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.