PJ2,
Yes it does take a vertical impact as little as 3G's to shut down both the recorders.The key word here being "shut down".
Having said that, yes,both recorders can withstand G's as high as 3,900g's.Keep in mind these high g's are tested for a maximum of 1/1000th of a second.That is to say for the moment of impact.Therefore it would be incorrect that these recorders can "withstand upto say 3,900g's".That statment would definitely not be true.
More importantly is another fact i'm making.The boxes cant make an impact of upto 3900g's AND KEEP RUNNING! They would've shut off on the first impact exceeding 3g's.BUT the design of the boxes is such that the data within would be completely retrievable even after 'momentary' g forces as high as 3,900 g's.Therefore making them "indestructible".
I would'nt want to live so long as to be able to see the day when a harddrive continues to function even after a 3,000+ G-shock....!! Cause I never will!!
Then there is the 'switch off logic'.Which requires the boxes to stop recording when the power cord is pulled or a 3g+ impact.In both cases the logic assumes that a crash has taken place and therefore there would be nothing more to record! This in my personal opinion is a design fault and needs to be rectified.As has been proven time and again when critical data was'nt available due recorders shutdown.For example dual engine failure on older airplanes.Or complete electrical loss on the same.OR,for that matter,a runway excursion such as this one,followed by a low G impact.Of course modern jets have worked around the problem by having an alternate sourceof power(such as RAT) to power critical systems,but I for one would much rather have a recorder which continues to run at least for a minute or so,on its own power,after the shut down logic has taken over.
Unless of course........(we could go on here).
What was the braking coefficient reported(if any).Because,a port engine failure at takeoff,coupled with a gusty wind from the port(weathercock effect) along with a marginally slippery runway and maybe less than perfect handling of it all, could well result in a runway excursion such as this one.
My two cents worth......
Now onto the real facts......
