Landing performance

[md-100]

In wet runway, does the regulation use thrust reversers for landing distance??

[Mad (Flt) Scientist]

The regulations don't consider wet runways at all - Part 25 only deals with landing on a dry runway (25.125 refers)

The operational rega just set landing distance for wet based on dry runway perf with a factor (15%) and dry data has no TR, so the wet "planning" distance has no TRs. But it's a fictional distance anyway, because you'll need rather more than 15% more distance in wet/slippery in most cases.

IF the OEM chooses to supply wet distance data for guidance then it probably does include TRs - but it's not a regulatory distance, just manufacturer's data.

[Jurassic Jet]

In the US, reverse for landing data calculations is used as follows:

Dry: Use the FAR dry demonstrated landing distance plus a 67% margin.
Includes the use of all spoilers, anti-skid and max manual braking without reverse thrust.
Includes the demonstrated air distance. (Threshold crossing at 50’, at Vref, with TL at idle)

Wet: Use the FAR dry demonstrated landing distance plus a 92% margin.
Includes the use of all spoilers, anti-skid and max manual braking without reverse thrust.
Includes the demonstrated air distance. (Threshold crossing at 50’, at Vref, with TL at idle)

Medium: Use the manufacturer’s estimated landing distance plus a 15% margin.
Includes the use of all spoilers, anti-skid and max manual braking with normal reverse thrust.
Includes the demonstrated air distance. (Threshold crossing at 50’, at Vref, with TL at idle)

Poor: Use the manufacturer’s estimated landing distance plus a 15% margin.
Includes the use of all spoilers, anti-skid and max manual braking with normal reverse thrust.
Includes the demonstrated air distance. (Threshold crossing at 50’, at Vref, with TL at idle)

These statements are a combination of the FAR’s and the SAFO that the FAA issued in 2006.

The SAFO calls for a minimum of 15% margin for Medium and Poor braking actions.

Other operators may have different numbers.

[oldebloke]

JAR/EASA rules allow credit for reverse on 'wet' runways,as is stipulated in the Airbus manuals(02.04.10)along with the reduced V1 and the 15'screen height.
the lates FAA references to 'wet' ops are in AC92.I understand the only type
that has demonstrated the 'wet' performance(as opposed to annalysis)is the B777.
cheers:ok:

[oldebloke]

My error,I only noted after sending that it was dealing with the Landing case.
I believe Boeing used to give credit for Reversers in the landing case.:ok: