Janner200
What you note is fair in general. This aircraft was levelled off at the time and controlling to speed by some form (ATR or manual thrust) and so the power setting would not be high when things went off the rails. It is common to have a level off in the departure out of JKT, even more common if departing out of Halim. The N1/N2 at the start of this is not going to be at a climb power level, they will be down quite low.... I found a copy of my old B735/56-3-20K FPPM.... (the accident plane was set up for -3B1 at 20K thrust) for the speed and alt that they were at, and for average pax weights, some cargo, fuel for outa nd back and reserve, the plane will be around 46T, and would have an N1 of around 67.7%, which is a low thrust setting. The actual setting on the day will be lower, which would give LRC for around 330 TAS, and they were well below that. Weight changes within a few tons doesn't change that much, so it is safe to assume that the engines going into the event were not at a high thrust setting. Hop in any 3,4,(5?) sim and set up the thrust, it will be low.
The photo shows a GV/Stator series, that is part circumference. With a disc failure, the characteristic failure is into 3 pieces for which the physics is interesting as to why. the immediate release trajectory is normal to the shaft and only parts remaining attached to the shaft if any would impact stators in front or behind the disc station. I would be considering that a partial stator circumference is consequential to impact breakup rather than direct evidence of a disc rupture. Its a while since I crawled into the wheel bay of a 735, but my recollection is that the HYD reservoirs which are accessible there, are not near the line of the turbines, the concern would be that, with a rupture of a disc, it may take out one HYD system directly related to the engine (the hyd lines to the EDP run along the way of the pylon...) and the other system could (unlikely but possible) be impacted, but the standby HYD system which you would really like to have if an engine failure occurs and you have no #1 and #2 HYD systems, would not be in line for debris impact, at least unlikely. The 737 has adequate handling; it deals with an engine failure normally, without too much issue. The ailerons are adequate, (they are a different design to the NG and MAX, shorter span but larger chord, which added to the buzz issues and the need for the outer series of VGs on the classic wing, but they are adequate) The rudder is adequate but needs HYD from some source. Without #1, #2 or the STBY RUDDER, then the plane is going to be less fun, and lateral directional control will be more interesting, no hyd, you have manual ailerons and elevators... no spoilers (actually spoilers will tend to rise partially in total loss of HYD). It will still take some time to get into difficulties, so from a speed of 250KCAS or thereabouts, to get down to losing lateral control would take some time, and that isn't consistent with the minimal information that exists so far.
Inadvertent TR deployment would be annoying but the plane was effectively well set up to have a mild controllability effect from such an event. It was not at a high power setting, and not at very high speed, or at very low speed. Still not much fun, but not usually catastrophic (not a Lauda type condition. Lauda 4 was at quite high power, and there was a window for recovery action of approximately 12 seconds, after which the event was going to be catastrophic)
Attitude instrument failure or erroneous displays are a pain and have excessively high loss rates. The Adam Air event was pretty unique, it's not often that a self-inflicted main attitude display failure occurs but it does happen ( the B744 with the new captain who did a "quick align" of the IRUs at the HP, and was then given an immediate TO clearance, rolled onto the runway with the PFD and NDs all flagged out, and rolled down the runway saying "she'll be right mate. they will come back at rotate..." which they didn't.. during the pre GPS type course the function of the TOGA switches may have been slept through). P2-CLC (MSN27323) was an EFIS cockpit, with an EADI and EHSI setup, so a failure of an attitude platform would result in a loss of the associated display and a fail message on the EADI. An alternate attitude source would have been available for selection.
Whatever happened, occurred rapidly, and led to a very low nose attitude, which still looks suspiciously like a lateral upset at the start. Silkair sim reconstructions showed that it was exceedingly difficult to get to the flightpath that was recorded, which is relevant only in the fact that it showed that to get a nose-low condition rapidly, a rollover was almost always needed, as USAir 427 and UAL585 also showed for other reasons. Flash/Sharm indicated other means by which a rollover could arise, and also led to a fair bit of acrimony in the analysis and the conclusions. The flight phase that this event occurred at is very different to Silkair and would make it improbable that a pilot caused event arose, not impossible, but extremely unlikely. Both pilots are almost certainly in the cockpit at that time, 4 minutes after takeoff, 10,000' around weather, no one is going to be in the bathroom or galley instead of their designated seat position. That doesn't say it is impossible, but it is extremely unlikely and would be novel in the experience of human factors forward of the flight deck door.
The recorders will give some answers and NTSC have some investigators and board members that have exhibited courage and integrity on a number of occasions, I expect that the report will disclose the truth.