Jump to content

Indonesian B737-500 goes missing, 5 mins after takeoff from Jakarta.


Recommended Posts

I have to opine that I find it hard to believe that an experienced Captain on a Classic B737-500 would have no ability to control a runaway trim event, given his extensive experience.

 

The original Boeing 737 advice on how to control runaway trim, upon introduction of the model, only covered 3 lines.

 

By year 2000, the Boeing runaway trim recovery advice, still only covered 4 memory items, and less than 20 lines in the QRH.

 

In every runaway trim event I can find, the event usually lasted for a reasonably prolonged period, and involved a "roller coaster" of aircraft flight movements. In a large number of cases, the crew called a Mayday.

 

In this incident, where the aircraft appears to have simply headed rapidly and directly downwards at a high angle, with little indication of any roller coaster fighting for control, I have to opine it represents a catastrophic airframe failure.

 

The catastrophic failure could easily have been a smaller component detachment, contacting another important control surface or component, resulting in a rapid and total loss of control.

 

The Boeing 737 Classic has a good record of trim control reliability - to the extent the NTSB does not consider 737 Stab Trim runaway or jamming occurrences, serious enough to warrant reporting as a major incident.

 

The SATCOM GURU has the most comprehensive analysis of 737 pitch trim events/incidents, that you're likely to find anywhere.

 

His analysis includes B737 MAX events, which tend to cloud the issue, when we are talking the purely B737 Classic model.

 

The introduction of MCAS in the 737 MAX (B737-7/8/9/10) is where all the trim problems started - and it wasn't related to jamming or runaway stab trim, it was an automated control logic problem.

 

But regardless, the number of pitch control events that have caused the complete loss of a Classic B737, are so low, as to even hardly register in the stats. 

 

http://www.b737.org.uk/runawaystab.htm#qrh

 

https://www.satcom.guru/2019/05/737-pitch-trim-incidents.html

 

 

 

 

 

 

 

 

 

 

 

Edited by onetrack
Link to post
Share on other sites

The aircraft involved in this crash, has been reported as accruing over 45,000 hrs TT, and over 24,000 cycles, in March 2012. Even allowing for the aircrafts lay-up for the period of the latter months of 2020, it's highly likely, using the previous average of approximately 2500 hrs annually, and 1333 cycles annually, that the TT of this aircraft had possibly reached 65,000 hrs, with possibly over 35,000 cycles.

 

One could definitely call this an old and "tired" aircraft, without any objection - and if you add in some possible deficient maintenance caused by COVID-19 penny-pinching - then the scene is set for a high potential for disaster.

 

Edited by onetrack
Link to post
Share on other sites
22 hours ago, onetrack said:

 and if you add in some possible deficient maintenance caused by COVID-19 penny-pinching - then the scene is set for a high potential for disaster.

 

Indo maintenance.......................................

  • Agree 1
Link to post
Share on other sites

The search for more aircraft pieces, bodies, and the CVR, was suspended Wednesday afternoon, as bad weather whipped up big waves and made diving conditions impossible.

 

However the weather has moderated today, and the search resumed this afternoon. No word yet, on when the FDR will be opened and read.

 

The authorities originally stated that it would be read within 3 days of being found. I suspect we will get no information from the FDR until early next week.

 

https://www.reuters.com/article/us-indonesia-crash/indonesia-to-resume-search-for-victims-black-box-of-crashed-sriwijaya-jet-idUSKBN29J0DL

 

It's not unexpected that the largest piece of the aircraft recovered so far is only around 5M long - and most pieces found, apart from the engine core, can be lifted by a couple of people.

Link to post
Share on other sites

Now something interesting has raised its head. A unnamed Sriwijaya pilot has revealed to the Indonesian Tempo newspaper, that this particular aircraft had "been having a repetitive autothrottle problem", for the last month.

 

https://bisnis.tempo.co/read/1423166/kata-knkt-soal-autothrottle-sriwijaya-air-yang-diduga-alami-masalah-berulang

 

While the pilot has not been named, and while investigations are still ongoing, it's interesting to note that an AD (AD/B737/149) relating to the autothrottle computer, as fitted to the B737-300/400/500, was released in December 2000.

 

The essence of the AD was the autothrottle computer originally fitted to the B737-300/400/500 was proving to be unreliable, and was responsible for incorrect thrust settings being applied, resulting in asymmetric thrust.

 

The AD background is as follows (my italics/bold):

 

"The aircraft manufacturer has received several reports of asymmetric thrust conditions during flight caused by irregular autothrottle operation in which the thrust levers slowly move apart, causing the aeroplane to bank excessively and go into a roll. This Directive requires replacement of the existing autothrottle computer with a new, improved autothrottle computer.

This action is intended to prevent a severe asymmetric thrust condition developing during flight, which could result in loss of control of the aeroplane."

 

The AD requirements were (my italics/bold, again):

 

1. Replace the existing autothrottle computer with a new, improved autothrottle computer in accordance with Boeing Alert Service Bulletin 737-22A1130 dated 24 September 1998.

 

2. Autothrottle computers with Part Numbers 10-62017-1, -2, -3, -4, -5, -11, -21, -23, -25, or -27 may not be fitted to any aeroplane to replace an installed computer.

 

https://www.legislation.gov.au/Details/F2006B02851/61540a27-d1c4-4048-a1a9-c9c2f7477bc3

 

This makes one wonder, if Sriwijaya Air, in its ongoing and current penny-pinching mode, may have replaced the autothrottle computer with a secondhand, early model, fault-ridden unit, with the Part Numbers listed above - and this faulty autothrottle computer has applied severe asymmetric thrust, creating an unintentional bank, and thereby leading to the track deviation, and obvious loss of control, that this aircraft has encountered. Stranger things have happened.

 

Edited by onetrack
  • Informative 2
Link to post
Share on other sites

Surely it would be obvious IF the auto throttle lost the plot, the PIC would quickly disengage it?  Assume hand flying and level out, problem solved?   They were at 10,000 feet so some kind of recovery should be possible before the aircraft was lost?

Link to post
Share on other sites

Jack, who knows what is likely to go on in the cockpits of low-cost Indo carriers, with pilots who often have poor understanding of aircraft systems? I trust the FDR information soon reveals what happened.

 

Here they are extracting the FDR from its casing and treating it, ready for reading.

 

 

 

Edited by onetrack
Link to post
Share on other sites

I believe some of the smaller low cost carriers used to train their pilots to let the aircraft do the flying and manual flying skills would suffer as a result, as would decision making during a “non-normal” event.

  • Informative 1
Link to post
Share on other sites

Having been a passenger on Indonesian internal airline flights I would consider anything possible.

  • Like 2
  • Agree 1
Link to post
Share on other sites

Reuters latest news is that the Indonesian National Safety Transportation Committee (KNKT) has issued a statement today that all the FDR data has been successfully extracted from the device.

 

The KNKT statement says that the FDR "has 330 parameters (in its memory), and all are in good condition". KNKT also stated that the information shows the engines were still operating up until the time the aircraft hit the ocean.

 

https://www.reuters.com/article/indonesia-crash/update-1-indonesia-downloads-data-from-flight-recorder-of-downed-sriwijaya-air-jet-idUSL1N2JQ0BN

 

 

Edited by onetrack
Link to post
Share on other sites
On 15/01/2021 at 1:05 PM, Yenn said:

Having been a passenger on Indonesian internal airline flights I would consider anything possible.

I agree Yenn.

 

In Surabaya I have sat watching through the cockpit door when the Pilot and 1st officer were tapping on a couple of inoperative engine gauges after engine start, then had a bit of a chat and obviously decided the Indonesian equivalent of "Stuff it, let's go anyway", ........ and off we went.

 

Anything is certainly possible.

Edited by Captain
  • Like 1
Link to post
Share on other sites

Flew down final into Jakarta in a Lion Air 737, the aircraft was banking 45 degrees either way. All the way down final, that late I thought it was going to scrape a wingtip. I refused to fly Lion Air after that so I travelled Sriwijaya Air!!!!!!! The flight crew start smoking as soon as they sit down, you can smell it throughout the flight and while they taxi in.

  • Informative 1
Link to post
Share on other sites

A quote reportedly coming from one of the Indonesian investigators, is along the lines of, "we are puzzled because the aircraft speed is too slow for that altitude" (at the point contact was lost).

If this report is correct, it appears to indicate that one engine may have been producing less thrust than required.

If the aircraft was in IMC, and the crew were occupied with other tasks, and not noticing asymmetric thrust starting to create a roll, that would likely explain how they failed to correct any autothrottle problem, until it was too late.

Asymmetric thrust creates both a yawing and a rolling moment. The pilots job is to identify asymmetric thrust quickly, and restore the thrust levels to equilibrium, as a priority. Any delay obviously results in an unrecoverable upset.

Compounding any asymmetric thrust problem that has developed as a result of an autothrottle fault event, is the lag in spool-up time of jet engines. I understand this can be 6 to 8 seconds.

That spool-up lag, coupled with any delay in troubleshooting, could mean trouble if a serious level of bank and yaw had already developed without crew awareness.

It's an interesting study, learning how quickly a swept-wing, large commercial jet can develop a flight upset, that can rapidly lead to aircraft loss, if the crew aren't "on the ball" with prompt troubleshooting and fault identification.

 

http://www.iasa.com.au/folders/Safety_Issues/others/aerodynamic_principles_of_large.html

 

  • Like 1
  • Informative 1
Link to post
Share on other sites

That LAG is more relating to some engines than others and it's usually from idle. IF the engine is "spooled up" say bleed valves closed there's NO lag unless an engine is damaged.. . A "decaying' engine  using altitude, V speed or attitude modes on the autopilot will not have stall protection . Other than take off, assymetric thrust is easily countered on rudder trim, after initially using the rudder in the usual way. At cruise level you are usually power limited so a loss of an engine normally requires a descent to about 7,000 ft (or a bit more) below where you were.. Nev

  • Like 1
Link to post
Share on other sites

Garuda 747 flight to London Gatwick many years ago we had three aborted take-offs in succession at Abu Dhabi, before eventually getting off-loaded to a tired looking Air Lanka 747 to Paris, then British Caledonian to Gatwick. Luggage arrived 3 days later. When boarding for trip home 2 weeks later noticed the name City of Jakarta on the nose, same aircraft that had problems outbound, did not inspire a lot of confidence.

Chatting to an engineer on the ground at Abu Dhabi, he said the captain had had problems ever since they left Denpasar and refused to fly it any further. Don't know what the cause was, but when hurtling down the runway each time to hear a loud bang, then engines shut down and hard braking, certainly get's your attention.

 

Edited by planedriver
  • Like 1
Link to post
Share on other sites

If you knew  everything that went on in the Aviation world, the shortcuts, the faulty instrumentation, the poor maintenance and quality of work on some cases,  doubtful pilots ability?

You would feel safer flying a Skycraft Scout, having done all your training on Youtube 🙂
 

  • Agree 2
Link to post
Share on other sites

The only seat I want to be in is the LH one up the front, then I have a fighting chance. Statistically flying is very safe and we had one very good year. Since then not so good. Most of the accidents are the result of a preventable situation and often a corner cutting exercise or a cost reducing one. Nev. 

  • Like 1
Link to post
Share on other sites

I always get concerned when I read about a crash pilot or FO (or both) being "very pious Islamic devotees, who always prayed 5 times a day, without fail".

 

The problem I see with these people is their highly fatalistic attitude, that nothing can be done when they are overwhelmed with a problem, and it is now, "Allah's Will!".

 

There is also often a very serious relationship fault between FO's and Captains in these societies, with junior employees in awe of senior employees, and an extreme reluctance to address any major errors in decision-making by the senior employee.

 

We have a saying in our family about religious fundamentalists (of any religion - be it Christian, Islamic or other variety) - it goes, "Too Heavenly-minded, to be any Earthly good!" 

 

These people let their religion transcend every facet of their lives, to their detriment of their application of everyday life skills. 

  • Informative 1
Link to post
Share on other sites

Indonesian airlines have never had good reputations. In 1975 there was an internal airline called Merpati & they were cheap. I don't thing they exist any more. The word amongst backpackers was never to fly on any of their aircraft. They had chooks, ducks, pigs etc accompany people in the cabin. I thought Indian Airlines were bad when I flew from Jammu to Srinagar in a clapped out Fokker Friendship in 73 & vowed never to trust a 3rd world airline again. I flew to Medan from Singapore & then went by bus & boat through Sumatra & Java & to Bali. By then I didn't trust Garuda either & waited a week to get a Qantas flight to Darwin.

  • Like 1
  • Agree 1
Link to post
Share on other sites

I think it was Merpati that I was on. I pointed out to the hostie that a bicycycle in the cabin gangway was not on. That didn't get her attention until I mentionad that I would report it to IATA if we took off. They stopped the plane and removed the bike.

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...