737-500 missing in Indonesia
Here's a better plot with infrared satellite overlay. While they almost certainly were in IMC when the problem occurred, it doesn't look like they came close to significant CBs.
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My dad is an LAE. From the flight pattern recorded, he suspect that the check valve is corroded. Due to the fact that most of the aircraft are grounded due to COVID-19, virtually no maintenance was done on them to save cost.
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Regardless of what has happened here, one thing is for sure. There will be many rusty pilots, engineers and aircraft flying around soon if the world ever gets back to normal flying. And in a lean financial market. Be prepared for a few incidents.
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katekebo
Far from me to give any conclusion but: this is rainy season and also season of mud dauber wasps which are active in Indonesia. I have been working in JKT for some years. There are airlines who never put pitot probes covers for night stops.
And some parking stations are close to ditches where wasps can collect mud.
I have pictures of aircraft's fuselage fully covered by mud dauber wasps (not a sriwijaya aircraft), taken some years ago. Not only maintenance staff is not trained to recognize them and possible consequences but also they do not take any action for inspection - at least - when there is presence of mud dauber wasps in vicinity of an aircraft not having been protected.
All my attempts to convince maintenance staff installing pitot probes covers were useless, even after I contacted safety Dept. (not sriwijaya, again)
Once again, this is a general situation, I do not blame particularly Sriwijaya and do not say that this is what happened.
On top of it, an obstructed pitot (obstructed by wasp's nest) should be at least detected by the crew during take off run when comparing speed between CAPT and FO, unless both of them are obstructed.
Obstructed Pitot by wasp's nest is not necessarily something you can notice from the ground during the turn around of the aircraft.
Far from me to give any conclusion but: this is rainy season and also season of mud dauber wasps which are active in Indonesia. I have been working in JKT for some years. There are airlines who never put pitot probes covers for night stops.
And some parking stations are close to ditches where wasps can collect mud.
I have pictures of aircraft's fuselage fully covered by mud dauber wasps (not a sriwijaya aircraft), taken some years ago. Not only maintenance staff is not trained to recognize them and possible consequences but also they do not take any action for inspection - at least - when there is presence of mud dauber wasps in vicinity of an aircraft not having been protected.
All my attempts to convince maintenance staff installing pitot probes covers were useless, even after I contacted safety Dept. (not sriwijaya, again)
Once again, this is a general situation, I do not blame particularly Sriwijaya and do not say that this is what happened.
On top of it, an obstructed pitot (obstructed by wasp's nest) should be at least detected by the crew during take off run when comparing speed between CAPT and FO, unless both of them are obstructed.
Obstructed Pitot by wasp's nest is not necessarily something you can notice from the ground during the turn around of the aircraft.
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My bet is on a ripped off vertical tail due to gusts / fatigue / rudder movement, as descending and decellerating like that indicates a very high drag (parachute like) configuration. Check AA 587. Maybe I'll try to calculate later what the drag coefficient must have been...
THUNDERTAILED
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Flexible response, no, groundspeed on FR24 doesn't depend on the actual aircraft's pitot static system. Groundspeed is groundspeed, not airspeed anyway.
For the PP's on here, how does this accident profile fit a deployed reverser in flight?
For the PP's on here, how does this accident profile fit a deployed reverser in flight?
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Last edited by WatchTheSkies; 10th Jan 2021 at 12:02.
Let’s face it, being in Indonesia it could be anything, maintenance, training, pilot error are all strong trends in previous accidents. We won’t know until the investigation is done so let’s wait for that.
waito
Nicely graphed, though the rounded time values on the X-axis are a bit irregular.
At the risk of stating the obvious, while the ROD (fpm) remained more-or-less constant during the descent, the flight path angle wrt the ground must have become shallower towards the end of the dive (i.e. the aircraft was beginning to pull out), since FPA is simply the resultant of horizontal and vertical velocity.
For example:
At 4000' (07:40:22) V/S 40,000 fpm (395 kts); GS 120 kts -> FPA -73°
At 2000' (07:40:25) V/S 40,000 fpm (395 kts); GS 210 kts -> FPA -62°
All values approximate, but the difference is marked enough to accommodate any slight variation.
Nicely graphed, though the rounded time values on the X-axis are a bit irregular.
At the risk of stating the obvious, while the ROD (fpm) remained more-or-less constant during the descent, the flight path angle wrt the ground must have become shallower towards the end of the dive (i.e. the aircraft was beginning to pull out), since FPA is simply the resultant of horizontal and vertical velocity.
For example:
At 4000' (07:40:22) V/S 40,000 fpm (395 kts); GS 120 kts -> FPA -73°
At 2000' (07:40:25) V/S 40,000 fpm (395 kts); GS 210 kts -> FPA -62°
All values approximate, but the difference is marked enough to accommodate any slight variation.
Last edited by DaveReidUK; 11th Jan 2021 at 06:24. Reason: calculator right way up now :-)
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The captain's wife was interviewed by the news website and said that he unusually apologized to her and their children. Coincidence or something siginficant related to the accident?
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Yes, but the 737 also had at least one high-speed rudder hard-over event in the cruise.
Due to their speed this crew were able to recover, but it was a major event that nearly turned them upside-down. But if the crew were less able, or disorientated due IMC, or if there was an airframe failure due to these stresses, then a high-speed rudder hard-over could result in a plunge into the ocean.
Indonesia locates black boxes after deadly plane crashIndonesia locates black boxes after deadly plane crash (bangkokpost.com)
"We have located the position of the black boxes, both of them," said Soerjanto Tjahjanto, head of Indonesia's transport safety agency.
"Divers will start looking for them now and hopefully it won't be long before we get them." A military vessel picked up the plane's signal, and divers recovered wreckage from around 23 metres below the water's surface, the transport ministry said Sunday, citing Indonesia's military chief Hadi Tjahjanto.
It did not specify if the signal was from the downed plane's voice and flight data recorder.
"We have located the position of the black boxes, both of them," said Soerjanto Tjahjanto, head of Indonesia's transport safety agency.
"Divers will start looking for them now and hopefully it won't be long before we get them." A military vessel picked up the plane's signal, and divers recovered wreckage from around 23 metres below the water's surface, the transport ministry said Sunday, citing Indonesia's military chief Hadi Tjahjanto.
It did not specify if the signal was from the downed plane's voice and flight data recorder.
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I have a genuine question about pitch control on 737s, maybe you would know?
The original 60s version had the low, thin, P&W engines.
The MAX has these large, forward CFM motors. These cause pitch-up under thrust and so necessitated the introduction of MCAS to fix it.
This model is the 2nd gen 500 from the 1980s, so it's too early for MCAS, I understand.
However, the 500 does have rather large CFM motors. It looks a lot like the MAX. So, presumably, it also had the pitch-up issue (though perhaps to a lesser extent than the MAX).
If so, my question is, what was done in the late 80s to mitigate the pitch-up tendency on the 500 series when it rolled out?
The original 60s version had the low, thin, P&W engines.
The MAX has these large, forward CFM motors. These cause pitch-up under thrust and so necessitated the introduction of MCAS to fix it.
This model is the 2nd gen 500 from the 1980s, so it's too early for MCAS, I understand.
However, the 500 does have rather large CFM motors. It looks a lot like the MAX. So, presumably, it also had the pitch-up issue (though perhaps to a lesser extent than the MAX).
If so, my question is, what was done in the late 80s to mitigate the pitch-up tendency on the 500 series when it rolled out?
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Unlikely
procede
the 500 has the shortest body, it’s tough as old boots, highly unlikely, the short body with the highest thrust engine options does make it a little more demanding engine out, but only at LOW SPEED at altitude this wouldn’t be an issue, this appears to be very rapid loss of control.
with regards to so called explosions reported by fishermen, could be thunder or sonic boom if it went down under power ballistically.
Only 15m of water so the front will be buried in the mud FDR should be on top
the 500 has the shortest body, it’s tough as old boots, highly unlikely, the short body with the highest thrust engine options does make it a little more demanding engine out, but only at LOW SPEED at altitude this wouldn’t be an issue, this appears to be very rapid loss of control.
with regards to so called explosions reported by fishermen, could be thunder or sonic boom if it went down under power ballistically.
Only 15m of water so the front will be buried in the mud FDR should be on top
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The dauber wasp theory is unlikely as the aircraft was on a 1:30hr turnround prior to the accident flight.
A downdraft of the magnitude required to get the vertical speeds recorded from the FR24 data is most unlikely as how would they dissipate before the surface. The fishermen nearby didn’t report hurricane force winds.
EIFFS mentions fishermen hearing ‘explosions’ that he purports may have been a sonic boom. After COPA 201 had a loss of control due to VG failure at FL250, it exceeded the speed of sound before breaking up at FL100. With the Vertical speed assumed from the FR24 data and the ground speed also recorded from the same source at the later stages of the dive, it can’t have been far off.
A downdraft of the magnitude required to get the vertical speeds recorded from the FR24 data is most unlikely as how would they dissipate before the surface. The fishermen nearby didn’t report hurricane force winds.
EIFFS mentions fishermen hearing ‘explosions’ that he purports may have been a sonic boom. After COPA 201 had a loss of control due to VG failure at FL250, it exceeded the speed of sound before breaking up at FL100. With the Vertical speed assumed from the FR24 data and the ground speed also recorded from the same source at the later stages of the dive, it can’t have been far off.
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042 to 030 in 6s = -2°/s
030 to 023 in 3s = -3.5°/s
023 to 006 in 3s = approx -6°/s ( approx -60ft/s)
006 to 339 in 6s = approx -5°/s ( approx -296ft/s)
339 to 338 in 2s = -0.5 °/s ( approx -413ft/s)
338 to 011 in 4s = approx +8°/s ( approx -681ft/s)
011 to 093 in 7s = approx +12°/s ( approx -736ft/s)
( when upright, heading reducing means left turn. Increasing means a right turn. Opposite direction when inverted, of course)
Initially there was a left yaw for 9 sec that became a nose dive. From the data you can see, when the aircraft pitched down, there was a huge forward acceleration vector which temporarily reduced the yaw vectors effect on the heading change. But as drag increases exponentially with velocity, the yaw vector caught up and increased the heading change again. The increase in lateral speed and direction of heading change is IMO best explained by the aircraft going inverted and the nose moving upwards relative to the horizon due to the exponentially increasing drag from the left engine
Last edited by WatchTheSkies; 10th Jan 2021 at 12:16.