Peroni
If you read the posts from 2nd Sept you will see that OUTWEST has confirmed that the floats were NOT armed at the time. They were, in other words, NOT LIVE at the time of inflation. The cause is sub judice until we get the full report on the incident which should be forthcoming very soon with any luck.
If you are not familiar with the system on the 139 then you should be aware that the system is designed to be 'safe' until the arming switch is selected ON. Then they can be inflated either automatically (primary method) or manually (secondary method).
The great concern was that an inadvertent inflation in cruise flight would be fatal and at least some good has come from this incident in that it provides a measure of reassurance to this is likely not to be the case. Such an unscientific 'trial' hardly constitutes a certification process but it will steady the nerves of those that are adherents to the FM requirement to have the floats armed at all times over water.
Incidentally the SOP whereby an altitude limit is imposed (Armed below 1000 or 500 feet depending on the company*) would appear to be a sensible compromise but as with all checks it doesn't matter where the check is in the SOP. When it's forgotten it is forgotten and that is at the heart of the philosophy to ARM at all times OVER WATER. As long as the crew doesn't forget the 'Descent Checks' all will be well. Maybe the descent check is a more 'defined' moment compared with the 'crossing the coast' check which perhaps is a less well defined as it does not precede or succeed a change in flight path.
I would be interested to know what the various 'schools of thought' on the subject think now.
G.
* NB Don't forget to get formal agreement from AW and/or your NAA if you vary the FM procedures in your SOPs.