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CRJ down in Sweden

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CRJ down in Sweden

Old 16th Mar 2016, 12:56
  #221 (permalink)  
 
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Yet some people jump with findings and conclusions, as pilot error and poor CRM. We have no clue what happened and we are very far to know why.
Better try to figure out what possible happened. As example, I think they did a good job by keeping the wings at horizontal. The aircraft flight path wasn't a spiral (as per radar data). Moreover, the available FDR data after 23:20:10 shows that the roll indication was really wrong, they didn't inverted the aircraft. The two reliable data, as ground speed increase and positive gees, +1.5g to +2.5g are incompatible with roll data (aircraft inverted). For some reason they were unable to level up before hitting the ground.
By the way, the pilot is still more sharp than automation, the strong exclamation what(!) came couple of seconds earlier than AP disconnect.
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Old 16th Mar 2016, 14:38
  #222 (permalink)  
 
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positive gees, +1.5g to +2.5g are incompatible with roll data (aircraft inverted).
_Phoenix
I can pull lots of g while inverted. To pull out of a dive requires that the g be applied in a consistent direction. If there is any significant roll rate, the time to pull out of a high speed dive ~ 20 seconds at modest g levels, will be much longer than the time to roll 180 degrees. SHK admits that they do not yet understand the roll data.
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Old 16th Mar 2016, 15:54
  #223 (permalink)  
 
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Machinbird, I was pretty clear:
ground speed increase AND positive gees, +1.5g to +2.5g are incompatible with aircraft inverted.
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Old 16th Mar 2016, 17:08
  #224 (permalink)  
 
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No, perfectly compatible.
Roll inverted any aircraft then pull.
You will accelerate and pull positive G
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Old 16th Mar 2016, 17:19
  #225 (permalink)  
 
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Syntax,

Sorry, but the crew WAS experienced. Why is it that people, even professionals still see hours as the ultimate?! It is irrelevant.
It are the amount of sectors flown which is important, and flying Night parcel cargo gives you plenty of sectors, at night, in all kinds of weather, often to smaller airports with less aids.



Your claim regarding the Nationalities of the crew not used to winter ops. Is again something I would expect from a wannabe who is completely wrong.
The crew was flying for the airline for several years,mand guess what, nearly all CRJ flights of West Atlantic are operated within Scandinavia.
Some of the worst Icing can be in Northern Spain by the way, and also France has its Icing issues.
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Old 16th Mar 2016, 18:34
  #226 (permalink)  
 
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Originally Posted by _Phoenix
ground speed increase AND positive gees, +1.5g to +2.5g are incompatible with aircraft inverted.
On appearances, you would be correct although an uncorrected roll rate (due to rolling PFD) could still foul up the recovery by turning the velocity vector.

However what is the source of the ground speed data? Is it the IRU or is it GPS? Once the IRU is corrupted, anything that it generates is suspect.

My personal opinion is that as long as the crew was operating from a corrupted attitude reference, the probability of recovery on a black night, possibly under instrument conditions, over sparsely inhabited terrain would be nil.

The altimeter would have told the story that they were being lied to and were out of control. They then needed to find a usable attitude reference such as the standby indicator and use that until level. Once stabilized they could go about selecting an operating IRU to display on the Captains PFD, or failing that, cover over the PFD with a piece of paper to prevent distraction. Any Instrument Rated pilot who cannot operate at a moments notice off the standby indicator is not ready to be flying instruments. You never know when the guy with the bony finger might administer a flight check of your competence.
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Old 16th Mar 2016, 19:04
  #227 (permalink)  
 
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Machinbird,

Funny you said it, my personal technic is to use one of my flight gloves to cover the affected ADI if its to distracting. However this will only work under positive g's....
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Old 16th Mar 2016, 19:11
  #228 (permalink)  
 
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Elevator problem?

This has probably been mentioned, but I don't have the time to check the whole thread:

According to the FDR traces in #173, the right elevator appears to be acting strangely. There are five or six areas on the trace where it is deflecting when the left elevator isn't and vice versa.

I wonder if there was a flight control problem? I have never flown the CRJ and I don't know its technical arrangement - is each elevator controlled by a different computer? Or perhaps they had a hydraulic system failure which only affected one side?
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Old 16th Mar 2016, 21:35
  #229 (permalink)  
 
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@uplinker

CRJ primary flight controls are mechanically signalled from cockpit to the PCUs - cables (mainly) and rods and levers - no computers involved. (There are electronics with pretty limited capabilities involved in the command of the Hstab and the spoilerons, bot not elevator, aileron or rudder). Also, both elevators are powered by dual hydraulics, so a single hydraulic would not prevent control on one side. (But see below)

Regarding the trace you comment on. Be very careful looking at left-right differences in FDR data. Often, as is the case here, left and right parameters are recorded asynchronously. The little dots show the actual data points - the lines are merely conjecture by 'joining the dots'. So in cases of rapid movement, the lines can appear to disagree because each is "cutting the corner" between mislaigned data 'dots'. As a result I would tend not to worry about any "spikes" where only one or two data points seem to disagree - you don't actually know what the position of the other elevator is AT THE SAME TIME. Both may be in step with each other for all you know.

There are two places where there seems to be a split between the traces - shortly after the point where the overspeed warning started according to the trace. It is possible that hinge moments on the elevator at high speeds and (relatively) high deflections at that speed slightly limited the elevator one side more than the other. There's no evidence of any hydraulic failure (we ought to have a warning I suspect, which no-one has yet pointed to, either on FDR or CVR) but IF such had occurred and affected a PCU on one side only, MAYBE that might explain HM limiting on one side only. But there can be other causes for that, including small amounts of sideslip, or roll, affecting the forces on each tail differently. Without some direct evidence of a hydraulic failure, I wouldn't conclude one from the elevator trace, personally.
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Old 16th Mar 2016, 22:57
  #230 (permalink)  
 
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OK, it seems weird - from the point of view of working out what happened - that the traces are not synchronised, but fair enough.
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Old 17th Mar 2016, 15:34
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The reason is more or less this: in 99% of cases the two asynchronous parameters are in sync anyway. So by recording them asynchronously I effectively get twice the sample rate for "elevator position". Only in the rare cases where they don't agree (disconnect pulled or mechanical failure, say) does that not apply. In the majority of THOSE cases, it's clear what is going on - for a jam, for example, you'd see one elevator stuck and one still moving. Add in CVR type evidence (which would confirm the disconnect had been pulled, for example) and you can pretty easily resolve any differences.

On older units, asynchronous recording was a way to capture both the required rates and record all the relevant items, since memory capacity was an issue. It's less so today, but old habits die hard.
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Old 17th Mar 2016, 18:34
  #232 (permalink)  
 
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To elaborate slightly, DFDRs record in "frames" - the 'major' frame is typically 1 second, a major frame is made up of multiple 'minor' frames (the minor frame size depends on the recorder - older recorders were often 250 ms, newer are much faster). Even within a 'minor' frame, the recording is not synchronous - the recorder cycles through hundreds or even thousands of parameters during that minor frame so it's not a snapshot as such.


I've looked at lots of engine data from DFDRs with the parameters normally recorded at once per second (although sometimes slower). You quickly learn that rapidly changing parameters are basically +/- half a second relative to other parameters.
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Old 20th Mar 2016, 03:06
  #233 (permalink)  
 
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Still nothing on this? Doesn't this seem a bit weird with thousands of the things still flying around?
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Old 20th Mar 2016, 10:21
  #234 (permalink)  
 
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I think they're waiting for the snow to melt, if it was a failure of the display or instrumentation, how would they determine the cause from those bits and pieces?
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Old 20th Mar 2016, 15:22
  #235 (permalink)  
 
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...how would they determine the cause from those bits and pieces?
Things like switch and knob positions may be available as well as non-volatile memory in some electronic devices. Witness marks will also validate the position of flight control surfaces and other movable components of interest.
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Old 21st Mar 2016, 12:51
  #236 (permalink)  
 
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TRF4EV3R

SHK has concluded there is something wrong with pitch, roll, heading data. FDR data shows values that would not correspond to the actual movement of the airplane. To further investigate this they need to recover instruments et al from the wreckage to study witness marks or other possible signs (knob positions) of what may have malfunctioned.

Right now the wreckage is frozen into what I would describe as a temporary glacier kind of environment. The snow on the impact point was very solid and melted temporarily when the aircraft struck. It then re-froze and to retrieve items from it would need special equipment. Problem is, this area is so remote there are no roads and the only way in during snow season is by snow mobile or helicopter. Obviously you can not transport heavy machinery on either of these transportation modes so we need to wait until spring when the snow melts. This would possibly mean May or even June, so until then there are few possibilities of recovery of important instruments.

Last thing I read about this was in Norwegian media (nrk.no) the 8th of March.
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Old 6th Jun 2016, 15:48
  #237 (permalink)  
 
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Any news on this one ? I guess weather should be more amenable these days...
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Old 6th Jun 2016, 18:50
  #238 (permalink)  
 
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"More amenable" is a relative term.

We are talking about a site in the sub-arctic (Lat 68░N) at 1000m elevation on an inaccessible mountainside, and buried by impact in the snow pack.

Could be August before the snow melts enough to be handled with man/helo-portable equipment. Current Troms° weather forecast indicates they are expecting rain and clouds most of this week, which may mean the mountain site is "socked in" and not accessible even to helos.
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Old 14th Jun 2016, 09:23
  #239 (permalink)  
 
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Sounds like work at the site is about to start up again - but not really for the sake of the investigation. Google translate (source):
The Norwegian postal aircraft that crashed in northern Lapland mountains this winter will now be brought in and the crash area to be cleaned up, reports the P4 Norrbotten.

A third of the fuselage and the black boxes were recovered this past winter. Now it's about to collect the debris by hand in the fragile mountain environment.

- Mainly for the animals. You do not want a lot of scrap that can get caught in the claws or whatever may happen to it, said Johan Strandberg at the Swedish Environmental Research Institute is responsible for the clean-up.

While all the mail that was spread over the mountain during the crash will be taken care of.
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Old 14th Jun 2016, 13:28
  #240 (permalink)  
 
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Kind of macabre, but is this not also possibly to recover the remains of the crew?
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