cabinet. I suspect that that reference still binds the operators to doing something useful in respect of contaminated runway operations.
Do keep in mind that the tech people in airworthiness and operations weren't the originators of many of the changes in recent years.... they often were vigorous opponents but were drowned out in the cacophony.
I have a reasonably pertinent background in the area in Australian operations and there are a few others in the ops engineering area who can throw some historical light on these matters.
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JT,
I have had many conversations with Neville and will undoubtedly continue to do so. The thread is still about getting some expert advice from our overseas brethren and I do not want to divert it too much.
However, your "There was a single note in one ANO which required that the heavies were certificated in Transport Category, so the question of RPT throught PVT was irrelevant" requires comment. If I choose to operate a 747 in PVT operations, I may do so without having to comply with one single RPT rule. I do not even have to have an OMEL and CASA can't force me to have one. The fact that the aeroplane is certificated in Transport category does not really affect what class of operation in which I may choose to use it. It would have some affect if I wanted to use it in a class of operation that required a higher level of airworthiness certificate, but that is not the case here.
Associated is not a good example, as it really was a CHTR operation regardless of what convenient blind eye was applied by the Mexican regulators and their special arrangements.
As for "would not, in reality, let you fly a serious heavy in other than a manner equivalent to RPT", I suspect that you may be wearing some rose coloured retrospectoscopes as the absence of an AOC keeps the regulator largely at bay and most efforts of "do-gooder" regulators to impose their personal fancies are restrained by the same law that they are required to apply. Ultra vires is a very current and fashionable doctrine!
The provisions in CAO 20.7.1B that deal with contaminated runways are paragraphs 6.3 for the take-off case and 11.2 for the landing case. The words for 6.3 are:
"6.3 - The accelerate-stop and take-off distances established in accordance with paragraphs 6.1 and 6.2 above must be increased by an amount approved by the Authority for operation from runways covered by slush, snow or a depth of water."
To the best of my knowledge, the Oz regulator has never provided any guidance on these factors and has never ensured that all relevant aeroplanes have such factors inserted in their Flight Manuals. 15% for "wet" (undefined) is a factor, not guidance! A letter written to TAA and Ansett ANA is not binding on Flight West or Sunstate or Kerry Packer, and given that the operating entities and their AOCs are different, probably not for Australian Airlines, QANTAS or Ansett International either.
Thank you for the message on behalf of the regulators at the coal face, I am well aware of how these things happen and I am generally particularly supportive of those folks. However, the dilemmas that I have described have not arisen in the last few years - they have been a problem since Mr Lum wrote the early letters (1973??) and nothing has actually been done to resolve the issues. Now we just have more abrogation and regulatory anarchy.
And no, I am not really barking at you, you just let me out of my kennel.
[ 13 July 2001: Message edited by: 4dogs ]
I have had many conversations with Neville and will undoubtedly continue to do so. The thread is still about getting some expert advice from our overseas brethren and I do not want to divert it too much.
However, your "There was a single note in one ANO which required that the heavies were certificated in Transport Category, so the question of RPT throught PVT was irrelevant" requires comment. If I choose to operate a 747 in PVT operations, I may do so without having to comply with one single RPT rule. I do not even have to have an OMEL and CASA can't force me to have one. The fact that the aeroplane is certificated in Transport category does not really affect what class of operation in which I may choose to use it. It would have some affect if I wanted to use it in a class of operation that required a higher level of airworthiness certificate, but that is not the case here.
Associated is not a good example, as it really was a CHTR operation regardless of what convenient blind eye was applied by the Mexican regulators and their special arrangements.
As for "would not, in reality, let you fly a serious heavy in other than a manner equivalent to RPT", I suspect that you may be wearing some rose coloured retrospectoscopes as the absence of an AOC keeps the regulator largely at bay and most efforts of "do-gooder" regulators to impose their personal fancies are restrained by the same law that they are required to apply. Ultra vires is a very current and fashionable doctrine!
The provisions in CAO 20.7.1B that deal with contaminated runways are paragraphs 6.3 for the take-off case and 11.2 for the landing case. The words for 6.3 are:
"6.3 - The accelerate-stop and take-off distances established in accordance with paragraphs 6.1 and 6.2 above must be increased by an amount approved by the Authority for operation from runways covered by slush, snow or a depth of water."
To the best of my knowledge, the Oz regulator has never provided any guidance on these factors and has never ensured that all relevant aeroplanes have such factors inserted in their Flight Manuals. 15% for "wet" (undefined) is a factor, not guidance! A letter written to TAA and Ansett ANA is not binding on Flight West or Sunstate or Kerry Packer, and given that the operating entities and their AOCs are different, probably not for Australian Airlines, QANTAS or Ansett International either.
Thank you for the message on behalf of the regulators at the coal face, I am well aware of how these things happen and I am generally particularly supportive of those folks. However, the dilemmas that I have described have not arisen in the last few years - they have been a problem since Mr Lum wrote the early letters (1973??) and nothing has actually been done to resolve the issues. Now we just have more abrogation and regulatory anarchy.
And no, I am not really barking at you, you just let me out of my kennel.
[ 13 July 2001: Message edited by: 4dogs ]
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4dogs,
Airplanes that have been certificated to the equivilat of the post March 1998 FAR 25 include the Airbus A319, A321, A330, A340, Boeing 737-600, 737-700 and 737-800. The resised part 25 included the wet runway information.
Under the FARs the wet runway info is not back dated, under the JARs it is through the operating regs. The JARs also take into account an aircraft line up allowance, the FAR do not.
In short the variables considered for wet runway takeoff data include ground speed, tire pressure, tire tread, runway surface texture, and depth of water on the runway. Unlike the old days, the calculated values must be backed up with flight tests.
Reverse thrust can be used in determining takeoff data, the screen at the end of the runway is lowered to from 35 to 15 feet. The wet runway requirements are said to add a typical 220 feet to the takeoff roll, the brake requirements an additional 150 feet, and the pilot reaction time requirements an additional 150 feet.
I will email you a report of which the last few pages summaries the FAA and JAA position on this issue.
Z
[ 13 July 2001: Message edited by: Zeke ]
Airplanes that have been certificated to the equivilat of the post March 1998 FAR 25 include the Airbus A319, A321, A330, A340, Boeing 737-600, 737-700 and 737-800. The resised part 25 included the wet runway information.
Under the FARs the wet runway info is not back dated, under the JARs it is through the operating regs. The JARs also take into account an aircraft line up allowance, the FAR do not.
In short the variables considered for wet runway takeoff data include ground speed, tire pressure, tire tread, runway surface texture, and depth of water on the runway. Unlike the old days, the calculated values must be backed up with flight tests.
Reverse thrust can be used in determining takeoff data, the screen at the end of the runway is lowered to from 35 to 15 feet. The wet runway requirements are said to add a typical 220 feet to the takeoff roll, the brake requirements an additional 150 feet, and the pilot reaction time requirements an additional 150 feet.
I will email you a report of which the last few pages summaries the FAA and JAA position on this issue.
Z
[ 13 July 2001: Message edited by: Zeke ]
