On Feb 2nd 2021 the KNKT chairman said in a press conference, that reports distributed by western media about a possible autothrottle malfunction causing asymmetric thrust are wrong. However, the KNKT sent 5 pieces of debris, including the autothrottle unit (but not identifying the other parts), to the USA and UK for further examination stating they want to find out why an autothrottle parameter changed. He re-iterated they don't know why that parameter changed and need confirmation from the parts sent to the USA and UK and the CVR. The maritime search for the CVR is still ongoing.

There is no evidence of an explosion of the aircraft prior to impact with the water, there is also no evidence the aircraft broke up before impact with water. Impact damage indicates the engines were still operating upon impact with water.

While climbing through 7900 feet the crew requested to deviate around weather at a heading of 075 degrees, ATC cleared them for a heading of 075 degrees but restricted their climb at FL110 due to conflicting traffic, later clearing the flight to climb to FL130. The crew acknowledged these instructions including the clearance to climb to FL130 normally. Less than a minute later the controller noticed the aircraft was turning left instead of turning right to 075 degrees and queried the crew, but did not receive a reply anymore.

http://avherald.com/h?article=4e18553c&opt=0

On 2/5/2021 at 12:48 PM, threegreen said:

While climbing through 7900 feet the crew requested to deviate around weather at a heading of 075 degrees, ATC cleared them for a heading of 075 degrees but restricted their climb at FL110 due to conflicting traffic, later clearing the flight to climb to FL130. The crew acknowledged these instructions including the clearance to climb to FL130 normally. Less than a minute later the controller noticed the aircraft was turning left instead of turning right to 075 degrees and queried the crew, but did not receive a reply anymore.

http://avherald.com/h?article=4e18553c&opt=0

It's been a while and still many questions remain. I'm still trying to form a picture of the very basics.

If I understand correctly, from the moment of takeoff, the speed and altitude profile seems to look fairly normal for almost exactly 4 minutes (7:36z-7:40z). And then something changed very quickly, but it could have been a problem already growing in severity somewhere in the space of those 4 minutes.

I don't have any current charts. I was looking at an old Cengkareng 2G SID chart. Not sure if they were supposed to be following a similar route from 25R. To me it looks like they continued along a roughly 280 heading longer than they should have. But that's one thing I still don't quite understand. Approximately where in those first four minutes did they first deviate from their assigned route and catch the attention of ATC.

Edited February 6, 20215 yr by Antipodeslonghaul
Typing on phone clicked send prematurely by accident

The prelim report has been been released: 

http://knkt.dephub.go.id/knkt/ntsc_aviation/baru/pre/2021/PK-CLC Preliminary Report.pdf

Points to thrust imbalance. Left engine  lever started reducing while right thrust lever remained in the same position.  

 

Edited February 12, 20215 yr by CYXR

12 hours ago, CYXR said:

The prelim report has been been released: 

http://knkt.dephub.go.id/knkt/ntsc_aviation/baru/pre/2021/PK-CLC Preliminary Report.pdf

Points to thrust imbalance. Left engine  lever started reducing while right thrust lever remained in the same position.  

 

Thanks for posting that link. All the basic information, the SID, headings, altitudes, communication with ATC etc. pretty clear and concise in there.

It sucks, but merde happens. People, any people, pilots, truck drivers, surgeons, whoever can get distracted. A proper and continuous scan of the instruments and engine parameters, throttle levers, of course that's ideal, but how quickly things can get out of hand.

We'll still see the final report, plus maybe CVR transcripts. But anyway good to have a basic report like this.

 

***EDIT

I hope some of my comments aren't mistaken for resignation. 100% safety is always the ultimate goal. To me it seems autothrottle imbalance is not much different from engine failure in terms of what the immediate reaction should be, maintaining control of the aircraft. No engines are 100% reliable, so neither are autothrottles. I don't necessarilly think the pilots should be blamed, although if they were too slow to react to a generally known condition, asymmetrical thrust, and a timely autopilot/autothrottle disconnect, maybe briefly throttles idle and nose down could have saved them, they'll probably be given the bulk of the blame. Just think these kinds of topics are generally very good, no matter how much speculation is thrown about, just to promote situational awareness.

Edited February 13, 20215 yr by Antipodeslonghaul

@CYXR, thanks for the link. Not had time to read the whole report but noticed the CVR hasn't been recovered yet. Pity. That would reveal more info.

Having flown in Indonesia myself in the early 90’s I noticed there was always an unrelenting faith in the magic of the autopilot. Which is a shame because the guys were actually really good stick and rudder pilots.
 

I hate to publicly second guess pilots but this sort event at 10,000ft although potentially startling and unpleasant should be quite simple to rectify, and should not have lead to a fatal outcome.

1 hour ago, jon b said:

Having flown in Indonesia myself in the early 90’s I noticed there was always an unrelenting faith in the magic of the autopilot. Which is a shame because the guys were actually really good stick and rudder pilots.

Definitely not limited to that region, we only have to look at that AF Airbus which essentially went down for no good reason at all; sure the unreliable iced up ASI probe meant that the AP disconnected, but simply putting the throttle in a manual position and leaving the thing to fly out of the ice was all that was really necessary to prevent disaster, but instead the guys freaked out the moment the magic autopilot switched off and then started doing stupid control inputs.

Frankly if they'd done nothing at all other than close the throttle and just let the thing drop out of the icing conditions they probably would have been okay. I know it's easy to be calm when you are sat at a computer discussing these things in comparison to actually being there, but I'm pretty sure a half decent pilot would have known that keeping the stick back when the stall warning keeps going off is not a great idea, which is what that AF pilot did because his stick and rudder skills were basically AWOL. Let's hope this accident isn't a repeat of that shockingly poor level of basic airmanship.

Edited February 13, 20215 yr by Chock

3 hours ago, Ray Proudfoot said:

@CYXR, thanks for the link. Not had time to read the whole report but noticed the CVR hasn't been recovered yet. Pity. That would reveal more info.

The CSMU of the CVR has not been recovered; search ongoing. (I can`t recall another event involving the memory stacks detaching from the CVR; that surprised me) I still can`t figure out why the loss of contact occured. 

Edited February 13, 20215 yr by CYXR