Originally Posted by
Concours77
Nose Down? Hmmm... how is the track yawing right? If he was trying to turn right, nose would not be down, crossed controls. .
I think he was madly trying to roll left, ailerons not effective... Rudder not effective... elevators not touched.
Pilot is making my case. No controls, not any effort to stop the roll or turn is visible, airframe totally ballistic... no attempt to arrest a 60 degree bank?
...
Originally Posted by
Concours77
how is the track yawing right?
Concours, are you referring to a track change to the right with an aircraft that is in a right bank? That is not indicative of yaw, it is indicative of a turn rate.
Originally Posted by
Concours77
I think he was madly trying to roll left, ailerons not effective... Rudder not effective... elevators not touched.
- madly trying to roll left, ailerons not effective...
There is a probability that the roll control is to the left by the pilot, that is a reasonable supposition, but if the wing has already reached a near stall AOA say, through the inadvertent deployment of the ground spoilers, then the ailerons are very ineffective in roll, in fact can be expected to reach an adverse roll state rapidly, causing the bank to steepen.
What do you base that statement on? If the AOA is high, then rudder effectiveness increases in the secondary effect. There is no discernible evidence of the rudder being applied to the left in the images I see, perhaps you have a better photo that shows left rudder applied.
When the window all goes green instead of blue, the instinctive response to a pilot who is not proficient in aerobatics and having awareness of the attitude of the aircraft, and why it is in that attitude, is to pull back, so you may well be correct to mention elevators, but I would contend that they are probably touched, increasing the g loading of the aircraft. At a high bank angle, the AOA stability of the aircraft, what we ordinarily term static speed stability is that the aircraft will attempt to recover towards the same AOA that it is in trim at. In this case, the aircraft is trimmed somewhere near 140K(IAS/CAS?) wings level, roll into a 60 degree turn, and the aircraft will have a pitch rate to attempt to retain the same AOA, and that means the g loading will increase, it ends up in a spiral dive in such a case. That is without touching the elevators, that's just an aircraft that behaves as a dart does, having positive static stability. In this case, the PRE1 type I understand has a stick pusher, and it will act against that to provide a nose down pitch input force to the elevators. That itself doesn't particularly degrade the flight path angle, having a high bank angle that continues to increase guarantees the aircraft is going into a steep nose down attitude rapidly. FWIW, the videos that exist so far are showing an aircraft that was likely already approaching the point of being unrecoverable at about 13-14 seconds into the video, impact happens out of frame at around 18 seconds. The maths on that is pretty straightforward, the only question is what the AOA did to enter the predicament. Any recovery required reducing the bank angle, and then applying as much g as was available to raise the flight path vector, and that also needs to resolve the issue that the aircraft went into a high bank in the first case. Elevators themselves as a recovery item are not relevant to the recovery; if the roll was related to a stall from a ground spoiler issue, then the only way to recover roll authority is to break the stall, and that comes from the stick pusher in part, and pilot action hopefully as well. Elevators didn't cause this, stick shaker should help, and I cannot blame any pilot at low level with a lot of buildings coming into the window to not pull on the prong, even at high bank angles... even with a stall warning going off.
Wake Turbulence. Wake turbulence is always able to mess up a lighter aircraft all by itself, but this particular airport has painfully generous wake separation that is applied religiously. If there was an aircraft "the same day" in front it would be a surprise. [this is true for approaches, for takeoffs, at this airport I have more than once had to advise ATC we would take a delay of X seconds for wake separation on departing traffic]
A bank of 60 degrees by itself does not indicate that an aircraft will reach a stall AOA, but the flight path angle will degrade if the achieved lift doesn't match weight, so the pitch will increase. Being at 90 degree bank doesn't stall a wing, being at or above critical AOA does. Will the plane permit level flight at 140kts 60 AOB with a stall speed of 108Kts? nope.
In this case so far, the indication is of a lateral departure from controlled flight that then resulted in a severe dive angle, and at the time that the aircraft started to go pear shaped, it is not pulling enough g to get to stall AOA, If anything, the aircraft was at a relatively high energy point and needed to slow down to the Vref for the approach, speed itself was not the issue, something upset their coffee, enough to get a wild bank angle going.
As far as data goes, the aircraft won't have a DFDR, it will have a CVR, probably still a Fairchild/L3 2100-1010, which should provide some information. For the investigators at CAAM, there is a test and readout capability for those in Jakarta, one of few around in the area. The flight display info may give some data, and the ECU for the engines, but the CVR will give RPM anyway, and there is little likelihood that engines are related to this incident. The ADSB-out will give good information to support the video and CVR.
P.S:
at t=1s. the aircraft is wings level, at t=4s, AOB is around 45, at t=6s AOB is greater than 60, that is a reasonable roll rate, but well within the roll authority of the aircraft in normal conditions. From around t=1s to t=13s the situation has gone from a relatively normal flight path to unrecoverable, with impact about 3-4 sec later. In that time, the pilot has to determine the cause of the upset while mitigating the effect it has on the flight path. That's about the same time that Laura 004's crew had to intervene and stop the loss of the B763 way back in the 90's. Might seem easy in an arm chair, but with an aircraft that has a mind of its own, not so much. That is a similar time that the Yeti crew had to work out what the ninny in the RHS had done by feathering both engines instead of closing the power levers in Nepal.
P.P.S.: The lift dump switch is the T-handle on the center console well behind the throttles, behind the rudder trim. It is well out of the sight line of the pilot. but has its own set of alerts and warnings.
