The cause of why the flaps weren't extended (i.e. pilots forgot or some malfunction) or why the TOWS alarms didn't go off (i.e. malfunction or someone tripped the circuit breaker) are still under investigation and not being especulated upon by the accident's commission so far.
All it's been said, in plain terms, by the accident's commission is that:
-The FLAPS never reached a position other than 0 degrees right before or during the take off (i.e. they were never lowered). Data flight recorder shows that. Remains of wings found confirm that (i.e. flaps couldn't have retracted on their own due to the impact in the circunstances they were found). Circunstances surrounding the accident agree with that. As we all know, trying to take off under the circunstances of that flight without the flaps/slats extended, could likely have caused it to stall due to insufficient lift for the calculated speeds.
**NOTE: This information is preliminary and CONTRADICTORY within the draft itself, where it's mentioned both, that flaps were at 0º and that they were found extended by 12cm.
-Nobody checked to see if the "bad take off configuration" alarm, that would've warned that the flaps weren't extended, was working for that particular flight (i.e. was checked on the earlier flight, but not this one). Checking it on every flight wasn't mandatory, but recommended. It is now recommended that this check becomes mandatory before each flight.
-And that the "bad take off configuration" alarm that would've warned of that situation with the flaps, finally didn't sound. The cause of this "malfunction" is not determined yet, but likely had to do with the electrical configuration (i.e. a faulty sensor or simply, a circuit breaker switch that had been flipped off). This is inferred by the prior RAT probe heater abnormal behavior, which is electrically related to the alarm's (TOWS) mechanism (i.e. they feed off the same ground sensor logic and share power through a common circuit breaker).
And that's it on their side.
While it's likely that human error is behind all of these circunstances (i.e. pilots "forgot" to deploy flaps/slats, someone "forgot" to update/incorporate Boeing's recommendations on the manuals, someone "forgot" to reset a circuit breaker feeding the alarm), other possible explanations, including mechanical or electrical malfunctions, exist, even if less likely, and they have not been fully discarded yet, as the investigation continues.
This preliminary report, once completed, is scheduled to be sent to the judge in charge of the judiciary investigation by Monday 22nd. Should be made public around that time. Anytime after Sat. 20th.
Last edited by justme69; 16th Sep 2008 at 14:10.