Indonesian aircraft missing off Jakarta
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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.
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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.
Thanks, that makes sense. But it doesn't rule out an intermittent pitot leak (cf GOL) scenario either.
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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].
Psychophysiological entity
This is not in response to our (not so) Mad Flt Scientist's post, but intended to augment post #368
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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 ...
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.
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
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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.
"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.
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.
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.
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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?
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?
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?
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.
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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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.
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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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.
In that area promotion pictures are more important then finding out the truth.
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
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
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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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.
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.