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737-500 missing in Indonesia

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737-500 missing in Indonesia

Old 20th Jan 2021, 11:15
  #341 (permalink)  
 
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You left out the important line above:
... starting January 11, 2021,” quoted from the letter obtained by Kompas.com, Monday (11/1/2021)."

This is all old news from the time before the FDR was even found - let alone downloaded. At this point, they basically had no facts about the accident and thus triggered the most generic news release - basically saying they will look into everything (maintenance, ADs, pilots, training, ...). No surprises there.

It'd be more interesting to know what actions they decided to trigger after the FDR was found (12/1/2021) and after its data is downloaded (13/1/2021)...
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Old 20th Jan 2021, 13:36
  #342 (permalink)  
 
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wait

I wouldn't read too much into this. many times inspections are publicised to calm the public while investigations continue with "what-ifs" and not enough evidence yet
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Old 20th Jan 2021, 18:16
  #343 (permalink)  
 
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Reads a bit like a minor technically issue leading to a wrong/disastrous handling by the chaps in the front office.
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Old 20th Jan 2021, 18:30
  #344 (permalink)  
 
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Read QDM360’s post above...
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Old 21st Jan 2021, 07:49
  #345 (permalink)  
 
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The list of 7 main aspects to be investigated contains 6 items?
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Old 21st Jan 2021, 09:07
  #346 (permalink)  
 
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netstruggler

"The list of 7 main aspects to be investigated contains 6 items?"

Item 7 relates to examining the implementation of Covid-19 measures.
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Old 21st Jan 2021, 13:03
  #347 (permalink)  
 
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Autothrottle suspected (WSJ article)

Wall Street Journal article, headline below (by-line - Andy Pasztor, Jon Emont & Andrew Tangel), reporting preliminary interpretation or review of flight data recorder, pointing to autothrottle problems and their aftermath. As mere SLF/attorney I'm not trying to restate the summary of sequence of events as described in article, which itself may or may not be valid and/or accurate in eyes of the aviators.

Headline, WSJ website, Jan 21 about 02;30 h:Indonesia Plane Crash Probe Centers on Engine Control Problems Information from the Sriwijaya Air jet’s data recorder points to pilots trying to deal with an engine-throttle malfunction.
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Old 21st Jan 2021, 14:43
  #348 (permalink)  
 
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https://www.bloomberg.com/news/artic...et-crash-probe

Indonesian investigators probing the Jan. 9 crash of a Sriwijaya Air flight are looking at the possibility that a malfunctioning automatic throttle could have led to the pilots losing control, according to a person familiar with the investigation.

The autothrottle was producing more thrust in one of the Boeing Co. 737-500’s two engines than the other shortly before the plane carrying 62 people crashed into the Java Sea, said the person, who isn’t authorized to discuss the matter publicly. The device had been having problems on previous flights, the person said.

Issues involving the autothrottle on the 737 have led to incidents in the past and a similar malfunction on another aircraft model was a cause of a fatal crash in 1995 in Romania.

Nurcahyo Utomo, the lead investigator at Indonesia’s National Transportation Safety Committee, confirmed that a malfunctioning throttle was “one of the factors that we are looking at, but I can’t say at this point that it’s a factor for the crash or there was a problem with it.”

Utomo’s team is working with engineers from Boeing to review the data from the aircraft’s flight-data recorder that was retrieved from the seabed last week. Rescuers are still trying to locate the memory module of the plane’s cockpit-voice recorder, which broke apart upon impact.

Unequal thrust from the engines can cause a plane to turn or even roll onto its side and descend abruptly, if it’s not handled properly. Pilots must compensate by manually setting the power or taking other actions.

If the autothrottle failure proves central to the probe, it’s likely to put the focus on pilot actions and training as well as how the airline maintained the plane.

Sriwijaya Air Flight 182 abruptly nosedived more than 10,000 feet (3,050 meters) in about 15 seconds just minutes after takeoff in heavy rain from Jakarta, according to tracker Flightradar24. All aboard died.

Boeing’s 737-500 model first flew in 1989 and, according to tracking website Planespotters.net, the particular aircraft that crashed earlier this month entered service in May 1994. The family of jets belongs to an older model than the 737 Max that was involved in two other deadly accidents, including one off the coast of Indonesia, in 2018 and 2019 and that led to a global grounding.

Indonesia’s NTSC hasn’t issued any details about what may have led to the crash. It said Tuesday it was planning on releasing preliminary findings within 30 days of the accident. Both engines appear to have been functioning prior to the plane hitting the water, according to the NTSC.

Indonesian publication Tempo reported in recent days that there had been recurring malfunctions of the plane’s auto-throttle system prior to the crash.

Like an autopilot, an autothrottle on the 737-500 can be used by pilots to set the speed automatically, thereby reducing their workload and wear on the engines.

Twin-engine jetliners such as the 737 are designed to fly on a single engine during an emergency, so an autothrottle failure that produced unequal thrust shouldn’t have been enough to take down the plane by itself.

However, a severe case of unequal thrust can cause a variety of issues with a plane’s controllability. If an aircraft is in clouds or pilots aren’t closely monitoring the plane’s condition, it can get severely out of control before crews respond.

In 2001, the U.S. Federal Aviation Administration ordered operators of the family of jets including the 737-500 to replace the autothrottle computer after reports of unequal thrust. While there’s no indication this specific issue occurred in the recent accident, it illustrates how it could create a safety hazard.

Boeing had years earlier issued instructions for how pilots should correct the problem -- known as a procedure -- but multiple incidents continued to occur in which crews failed to recognize what was happening soon enough and FAA said more specific repairs were needed.

“This procedure does not take into account human factors that may result in the flightcrew failing to recognize an abnormality that develops over an extended period of time, resulting in an excessive bank angle for the airplane,” the FAA said in the 2001 notice to pilots.

Out of eight incidents in which pilots didn’t respond properly, two aircraft rolled more than 40 degrees, according to the agency.

Unequal thrust on an Airbus SE A310 and a pilot’s inadequate response caused a Tarom airlines flight to crash near Bucharest in 1995, according to Romanian investigators. All 60 aboard died.

— With assistance by Julie Johnsson
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Old 21st Jan 2021, 15:24
  #349 (permalink)  
 
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https://www.bloomberg.com/news/artic...et-crash-probe

good summary of what they read on PPRuNe.

Now all we need is a complete investigation of this and other possible causes.

I seem to recall a China airline B737 that likely crashed after auto-throttle issues but the report was not made available by the time of the Tarom crash.

autothrottle malfunctions are low grade technical faults except with poorly trained crew so this latest accident has no cause yet in my mind until/unless all avenues are explored
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Old 21st Jan 2021, 17:01
  #350 (permalink)  
 
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Originally Posted by lomapaseo View Post
Now all we need is a complete investigation of this and other possible causes.
Is there any reason to believe that we won't get that ?
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Old 21st Jan 2021, 17:04
  #351 (permalink)  
 
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Having folllowed this discussion, today I asked an ATPL who used to fly later model 737's about how the autopliot possibly hands back controlto the P1 when it can't cope any longer..
He told me with autopilot selected both the yoke and rudder pedalsa all move in sympathy with it, so the crew should be constantly alerted & aware of any deviant controls correction taking place.?
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Old 21st Jan 2021, 17:18
  #352 (permalink)  
 
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DaveReidUK

yes. It’s Indonesia.
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Old 21st Jan 2021, 17:22
  #353 (permalink)  
 
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Iím not jumping to conclusions. However, Iíve flown this model of 73 and Iíve had asymmetrical thrust due to a ďlazyĒ left engine when the thrust was commanded above idle. The roll and yaw was pretty drastic.
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Old 21st Jan 2021, 17:35
  #354 (permalink)  
 
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Standard procedures

4runner

The investigative team have already gone on the record that it is their objective to publish the preliminary findings within the usual 30 day framework.

Sorry if that does not comply with the keyboard investigator's timelines, but that is the way it works.
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Old 21st Jan 2021, 20:17
  #355 (permalink)  
 
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Quite so. That's what happened with the KNKT's Preliminary Report on the Lion Air crash. I see no reason to doubt that it will apply this time, too.
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Old 21st Jan 2021, 20:30
  #356 (permalink)  
 
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4runner

Indeed same here, this is not an uncommon problem on the classics. Come to think of it wasn't stagger partially implicated in Perm? Not a direct cause, but one of the many factors.
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Old 21st Jan 2021, 20:44
  #357 (permalink)  

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Many years since I last flew one, but AFAIK the autopilot on the classic isn't connected to the rudder.
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Old 21st Jan 2021, 21:26
  #358 (permalink)  
 
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4runner

Yes, but it’s nothing worse than an engine failure which we all should be able to control and recover from. Probably easier since a bad auto throttle can only command idle thrust, not stop the engine.
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Old 21st Jan 2021, 21:34
  #359 (permalink)  
 
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Nurcahyo Utomo, the lead investigator at Indonesia’s National Transportation Safety Committee, confirmed that a malfunctioning throttle was “one of the factors that we are looking at, but I can’t say at this point that it’s a factor for the crash or there was a problem with it.”
Ok, this is key. Not outspoken, but a Throttle issue is likely or among the suspects. And then it makes sense they need CVR to detect, why crew was not able to control that situation.

A/P acting on Rudder in 737? Y/D is no A/P
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Old 21st Jan 2021, 21:46
  #360 (permalink)  
 
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Originally Posted by ManaAdaSystem View Post
.... which we all should be able to control and recover from.
What? A bit like a Stab Trim Runaway then...?
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