(page 18 of BEA AF447 prelim report, english version)
1.6.4 Condition of the aircraft before departure
On arrival of the Paris-Rio de Janeiro flight the day before the accident, the Captain reported a problem at the level of the VHF1 selection key on RMP1. The aircraft has three RMPs:
RMP1 on the left-hand side, RMP2 on the right-hand side and RMP3 on the overhead panel.
The ground engineer had switched round RMP1 and RMP3 to allow the aircraft to leave, in compliance with the regulations (departure covered by a MEL). The departure covered by this MEL item did not have any operational consequences.
The 3 Brazil ATC requests were not replied to and the VHF radio had been repaired prior to take off. Coincidence? Cockpit non-response is hard to believe as they were continuing radio comms made seconds earlier. ATC tried 3 times. Also no further AF447 VHF comms after this point for 30 mins (breaking the off radar 10 min report in SOP?).
VHF is triple redundant however if one fails how do you know unless you do a test? Perhaps the earlier MEL was incorrectly identified as RMP1 switch but was actually an issue with VHF1?
Only a minor item but I want to ensure all the valid data points on the table.
[ VHF radio description:
Each RMP (Radio Managment Panel) is associated with a particular VHF (Very-High-Frequency) Radio. RMP1 is associated with VHF1, RMP2 is associated with VHF2, and RMP3 is associated with VHF3. All VHF Radios can be tuned by each RMP. When the VHF Radio selected by the RMP is not associated with that RMP, the SEL Light on that RMP as well as the RMP associated with the VHF Radio illuminates. For instance, if RMP2 has selected VHF1, the SEL Lights on RMP2 and RMP1 will illuminate.]