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737-500 missing in Indonesia

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737-500 missing in Indonesia

Old 10th Jan 2021, 22:20
  #141 (permalink)  
 
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I know several have tried to make sense of the FR24 Speed and Altitude recording during the descent. However if you look carefully at the precceding information it is gives a better clue as to what has happened.

Before timestamp 7:39:28 both the altitude and speed were increasing, i.e both Kinetic and Potential Energy were increasing normally, as they passed 10,000ft.
After this the speed remains constant at 270 knots, maybe because of autopilot speed hold. During this period of constant speed the energy increased by 33ft/s x 100,000lbs auw. i.e = 3300,000 ft.lb/s , which divided by 550 give a horsepower equivalent to 6000 hp.

Then at 7:40:05 the climb stops and the airplane starts to descend, it looses any further energy input from the engines.
Then at 7:40:09 (4 seconds later.) the speed also starts to vary. The data beyond this point is meaningless as we don't know the pitch angle of the aircraft.

So it looks as if either one or more engines suffered a catastrophic failure, as the +ve energy input stops abruptly at that 7:40:05.

Last edited by phiggsbroadband; 10th Jan 2021 at 23:36.
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Old 10th Jan 2021, 22:37
  #142 (permalink)  
 
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Disgraceful

As is so often the case, a myriad of MS flight sim warriors and PPLs pontificate to aggrandise themselves. They use professional jargon they have googled and then extemporise at length. Some worse than others. They even squabble over semantics. FFS! A lot of people have died here and the men in the front watched it all unfurling. What that must have felt like is beyond understanding. For pities sake, leave it alone. There are a few that clearly work in this business, as do I but most of you equally clearly donít. You are disgraceful
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Old 10th Jan 2021, 22:45
  #143 (permalink)  
 
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Where does this conical piece belong?
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Old 10th Jan 2021, 22:49
  #144 (permalink)  
 
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Looks like the trailing cone of a flap track fairing...
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Old 10th Jan 2021, 22:57
  #145 (permalink)  
 
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Thank you. Then what is this cone which looks much smaller?
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Old 10th Jan 2021, 23:00
  #146 (permalink)  
 
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DaveReidUK

Missed this earlier. There’s an error in your second calculation; according to the velocity numbers given the FPA at 2000’ is -62į, which would explain why the V/S does not change significantly.

(For interest, the number you calculated would have correlated to a 5G pull during those 3 seconds, which if continued might have had them on track to escape, just... it would certainly have shown up on the V/S plot).

Last edited by Easy Street; 10th Jan 2021 at 23:20.
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Old 10th Jan 2021, 23:02
  #147 (permalink)  
 
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Originally Posted by Buswinker View Post
Question, I read the flight was scheduled to be operated by an -800 and the -500 was a last minute swap in. Would the same crew operate both? Are there significant enough differences between the two for that to cause issues?
The short answer is yes. Itís certainly legal in many countries, and is common practice at numerous airlines. How easy it is to do depends on a number of factors. Experience and recency being the main ones. The other being the cockpit setup. ie. some glass or old school analogue instrumentation.

If youíve been flying an NG predominantly, and have little recency and/or experience in a Classic 737 (300/500). It can be a bit of a shock to the system for the first hour. Itís completely dependent on the crew.

Regarding the cockpit differences. Imagine expecting this -




and instead, find this at the gate -




Iím sure some will disagree with regard to the differences, and their significance.

One other point about this tragic accident - the altitude it began at. One wonders if a pressurisation event occurred ? Either mechanical or self inflicted. Unfamiliar cockpit, distraction, weather in the area. Swiss cheese model perhaps ? Or itís irrelevant.
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Old 10th Jan 2021, 23:06
  #148 (permalink)  
 
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I see all the data here on speed, time, altitude, plotted as nice precise points, but I don't see anything on measurement error.

Time - I'm assuming no measurement error (or perhaps a few ms at most)
Speed - what's a reasonable error bar here? What factors would increase that error bar?
Altitude - what's a reasonable error bar here? What factors would increase that error bar?
Location - I'm assuming this is GPS, so with a few feet. Fair?
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Old 10th Jan 2021, 23:18
  #149 (permalink)  
 
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brika

The second photo definitely shows a flap track fairing cone (two on each wing, not identical but roughly similar), but the first one does not look right. For one, there is no black ring visible on the fairing cones on any recent photo of PK-CLC, and it appears to be the wrong shape (but this could just be the photo angle). I cannot readily match it to any other part of a 737.

EDIT: as others correctly pointed out below, both are flap fairing cones, the dark band is merely a strap around the first one, second photo is very clear. Good lesson in not jumping to conclusions.

Last edited by andrasz; 11th Jan 2021 at 09:15.
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Old 10th Jan 2021, 23:40
  #150 (permalink)  
 
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I don't understand why I see people persist in stating there is a problem with Boeing's having engines mounted below the wings being different in creating a pitch up vs a similar Airbus. Newtonian physics has not changed. An engine providing thrust below the CG is going to produce pitch up. Sum of the forces around the centroid creates a moment. To create stability it must be countered by another force, in this case the horizontal stabilizer pitch down. Classic example is the DC-10 and Bryce McCormick realizing the engineering of the engine placement gave him ability to control his plane when the cargo door blew off, the floor collapsed. Mr McCormick could pitch up by increasing thrust on the wing engines, pitch down using the high mounted tail engine. Mr McCormick save a plane, crew and passengers using his time evaluating how he could use thrust vectors to his benefit. On PPRuNe is still read of pitch up being a 737 problem first instituted when the CFM56 was introduced. Got news for you. The JT8D had a pitch up vector although not s large. Installation of the CMF56 introduced a pitch up similar to that of the A320 - lay a profile of the planes against each other. The implementation of the LEAP modified how the pitch up changed with the design of the nacelle and MCAS was implemented to in theory, make it handle like the Classic and NG. If you want something better - the Comet had engines in the wing but they were still slightly below the CG - but define the CG. CG with full fuel, full cargo, full passengers? That's why you have trim. Both Boeing and Airbus have had pitch up events that resulted in crashes. How it can be blamed here with no evidence is beyond human understanding. Even thought my degree was mechanical engineering and my studies were in the time when the B-707 and DC-8 were in their prime, I still remember a lab in which we verified the technology.
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Old 11th Jan 2021, 00:02
  #151 (permalink)  
 
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NWA SLF

My understanding is that the critical difference is that with the A320 (and the 777 and I assume the 787) there is no 737-style pitch up because the fly-by-wire automatically compensates for it.
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Old 11th Jan 2021, 00:07
  #152 (permalink)  
 
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The Boeing FBW logic "mimics" a conventional aircraft. If you increase thrust, the nose will raise and after a few damping oscillations the pitch attitude will establish to maintain the trimmed speed in a climb.

TheAvionicsHandbook_Cap_11.pdf (davi.ws)
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Old 11th Jan 2021, 00:16
  #153 (permalink)  
 
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10,000 feet..aaah...time to relax a bit, accelerate beyond 250 kts, call for a cuppa, and one of you to take a natural break. Normal. (It having been at least an hour since you both strapped in, had your coffee/water, briefed, programmed, closed the cockpit door, run checks, pushed back, taxied, prepared for flight, lined up, took off and climbed with the SID).One leaves the flight deck, the other does the deed.

Just one of a bunch of ideas, but not to be dismissed so readily.

My own guess is a mis-handled rudder hard-over, or a reverser deployment, either of which was probably not recognised and acted upon suitably or swiftly enough. Hazards of aviation.
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Old 11th Jan 2021, 01:08
  #154 (permalink)  
 
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andrasz

The black ring around the one conical fairing does raise doubts on where it is from when looking at a photo of the port side of CLC.

Port side CLC showing 3 fairings
None has the black ring.

Was there perhaps another aircraft involved? The left turn driven by a TCAS warning?
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Old 11th Jan 2021, 01:41
  #155 (permalink)  
 
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Another angle:

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Old 11th Jan 2021, 01:45
  #156 (permalink)  
 
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In the second photo, that doesn't appear to be a painted stripe - looks like a strap of some sort.
I'm sticking with flap track fairing.
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Old 11th Jan 2021, 01:45
  #157 (permalink)  
 
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flynerd

To my eyes the cone in #146 is a trailing edge cone with a piece of black strapping around it, presumably from the salvage effort. You can see a short length of it continuing on the plastic sheet upon which the items have been laid. And the semi-cone in #149 looks to be from the leading edge of a flap fairing. I'd not jump into second-aircraft theories on the basis of these photos, at any rate.

Edit: just beaten to the draw by tdracer!
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Old 11th Jan 2021, 01:49
  #158 (permalink)  
 
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If you look closely in the first picture you can see what looks to be the end of a strap on the ground.

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Old 11th Jan 2021, 01:54
  #159 (permalink)  
 
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tdracer

I agree.

Peter Lemme at Satcomguru are open for the idea that the data so far (ADSB data) might suggest that the aircraft may have rolled to the left, through inverted and nearing wings level again at the moment of impact.
Satcomguru
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Old 11th Jan 2021, 02:37
  #160 (permalink)  
 
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Originally Posted by otech View Post
Few posts up, alternate view looking down on cone - can't post URL's apparently...
The twitter link herein:
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