Prohibited VHF and HF Frequencies
Plowing through a tech refresher presentation (for the B737-800), the section on Radio and Navigation Systems mentions frequencies (120.000MHZ on VHF 2 or 3) and a list of several HF Frequencies (including 2 relating to a few specific airframes) that should not be used. No reason was given and can’t see anything in the technical manual. Can someone explain the reason? (Out of interest, not querying the need to observe the limitations.)
I remember reading one of those old From The Flight-deck books years ago, that mentioned transmission on a certain HF frequency on a 747 Classic would drive the outflow valve open!