Originally Posted by mark147
If that were true, would it not make the 'speechless code' illegal also? (you know, 1 click=yes, 2 clicks=no, 3 clicks=say again etc. for use in case of microphone failure). Red herring I think. It's just the CAA doesn't want to allow it.
Emergency procedures are different from routine operation inaccordance with the relevant regulgations. Agaricus bisporus has given you all the details about why it is not permitted in the UK. What is interesting is why some other countries allow it despite international regulations to the contrary.