No, it does not have to "be assumed". You have to be very clear on the distinction between known facts, conclusions that you can draw on those facts and assumptions.
If you present an assumption as if it was a fact, and then use that to pretend to draw further conclusions the value of those are small to none.
There are situations where you just have to say "we do not know". Especially if there are many possible actions that may lead to the same result.
For example when it comes to the use of the VHF to broadcast a Mayday. You may have bad quality in the transmission for many different reasons:
- You are broadcasting on a 25w fixed set, but the antennas are not vertical.
- You are broadcasting on a 5w handheld set over a longer distance
- There are physical objects between your antenna and the recipient, blocking the traffic
- The person broadcasting is not used to the specific set, and therefor is not holding the microphone at the proper distance from the mouth
- Noice levels around the person broadcasting is high
- Wind noice is disturbing the broadcast
- Multiple people are broadcasting from different sets, thereby stepping on each others
Those are just some of the reasons that I could come up with right out of my head, since I have experienced all of them. If you assume just one of them without facts you go wrong.
Not according to JAIC. If you want to make your own timeline you have provide a source for it.
The Timeline in the JAIC reports puts the list after 01:15.
And we do not know why. Maybe nobody tried to send it earlier than that. Maybe the sets where out of commission after main power was out but before emergency power was restored. We just do not know.
We have multiple recordings, but since the Europa was the closest recording to the source, they had the best quality. As expected for Marine VHF traffic. I experience it regularly when the coastal stations pick the wrong base station to broadcast on. Even though they have a lot of power, I still receive it badly, and have to tell them to switch to a base station closer to my location.
No, it does not dispute it. If you broadcast with a handheld 5W device with a small antenna, of course the transmission will not be good over distance.
So the bridge had a log. Good for them, but of course completely normal. A log tells you where you have been, not where you are.
The conclusion (not assumption ) is that there is no communication blackout, since we know we can listen to the recorded traffic.
According to the JAIC report the main engines failed at around 01:24, and after that the emergency genset took over. This would lead to blackout where a lot of equipment and lights would stop working.