oblivia

They may care, but only as they see it affecting their bottom line and their judgment about the cost of safety vs the probability and cost of accident is flawed.

it happened over time, the accumulation of bad management decisions with less than obvious consequences compared to the immediate and obvious costs.

Winemaker

The suggestion was made that it’s possible for the auto thrust clutch to fail, and that could lead to the power of one engine to reduce, possibly all the way back to idle. I’m not on plan B, so not sure if they are suggesting the throttle itself would move too, but I would guess it would. Having one engine at idle, and the other at climb thrust would obviously induce a yaw. If this would happen with the autopilot on, the autopilot would try to maintain the path with ailerons deflection, but it has no automatic rudder trim, so the aircraft would have a sideslip. I would think that as long as they were climbing in an airspeed mode the speed would not have gotten low enough to get near to any Vmc condition. It is possible that, perhaps because of the loss of performance the pilots selected a higher climb rate using vertical speed, and the speed loss that followed lead to an autopilot disconnect and loss of control because of the out of trim situation, but that is pure speculation.

hans brinker

The thrust lever won't close by itself ordinarily, although there is one particular case where that certainly will occur. A clutch problem will leave the thrust lever at a position, anywhere along the available TLA's.

The problem with an asymmetry while on APLT and without rudder input is not a VMCA issue, it is simply that there is an APLT roll input to maintain attitude due to uncorrected yaw, and the APLT will happily apply the roll input until it doesn't. If the APLT roll authority is limited, then eventually a roll-off that exceeds the APLT limits can occur and the APLT disconnects. at that time, the Roll input is removed, the yaw remains and a rapid roll occurs. The authority to stop the roll is lower than normal due to the roll induced by the yaw, so recovery is less than expected in normal handling, and on occasions that has resulted in confusion in the cockpit. (I observed that in a B744 on one occasion, and the roll in the screw up was sufficient o leave a well-deserved scar on the loopy captain's RH forehead from the storm light switch poetically shaped as a blade).

Within the normal envelope of the APLT, if the APLT is disconnected the crew may not be ready for the removal of the force of the APLT on the ailerons, which will rapidly return to neutral unless counted by the driver. That may seem obvious, especially when the driver is going to be trying to pickle off the APLT from a control position that is decidedly not neutral, but often crew will not be ready for the loads that are being assumed by them to maintain the current control position. An insidious problem can be encountered as well if the driver happens to mistakenly use aileron trim instead of rudder trim while the APLT is engaged. On too many aircraft, doing that will not disconnect the APLT immediately where using the stab trim will, but the extent of trim input is not observable on say, Boeings... and so a wild ride can occur at disconnect if it is not recognized.

All of these issues should be nonissues, but then that is the case with most accidents and most human endeavours; when the humans understanding of their state differs from actual, wild rides happen. If you are not used to wild rides (and even when you are) they can escalate rapidly as the human scurries to get back into the loop, which means doing all of the OODA stuff in quick time. The normal envelope of +/- 35, +25/-10 (or whatever the limits of your ride are set at) leaves a lot of attitudes and accelerations that the driver doesn't get to spend time experiencing.

Tim27

Not only that a hand should be on thrust levers at ALL times when the AT is active. Ie when making significant movements. Caught out the guys in Emirates, big time, crashing a perfectly serviceable jet.

....and during a coupled approach hard to believe that guys are not following through on both yoke and thrust levers.

Only if company sop's don't prohibit such action.

Which is exactly why we practise them in the sim every six months. Jet Upset, UAs, limited panel etc, for a good reason.

Surely every airline SOP mandates on a coupled approach, following through, hands on controls and thrust levers during final approaches. (My Company B 747,below 1000ft.) And most importantly on a Go Around. EK would not have lost the 777 at DXB, due this omission.
Basic Airmanship?

Trasport airplanes (Icao)
 

(Maneuver diagram Icao)
Transport category aircraft

upset
pitch of + 25 ° / -10 °
Roll +/- 45

RetiredBA/BY

I don't follow through. I put the yoke and levers where I want them and usually find the autopilot and auto throttle agreeing with me.

Some aircraft may require 'follow through' from certification.
e.g. autopilot runaway above 1000 ft may use a 4 sec reaction time. Below 1000 ft, 2 sec could apply providing the pilots is 'hands on' to reduce height loss, quicker reaction.

jimtx, if you imply that you are over-riding the autopilot - applying force other than that from the AP, then be prepared for a surprise: - back driven trim, sudden force disconnect.

Icarus2001

As do the crews that end up out of sorts. UAL, USAir, etc had upset training before 587, 585, 427... and had bad days. So did a bunch of 604 drivers, AF447 etc. Now, before the cries of but the b737 rudder PCU....!, note that the roll rates were well above flight control available rates, so autorotative effects were in pkay on 427 and 585, and lo, 427 elevators are NU throughout the sad event. 585 rates... Etc.. NTSB was silent on rates achieved.

Anyway, if you aren't in the head, have conpetency and are aware of what and preferably why, and are not inconvenienced by the accelerations and vibrations at your seat, then it is all good. For the rest, the training hopefully gives a capability to sort out what they got and undo it.

The B717 stall video shows a competent crew having a wild old ride.. As did perpignan. A while back i did a BFR in a SE jet with a sharp examiner. While he was doing a barrel roll it turned into a half cuban, but with an entry of around 350kts... And not so much height for what then occurred, an indecision on which way to roll, he had to look behind the wing or in the mirror for the horizon, and then he went for a pull through rather than a roll out to a recovery, which was at about 450kts indicated and 7g. We were well clear of the ground, but not by design. It had enough margin for the recovery to be talked through, but the split S was not a manoeuver i was expecting to see a good driver get into outbof a barrel roll. Post flight, the examiner noted he was disoriented with trying to acquire the horizon and needed to follow the recovery that was being called. It was a non event, but was still curious in the recovery attempted and the reason why. There but for Grace etc...

PEI_3721

It's just a semantic mindset. I don't apply force to the yoke.

fdr

Yes, I agree with all that. Was just trying to explain in non pilot terms to self proclaimed SLF what could have happened.

cessnapete

Don't disagree, always have my hand on controls per SOP below 2500' AAL, but FWIW tactile feedback doesn't happen on brand A. (and that is easily the worst thing)

is the search still on for the missing part of the CVR?

As of 3 days ago the KNKT were still talking about "if we find the flight recorder ...", which would imply that the search continues.

No official report, but


Victims families are suing BOEING

I’d be interested to know from any 737 drivers here, how obvious a sideslip is when engine thrust is asymmetrical. I assume it much depends on how out of balance the thrust is, but....something you can feel easily in seat of pants?....

When you are disorientated, seat of the pants does not help. AF 447 descended at 10000ft/min yet the crew held the stick full back. Although I did 'upset training' in the commercial world it was of little use and I relied upon training received in the military.

Joejosh999

Depends on the situation at the time of engine failure.
If the autopilot is engaged in level flight for example, then the control wheel will be displaced (turn) towards the "live" engine. If there is no rudder input to counteract yaw, then the autopilot will disconnect when the AFDS cannot cope.
Without an autopilot engaged, then the turn and slip indicator will show the pilot the sideslip. Boeing do not recommend trimming the rudder to completely get rid of the sideslip, as a "neutral" control column is desired which avoids inadvertent spoiler extension which causes increased drag and a reduction in lift.

"Depends on the situation at the time of engine failure"..correct,

During every return to lease flight we do this
CRUISE AT OR ABOVE 37,000 FEETA. DUCT PRESSURE

(1) Check that duct pressure regulates between 34 to 50 psig _____

B. ENGINE ACCELERATION & HIGH STAGE BLEED CROSSOVER

(1) Engine IgnitionCONT

(2) AutothrottleOFF

(3) Maintain stable flight at cruise altitude.

a) FMC N1 page select CON ____

(4) Engine #1

a) Set No. 2 thrust lever to MCT.

b) Rapidly retard No. 1 thrust lever to idle.

c) Check for crossover indicated by sudden duct pressure increase _____

d) Allow RPM and EGT to stabilize.

e) (Timed event) In approx one second advance the No. 1 thrust lever toward MCT. Set thrust lever approx 1 knob width below engine No. 2 to avoid overboost.

Start timing when thrust lever is advanced and stop timing at 90% N1.

f) Record acceleration timesec.

g) Engine should accelerate smoothly and without compressor stalls ____

The reason I post this is to simply emphasise that the aircraft does not fall from the sky or lurch hopelessly one way or the other and a small control column deflection and rudder input is sufficient, the big difference being we are mentally prepared for the event.
If you loose an engine in the climb or turn and do not revert to basic airmanship and problem diagnosis there is a likelihood of the incorrect actions being taken. The A/T should not retard the TL in the climb unless the target altitude had been captured in the MCP +/_ the limits of VNAV or LVL Change, VS does not count here as climb in VS the AT is controlled by the MCP speed. During an engine failure in the climb yaw would be fairly significant, but again, there would be no commands to the AT servos unless some signals had been given to the system either in terms of MCP speed reduction in VS or "Capture" in another mode.
An A/T servo failure during TL retard should be spotted by the crew but is not a reason to have a jet upset and certainly not regarded as so "time critical" that diagnosis cannot be performed. To be honest, the turn and slip is more of a comfort thing, the yoke displacement is a more natural indication and does not lag as much as the ball.
Apart from EFATO, at a safe height, the excessive use of rudder trim is not recommended as unless you are terrain critical and need to continue the climb, as normally you would simply stop the climb and after the diagnosis trim of the QRH recommends it.
The reasons for this accident are yet to be established and the whole engine, TL, AT debate is speculation, it could just as easily be a jammed or broken flight control.

Good write up KG.
Your last comment is wise regarding speculation. Until all relevant information is collected it is wise to be cautious in arriving at an early conclusion.

Hi Folks. Just joined this thread with not having read it all but I have been browsing. There seems to be little doubt that the A/T malfunction was the fault which was the precursor to the crash. Is that correct?
If so, and I apologise if that is not a correct assumption, then the A/T was not the >cause < of the crash.No auto throttle fault (because it not required for dispatch or flight) should be of the least concern to the crew.
Certainly that is my experience of 10,000 plus hours on the 737 all variants (except the MAX) and I would love to fly that of course. No auto-thrust? Set manually. Split thrust - disconnect and set the correct power. One T/L moves when it shouldn't? Put it back and if it doesn't behave, disconnect. So I am not sure where all the discussion about the A/T is going here. Seems that the most likely scenario is that a thrust asymmetry occurred ( given its history on this plane it would have been expected and not a surprise) which would cause the autopilot to put in aileron to counteract the thrust imbalance. [The rudder cannot act in this way so is not involved] This would be blindingly obvious to the pilots because the thrust levers are no longer aligned and the ailerons are displaced. If it wasn't noticed, which seems very strange, then the A/P hits the authority limit at about 25 degrees of aileron and then AP disconnects. A rapid roll would ensue. The remedy is again part of our training ( I am assuming that the people reading this haven't been trained in such a situation) which would be to set symmetrical thrust and roll wings level using full aileron.
I am being lazy here but there are so many pages that I haven't found this mentioned yet. Looking forward to the latest information which must be known by now. The memory card for the VCR? Hard to find in deep water in mud I would think but that is a terrible shame since there lies the complete answer.

Hi,
When the media are talking about the search of the "memory card", "memory unit" or "memory module" of the CVR, do they mean that barrel-shaped, armored steel capsule that is, by volume, several times the size of the already found pinger?
Or do they actually mean smaller parts that have somehow gotten out of their protective container during the crash?

It's highly unlikely they will find the latter without the former.

Safety of the divers is very important when working in all kinds of weather. Continued searches likely need additional equipment. It takes time to sort out what equipment exists and is available on short notice. Meanwhile you standdown part of the investigating team and reorganize later. Some of the landlubbers get sick while bobbing in flat bottom boats at sea for days

M68

There is a picture posted many pages back that shows the pinger and the destroyed remains of the CVR. The memory module is not there. There are 2 pingers, the destroyed remains and the FDR in the box.
https://cimg7.ibsrv.net/gimg/pprune....2f519c7905.jpg

How on earth did you come to that conclusion?
Everything is on the table so far.

Hi Icarus2001. I did say it as a question because as I said I am new to this thread. I said. >>> Is that correct?
If so, and I apologise if that is not a correct assumption? However I have been reading the the subject aircraft had been suffering AT problems for a few days and here is REUTERS a couple of days ago but it has been in many other reliable journals. Of course the Indonesian AAIB will have that information and a 30 day report should be out soon. Indonesia probing whether faulty system contributed to Sriwijaya Air crashAgustinus Beo Da CostaJAKARTA (Reuters) - Indonesia’s air accident investigator is probing whether a problem with the autothrottle system, that controls engine power automatically, contributed to the Sriwijaya Air crash on Jan. 9 that killed all 62 people on board, an official said on Friday.

National Transportation Safety Committee (KNKT) investigator Nurcayho Utomo said a problem with the Boeing 737-500’s autothrottle system was reported after a flight a few days earlier.

“There was a report of malfunction on the autothrottle a couple of days before to the technician in the maintenance log, but we do not know what kind of problem,” he told Reuters. “If we find the CVR (cockpit voice recorder) we can hear the discussion between the pilots, what they talked about and we will know what is the problem.”

It remains unclear whether a problem with the autothrottle system contributed to the crash, Utomo said, adding he could not recall any other issues raised in the maintenance log.

It is acceptable for a plane to fly with an autothrottle system that is not working because pilots can control it manually instead, he said.

Sriwijaya said he was unable to comment on technical matters involving the investigation before an official statement was made by KNKT. A preliminary report is expected to be issued within 30 days of the crash, in line with international standards.

The plane’s flight data recorder (FDR) has been recovered and read by investigators but an underwater search for the CVR’s memory unit at the crash site in the Java Sea is continuing.

Citing sources close to the investigation, the Wall Street Journal (WSJ) on Thursday reported the FDR data showed the autothrottle system was not operating properly on one of the plane’s engines as it climbed on departure from Jakarta.

Instead of shutting off the system, the FDR indicated the pilots tried to get the stuck throttle to function, the WSJ said. That could create significant differences in power between engines, making the jet harder to control.

If there was a tech log entry for the A/T system the engineers should have carried out the required tests, for those of you with interest they can be seen on the video here:
https://www.sjap.nl/?s=autothrottle
In any event, a failed A/T should not be a reason to crash, presuming the pilots are " in the loop" and competent to diagnose and apply the appropriate actions, the QRH directs the pilots to the most appropriate actions: Re-engage or Disconnect. Taking actions outside of the manufactures guidance is not advised, however, again we are in the realms of speculation, and in this part of the world when anyone says a "source close to" take it with a very large pinch of salt.

Without the CVR, what output to the DFDR would confirm what the pilots were doing to the auto-throttle? Is it not possible that the pilots showed no recognition nor took any action until an upset?

The DFDR should have throttle position - if it splits with the autothrottle on, that would be pretty good indication that a clutch was slipping, if that split persists it would similarly be a good indication that the crew wasn't addressing the problem (or, in the case of a seized throttle, was unable to address).
They're going to need the CVR to understand the why.

BTW, it would be pretty much unheard of for the memory module to come out of it's protective steel (or titanium) protective shell. I can't tell much from the photo above, but I suspect the protective shell separated from the rest of the CVR module - it's that protective shell they need to find. If it's steel, they may be able to use a magnetic anomaly indication to help locate it.

Parts sent to the US and GB (Reuters)

"Indonesia’s air accident investigator has sent five components of a crashed Sriwijaya Air jet to the United States and Britain for examination, including the autothrottle that controls engine power automatically, the agency’s head said on Tuesday."

Am I being simplistic, but why on earth should any A/T malfunction/ unserviceability cause any aircraft to crash? All aircraft are cleared to fly with the A/T u\s. On my last type we could even carry out CATIII autolands manipulating the Thrust Levers manually.
On first sign of malfunction when airborne, disconnect and operate the Thrust Levers manually as normal. Even if required, possibly disconnect the autopilot and fly manually while you sort out the automatics. Or am I missing something?

1. It's still a rumour, isn't it?
2. Can you imagine an aircraft crash due to a blown bulb in the landing gear annunciator panel?

2 = Everglades?

On 2021.02.01 Chairman of the KNKT Soerjanto Tjahjono announced that search operations for the CVR resumed after being suspended for 3-4 days due to bad weather & high waves.

From a translation, it appears teams of three divers are inspecting 5M x 5M sections of a grid pattern for twenty minute intervals before moving to a fresh section.

Parameters.
 

Hi.Folks.
I ask an engine mechanic, if the small dynamic air tube on an engine
becomes blocked, what would happen to the engine parameters?

Many thanks.

If you are referring to the PS3 sense pressure line, there can be loss of "automatic thrust control" as the FCU will attempt to adjust the fuel flow and hence shaft speed to the Thrust lever position, however, as the CDP (compressor discharge pressure or PS3) is an element required by the FCU To adjust the calculated fuel flow to the current air density at the combustor inlet, the FCU needs at least the inputs of the compressor inlet temperature (CIT AND the compressor discharge pressure (CDP or Ps3) additionally to the N2 speed and the power lever input.
If the inputs are not available there is a potential for the engine to either operate outside the surge limits or flame out limits, in which case the crew would need to carry out the associated QRH or recall (memory items) and either operate with the engine shut down or manage within the limits (surge only).
Another video here for the tech heads!

EPR increases while N1 remains stable. Read the Swiftair MD-83 accident report for full details: https://reports.aviation-safety.net/...D83_EC-LTV.pdf