Do you really trust that wet runway performance data

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pelmet
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Do you really trust that wet runway performance data

Post by pelmet »

I wouldn't trust the wet runway performance data. It doesn't come from actual flight tests. It comes from.....calculations based on assumptions agreed to by the regulator. It is a guess and that's it which is why it is called Advisory Data. So if the runway performance is tight but appears to be just within limits, you might just want to re-consider.

Here is what the FAA says in a SAFO....

" Landing overruns which occur on wet runways typically involve multiple contributing factors such as long touchdown, improper use of deceleration devices, tailwind and less available friction than expected. Several recent runway landing incidents/accidents have raised concerns with wet runway stopping performance assumptions. Analysis of the stopping data from these incidents/accidents indicates the braking coefficient of friction in each case was significantly lower than expected for a wet runway as defined by the Federal Aviation Administration (FAA) in Federal Air Regulation (FAR) 25.109 and Advisory Circular (AC) 25-7C methods. These incidents/accidents occurred on both grooved and ungrooved or non-Porous Friction Course overlay (PFC) runways. The data indicates that applying a 15% safety margin to wet runway time-of-arrival advisory data as, recommended by SAFO 06012, may be inadequate in certain wet runway conditions.

Discussion: The root cause of the wet runway stopping performance shortfall is not fully understood at this time; however issues that appear to be contributors are runway conditions such as texture (polished or rubber contaminated surfaces), drainage, puddling in wheel tracks and active precipitation. Analysis of this data indicates that 30 to 40 percent of additional stopping distance may be required in certain cases where the runway is very wet, but not flooded.

For non-grooved or non-PFC runways, experience has shown that wheel braking may be degraded when the runway is very wet. If active moderate or heavy precipitation exists, the operator should consider additional conservatism in their time-of-arrival assessment.

For grooved or PFC runways, experience has shown that wheel braking is degraded when the runway is very wet. If active heavy precipitation exists; the operator should consider additional conservatism in their time-of-arrival assessment.

Possible methods of applying additional conservatism when operating on a runway which experience has shown is degraded when very wet are assuming a braking action of medium or fair when computing time-of-arrival landing performance or increasing the factor applied to the wet runway time-of-arrival landing performance data.


Of course, it all seems pretty obvious if you think about it but it just shows how the perfomance data can lie.

This accident report covers the above information. In fact, the aircraft may very well have been OK if proper procedures had been followed but it is interesting nonetheless....

https://app.ntsb.gov/pdfgenerator/Repor ... l&IType=FA

https://www.nbaa.org/ops/safety/SAFO15009.pdf
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AuxBatOn
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Re: Do you really trust that wet runway performance data

Post by AuxBatOn »

I am/have been involved in reduced runway friction coefficient flight testing down to 0.35 CRFI values. Your performance section should say how it got the data (chart header normally). I would be really surprised for part 25 that the model they used to produce charts wasn't spotted checked by flight test.
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Rockie
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Re: Do you really trust that wet runway performance data

Post by Rockie »

We don’t use CRFI anymore even as an advisory “second opinion”, since late 2016 we are required to use manufacturer TALPA numbers. Both the accident and the FAA SAFO documents posted by Pelmet predate TALPA. If anything from experience TALPA landing distances seem quite conservative and we can consistently outperform them at least with dry and wet runways. I haven’t seen enough contaminated landings yet to adequately compare those numbers with reality.
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AuxBatOn
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Re: Do you really trust that wet runway performance data

Post by AuxBatOn »

CRFI or TALPA, the bottom line is that your landing distance on a contaminated runway will likely be flight tested.
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pelmet
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Re: Do you really trust that wet runway performance data

Post by pelmet »

Rockie wrote: Tue Aug 28, 2018 3:16 am We don’t use CRFI anymore even as an advisory “second opinion”, since late 2016 we are required to use manufacturer TALPA numbers. Both the accident and the FAA SAFO documents posted by Pelmet predate TALPA. If anything from experience TALPA landing distances seem quite conservative and we can consistently outperform them at least with dry and wet runways. I haven’t seen enough contaminated landings yet to adequately compare those numbers with reality.
Thanks for the reply,

TALPA can be useful....if you have the manufacturer data and an airport providing condition codes.

A lttle more about TALPA from the NBAA.....

"Gertsen said that business aviation supports the Runway Condition Assessment Matrix (RCAM), which is at the core of TALPA. The RCAM assigns runway condition codes (RwyCC) between zero and six for each third of the runway, with higher numbers indicating more favorable conditions. This information is then disseminated to pilots via NOTAMs.

Gertsen moderated a panel on the topic at the recent International Aviation Snow Symposium in Buffalo, NY. Panelists included representatives from the FAA, the Air Line Pilots Association and the National Air Traffic Controllers Association.

The problem is that although Part 139 air-carrier airports must use the RCAM, it’s voluntary for the airports often frequented by business aircraft. Gertsen acknowledged the challenges these smaller, often understaffed airfields sometimes face in providing timely field condition reports, adding that the FAA has created an online tool to facilitate expeditious NOTAM filing.

“We urge airfields to provide runway condition information and to file FICON NOTAMs for contaminated runways, and we strongly encourage more airports to report wet runways,” said Gertsen. “The change by the FAA, making wet runway reporting voluntary, presents a challenge to business aviation, which relies on these reports.”

Another challenge to wider TALPA implementation is a lack of time-of-arrival landing performance data for business aircraft. “TALPA relies upon manufacturers providing this performance data, which corresponds with reported RwyCCs,” said Rich Boll, chairman of the ATC, Airspace and Flight Technologies Working Group of the NBAA Access Committee.

“That’s a significant challenge, particularly for older aircraft,” added Boll. “However, we need manufacturers to provide operators with time-of-arrival landing data based on the RwyCC, or tell operators how to use their existing data in conjunction with the RwyCCs.”

Boll also encouraged airports to provide more timely and accurate runway-condition reports.

“Pilots must be able to trust FICONS and RwyCCs if we expect them to make operational decisions based on them, so these reports must be reliable, accurate and timely,” he said. “The process is in place, and now it must be refined.”

The FAA’s TALPA working group will host a public TALPA update meeting on July 11-12 in Washington DC. Operators are encouraged to attend and provide feedback. Learn more about the meeting."


Unfortunately, not everyone is flying into places like La Guardia or O'Hare with their runway condition codes. As was the case for the incident in Conroe Texas that I posted. What's your plan when you have no runway condition data and it is raining?

Beware of uncertified wet runway data.
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Last edited by pelmet on Tue Aug 28, 2018 9:43 am, edited 1 time in total.
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Re: Do you really trust that wet runway performance data

Post by Taco Joe »

AuxBatOn wrote: Tue Aug 28, 2018 6:07 am CRFI or TALPA, the bottom line is that your landing distance on a contaminated runway will likely be flight tested.
Not always.

For the LJ45XR, which is a Part 25 certified aircraft. This is also the only data we have available for landing on a wet runway:

Title Page:

Contaminated Runway Data

The performance information in this addendum is not FAA approved. These data represent the best available information for planning and use during operations on contaminated runway surfaces. Data were derived by calculation methods which are recognized as aviation industry standards.

Page 1:

Contaminated Runway Performance Data

General
The following information and procedures have been prepared by Learjet for use when operating on runway surfaces contaminated by standing water, slush, loose snow, compacted snow or ice.

- The data have been prepared using prepared using industry accepted calculations to determine the effects of contaminated runway surfaces on the accelerated ground roll and braking ground roll. The effects of actual conditions may differ from those used to establish this data.

My interpretation of those statements would be that Learjet did not do flight testing for these values and they were just calculating them. This was also relayed to me on my initial by my sim instructor, who was one of the flight test pilots for Bombardier on the Lear 45 when they were developing and delivering the aircraft.
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Rockie
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Re: Do you really trust that wet runway performance data

Post by Rockie »

AuxBatOn wrote: Tue Aug 28, 2018 6:07 am CRFI or TALPA, the bottom line is that your landing distance on a contaminated runway will likely be flight tested.
My understanding is that CRFI numbers have been flight tested by Falcon 20 aircraft as they were deemed most representative. However contaminated runway ops are not part of the certification and are not flight tested by manufacturers. For example, balanced field conditions are not always possible with a contaminated runway and there is a grey zone between a reduced V1 and VR where you are not guaranteed to either meet single engine climb performance or stop on the remaining runway.

There are simply too many variables with contaminated runways, so manufacturers are only required to certify takeoff performance dry (without reverse) and wet (with reverse) only. TALPA contaminated numbers are not to my knowledge flight tested.
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pelmet
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Re: Do you really trust that wet runway performance data

Post by pelmet »

Contaminated data is not flight tested. That is why it is unapproved data. To clarify, for part 23 aircraft like the Phenom, the wet runway data is based on calculated assumptions.

But for airline ops, it is nice to say, hey....lets just use the TALPA runway condition report or some sort of equivalent but are you really going to have a report. Remember the WJ runway overrun at YUL. They had no condition report. But they knew(or should have known) that moderate to heavy rain started a few minutes before landing. So now what? Should one assume a wet runway or a contaminated runway? They treated it like a wet runway and assumed that they would have decent braking at the far end of the runway. Then they slid off the runway. Admittedly, this was a bit of a unique situation in how they handled a landing on a long runway, but it in a way, they turned it into a situation where it was equivalent of a shorter runway.

Beware and don't just hope that TALPA will save the day.

http://www.bst-tsb.gc.ca/eng/rapports-r ... 5q0075.asp
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Rockie
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Re: Do you really trust that wet runway performance data

Post by Rockie »

pelmet wrote: Tue Aug 28, 2018 9:39 am But for airline ops, it is nice to say, hey....lets just use the TALPA runway condition report or some sort of equivalent but are you really going to have a report.
First, you determine yourself what the runway conditions are either from the ATIS (wet / dry) or runway condition report in winter conditions. From that you use RCAM codes, or more detailed analysis to determine your landing distance under TALPA.

Second, while there is a dispatch requirement for factored landing distance there is no regulatory requirement for the crew to calculate actual landing distance for every landing. Any airline I've been involved with has stipulated conditions under which a landing distance shall be calculated, but if it's not contaminated or any of the other criteria at an airfield you've landed at many times there usually is no company requirement either.

BTW, there were several contributing factors in the incident you mention that even singly would invalidate any landing distance calculation had they made one. And the airplane was certainly capable of landing even in the prevailing conditions at the time.
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pelmet
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Re: Do you really trust that wet runway performance data

Post by pelmet »

Rockie wrote: Tue Aug 28, 2018 11:46 am
pelmet wrote: Tue Aug 28, 2018 9:39 am But for airline ops, it is nice to say, hey....lets just use the TALPA runway condition report or some sort of equivalent but are you really going to have a report.
First, you determine yourself what the runway conditions are either from the ATIS (wet / dry) or runway condition report in winter conditions. From that you use RCAM codes, or more detailed analysis to determine your landing distance under TALPA.
Disregarding winter conditions(assumed to mean frozen contamination) because the thread is about wet runway conditions, getting the info from the ATIS is where the problem starts. The ATIS says it is raining. The ATIS is 30 minutes old(winter condition reports can be even older by the way). Wet runway is used but it is actually now moderate to heavy rain. ATC hasn't advised of anything new(does that ever happen in the Caribbean). Wet runway calculations are made. Braking action turns out to be closer to poor. Big surprise happens. Don't blindly trust the ATIS or runway condition report in active precipitation. Contaminated may be more appropriate. Runway condition code 2 may be better than 5...

https://www.faa.gov/about/initiatives/t ... t-RCAM.pdf
Rockie wrote: Tue Aug 28, 2018 11:46 am BTW, there were several contributing factors in the incident you mention that even singly would invalidate any landing distance calculation had they made one. And the airplane was certainly capable of landing even in the prevailing conditions at the time.
Correct, which is why I clearly mentioned that. But it was a great example of changing conditions which seem to have been assumed to create only wet runway when it was in fact much worse. Wouldn't have been a problem if the runway was just wet but it was actually contaminated.
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Rockie
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Re: Do you really trust that wet runway performance data

Post by Rockie »

pelmet wrote: Tue Aug 28, 2018 1:16 pm But it was a great example of changing conditions which seem to have been assumed to create only wet runway when it was in fact much worse.
That seems to be the case in the incident mentioned. But it's then a case of misidentifying runway conditions, not being able to trust the correct numbers as the title of the thread suggests.
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pelmet
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Re: Do you really trust that wet runway performance data

Post by pelmet »

Rockie wrote: Tue Aug 28, 2018 1:40 pm
pelmet wrote: Tue Aug 28, 2018 1:16 pm But it was a great example of changing conditions which seem to have been assumed to create only wet runway when it was in fact much worse.
That seems to be the case in the incident mentioned. But it's then a case of misidentifying runway conditions, not being able to trust the correct numbers as the title of the thread suggests.
I will accept that statement as realistic but......

The SAFO that I posted earlier, which you mentioned pre-dates the new TALPA performance calculations, is still on the FAA website. And it still says...."Analysis of this data indicates that 30 to 40 percent of additional stopping distance may be required in certain cases where the runway is very wet, but not flooded." Yet as far as I know, the TALPA performance calculations for wet runway did not increase landing distance requirements by 30-40%. So as far as I am concerned, the wet performance data cannot be trusted as it was likely made under ideal conditions.

Your ability to consistently outperform the new TALPA wet distance performance is likely because you have not encountered a really wet(but not quite flooded) runway combined with other factors such as reduced friction characteristics. Likely this is a rare situation and even when encountered is compensated for by longer than required runway length. I suspect that it is considered to be a situation that still happens often enough that the FAA still recommends following the SAFO.
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Rockie
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Re: Do you really trust that wet runway performance data

Post by Rockie »

I can't explain why the FAA has on their website a SAFO recommendation that has been superceded by the TALPS-ARC recommendations - now regulation. Maybe you should ask them.
pelmet wrote: Tue Aug 28, 2018 3:08 pm
Yet as far as I know, the TALPA performance calculations for wet runway did not increase landing distance requirements by 30-40%. So as far as I am concerned, the wet performance data cannot be trusted as it was likely made under ideal conditions.
Well, wet runway conditions are not "ideal" conditions. And when the FAA made their original 30-40% additive recommendations it was a gouge, a rough hack, a wild ass guess. TALPA is not. Do not make any kind of equivalence between the two.
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pelmet
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Re: Do you really trust that wet runway performance data

Post by pelmet »

Rockie wrote: Tue Aug 28, 2018 3:52 pm I can't explain why the FAA has on their website a SAFO recommendation that has been superceded by the TALPS-ARC recommendations - now regulation. Maybe you should ask them.

Well, wet runway conditions are not "ideal" conditions. And when the FAA made their original 30-40% additive recommendations it was a gouge, a rough hack, a wild ass guess. TALPA is not. Do not make any kind of equivalence between the two.
Thanks for your interpretation of how the regulator came up with their advice to turbojet operators on how to safely operate an aircraft. I have no plans to ask them anything further and plan to take their advice seriously and recommend others do as well. If there is an overrun, I don't think the NTSB or TSB will put much credibility in a pilot saying he disregarded FAA landing performance recommendations because someone called Rockie on one of the pilot forums said that the FAA were just making wild ass guesses.
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Last edited by pelmet on Tue Aug 28, 2018 6:42 pm, edited 1 time in total.
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Re: Do you really trust that wet runway performance data

Post by delta1 »

No.

It’s for the lawyers and that’s all that maters.
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Rockie
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Re: Do you really trust that wet runway performance data

Post by Rockie »

pelmet wrote: Tue Aug 28, 2018 5:07 pm
Rockie wrote: Tue Aug 28, 2018 3:52 pm I can't explain why the FAA has on their website a SAFO recommendation that has been superceded by the TALPS-ARC recommendations - now regulation. Maybe you should ask them.

Well, wet runway conditions are not "ideal" conditions. And when the FAA made their original 30-40% additive recommendations it was a gouge, a rough hack, a wild ass guess. TALPA is not. Do not make any kind of equivalence between the two.
Thanks for your interpretation of how the regulator came up with their advice to turbojet operators on how to safely operate an aircraft. I have no plans to ask them anything further and plan to take their advice seriously and recommend others do as well. If there is an overrun, I don't think the NTSB or TSB will put much credibility in a pilot saying he disregarded FAA landing performance recommendations because someone called Rockie on one of the pilot forums said that the FAA were just making wild ass guesses.
Try reading what I wrote Pelmet before making an idiot of yourself.
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pelmet
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Re: Do you really trust that wet runway performance data

Post by pelmet »

According to the SAFO.....

"Analysis of the stopping data from these incidents/accidents indicates the braking coefficient of friction in each case was significantly lower than expected for a wet runway"

"The data indicates that applying a 15% safety margin to wet runway time-of-arrival advisory data.....may be inadequate in certain wet runway conditions."

"Analysis of this data indicates that 30 to 40 percent of additional stopping distance may be required in certain cases where the runway is very wet, but not flooded."

The FAA talks about data and analysis of it. Perhaps some evidence could be shown how it was instead a "Wild Ass guess" in how they came up with this recommendation. However, I do think the term ass can be applied to someone here.
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Rockie
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Re: Do you really trust that wet runway performance data

Post by Rockie »

Check the dates on your documents versus the TALPA regulation implementation date Pelmet. The ones you're quoting are at least a year before the implementation of TALPA and do not even mention it.

Really...stop. Betraying yourself as a moron is not worth another pointless argument with me.

Or...continue. This should be good...
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pelmet
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Re: Do you really trust that wet runway performance data

Post by pelmet »

Rockie wrote: Tue Aug 28, 2018 6:58 pm Check the dates on your documents versus the TALPA regulation implementation date Pelmet. The ones you're quoting are at least a year before the implementation of TALPA and do not even mention it.

Really...stop. Betraying yourself as a moron is not worth another pointless argument with me.

Or...continue. This should be good...

I could continue. For example. How does Rockie determine that a SAFO(Safety Alert For Operators) is out of date? By the fact that it is still on the FAA website which might just prove that it is still valid? Because some updated performance recommendations were made and therefore he ASSUMES that it makes an earlier SAFO out of date?

How does Pelmet determine that a SAFO is out of date? He goes to the FAA website and sees examples of SAFO's that have been cancelled or superseded and realizes how the process works as we can see in this link....

https://www.faa.gov/other_visit/aviatio ... all_safos/

For the 2007 year of issuance, one SAFO is cancelled, one is superseded(of course the one I posted a link to is still valid).

Now it is possible that the FAA did forget to amend this SAFO(call them up yourself). But until it is cancelled, superseded, suspended, etc., I consider it to be valid and I expect it is still valid for good reason too.

I think we can see who the moron is here. The same one who loses the argument with me every time. If you happen to be an IP and have been training otherwise, I suggest you contact all former persons who you gave your bad information to and correct it(or get them to read my posts) :wink:
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Rockie
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Re: Do you really trust that wet runway performance data

Post by Rockie »

pelmet wrote: Tue Aug 28, 2018 7:32 pm For example. How does Rockie determine that a SAFO(Safety Alert For Operators) is out of date?
By simply looking at the date on the SAFO which is 8/11/15. TALPA regulations came in force October 2016.

Keep going Pelmet, this is interesting.
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