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I’m always surprised at the pilots who do not follow through with their hand on the thrust levers when on final approach...it’s fundamental IMHO
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Yes definitely but having only two hands it can easily happen when one hand is on the mcp and the other on the control column.
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If you've got one hand on the MCP for any more than a few seconds at a time down final you're doing it wrong. Get your mate to do it.
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Too many times you see crews failing to nail a simple request like "approximately 40%", will not wait for the engines to react and push even more forward asking 60-70%. We also see PM's who "back up" the thrust levers as they move under TOGA and then for some reaon keep their hand behind the thrust levers while the PF has his hand on the thust levers. Old Wives Tales again from DC3 era about throttles and dodgy friction nuts. if the PF suddenyly chops the throttles to abort, the PM is in danger of severely damaging his hand caught between the aft edge of the throttles and the start levers in the 737. |
DDG-37
part of the CVR was found but not the Memory Unit, and the search extented till 21/01 |
According to KNKT, the flight data recorder (FDR) was filled with 370 flight parameters from 27-hour flight recording, which is in total 18 flights that include its tragic final flight. |
"...even when FO was flying"
Fortunately these days are over. |
In my two posts on 11.1.21, which were deleted for some reason, I stated (in my opinion as someone who has worked on various aspects of aircraft safety) that the CG position on SJ-182 could be “marginal...too far forward”, but that a trigger event such as “a throttle back” would be needed in order for a sudden pitch down ‘incident’ to occur. An auto-throttle fault could be just such a trigger; the CG problem would worsen and the situation could be unrecoverable.
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Amazing how some people here seems always to know better without even knowing the details of the event. I have many PIC hours on the 737 so I am not your newbie you can teach on a forum on how to fly, It was easy to recognize and correct. But it can happen. It also happened on initial approach before LOC capture nowhere near final (that's your wrong assumption) and the hand was on the MCP for just few seconds, enough to develop some asymmetric thrust that was then quickly corrected. Not saying that this is what happened here, just saying that it can happen to anyone.
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VicMel As someone who did load control on just about every 737 variant built, I can say with some degree of confidence that you have to work really-really hard to get a -500 out of forward CG limits. Should this happen, the first thing the pilots will notice is that it will refuse to rotate after the Vr call.
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Umm, did you mean to say ‘VR’??
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Yes I think he did , but even VR, that did not prevent aircraft from trying to take off before , albeit sometimes scrapping the tail but generally managing to get airborne. and none resulted in an accident.( western passenger aircraft that is ) so not really relevant here I would say.
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MCP = Mode Control Panel. (In Airbus world it’s called the FCU - Flight Control Unit.) In either case it’s the centre instrument panel mounted on the glareshield. It’s where the flight path controls are located - heading, height, speed, flight directors, autothrottle, autopilot etc.
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Originally Posted by Centaurus
(Post 10970883)
Couldn't agree more. Seen that in 80% of simulator sessions in the 737. Just as illogiocal are those who overshoot the approximately 40% N1 advice during the rolling start, then hurriedly reduce power back to approx 40% N1 when they realise what has happend and then shove open to takeoff power hitting TOGA on the way, oblivious to the fact that they are eating up runway distance and invalidating V1 in some cases.
that is a natural response to the way we do an evaluation of crew performance. it is a measurable "error" that an instructor or examiner can comment on, so commentary on that and a consequential irrational emphasis can result. The problem of being human. Institutional training devolves over time towards a firm grasp on the trivial, unless an independent review of system behavior occurs. As you describe, the outcome from an excessive concentration on a specific value rather than the underlying reason for a value, (achieving near symmetric acceleration of the engines results in a loss of SA on the equally serious matter of achieving takeoff performance. it's a good example of consequences, as was the overemphasis on automation use which led to loss of skills and more importantly, loss of SA of many crews reliant on automation.
Originally Posted by Centaurus
(Post 10970883)
We also see PM's who "back up" the thrust levers as they move under TOGA and then for some reaon keep their hand behind the thrust levers while the PF has his hand on the thust levers. Old Wives Tales again from DC3 era about throttles and dodgy friction nuts. if the PF suddenyly chops the throttles to abort, the PM is in danger of severely damaging his hand caught between the aft edge of the throttles and the start levers in the 737.
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BuzzBox
Vr comes after V1, so techically he is correct. Probably not what he meant though. |
VicMel
ANDRASZ's answer covers this matter as being remote. My own flight testing on the -500, we were required to do baseline stalls of the aircraft at its limit cases, fore, and aft, at high and low weights. Those we had to meet by having a couple of tons of drinking water from Sams Club and moving from aft hold to forward hold, we also had movable ballast inside the aircraft so that the TO and LDG were done within the basic envelope of the aircraft. longitudinal stability was adequate at all times. The only notable curiosity in the plane was a clean stall where the slat rigging could result in a minor amount of roll but it was a non-event. On the autothrottle musings, the info available so far doesn't match well to a thrust change occurring leading to a yaw/roll/APLT disc/uncommanded open-loop roll departure. it is a simple scenario, but with a relatively steady state before the upset, a thrust change is not evident. That may be the data granularity, or the scenario doesn't fit. It is unlikely that the asymmetry was there for minutes undetected, so a change in rates immediately before the upset would be expected in the ATR clutch scenario, and that doesn't seem to be there. |
The aircraft track shows 10 seconds of an absolutely level LH turn from the departure track of 045° onto 015°, followed by a further 10 seconds of continuing but descending LH turn onto about 340°, before starting the 12 second RH spiral descent which continued all the way to impact.
[insert compatible scenario here] |
Originally Posted by BuzzBox
(Post 10971424)
Umm, did you mean to say ‘VR’??
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AvHerald:
The KNKT have already developed a general picture of the accident, however, need further data from the cockpit voice recorder before publishing any information. Inspections of Boeing 737-300, 737-400 and 737-500 in Indonesia have been ordered. A first hint that Technical Causes played a role. |
Not necessarily
“In the letter signed by the Executive Director of Airworthiness and Aircraft Operations Udi Tito Priyatna, DKPPU will conduct an examination of 7 main aspects, namely: – Implementation of the airworthiness directive (AS) compliance – Carrying out routine inspections and major inspections – Repetitive monitoring – Implementation of pilot training – Implementation of a pilot professional check – Crew duty time” http://netral.news/en/ministry-of-tr...indonesia.html |
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)... |
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 |
Back at NH
Reads a bit like a minor technically issue leading to a wrong/disastrous handling by the chaps in the front office. |
Read QDM360’s post above...
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Back at NH
The list of 7 main aspects to be investigated contains 6 items? |
netstruggler
"The list of 7 main aspects to be investigated contains 6 items?" Item 7 relates to examining the implementation of Covid-19 measures. |
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. |
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 |
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 |
Originally Posted by lomapaseo
(Post 10972865)
Now all we need is a complete investigation of this and other possible causes.
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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.? |
DaveReidUK
yes. It’s Indonesia. |
I’m not jumping to conclusions. However, I’ve flown this model of 73 and I’ve had asymmetrical thrust due to a “lazy” left engine when the thrust was commanded above idle. The roll and yaw was pretty drastic.
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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. |
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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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. |
Many years since I last flew one, but AFAIK the autopilot on the classic isn't connected to the rudder.
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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. |
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.” A/P acting on Rudder in 737? Y/D is no A/P |
Originally Posted by ManaAdaSystem
(Post 10973117)
.... which we all should be able to control and recover from.
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