I was doing an FCL check once, on the 737. It includes a performance calculation before we enter the sim. I was handed the following runway state message:
R22/520194
Metar: EFHK BKN006
200/05 04/02 Q1005
With all that info I started entering the relevant tables in the FCOM/QRH. Decided that despite the 25% coverage of wet snow, which would allow me to do a derated takeoff, I went for the full rated takeoff because the braking action was 94. (Medium to good)
So, slippery runway, medium to good, full rated as per fcom.
Instuctor said: “Wrong. You should have derated, because the runway is only covered by 25%. FAIL.”
Lengthy discussion followed, where I tried to point out that my decision was safer.. Did not even make it inside the sim. Ended up in the training department. Eventually ended up calling the union, which solved this whole charade within 5 minutes, albeit 24 hours later.
I learned a lot that day.