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BREAKING NEWS: airliner missing within Egyptian FIR

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BREAKING NEWS: airliner missing within Egyptian FIR

Old 4th Nov 2015, 05:12
  #781 (permalink)  
 
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they say all pressure data (pressure altitude, TAS, vertical speed) are unreliable right after the "event"
If the origin of the data considered is "pressure" wouldn't that mean it's derived from the static system? The static ports could have been sensing wildly varying airflow if an "event" caused departure from controlled flight?

I'm not knowledgeable on FR24, so cannot comment about the value of that data, but in general, perhaps civil data gathering is reaching a point where instantaneous information is available at previously unseen resolution? There's just more to consider?
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Old 4th Nov 2015, 05:30
  #782 (permalink)  
 
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Pitot-static system, so you have both dynamic and static pressures. There are many factors which can make their reading unreliable, including pressure changes related to the event, the changing orientation of the aircraft or sensors, and of course physical damage to the system itself.
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Old 4th Nov 2015, 05:36
  #783 (permalink)  
 
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ENOUGH?

Personally I think FR24 is improving all the time. Progress is difficult for us old guys to accept, especially when we thought we had the world all figured out long ago. I feel it as much as anyone. Though sheetsky for us.

FR 24 is not perfect, but has it shown anything demonstrably wrong in its overall picture of what happened out there on the northeastern Sinai Peninsula?
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Old 4th Nov 2015, 05:51
  #784 (permalink)  
 
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Originally Posted by thcrozier View Post
ENOUGH?

Personally I think FR24 is improving all the time. Progress is difficult for us old guys to accept, especially when we thought we had the world all figured out long ago. I feel it as much as anyone. Though sheetsky for us.

FR 24 is not perfect, but has it shown anything demonstrably wrong in its overall picture of what happened out there on the northeastern Sinai Peninsula?
thcrozier, I agree with your comments on improvements, but I don't see a wide distribution of this kind of data as "progress", first because very few viewers are capable of meaningfully interpreting flight data; the experienced, old guys and gals have a tough enough time!, (remember the AF447 thread after the recorders were found...anything but conclusive).

My view is that interpretations without knowledge and experience is just this side of guessing and for many is short-term, non-serious engagement.

Under the heading of the old phrase, "everyone's an expert", I hasten to add that we dwell in an age in which it is generally thought of as impertinent to claim expertise, experience and knowledge when actually one has been doing such work for decades, and instead believing that because the technology exists, everyone should get "flight data" and have the right to read the tea leaves, etc., etc. But I have seen far more incorrect conclusions drawn over the years than insightful, correct conclusions drawn regarding what actually happened. In my view, many of the posts on this and any thread post-accident, illustrate this phenomenon.

I am not being critical of speculation or even rumour and I mean no disrespect for those who built/are building FR24 is intended. What is instead intended is a clear caution that while the technical capability exists to capture a few parameters, (less than are required by the FAA for this age of aircraft, it should be understood), that is less than half the battle when confronting what the airplane/crew/environment was actually like and what actually occurred.
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Old 4th Nov 2015, 05:52
  #785 (permalink)  
 
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compare FR 24 data with FDR data
If our hunch of the tail separating early in the sequence is true, there will be no FDR data to compare to (though perhaps the QAR will hold some recoverable data).
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Old 4th Nov 2015, 05:59
  #786 (permalink)  
 
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Not at all, the garbled data is consistent with the in-flight breakup and unusual antenna attitudes. Problem starts when people analyze that garbled data and start to draw conclusions from it.
Exactly my point.

first because very few viewers are capable of meaningfully interpreting flight data; the experienced, old guys and gals have a tough enough time!,
Of course.

As in 'the plane fell out of the sky', no. But trying to use the questionable data to explain why is fallacious and pointless.
Yes, yes, yes.

Pitot-static system, so you have both dynamic and static pressures.
The pilots and therfore, ground stations CANNOT read static source information. It all goes through ADCs (air data computers). By the time some data is sent via ADS-B then dealt with by a ground station it has been processed so much it is impossible to draw a conclusion about what a static port was "seeing".

From FR24 data we can say:

The aircraft went UP in a steady climb and came DOWN in an erratic uncontrolled fashion.

Which would be evident WITHOUT FR24 data as the wreckage is now sitting on the ground.

Any other "conclusion" or "theory" people try to derive from the data is purely supposition.
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Old 4th Nov 2015, 06:12
  #787 (permalink)  
 
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The aircraft went UP in a steady climb and came DOWN in an erratic uncontrolled fashion.

Which would be evident WITHOUT FR24 data as the wreckage is now sitting on the ground.
That's actually not correct.

If we only had the wreckage, then for all we know the pilots might have descended the aircraft controllably for some time (e.g., to attempt an emergency landing with no comm) before an eventual breakup in the air, say at mid-altitudes.

The reason we can surmise that there was something sudden and catastrophic near cruise altitude is because of the FR24 data, as reflected in the graphs.
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Old 4th Nov 2015, 06:13
  #788 (permalink)  
 
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If our hunch of the tail separating early in the sequence is true, there will be no FDR data to compare to (though perhaps the QAR will hold some recoverable data).
Yep, of course. In hindsight I should have written "if we can compare FR 24 data with FDR data."

All FR24 confirms is the blindingly obvious that something catastrophic happened at altitude....IMHO it's pointless using FR to attempt forensic analysis.
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Old 4th Nov 2015, 06:26
  #789 (permalink)  
 
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many thanks for the Graph, Peekay. Could you please post an overlaping Graph of Gspd and vspd?

(Abnormality around 345 seems like a huge aerodynamic drag, but could also be an atmospheric or position based interference)
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Old 4th Nov 2015, 06:27
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@ peekay4: I was curious about how accurate the GPS derived VS would be, so I made an experiment. In this .cvs you'll find a few new columns:

- c_alt contains the change in altitude from vertical speed over time
- n_alt contains the new altitude calculated from previous n_alt + c_alt
- d_alt contains difference between (baro) altitude and n_alt
- vs_alt contains altitude calculated from last trusted altitude and GPS VS after upset

The difference before upset is never more than a few tens of feet, and at the moment things start to happen (t=793.671) the difference is 19.5 feet. So for as long as the GPS precision remains good (which is not all the way to the end), I think the GPS VS and consequently calculated altitude is fairly trustworthy - at least compared to the old data.

My apologies to the folks who are not of the FR24 persuasion.


Last edited by RYFQB; 5th Nov 2015 at 23:47. Reason: Added a map with some of the points, like where GPS precision deteriorated. Coords of last points (p0) should not be trusted.
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Old 4th Nov 2015, 06:31
  #791 (permalink)  
 
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Any other "conclusion" or "theory" people try to derive from the data is purely supposition.
I concur. Attempt to over-interpret data of dubious quality. Let's look at the black box data - I bet we will see something completely different, the only problem being neither Egyptians nor Russians feel any sense of obligation to share this info.
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Old 4th Nov 2015, 06:32
  #792 (permalink)  
 
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I have not seen any specific photos of any part of the cabin floor, the condition of which would be a prime indicator of any cargo hold explosion. A major overpressure event from the CH generally results in visible upward buckling of the cabin floor.
I have seen a photo of a truck-mounted crane lifting a fuselage section using a steel wire rope - operated with what appears to be a lack of care towards preserving any overpressure buckling evidence.
Fuselage wall or cabin floor components that are buckled again by careless lifting techniques would not assist crash investigators one iota.

The investigating (Russian) medics are stating that approximately one-fifth of the bodies have suffered severe burns.
This then extrapolates to mean that 4/5ths are not showing any severe burns, and that the fire in the aircraft was limited to approximately 20%, or less, of the fuselage.
What has also been revealed is that numerous bodies are severely fragmented - thus indicating the high possibility of an explosive event.
I would say that the Russian medics will know already, from examining the bodies - whether those bodies have sustained injuries consistent with flying fragments penetrating those bodies under high velocity, as in a nearby high-explosive event - or whether they were merely fragmented from impact with high-speed aircraft debris, as the aircraft broke up and impacted the ground.
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Old 4th Nov 2015, 06:53
  #793 (permalink)  
 
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Originally Posted by thcrozier View Post
Those were frightenly high frequency phugoids, on the order of 8 seconds bottom to top. What's the expected frequency for an intact A321?
Probably of the order of minutes so these aren't really true phugoids at all...
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Old 4th Nov 2015, 07:03
  #794 (permalink)  
 
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It will be very interesting to see the differences in how Putin and his government approach this enquiry vs the MH17 one. Hypocrisy is already evident.
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Old 4th Nov 2015, 07:03
  #795 (permalink)  
 
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Originally Posted by onetrack View Post
...What has also been revealed is that numerous bodies are severely fragmented - thus indicating the high possibility of an explosive event.*.
Onetrack... it does not necessarily that all.
It might but much more likely is that the forces of deceleration, pitch, yaw and translational forces were very high.. which we suspect/know already.
Any bodies that were thrown free will likely have had additional trauma.
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Old 4th Nov 2015, 07:46
  #796 (permalink)  
 
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@RYFQB

That's a nice experiment! It again suggests no phugoids.



@Sokol

Below is the correlation between GPS Ground Speed vs. Vertical Speed:

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Old 4th Nov 2015, 08:11
  #797 (permalink)  
 
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I'm thinking there were phugoids. Most of us probably built model or paper airplanes as kids, and we all probably all saw what happens when the tail comes off. Not a ride you'd want to take but a tuck under to an high frequency inverted stall which may have developed into a spin.


I'm suggesting that after losing its empennage, the plane entered an aerodynamically stable maneuver which had a constant rate of change with respect to several variables - Included among them would be increasing air density, decreasing weight, changing center of gravity, and others. It would be a complex differential equation with all those variables affecting the frequency and amplitude of the oscillations.


peekay's chart has a certain symmetry to it and although it is beyond my mathematical abilities, I think it could be modeled.
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Old 4th Nov 2015, 08:17
  #798 (permalink)  
 
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Not sure how Russians feel about wearing seat belts while the ride is smooth if there anything like the people I see in my neck of the woods most would have them comfortable unfastened .
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Old 4th Nov 2015, 08:28
  #799 (permalink)  
 
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Originally Posted by thcrozier
I think it could be modeled
I'm sure it could be, however what happened to the rest of the airplane after the tail parted, and how that may relate to FR24 data is entirely incidental to the cause.
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Old 4th Nov 2015, 08:31
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Flightradar data:

Quote:
The altitude value is derived via a pressure sensor, which can be affected by changes in pressure outside the aircraft. In this case, what we’re learning about the state of the airframe calls into question the validity of the altitude readings during this time period.

I think that what they mean here, is that if the aircraft had started tumbling, disturbing the airflow over both pitots and static ports, then both the altitude and airspeed transmitted will be unreliable.

In which case the Flightradar data may suggest that the aircraft lost control in the climb-cruise phase, and not in the descent. So the loss of control was immediate and catastrophic, and was the cause of the sudden descent.

Silver

P.S.
From the data-graph posted by Peekay4 in post 509, we see four data extremes within 12 seconds. If the data excursions were caused by airflow disturbances over the pitot and static ports, this could well indicate that the aircraft was rotating in pitch or yaw (or oscillating in pitch or yaw), every 3 seconds.

There was a video earlier of a Russian transport aircraft crashing, because of a loss of tail surfaces, and that was almost managing a 3 second rotation. Rapid pitch or yaw motion (without changing the altitude significantly) to disturb the pitot-static system could be achieved by a loss of tail surfaces, or by runaway computers/hydraulics. I am thinking of that 747 that had runaway pitch commands to the elevators on take off from Heathrow, many Moons ago. An elevator actuator had a transient oscillating glitch, but the other actuator kept the aircraft more or less stable.

Silver

Last edited by silverstrata; 4th Nov 2015 at 08:45.
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