Unpaved Runways Performance

[Sirius Flying]

One question about operating from unpaved / semi-prepared runways: How do you perform your performance calculations (To & Ldg distances) for those runways? Heard that on the Herc it's done via some extra parameters (RCR & RSC ?) ? Can anybody explain how it works or is there some technical information on it somewhere on the web ? Google won't help me.
Thanks in advance,
SF

[Jambo Jet]

Exactly like Perf A calculations but with reduced safety factors dependant on the risk authorised.
Eg Landing Perf A Safety Factor 1.67; Strips nearer to 1
Adjusted also for surface condition and ignore the engine failure case.

[Sirius Flying]

Jambo,
thank you for you reply. How do you adjust for surface condition?

SF

[Jambo Jet]

Surfaces. Not exactly performance issues however for different surfaces use different tyre pressures and varying use of brakes iaw graph in pilot notes and length of available strip. Different braking techniques for different surfaces.

Do not accept contamination of surface by ice/etc.

[prang one]

Some aircraft come from the Manufacturer with Perf Data for paved and unpaved Take off distances.
The ones I used had a ref for "approved" unpaved surface. In so far as the nose wheel track could not be more than 10 mm deep. If deeper you were outside of the test data and making your own if you attempted a take off.
I think it realy comes down to
A : the manufacturer releasing this data.
B : the data even being produced in testing