Translation of a report about remarks made by Chairman of the KNKT Soerjanto Tjahjono on 2021.02.03.
I have seen other translated reports of the Chairman's statement that repeat the quote about the CVR. I was unaware that the CVR memory module had been found and I wonder whether there is an error in quotation or misstatement by the Chairman (CVR vs FDR).

I haven't seen any reference to that before - up to now, the received wisdom seems to have been that it was a problem that stopped the climb at FL110, rather than an ATC instruction.

Regarding status of the CVR. A different report has a subtle variation in the Chairman's remarks and indicates the search for the CVR continues:

Tempo.Co (English Version)
Editor: Laila Afifa
2021.02.04
.
... a maritime search is going on for the cockpit voice recorder’s (CVR) memory unit that Tjahjono said would help explain any human factors behind the crash.

“If we only have the FDR, we do not know why the parameter changed, what was the reason,” he said of the autothrottle. “We need confirmation from the components that we sent to the US and UK and the CVR.”

This was published on AVH two days ago, but apparently preoccupied with the autothrottles nobody here picked it up. The information is clearly from ATC tapes, not CVR.

no it’s not Herod. Except yaw damper.

Cessnapete
You’re not missing anything. It’s not the A/T nor the A/P that caused this crash. It’s a 737. It requires no automatic systems to fly perfectly well. It requires - uniquely today- no hydraulic power nor
AC electrical power either. So as some have said it must be something else. Pilot training perhaps? Something catastrophic? But an engine failure, AP or AT fail don’t cut it with correctly trained pilots.
CVR missing is a real problem. But they already know what happened. Just not quite what conversation took place aboard during the event

Have we reached the point where when "nice to have" automatic systems fail there will be an inevitable crash. Amazing.

We've already passed that point, where ,poorly trained pilots are unable to throw away the automatics and manually fly while sorting out malfunctions in a an emergency. Or a trained in mindset that manual flight is an emergency.
Or blind faith in the automatics causing the accident.
I.e. DXB EK B777. Press TOGA, no monitoring that it works, as no hands on A/T during a critical phase of flight. A B777 doesn't Go Around well at idle power! Simple piloting skills lacking, or that disappearing “skill” Airmanship.

Peculiar term
 

"The pilot, he said, then received a traffic guide's instruction to fly at an altitude of 11,000 feet."

TCAS ?

Teddy Robinson:

From the translation supplied in a previous post:

" Chairman of KNKT Soerjanto Tjahjono explained that after takeoff, pilot Captain Afwan had asked the air traffic guide to change direction to avoid bad weather

The pilot, he said, then received a traffic guide's instruction to fly at an altitude of 11,000 feet."

(My emphasis) The "traffic guide" apparently means ATC, not TCAS.

Euclideanplane

Apparently the bahasa Indonesia for ATC is: pemandu lalu lintas udara. lalu lintas means "traffic," and udara "air": pemandu is translated in an online dictionary as "guide", "leader", or "wizard". The name, then, respects the captain's authority whilst praising the skill of ATC.

I mentioned a few weeks ago that the aircraft could have levelled off at 11000’. In fact one of the departures has a level off altitude of 11k. (Different Dep to this one though).
FR does actually show a reduction of V/S from around off 10k.

my post was deleted for whatever reason.

Lets run with the A/T malfunction for a moment.
Previous poster said this has never happened in the climb. However, the A/T clutch etc, could fail at anytime. In the climb this would be no big deal until top of climb when the power comes off. At high altitude and assuming M.72 for the cruise, one TL only retards and the other is stuck. The TL will retard to maintain the selected or managed speed. At high altitude this should not present a problem with the Autopilot as the thrust reduction and subsequent yaw would not be great enough to disconnect it. The pilots should have enough time to figure out what is going on.
However at 10000’ the autopilot would not be able to cope, without any intervention from the pilots the aircraft would quickly roll and enter a spiral dive.

What was the trigger that caused the upset, assuming A/T failure?

On this flight the aircraft was actually cleared to FL290, (from YouTube). There should not have been any level off. The only indication is the few seconds at 10900’ for whatever reason. Question? Did the pilots have a selected altitude of 11000’ in the window.

retired guy

Correct.
An instructor where I work does an exercise in the sim. where you are taken to 30,000 ft and every unguarded switch on the overhead panel is switched off.
The aircraft still flies.
But this incident , and others ( Ethiopian , Lion etc. ) make me think that the days of relying on the manipulative skills of pilots are over.
Airbus philosophy has won.

James7

I don't understand why it's no big deal to have split throttles in climb. Arguably the pilot response time required may vary, but most of the accidents I've seen at various power conditions were because the pilot did not understand or detect what was going on

I think he means that, in the scenario he is describing, the thrust levers would not split until the autothrottle tried to move the levers back at top of climb or interruption of the climb.

Which pretty much eliminates the 'catastrophic' scenario.

lomapaseo

quite right Dave, problem would only arise at level off. aircraft levelling off and possibly distracted by making a turn, easy to miss that one throttle is stuck in the climb position. Even easier if the turn was to the reducing engine. This would also exacerbate the induced roll and yaw caused by the opposite engine on climb power.

Just to be clear, this would be the scenario.
assuming right throttle stuck in climb. Aircraft starts to level off, only the left throttle would retard. Pilot makes a turn to the left, he may not notice the right throttle is stuck. Aircraft makes the turn, pilot thinks all is ok as the engine would cause roll and yaw to the left. It would only be after a few seconds or so that things would start to get interesting, then the aircraft would quickly enter an upset. With the aircraft in IMC, pilot not fully up to speed because of the pandemic. The pilot would have to be pretty quick to make the corrections. Recovering from this type of 'powered’ upset, only relying on instruments, requires training. Unless the throttles were closed the aircraft would never recover. - Spin recovery technique.

The Captain was more used to flying the NG by all accounts. A/t system is much more reliable, probably not paying much attention to the throttles.

I was a captain on the NG and classic for many years and from a pilot's point of view I cannot say that there was any obvious difference in the autothrottle operation. I can remember only a handful of flights with the auto throttle u/s, so manual thrust lever operation in all phases of flight was a pretty rare occurrence and required some thought. Once you got your eye in so to speak it was simple. But it is not a mode everybody spends a lot of time practising on the line. Obviously you train a lot of the time in the sim without the auto throttle, but then again that is mainly one engine out and the aircraft does things more sedately. But it is frankly not the sort of failure that you would expect to cause anyone a lot of problems.

James7

Am conflicted by the wording. The scenario would go close to the upset that occurs here. If the APLT trips, the crew are going to be further behind the aircraft when they start putting in any corrections, assuming that they recognize that the problem is an actual roll event, not an instrument error, lots of accidents that the crew has assumed it is an instrument, and as many where the crew have followed flagged info or failed info without flags.

If the trigger event is the split thrust lever condition, with one at climb power, then recovery would still be achievable up to some point in the dive with the thrust lever remaining where it is, Optimal is getting rid of the asymmetry by going to idle, most times a safe bet, or increasing thrust on the other engine. coming back to idle is the fastest way of achieving a balanced known thrust, acceleration is slower at lower RPMs, and thrust output change for a change in RPM is greater at higher RPM. grabbing the levers and bringing them back to idle is not complicated. by omitting to disconnect the ATR. But, in any case, until well into the dive, the yaw and roll authority that remains even with an asymmetry is able to be countered. Not ideal, but possible.

Any time an aircraft is out of control, the action of closing the throttles and neutralizing the controls will result in the aircraft stabilizing in a dive, either right way up, or upside down, but in a dive. There are one or two notable exceptions to that, but historically crew response to a surprise upset is to exacerbate the problem.

Spinning or autorotation, in this case, is not needed but could happen, if the crew had added large amounts of elevator and stalled with the yaw still happening. That would make for a tough recovery in IMC or broken visual horizon conditions. That needs a 3 1/2 to 4 g pull to happen, which could be possible, but it is not needed.

USAir427 may have benefited from hands-off. UAL585 probably not. AF447, certainly would have. Perpignan, nope. CAL Nagoya, Nope/maybe, CAL TPE, yes, Soichi, yes, The B717 stall test pull though, yup.

Years back, checking an examiner in an NG sim, the crew he was instructing was given a microburst scenario, off-axis entry. the aircraft flicked upside down and faceplanted. Repeat did the same thing. They called a coffee break and called in the techs. I flew the same scenario, and if the aircraft was not loaded up, it flew through the microburst happily. Alternatively, pulling hard enough to stall led to autorotation due to the yaw that was coming from the off-axis entry. I flew the QTG for the sim at the same time, and that matched nicely in all respects. The sim wasn't faulty, the crew's awareness of the conditions had holes. Flying that manoeuver essentially hands-off, the microburst was able to be negotiated without a face plant.

Autorotation, off axis entry and flying through a microburst hands off?

You are better than me, I don’t have a clue what you are talking about. Aeroplanes, helicopters or holding patterns?