In my QRH it mentions distance and adjustments for, GOOD, MEDIUM and POOR are increased by 15% but it also mentions in the advisory information part Normal conditions - 115% for Slippery runways.

 

I understand the wet figures are the dry factored figures increased by a further 15% but what is the 115% for?

Also does TOPCAT add 15% if wet runway and also the additional 1.67 or 67% to the CLDdry ?

Honestly, that is an Aerosoft forum question.

Its performance though? And hoping some guru would knows this. But i got the answer -

 

You should have a reported runway state which will tell you the level of contamination of the runway and the associated braking action for that contaminant.

 

Icao codes run:

6-dry

5-wet, frost, water or slush upto 3mm deep

4-Compacted snow <-13C

3-wet (slippery),dry or wet snow upto 3mm, compacted snow <-3C >-13C

2-Water or slush > 3mm, dry or wet snow >3mm, compacted snow >-3C

1-Ice

0-Water over compacted snow,Dry or wet snow over Ice/wet ice,Ice >-3C

 

This will give you your braking action which is then applied to your landing performance.

 

ALD is the actual landing distance required to bring the aircraft to a stop from 50' above the runway.

A safety margin is applied to the ALD in accordance with EASA Ops

Required landing distance RLD is as follows:

RLD (dry) = 1.67 x ALD on a dry runway

RLD (wet) =1.15 x RLD (dry)

(effectively 1.92 x ALD)

 

RLD(contaminated) = 1.15 x ALD on the contaminant specified as the table (0-6) above.

 

So you would ascertain the contaminant, calculate the braking action dependent upon the contaminant (dry, good, good-medium, medium, medium-poor, poor, nil), enter the landing performance tables for the given weights, braking actions and met then multiply the distance given by 1.15 or 15%.

 

So, for the Boeing 777, the reference distance on a DRY braking action runway is 1185m at max manual braking, the same distance with POOR braking distance is 2555m so taking into account no other factors if the runway is contaminated I would need 2555m * 1.15 which would be 2938m

Its performance though? And hoping some guru would knows this. But i got the answer -

 

Yeah, of course it's performance, but let's be real here:

 

An apple falls off a tree and hits the ground. The time it takes for said apple to hit the ground can be calculated using Arbor Calculator 2000^TM. You calculate the time using the rain function to see how the rain affects the time. It gives you a value that makes you curious enough to ask a question.

 

Do you ask the tree, or do you ask the people who made the calculator?

 

The performance of the apple is what's being calculated, but the question actually lies with how the calculator is getting the number it's getting, ergo you'd ask those who made the calculator.