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Indonesian aircraft missing off Jakarta

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Indonesian aircraft missing off Jakarta

Old 1st Nov 2018, 16:36
  #401 (permalink)  
 
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Originally Posted by Airbubba View Post
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?
CWS is still there on the NG, but have never seen anyone use it, in decades of flying. Most absurd system ever invented.

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
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Old 1st Nov 2018, 16:45
  #402 (permalink)  
 
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Originally Posted by silverstrata View Post
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.
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Old 1st Nov 2018, 16:50
  #403 (permalink)  
 
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Originally Posted by Toruk Macto View Post
Classic third world response..... ,
Matched only by such a third rate invective!
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Old 1st Nov 2018, 16:58
  #404 (permalink)  
 
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Originally Posted by EDLB View Post
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.
Thanks, that makes sense. But it doesn't rule out an intermittent pitot leak (cf GOL) scenario either.
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Old 1st Nov 2018, 17:12
  #405 (permalink)  
 
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Originally Posted by Mad (Flt) Scientist View Post
Not that absurd. (And not unique to B737 either...).
I remember it on A300/A310 as well, but never touched it in 20 years of my flt times We use to say "fly manually with a/p engaged"
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Old 1st Nov 2018, 17:30
  #406 (permalink)  
 
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Originally Posted by DaveReidUK View Post
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.
Almost certainly, but what might be very interesting and useful is if that system's data was copied off the previous night and has the info from the previous days flight. Data isn't a lot of use if it is never analysed so logically it must get taken off the onboard server sometime...

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].
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Old 1st Nov 2018, 17:38
  #407 (permalink)  
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This is not in response to our (not so) Mad Flt Scientist's post, but intended to augment post #368

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Old 1st Nov 2018, 17:44
  #408 (permalink)  
 
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Originally Posted by unworry View Post
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 ...
Problem is that finding the vertical stabilizer intact and separate from the rest of the wreckage is not an indication of pre-impact separation - they are pretty strong, in a relatively protected position in most impacts, and tend to come off in one piece.

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.
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Old 1st Nov 2018, 17:46
  #409 (permalink)  
 
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Originally Posted by infrequentflyer789 View Post
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].
I don't know - my Portuguese isn't good enough to do a verbatim translation of the report.

But if yours is: RELAT”RIO FINAL IG - 014/CENIPA/2013
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Old 1st Nov 2018, 17:58
  #410 (permalink)  
 
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Originally Posted by Airbubba View Post
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.
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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Old 1st Nov 2018, 19:18
  #411 (permalink)  
 
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Originally Posted by Rananim View Post
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).
Unfortunately you canít make that assumption - humans sometimes donít 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 (didnít 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.
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Old 1st Nov 2018, 19:36
  #412 (permalink)  
 
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Originally Posted by Bleve View Post


Unfortunately you canít make that assumption - humans sometimes donít 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 (didnít 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.
Indeed you can't and you mustn't, especially in the right seat; see https://en.wikipedia.org/wiki/Birgenair_Flight_301

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.
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Old 1st Nov 2018, 19:43
  #413 (permalink)  
 
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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?
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Old 1st Nov 2018, 19:53
  #414 (permalink)  
 
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Originally Posted by rh2600 View Post
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?
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.
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Old 1st Nov 2018, 20:05
  #415 (permalink)  
 
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Originally Posted by DaveReidUK View Post
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.
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Old 1st Nov 2018, 21:27
  #416 (permalink)  
 
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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.
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Old 1st Nov 2018, 21:40
  #417 (permalink)  
 
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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.
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Old 1st Nov 2018, 22:05
  #418 (permalink)  
 
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Originally Posted by CaptainSandL View Post
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:
ē STS Mach gain is fully enabled between 100 KIAS and Mach 0.60 with a fadeout to zero by Mach 0.68
ē 10 seconds after takeoff
ē 5 seconds following release of trim switches
ē Autopilot not engaged
Thanks for that, CaptainSandL. I note that Boeing seem to have extended the operating airspeed range for the STS for the MAX; on the NGs the operating range was 100 Ė 300 KIAS.
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Old 1st Nov 2018, 22:11
  #419 (permalink)  
 
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Originally Posted by bobdxb View Post
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...
Has there been any confirmation on exactly which call JT610 made - MAYDAY or PAN? Or neither? In the Australian press one expert commentator is suggesting that a MAYDAY call for a UAS was a sure sign that the crew panicked. I've yet to see a confirmation that JT610 actually declared a MAYDAY.
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Old 1st Nov 2018, 22:33
  #420 (permalink)  
 
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Originally Posted by Smott999 View Post
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.
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_
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