Extrapolation of VMCa to minimum weight

[chti_guillaume]

Hello,

I would like to know if some of you have ever participated to VMCa testings.

I have found in the FTG from CS-23 or FAR-23 guidance for extrapolating a value obtained at a given density altitude to SL - ISA conditions (it's quite easy since it's just a kind of thrust correction).

However, this method doesn't propose any correction to account for the aircraft (since VMCa is determined at a 5° bank angle, but cannot always be tested at the certification minimum weight).

If any of you has developped a method to account for the weight in VMCa determination from flight tests, a few tips would be appreciated.

thanks!

[Mad (Flt) Scientist]

AC25-7B (http://www.faa.gov/documentLibrary/media/Advisory_Circular/25-7B.pdf) contains two appendicies which provide some general guidance on correcting VMCA test results. If the required additional aerodynamic data are known, correction for weight is possible using the Appendix 3 or Appendix 7 methods. if a properly validated simulation model of the aircraft is available (note: that means better than the match-where-it-touches Level D sim) that could be used as well.

[chti_guillaume]

Perfect, thank you. I did not think of looking at 25 FTG ...

(A little bit of rewriting the equations and I could have approached the solution by myself, but at least I'm sure to follow an approved method which won't call any discussions).

Again, thanks for your quick answer.

Chti