Originally Posted by Airbubba
(Post 10298291)
Is CWS still used in the 737? It's been disabled for years on the larger Boeings that I've flown. Is it still an option?
A bit like the 737 eyebrow windows, which have never been used by anyone since first flight in 1967. They are normally blocked off by safety cards, to stop the sun blinding the pilots. And regards the speed-trim system, it ALWAYS trims in the wrong direction. Whenever it operates, you just trim it back the other way. Most absurd system ever invented. Silver |
Originally Posted by silverstrata
(Post 10299008)
And regards the speed-trim system, it ALWAYS trims in the wrong direction. Whenever it operates, you just trim it back the other way. Most absurd system ever invented. Not that absurd. (And not unique to B737 either...) Part 25 regs require that there be a minimum stick force "per knot" (actually, per 6 knots, to be pedantic) to change speed from the trim condition (as a demonstration of static longitudinal stability). Achieving this under all conditions can be tricky. So a design solution applied is to have an automatic system act to increase the required force - to introduce a degree of "artificial stability" in effect. One way to do this is to have the aircraft automatically "trim the wrong way". that way, when hand flying (and not trimming) you find you have to pull more to slow down (part of the pull is the natural pull the aircraft requires, part is to fight the opposite auto-trim), and similarly push more to accelerate. Unfortunately these systems are often called things like "auto trim" or have "trim" in their name, and that leads people to sometimes think that their intention is to HELP the pilot trim the a/c, whereas they are designed to do the exact opposite. |
Originally Posted by Toruk Macto
(Post 10297528)
Classic third world response..... , |
Originally Posted by EDLB
(Post 10299002)
Probably because on the static side the 80kn check on take of would be o.k. You only figure on climb that the indications are bad. With pitot covers on they should have aborted the takeoff.
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Originally Posted by Mad (Flt) Scientist
(Post 10299013)
Not that absurd. (And not unique to B737 either...).
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Originally Posted by DaveReidUK
(Post 10298916)
Yes, I think we've now established that the suggestion in the original post (which didn't quote the source, but is presumably this: ABC News: Even as Lion Air jet's black box is found, some answers may be back in the United States) that the flight could have been sending loads of FDR-type data that would be helpful to investigators via satcom in real time is almost certainly a red herring.
Incidentally, that incident you posted about with the failure to fully reconnect pitot feed in the radome, did the UAS manifest only beyond certain altitude or pitch levels? [I think some on this thread are discounting pitot failure because it would/should have been picked up on takeoff roll]. |
This is not in response to our (not so) Mad Flt Scientist's post, but intended to augment post #368
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Originally Posted by unworry
(Post 10298669)
A former colleague suggested this evening that a large piece of rudder or stabilizer were found early on in the search and reasonably intact ... some distance from the now main site of the fuselage wreckage.
Can anyone confirm this was the case or care to speculate whether a failure in the empennage could explain the profile suggested by the ADS-B data. Honestly wondering ... XL888 vertical stabilizer was found intact, and floating, as was AF447. In the 447 case we had a few years of speculation on here about attachment failure (cf. AA587) before the black boxes confirmed it was an intact impact. |
Originally Posted by infrequentflyer789
(Post 10299050)
Incidentally, that incident you posted about with the failure to fully reconnect pitot feed in the radome, did the UAS manifest only beyond certain altitude or pitch levels? [I think some on this thread are discounting pitot failure because it would/should have been picked up on takeoff roll].
But if yours is: RELATÓRIO FINAL IG - 014/CENIPA/2013 |
Originally Posted by Airbubba
(Post 10298994)
Here's a Reuters report about the earlier flight where a Pan was declared after which the plane proceeded to its destination of Jakarta.
"The captain himself was confident enough to fly to Jakarta from Denpasar," said Herson, who goes by one name, speaking by phone from Bali and referring to the resort island's airport. The pilot of another plane that was approaching Bali just after the Lion Air jet had taken off said he was ordered to circle above the airport and listened in to a radio conversation between the Lion Air pilot and air traffic controllers. "Because of the Pan-Pan call, we were told to hold off, circling the airport in the air," said the pilot, who declined to be named because he was not authorized to speak to the media. "The Lion plane requested to return back to Bali five minutes after take-off, but then the pilot said the problem had been resolved and he was going to go ahead to Jakarta." Pilots use 'Pan-Pan' calls to flag urgent situations. They are a step down from 'Mayday', which signals severe distress. The Denpasar-Jakarta flight landed at the Indonesian capital's airport at 10:55 p.m. local time on Sunday. |
Originally Posted by Rananim
(Post 10298955)
What can we reasonably infer from the write up?a)That the UAS was not detectable on the takeoff roll(otherwise they would have aborted).
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Originally Posted by Bleve
(Post 10299139)
Unfortunately you can’t make that assumption - humans sometimes don’t act reasonably. In the recent Malaysian Airlines incident at Brisbane (pitot covers left on), both pilots observed red speed flags on their PFDs during the takeoff roll (didn’t say or do anything), the CPT (PM) called the 100 knot airspeed check based upon ground speed and they got airborne with no valid airspeed indications. One of the driving forces for the creation of CRM and the timely destruction of the fallacy that the "Skipper's always right. Period." mentality. |
Apparently, we're not the only ones trying to figure out if its the FDR or CVR - just heard on Radio NZ that "the authorities now say they are not sure if its the the CVR or FDR"
On another note, I was surprised to see the FRD/CVR being handled by Chief of the National SAR Agency. I thought these things needed to sit in water (if recovered from undersea) and be carefully delivered to experts who painstakingly ensure a careful process is followed, not being waved around and brandished with bare hands in the dry in a manner that could see it in any way compromised/dropped/shaken etc. Just classic grandstanding or am I missing something? |
Originally Posted by rh2600
(Post 10299160)
Apparently, we're not the only ones trying to figure out if its the FDR or CVR - just heard on Radio NZ that "the authorities now say they are not sure if its the the CVR or FDR"
On another note, I was surprised to see the FDR/CVR being handled by Chief of the National SAR Agency. I thought these things needed to sit in water (if recovered from undersea) and be carefully delivered to experts who painstakingly ensure a careful process is followed, not being waved around and brandished with bare hands in the dry in a manner that could see it in any way compromised/dropped/shaken etc. Just classic grandstanding or am I missing something? |
Originally Posted by DaveReidUK
(Post 10299170)
I think the procedure for retrieving data from a recorder that's had a swim in the sea is pretty well practised by now, as we saw with the recent Air Niugini B738, whose recorder was flown 1200 miles to Port Moresby before the memory modules were carefully removed and decontaminated.
DaveReidUK is right. These days are not like the old days - FDR/CVR is written to solid state memory modules and doesn't necessarily need to be 'transitioned' from retrieval depth to surface depth. In all honesty, these days, it feels more like the most protection that FDR/CVR Modules need when recovered is to keep them safe from "those that might seek to do them harm" before data can be retrieved and analysed. A sad state of affairs. |
As a non-pilot, the STS seems very important to me and also - a bit scary?
Is it possible that the STS, given an (incorrect, too-slow) air-speed, after the AP was disengaged (perhaps because AC noticed the conflicting AIS and is following the QRH)....might then trim nose-down to compensate for the erroneous low airspeed? It does seem from the info thus far that there was a fairly abrupt nose-down shortly after TO? If so that must be stressful for AC...? Can STS be disengaged just like AP or AT? Just wondering how much the pilots might have had to work against STS. Thanks for such an informative forum. |
That thing will get into it's protective box AFTER EVERYBODY with a rank higher then "mother in law" has been photographed with it.
In that area promotion pictures are more important then finding out the truth. |
Originally Posted by CaptainSandL
(Post 10298627)
From the MAX FCOM 9.20.8:
Speed Trim System The Speed Trim System (STS) is a speed stability augmentation system designed to improve flight characteristics during operations with a low gross weight, aft center of gravity and high thrust when the autopilot is not engaged. The purpose of the STS is to return the airplane to a trimmed speed by commanding the stabilizer in a direction opposite the speed change. The STS monitors inputs of stabilizer position, thrust lever position, airspeed and vertical speed and then trims the stabilizer using the autopilot stabilizer trim. As the airplane speed increases or decreases from the trimmed speed, the stabilizer is commanded in the direction to return the airplane to the trimmed speed. This increases control column forces to force the airplane to return to the trimmed speed. As the airplane returns to the trimmed speed, the STS commanded stabilizer movement is removed. STS operates most frequently during takeoff, climb and go-around. Conditions for speed trim operation are listed below: • STS Mach gain is fully enabled between 100 KIAS and Mach 0.60 with a fadeout to zero by Mach 0.68 • 10 seconds after takeoff • 5 seconds following release of trim switches • Autopilot not engaged |
Originally Posted by bobdxb
(Post 10299081)
Pilot using PAN PAN call and then downgrading to all clear should have reported incident to the Company using Safety Report Form (my ex-company SOP required also tech log note of raised Safety Report in order to alert next crew about it), it could have saved lives of 189 ppl...
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Originally Posted by Smott999
(Post 10299244)
Is it possible that the STS, given an (incorrect, too-slow) air-speed, after the AP was disengaged (perhaps because AC noticed the conflicting AIS and is following the QRH)....might then trim nose-down to compensate for the erroneous low airspeed? It does seem from the info thus far that there was a fairly abrupt nose-down shortly after TO? If so that must be stressful for AC...? Can STS be disengaged just like AP or AT? Just wondering how much the pilots might have had to work against STS. Thanks for such an informative forum. |
Trim Wheel
Can’t you just grab the trim wheel and immobilize it if necessary? Seems to me that was the case in Mr Boeing’s KC-135. |
"I also am concerned that STS as an automated system that uses airspeed as an input could work against the pilot. I note in the training video above the trim wheel merrily spinning back and forth uncommanded after AP and AT disengaged. Can STS be disabled? should it be? for uas_""
Can be disabled immediately by a quick blip on the pitch trim. Can’t you just grab the trim wheel and immobilize it if necessary?" No, it is very powerful" Regards Exeng |
Originally Posted by TangoAlphad
(Post 10296243)
Modern Jet pilots are more and more reliant on what is inside. I often see 'visual approaches' almost entirely flown head inside following the ILS indications. It is sad (and deeply concerning) but I can honestly imagine a pilot on a cavok day trying to cross compare and make sense of instrumentation and ignoring what is outside entirely.
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Salute!
Guess we are heading toward a sub-thread about the "STS" and all the concerns about how much automation you can handle and how to revert to manual flying unless in an Airbus. And then there's all the "sub-modes", the reversion sequences, what is working versus what is not, and so forth. The Boeing is not an Airbus with 100% fly by wire. But it appears that a few systems have "help" from HAL.. And the STS is one Looks like the STS implementation feeds back to the controls to provide some kinda force feedback. Wonderful. But if that system is corrupted, then you might feel something the opposite of what the aero conditions are normally telling you. For now, I am sticking with a combo of erroneous air data and a mechanical problem with the stab. Gums opines... |
Originally Posted by Mad Flt Scientist
So a design solution applied is to have an automatic system act to increase the required force - to introduce a degree of "artificial stability" in effect. One way to do this is to have the aircraft automatically "trim the wrong way". that way, when hand flying (and not trimming) you find you have to pull more to slow down (part of the pull is the natural pull the aircraft requires, part is to fight the opposite auto-trim), and similarly push more to accelerate.
Unfortunately these systems are often called things like "auto trim" or have "trim" in their name, and that leads people to sometimes think that their intention is to HELP the pilot trim the a/c, whereas they are designed to do the exact opposite. |
It is interesting to consider that a contributing factor to this accident may have been the Boeing (vs Airbus) approach to introducing automation into the cockpit. Both the STS and elevator feel systems are provided to make the retained Boeing yoke feel (in some flight modes) as if you are flying a simple manual and longitudinally stable aircraft, with assigned stick force per G, and apparent aerodynamic feedback through the controls.
It seems questionable to me if these systems are coded to continue at all in the UAS condition, as they will substantially increase workload and the chance of catastrophic upset if they are being fed with bad airspeed data. The elevator feel system (which just applies force at the yoke) will be quite unhelpful, but the STS is worse as it is physically altering the horiz stab incidence. It doesn't seem hard to imagine that although most experienced but automation-centric crews will not be overwhelmed dealing with the UAS with these additional challenges (as appeared to occur in the flight before the accident), some may leading to catastrophic upset (possible explanation for this flight). |
Is it possible that the STS, given an (incorrect, too-slow) air-speed, after the AP was disengaged (perhaps because AC noticed the conflicting AIS and is following the QRH)....might then trim nose-down to compensate for the erroneous low airspeed? It does seem from the info thus far that there was a fairly abrupt nose-down shortly after TO? If so that must be stressful for AC...? Can STS be disengaged just like AP or AT? Just wondering how much the pilots might have had to work against STS Well,youre into engineering territory but from a pilots perspective....yes,STS(manual flight) just like AP stabilizer trim(automation engaged) would exacerbate an already bad UAS event.FCC controls both STS and AP stab trim and it gets CAS,AoA,IVSI from ADIRU as well as engine N1 from DEU and flap position from FSEU.If speed sensed is low it commands trim down providing certain parameters are met:a)airborne more than 10 seconds b)AP not engaged c)can not oppose pilot commands(ie if the pilot is pulling on the column it wont trim down) d)pilot hasnt operated electrical main trim in the last 5 seconds etc etc If the ADIRU input of CAS to the FCC is corrupted,you will get the "wrong" trim.This explains the write up of the previous flights commander who reported STS trimming the "wrong way".So if the CAS sensed is low(ASI is under-reading in a climb due static vent blocked) then it will trim down.In reality the speed/AoA is not low at all so the trim is opposite of what is required.Every time the pilot pulls on the column to counteract the unwanted trim the STS cuts out but it will trim again if back pressure is released.This would explain the rollercoaster effect.Similarly,if you are climbing in icing conditions with automation engaged and the pitots ice up,the AP stabilizer will start to trim up to counteract the sensed CAS (ASI overreads in a climb with blocked pitot).If it goes unnoticed by the pilots,it could be very dangerous. To disable STS you would place the AP stab trim cutout switch to CUTOUT.This is not mentioned in any NNC or FCOM. The commander of the previous flight got the plane back safely at FL280(non RVSM).Maybe this is because they disabled AP stab trim during trouble-shooting and were naturally reluctant to reinstate it .He may have got the FO to hand fly home below RVSM airspace with AP stab trim in cutout I dont know. Only one FCC sends the STS signal.On power up it is FCC A .If power remains to the FCCs during turnaround,the squat switch will send a signal to change it to FCC B for next flight.If power is interrupted during turnaround,FCC A will command the STS signal for the next flight too. |
Originally Posted by Machinbird
(Post 10299301)
Can’t you just grab the trim wheel and immobilize it if necessary? Seems to me that was the case in Mr Boeing’s KC-135. |
Good points Rananim. The one issue I see here is with your more complex airspeed unreliable scenario with STS trim involvement is that you need to recognise that there is a linkage between the two, and then do the "Runaway Stabilizer Trim" memory items in addition (should have already covered the initial items in the Airspeed Unreliable initial memory items, Autopilot Off, Autothrottle Off),then Stab Trim Cutout switches (both) cutout, and you are back to a "plain vanilla" (not to diminish the degree of difficulty) airspeed unreliable.
Similar to the windshear escape, it helps to "blip" the trim every couple of seconds so you aren't wrestling the trim during the escape. |
Originally Posted by rh2600
(Post 10299160)
Apparently, we're not the only ones trying to figure out if its the FDR or CVR - just heard on Radio NZ that "the authorities now say they are not sure if its the the CVR or FDR"
|
Originally Posted by bobdxb
(Post 10299399)
On this video they show recovery of the MU, however I wonder what was in hand of 1st diver? Maybe someone could translate what they are talking about in local language...
get (the basket) close (next to the divers) dont throw (that thing) (after the black box slipped in) it’s quite heavy, let the water spoil a little bit be careful , don’t fall (someone fell to the sea to push the basket from bottom) step aside (Please) make a report |
Originally Posted by bobdxb
(Post 10299399)
On this video they show recovery of the MU, however I wonder what was in hand of 1st diver? Maybe someone could translate what they are talking about in local language...
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My God, what a nonsense (unless it was meant as a joke) |
Originally Posted by bobdxb
(Post 10299399)
On this video they show recovery of the MU, however I wonder what was in hand of 1st diver? Maybe someone could translate what they are talking about in local language...
Basically - we found this black box, I think it's important, be careful with it, we should report this right away... Like I said, nothing special... |
Aviation Herald Report
On Nov 1st 2018 the airline confirmed one of their maintenance engineers was on board of the aircraft during the accident flight. This was an "anticipatory measure" in the event of technical problems with the new aircraft. As such, "the presence of the technician has nothing to do with the condition of the aircraft before taking off."
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Originally Posted by sSquares
(Post 10299486)
On Nov 1st 2018 the airline confirmed one of their maintenance engineers was on board of the aircraft during the accident flight. This was an "anticipatory measure" in the event of technical problems with the new aircraft. As such, "the presence of the technician has nothing to do with the condition of the aircraft before taking off."
Yes, it's not unknown for airlines to carry a flying spanner on a route where there's no engineering support at the far end, but on a route that has 6 daily rotations it's hard to believe that's the reason either.. |
FDR or CVR?
Should be no problem to id the recovered item. The attached cylindrical item (that looks like a grab handle) is the Underwater Locator Device. (Pinger).
It has a unique serial number and expiry date. The aircraft's delivery docs will show which unit had that ULD attached at Boeing prior to delivery. |
Originally Posted by tdracer
(Post 10299464)
According to my Indonesian wife, it's not very interesting.
Basically - we found this black box, I think it's important, be careful with it, we should report this right away... Like I said, nothing special... Head of Marine Technology and Survey Center for Technology Application Assessment Agency (BPPT) M Ilyas is optimistic the team will find CVR. He estimates that the distance between the FDR and CVR is not far from the sea. "It is approximately 200-300 meters, not too far from (CVR)," he said at the Jakarta International Container Terminal II Basarnas Post , Tanjung Priok, North Jakarta, Thursday (1/11). Ilyas said, in fact we ship BPPT to have captured two ping locater signals from FDR and CVR. However, BPPT ships must move locations because many scattered fragments are captured by ship sonar scans. So you have to sail to the rubble which is suspected to have CVR instructions. Pertamina's pipes and strong currents under the sea are also obstacles. So, said Ilyas, the team had difficulty removing the anchor and could not reduce the Remote Operated Vehicle (ROV) or underwater robot technology to look for objects. "The obstacle is that there is a Pertamina pipeline. So that we cannot anchor our ships there to do more detailed ROV. We have to be outside about 550 meters from that location to carry out this ROV operation with the difficulty of the current being very strong there , "he said. He said, the CVR could last for 30 days starting from the plane falling. The signals sent by FDR and CVR are also very strong, because Lion Air PK-LQP is a new aircraft. "So the shipment is fast, ping ping is like that. So it is heard (ear) it is a bit different from the other signals. Just because there are many dives today, many ships operate so we have a lot of errors, lots of noise" he explained |
Tempo(dot)Co report on ATC Transcirpt
Stated in the report that the transcript was not verified. Some correlation to previous theories posted here.
Lion Air pilot Bhavye Suneja asked his airspeed to the ATC after experiencing a technical issue less than two minutes after take-off at 06:21.53. The pilot’s request to change altitude to 5,000 feet was approved by ATC and was requested to maintain altitude at 06:24.58. During this exchange, Bhavye asked the ATC to confirm the plane’s airspeed to which the ATC answered 332 knots. at 06:29 the ATC saw Lion Air JT 610 left 5,000 feet followed by the Bhavye communicating to the ATC upon a problem with the plane’s flight control and asked for his plane to be given 3,000 feet separation with other aircraft in his airspace. at 06:32, ATC asked the pilot whether Bhavye was ready to land again at Soekarno-Hatta, but the pilot did not answer and seconds after, Lion Air flight JT 610 vanished from the ATC’s radar. flight data recorder (FDR) from the plane’s wreckage submerged under the seabed just 500 meters from its last contact with ATC. Suggested UAS followed by flight control problem. |
CVR
"He said, the CVR could last for 30 days starting from the plane falling. The signals sent by FDR and CVR are also very strong, because Lion Air PK-LQP is a new aircraft."
Just small correction, the CVR and the FDR underwater locator beacons could last for 90 days starting from the plane falling. |
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