Wet Runway Landing Performance

[exM20K]

My Acclaim POH has no notation on the landing distance charts for wet or contaminated runway conditions.  Has Mooney ever published such numbers for the other long body airplanes?

-dan

[carusoam]

The O1’s got some data the later ones did not...

Soft field T/Os for example...

My POH is about 20 miles away...

Lets see if somebody has a real answer...

I can check my POH on Monday...

Best regards,

-a-

[Ibra]

I need to find a reference but I think there are some generic factors that people will have to apply when data is not available in POH: 1.5 for wet, 2.0 for snow & water and 5.0 for ice 

 

Edited May 18, 2020 by Ibra

[Mooneymite]

5 hours ago, Ibra said:

I need to find a reference but I think there are some generic factors that people will have to apply when data is not available in POH: 1.5 for wet, 2.0 for snow & water and 5.0 for ice.

Define "wet".

In the world of aircraft performance for part 135 aircraft, this is a murky subject when the definition of wet can determine the legality of the takeoff, or landing.  While "wet" may be obvious to some, legally/technically, a pilot needs to confer with 6, or 7 Philadelphia lawyers when the runway is "not dry".  However, if your jet goes sliding smartly off the end of the runway virtually all the lawyers will agree the pilot's determination was wrong.

[GeeBee]

The problem with wet data for an airplane like a Mooney is there is no systems such as anti-skid to apply a consistent and predictable pressure, or modulation of pressure. So any data would be so technique bound as to be largely useless.

 

 

[Ibra]

Yes agree, I would go with "not dry" as lawyer definition  I read the technical definition is when 25% is covered by less 3mm water/moisture film: that is about 75% dry and 25% not sure about, obviously it does not make much difference if 25% is at end of the runway or at start of the runway? but I guess 25% wet at the end imply some downslop or tailwind, which also needs similar adjustment? If the water ends up there the aircraft will follow...

In Mooney private ops (part 91), one can go without wheel breaks every landing and purely use aerodynamic breaking and take the numbers from there, others may change the tires or decide how many psi 

On single pistons, the runway constraint is less on the breaks more on the power, the takeoff roll is usually bigger even twice the landing roll...

 

Edited May 18, 2020 by Ibra

[Bob - S50]

If we are going someplace that we need maximum braking in order to stop, and reduced braking action due to wet runway conditions might make a difference, judgement tells me we might be better served by going elsewhere.

From a purely academic point I seem to remember from my Air Force days that they said wet was an extra 25%.  But that was provided the water was not deep enough to cause hydro-planing.  But the actual distance will depend on depth of water, tire tread condition, and tire pressure.

[Mooneymite]

1 hour ago, Bob - S50 said:

.....  But that was provided the water was not deep enough to cause hydro-planing. ....

In the fine art of guestimating, one should not confuse a "wet" runway with a "contamined" runway.  Two very different sets of performance numbers.  Standing water may make a runway "wet", but the numbers don't work at all.

To further confuse the pilot, depending on the manufacturer's data, when it rains, a grooved runway may be contaminated (standing water), but not wet.

Huh?

[exM20K]

2 hours ago, Ibra said:

n Mooney private ops (part 91), one can go without wheel breaks every landing and purely use aerodynamic breaking and take the numbers from there,

right - that's pretty much my worst-case threshold now: I know what distance the plane requires with no braking, so I've got at least that much performance.  Wet can mean a lot of things - the Citations with no buckets publish all sort of distances with columns for wet, various depths of water, snow, and ice.

practicing wet runway braking, i managed to flat-spot a tire last year: betweenbose headsets and wet runway, I had no indication the wheel had locked up..D'oh.

-dan

[MB65E]

Landing Factors we can use are 1.0  Unfactored 1.67, dry. 1.92 wet, 2.42 contaminated. Mainly for part 25 certified aircraft, and part 135 ops. Why not listen to what part 135 &121 does?

This SAFO 19001 gives a good discription. In 2015 the definition changed to the stupid “if it’s not dry, it’s wet”

https://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/safo/all_safos/media/2019/SAFO19001.pdf

Good Stuff! It gets complex quickly! Adding wind corrections and gust factors, the runway goes away fast! 
-Matt

 

[Ibra]

Thanks MB65E for the references !

Also, one may need dry breaking discs to fly in wet runways, unless you have heated hangars the breaks will usually takes more rust abuse from the water than from pilot breaking on wet runways

I now think twice before pressing the breaks: flat spots & if it fails on one side... 

 

 

 

Edited May 18, 2020 by Ibra

[Mooneymite]

37 minutes ago, MB65E said:

 

 

Good stuff, for sure.  However for me, there is seldom anyone to determine, or disseminate a runway condition code.

The closest I've ever come to running off a runway was on an unattended new-to-me grass strip.  I found out two things:

1.  Wet grass may have a zero braking coefficient.  (I have done better on ice!)

2.  You can't see "wet" until you land.