falconer171

Can somebody confirm that we make the weight correction on wet runway to determine the Max T/O Weight for the runway we will takeoff.

Do we still need to add up the weight penalty to the actual weight when we're selecting the speeds and derate setting ?

de facto

The NG has no weight penalty data for WET runways therefore only a V1 speed correction is needed.
The speed correction/use of reverse credit rebalance the field until you are ASD limited.(vmcg).
For aircraft types with WET weight penalty,there are instances when the Wet Weight is LESS limiting than the DRY weight,therefore the DRY limit must be used.

falconer171

I am afraid you're wrong there is weight penalty for slippery runway (which is wet) takeoff on 737 NG in PI section.
What I am asking is that, after we made the weight correction for Max Takeoff Weight for slippery runway, do we still have to make another slippery runway correction to the actual takeoff weight on DERATE setting (e.g. 22K) to select the speeds.

de facto

Definition of WET is not the same as SLIPPERY.back to basics?
If you use decide to make a weight reduction for slippery/contaminated then the weight penalty should be made on the rating you will use.
As long as your actual weight is below your rating perf limit then no,,,use the actual weight to get Vspeeds.

piratepete

De Facto: Mr BOEING states that for performance purposes, a WET runway is equivalent to a SLIPPERY runway where the braking action is MEDIUM.The applicable performance penalties will thus be the same, applicable on all Boeing types.Peter.

de facto

Piratepete,

Did the OP mention MEDIUM braking action?
No,he just mentioned WET.
So,again.....a WET runway is a runway which appears reflecting with no standing water,3 mm or less of water.BRAKING ACTION GOOD 0.4 or more.

Now, a SLIPPERY runway is one on which,braking performance is less than on a WET one and Braking action is reported as less than GOOD..(below 0.4).

You are saying that a WET runway is equivalent to a slippery runway when the braking action is MEDIUM...
You can not define a runway of braking action Medium as WET.
If the braking action is reported as MEDIUM then the runway is SLIPPERY and not WET.
SLIPPERY data then must be used,

So for the OP,a WET runway needs no weight adjustment if perf is calculated via the FCOM(PI).

piratepete

De Facto, this info is not from Piratepete, it is directly quoted from a Boeing performance engineer in response to a query about performance penalties.

de facto

Piratepete...
One question.
You have a reported WET runway and BA is reported is GOOD (0.4).
Will you use medium braking action under slippery and make a weight adjustment?


I have also a Boeing source and a very clear email form boeing performance....

The NG is certified for wet data, best is to use it.

Denti

The Boeing OPT gives very different performance values for wet and slippery runways. I would trust their official performance data more than some "source" within boeing, wich is after all a very large company with many employees of which not many have the required knowledge.

de facto

True Denti.
Apparently the OP is either unaware his Airline provides WET perf or Slippery on request or his Airline is decades behind letting their pilots use appoximate Information data that is simply approximate and mostly over conservative.

piratepete

According to Boeing, and I quote, a WET RUNWAY is by definition a SLIPPERY RUNWAY.

Derfred

Wow, it's amazing something so simple can be so confusing.

According to my Boeing manuals, a wet runway does not need to consider braking action at all.

Only a contaminated or slippery runway must consider braking action.

This is why the performance OPT application for my Boeing aircraft asks whether the runway is:

1. Dry
2. Wet
3. Good
4. Good/Medium
5. Medium
6. Medium/Poor
7. Poor

Options 3-7 are for contaminated or slippery runways only.

So, go ahead piratepete, and use option 5 every time there's a bit of rain. It will cost you around 6000kg of payload on a typical 2250M runway.

The rest of us in the world will use option 2, as prescribed by the Boeing manuals.

peekay4

You are ALL correct.

It's just that the terms "wet" vs. "slippery" vs. "contaminated" aren't always precisely defined and may vary depending on the jurisdiction.

Direct quotation from Boeing FCOM (emphasis added):
In a hierarchy, it might look like:

1. Dry
   • 1.1 Damp**
2. Slippery
   • 2.1 Wet (e.g., <= 3mm of water)
   • 2.2 Contaminated (e.g., > 3mm of water)

If the runway condition is reported (as "Good", "Medium" or "Poor") then it is slippery (per Boeing's definition) and a safety margin is required.

Except, Wet is a special case because it is not "dry" but also not "contaminated". So as an exception FAA/EASA/ICAO rules allow the use of "Wet" performance data if it's available and better than "Good" (but no better than "Dry"). Hence the OPT choices as listed by Derfred above lists "Wet" separately from Good/Medium/Poor.

** EASA considers Damp to be "effectively dry", but the FAA considers it to be Wet.

falconer171

defacto I advise you to check B737 FCOM Performance Inflight section rather than your "source", because in accordance with official manual of B737 if a runway is wet, it is defined as "Slippery" it also includes performance data for good-medium-poor braking condition. Beside I didn't ask what is wet or dry. I've just asked a specific performance question about a certain condition. If you have answer I will be glad if you share if not please do not interfere the subject with irrelevant information.