AirBear

This will affect Part 135 and Part 91k quite a bit, I can remember many times we were very close on the wet runway numbers:

https://www.ainonline.com/aviation-n..._hsmi=74566320

Recent data indicates that applying a 15 percent safety margin to calculate wet runway stopping distance, as recommended by previous guidance, may be inadequate in certain conditions to prevent a runway excursion, according to a new safety alert for pilots (SAFO 19003). This new alert replaces the guidance in previous SAFO 15009.

“Several recent runway-landing incidents/accidents have raised concerns with wet runway stopping performance assumptions,” according to this new alert. “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.” These mishaps occurred on both grooved and un-grooved runways.

Takeoff and Landing Performance Assessment (Talpa) procedures implemented by the FAA on Oct. 1, 2016, added new insight as to how flight crews can evaluate runway braking performance before landing. Talpa defines a “wet runway” as damp to 1/8-inch depth or less of water, while a “contaminated runway” is a surface covered with “greater than 1/8-inch of water.”

The FAA recommends that airports report “wet” conditions, but that is not required. Further, an airport may not be able to generate an accurate report from sudden rain showers that result in water on the runway more than 1/8 of an inch in depth ("contaminated"). The alert concludes that because “Rainfall intensity may be the only indication available to the pilot that the water depth present on the runway may be excessive, it is recommended that pilots use landing performance data associated with medium to poor braking.” However, the FAA notes that using all available data to prevent a contaminated runway excursion is moot when the landings involve delayed touchdowns, improper application of deceleration devices and landing with a tailwind.

TiredSoul

I’ll be the first one to admit it’s harder then it sounds but as aircrew we’re getting paid to say no.
With scattered rain showers in the forecast you need to plan wet numbers or contaminated.
If it’s tight then better tell the principle they have a 50/50 chance of going to an alternate.
A 60-70 mile drive is not a real inconvenience vs going off the end.
I’ve had to explain once that I’m sorry but I can’t tell you I can get you where you need to go till we’re on final with the runway in sight.
Limo’s were arranged for two alternates.
Non towered airport, 5000’ and our wet numbers where above that.

AirBear

I can't tell ya how many owners I've had say "but sales told me this airport was no problem" I tell them yes, when it's bone dry it shouldn't be a problem but if so much as a mouse stops and takes a whiz on the runway we won't be taking off or landing. Hilton Head was one, Ocean Reef, East Hampton, etc.

TiredSoul

Yep and the Pilatus jet landing on a grass runway will have them go off the end like lemmings.

cougar

SAFO Recommendation:
Directors of Safety and Directors of Operations (Part 121); Directors of Operations (parts 135, and 125), Program Managers, (Part 91K), and Pilots (Part 91) should ensure pilots verify, prior to initiating an approach, that the aircraft can stop within the Landing Distance Available using a RwyCC of “2” whenever there is the likelihood of moderate or greater rain on a smooth runway or heavy rain on a grooved/PFC runway.

TiredSoul

Recommendations are advisory and can be completely ignored.
It’s a feel good and will not change anything.
Since when have you seen anybody follow a recommendation especially in 135?