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AF 447 Search to resume

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AF 447 Search to resume

Old 8th Aug 2010, 15:06
  #1841 (permalink)  
bearfoil
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Hello mm43.

In emergencies, things need to get simple. I agree with you of course that change can be glacial in the industry.

Nothing focuses one's attention more than execution at dawn. It is tempting to rely far too much on ACARS in this specific accident. It was rather a fluke the data was made public. Without it, the several searches would have been even more broad and haphazard.

A more intensive data link triggered on Pilot/A/C thresholds could of course be route specific, the equipment made modular, and training would be somewhat straightforward. It is too much to ask, even with a fully cooperative roster of players.

Beyond this is the capability of displaying absolutely essential flight data to the cockpit as well. No offense intended.

bear
 
Old 9th Aug 2010, 05:15
  #1842 (permalink)  
 
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Weewinkywilly, there are some nice HF transmission tools that chiefly work via NVIS, Near Vertical Incidence Skywave. This depends on common properties of the ionosphere over the HF spectrum. It can be reduced to virtually a telephone technology using ALE, Automatic Link Establishment. It is claimed the military squeezes as much as ISDN level bandwidths out of HF, 128kbps. Link establishment time is small. And for data transmissions of low data rate aircraft information these might do well.

Again, two problems exist, frequency allocations and polar regions.

Frequency allocations can be squeezed out, perhaps. While HF broadcasting is in severe decline squeezing out more bands for amateur radio has proven very difficult. Were these inactive or no longer needed HF broadcasting frequencies no longer needed obtaining new ham bands should, logically, be easy. So I suspect this will be a serious problem even for aircraft safety issues. A lot of frequencies will be needed and significant weight additions for the new transceivers, antennas, and computers will exist. These can all be dealt with.

Polar regions remain the tough spot. I am not well versed in the ionosphere's configuration at the magnetic poles. I'm not sure it has been studied. It WILL be vastly different due to the interactions with the Earth's magnetic fields. And we have auroras in the polar regions. Auroras shred and spread signals. Most transmissions, AM, FM, or CW sound more like they've been fed through something for audio like shredding is to junk credit card offers. SSB works, in so far as it is "understandable", amazingly so compared to CW. AM and FM are generally unintelligible unless the power is very high. Since SSB can get through that suggests that somehow data should be able to get through at about the bit rate for vocoded speech, 100 to 200 bps, using brute force techniques. Maybe an off the shelf technology to deal with it exists. I'd expect it still would be classified if it does. How many wars do we fight in the polar regions?

Maybe this can be done. But the proposal needs more polish performed by people with more current experience with recently unclassified systems than I have at this moment.
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Old 9th Aug 2010, 17:22
  #1843 (permalink)  
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From the NTSB/Rudder thread, a question for 330 pilots. RTLU fail/prior limit is reported as 7.9degrees, full sweep, by inspection. The Limit in a/s> 272knots is the last one before Law switch, but even at 4degrees each direction, with no modulation of rate of deflection, and a fully powered Rudder, what is the effect of rapid cycling of Rudder: at m.82, at m.82 with a stop @4degrees, and with a 7.9 degree deflection (stop to stop) ? Under what conditions would the Rudder be used at that velocity?

JD-EE, For purposes of this discussion, and a proposed fit of enhanced Comm over areas of low likelihood of FDR/CVR recovery, wouldn't ice be considered a similar deck as land?
 
Old 9th Aug 2010, 21:18
  #1844 (permalink)  
 
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Bearfoil wrote:-

RTLU fail/prior limit is reported as 7.9degrees, full sweep, by inspection.
If you are referring to the AF447 rudder, the recovered RTLU provided a limit function based on a +/- deflection of 7.9 either side of the centered position, i.e. a total "sweep" of 15.8.



The best description on the design criteria and in service use I have seen can be found at:-

http://pilotlab.net/aircraft-manufacture/airbus/rudder-loads.pdf

mm43

Last edited by mm43; 9th Aug 2010 at 23:48.
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Old 9th Aug 2010, 22:15
  #1845 (permalink)  
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mm43

Thank you for the link, it is most helpful. Help me with some nomenclature if you would. My reading of both the second report and the initial one tells me that "Rudder Angle" (a singular) to me has historically meant the angle between the longitudinal line of the Fuselage and the angle described by the Rudder face.relative to same. Sweep describes the arc between stops (or input, as the case may be. They are two different things. The Graph likewise shows a ~4degree angle consistent with RTLU default after Law Change for the assumed speed, 272 knots. Since the angle available on each side is certainly not necessarily utilized, the descriptor it seems to me would relate to a single condition, (deflection) independent of (though certainly made possible by) the restriction (Mechanical stops). Here to learn.

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Old 9th Aug 2010, 22:16
  #1846 (permalink)  
 
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Rudder travel

Doesn't the A332 have a larger VS than the A333? (due to the -200 being shorter ie to provide the same stabilising moment). Is the rudder the same between the -200 and the -300, with the same deflection limits? or is the rudder larger on the -200 with different deflection limits?
thanks
Ian
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Old 9th Aug 2010, 23:34
  #1847 (permalink)  
 
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Bearfoil

I'll get back to you on the substance of your question, but I think you should have a look at the FCOM for the A330. You can download it, or just view it at:-

A330 - Flight Controls

FluidFlow

I haven't got the precise dimensions of the V/S for the A333 series, but am aware that the height of the A332 V/S is about 55cm greater than the A333. The rudder limits are the same, and I am assuming that the rudder area has been varied to match the different V/S designs.

mm43

Last edited by mm43; 11th Aug 2010 at 08:50. Reason: changed 50cm for 55cm
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Old 10th Aug 2010, 00:06
  #1848 (permalink)  
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Thanks, I look forward to your reply. Meantime, and without the "Bird", a pilot has no heading (crab) reference, and if Rudder is used to return 447 to "En Ligne de Vol," he has a critical need to know the response his control input has had. Should he stop too soon, or too late, the Rudder gets rapidly out of sync with the Fuselage direction, and each subsequent Rudder input puts the machine more out of whack, until shock loads rip off the VS. This assumes that the Rudder has mechanical stops, but no rated deployment; the Rudder slams to its stop each time he applies any Rudder at all..And below 272 knots, as 587 shows, the engines are scraped off.
 
Old 10th Aug 2010, 03:15
  #1849 (permalink)  
 
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Bearfoil, "JD-EE, For purposes of this discussion, and a proposed fit of enhanced Comm over areas of low likelihood of FDR/CVR recovery, wouldn't ice be considered a similar deck as land?"

Ice is going to be very pure water, which is an insulator. It will have a different dielectric constant. So there will be some reflection. It also is not a very good insulator so there will be dissipation. I do know that you can speak by radio, sometimes. from Antarctica to the US on amateur radio. But that's using techniques for low angle radiation rather than NVIS, which has a design range of a couple hundred miles. In practice it works fairly well from ONT up towards Portland, Or. and Seattle at night. In the day time other modes with far longer ranges seem to predominate. But there will always be a workable frequency for NVIS modes if you have enough freqeuencies available. (And ALE is a good tool for passively discovering this based on control station's beacon transmissions. If you hear something like turkey gobbling on HF when listening for SSB that's ALE.)

My sticking point is that I have absolutely no idea how NVIS works very near the poles. But at those locations working via longer range modes might be workable with several master stations in strategic locations around the world. The South Pole would be miserable to setup. The North pole has a good land ring around it that could support 1000 mile single hop communications in a pseudo-NVIS mode.

I'm not advocating scrapping the idea over the South Pole. I've not heard of any planes having difficulties let alone dropping down there on flights from Oz to South America. So it would be a lot of expense for modest reward. The plane would leave quite a splash on the white surface, I'd imagine. Surveying for it would not be nearly as difficult as the AF447 case.
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Old 10th Aug 2010, 04:29
  #1850 (permalink)  
 
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"the height of the A332 V/S is just under 3 meters greater than the A333"

mm43, the difference in VS height is around 50cm, not 300.
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Old 10th Aug 2010, 06:05
  #1851 (permalink)  
 
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kwateow

Thanks for correcting me. I've corrected the original post.

mm43
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Old 10th Aug 2010, 06:53
  #1852 (permalink)  
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bearfoil;
Meantime, and without the "Bird", a pilot has no heading (crab) reference,
Not quite...the PFD and the ND have a full-time (green diamond) "track" symbol on the compasses so that the pilot can compare track with heading (blue triangle) and thus derive drift. Also, there is a full-time wind symbol on the ND, top-left.

Clearly, (when not in NAV mode), in HDG/VS mode the Heading/Track symbol overlays the heading, (yellow lubber line at the top of the ND) and in TRK/FPA mode the Heading/Track symbol overlays the green diamond track symbol and lines up with the green track line, (4th graphic in HDG-VS, 5th in TRK-FPA). One can see the drift in either mode or even if the FD's are off as in this case. In NAV mode, the Heading/Track symbol is removed.

The presentation is visible at all times no matter what mode the FD is in, even if it's off. The bottom graphic shows the relationship between the Bird and the Track.

Here are three graphics which illustrate the symbols:




















Hope this helps. Thanks for your note on the other thread.

PJ2

Last edited by PJ2; 10th Aug 2010 at 07:55. Reason: add graphics/explanations
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Old 10th Aug 2010, 12:52
  #1853 (permalink)  
 
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Scientific Report from the BEA Drift Group available

A report describing the BEA effort to model the tracks of the AF447 debris field prior to the Phase 3 at sea search is now available...

http://www.bea.aero/en/enquetes/flig...oup.report.pdf
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Old 10th Aug 2010, 15:44
  #1854 (permalink)  
bearfoil
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PJ2

Thank you for the excellent post and graphic. From memory (different computer), I recall an ACARS entry Re: FPV. Was it not selected and reported by the Flight Computer as unavailable? My assumption then is that the crew wished to select The FPV (bird) due to some need for it, in a cockpit that had become if not unintelligible, at least highly demanding? If flight data was displayed, and serviceable, augmenting the available cues with duplicative data might have been extraneous? The crew would have wanted to simplify the screens and distill the cues to regain control, no? The FPV u/s record fits with a screen that was either too busy or unavailable and a crew who were attempting a recovery from upset? The other possibility would be that the A/P trip happened after loss of control and the pilots may have been incapacitated due to the loads of uncontrolled flight and the computer volunteered an admission of degraded control/available instrumentation?

bear
 
Old 10th Aug 2010, 17:00
  #1855 (permalink)  
PJ2
 
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bearfoil;
You're welcome - glad it's of use. Even though retired, the questions remain engaging.
The FPV (bird) due to some need for it, in a cockpit that had become if not unintelligible, at least highly demanding? If flight data was displayed, and serviceable, augmenting the available cues with duplicative data might have been extraneous?
I wouldn't place too much emphasis on the FPV selection or loss of the information, (which was likely due to loss of other systems). This is a relatively small piece of information which a crew, wrestling with rapidly unfolding occurences and a rapidly degrading situation, would not reach for.
The crew would have wanted to simplify the screens and distill the cues to regain control, no?
No, I can't see this as part of any crews' thinking. "Screen clutter" is not an issue nor would one resolve this by de-selecting the FPV, (which re-selects HDG/VS).
The FPV u/s record fits with a screen that was either too busy or unavailable and a crew who were attempting a recovery from upset?
AFAIK, with one exception, the DMUs do not become "too busy", (over-loaded) and thereby struggle to display information. That one exception is, (and I have seen it), when "Navaids" or "Waypoints" is selected for display and the scale of the ND is on 320nm. If there are a lot of these in the database, the display will sometimes flicker, but I think it is a non-issue in these circumstances.
The other possibility would be that the A/P trip happened after loss of control and the pilots may have been incapacitated due to the loads of uncontrolled flight and the computer volunteered an admission of degraded control/available instrumentation?
Abnormal Attitude laws disconnect the A/P at 25degNU, 13degND and 50deg Bank, (if I recall correctly - not near my FCOM at the moment). Such attitudes are a long way from causing an incapacitation of the crew "due to the loads of uncontrolled flight". IOW, while such attitudes are extreme, they are still within the realm of crew controllability, while upside-down or pitch-vertical (up or down), would become a far greater challenge.

In terms of upset, "wings level" would come first, even before pitch, primarily because of the potential for spiral dive if wings are not first leveled. The exception, some will argue, may be in very high pitch angles where a "roll-off" to get the nose down first, may be more successful than a maximum-effort push-over. In any case, the FPV is not the information to be sought regarding these priorities as the primary guidance is attitude (closely followed by speed), in the moment, not trajectory which is what the FPV displays - in short, one uses as much sky as is necessary and available to return to controlled flight.

I think another way to put it might be, these are not moments where fine-tuning the response is a priority and such selections (or even paying attention to) lateral 'g' loads as indicated by the FPV, is not going to happen - unless heavily trained for and often (and we as an industry don't do this), the reaction (once past "startle") is more instinctual than measured.

I believe the crew had both PFDs (horizons) but stand to be corrected given the time that has passed since I read the reports.

Regarding rudders and fins, parts of the Canadian TSB Report on the Air Canada upset is worth reading I think.

Cheers,

PJ2.

Last edited by PJ2; 10th Aug 2010 at 17:07. Reason: adding comments re FPV
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Old 10th Aug 2010, 21:09
  #1856 (permalink)  
 
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bearfoil - in reply to Post # 1847

RUDDER ANGLE
The acute angle between a water or airborne craft's fore-and-aft line and the current longitudinal center-line of the rudder.
The Graph likewise shows a ~4degree angle consistent with RTLU default after Law Change for the assumed speed, 272 knots.
Wrong! The graphic shows 7.9 of rudder angle at 272KCAS - the value that is "locked in" (when the flight law changed to Alternate) until slats extension, when it reverts to that available in Normal Law.

The 4.0 angle is that available at 350KCAS and beyond when in Normal Law, and would be the value "locked in" if an overspeed event had resulted in a change to Alternate or Direct Law. The 4.7 angle was included as a reference as to the angle at FL350 and M0.86 / 330KCAS.

Maximum rudder travel is therefore automatically limited as a function of aircraft KCAS to prevent structural overloading. In this respect, the "travel" is the angular deflection from the fore-and-aft line as described above. I haven't seen a schematic for the RTLU, but I suspect that a worm screw driven device creates a "feedback" position that inhibits hydraulic pressure to the operating rams beyond the set point. In this respect, the RTLU position is utilized by both port & starboard rams.

mm43
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Old 10th Aug 2010, 21:21
  #1857 (permalink)  
 
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cc45

Thanks for posting the link to the BEA's extensive report on how they determined the area to be searched during Phase 3. The report is complex and shows the difficulties that were faced in backtracking debris. For those who wish to wade through it, the link to the PDF file is:-

Phase 3 Search Zone Determination Report

Be warned - the file is large - 37MB.

mm43
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Old 10th Aug 2010, 23:28
  #1858 (permalink)  
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mm43;
I haven't seen a schematic for the RTLU, but I suspect that a worm screw driven device creates a "feedback" position that inhibits hydraulic pressure to the operating rams beyond the set point. In this respect, the RTLU position is utilized by both port & starboard rams.
RTLU schematic below.

There are six "stops":

Rudder Pedal Stops - non-adjustable, which limit pedal maximum travel
Pedal Travel limitation unit - PTLU - limits maximum pedal command
Servocontrol input linkage fixed stop - limits masimum servocontrol command
Rudder travel Limitation Unit - limits the masimum input to the servo controls
Rudder Travel Stops - non-adjustable servocontrols stroke-end stops
Rudder Structural Stops - when servo controls are not installed

Note - There is no special stop between the rudder and the structure of the vertical stabilizer.













Last edited by PJ2; 10th Aug 2010 at 23:41. Reason: Getting the sizes right
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Old 10th Aug 2010, 23:45
  #1859 (permalink)  
 
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PJ2

Thanks for posting the drawings of the RTLU. Turns out the device is similar to what I had envisaged.

mm43
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Old 11th Aug 2010, 21:31
  #1860 (permalink)  
 
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The following is an extract from the Phase 3 Search Area Determination Report:-

Appendix 7: a SAR detected pollution spot
On June 2 2009 at 8h16, a possible pollution spot was detected near 3030.5W 243.4N by the synthetic aperture radar (SAR) on board the COSMO SkyMed 1 satellite.

Figure A7_1
below shows the cusp shaped spot detected, which does not have the characteristic elongated form of an oil spill coming from a ship. CLS and CEDRE experts were not able to understand its origin. Report by G. Hajduch, P. Lozach & F. Collard gives other SAR images with well-identified signatures from ship tracks and oil spills.

Figure A7_1
Cusp-shaped pollution spot seen on a COSMO SkyMed SAR image (on June 2 2009 at 8h16).


A 330 m wavelength swell (propagating southward) is also visible (the SAR resolution is 30 m). We have seen in chapter II (section on particle trajectories), that the back track (to June 1 at 2h15) of this pollution spot falls (within one or two kilometres) under the plane flight line roughly 10 nautical miles south southwest of LKP (one minute of flight time). This prompted us to check if such a spot could correspond to some kerosene (aviation fuel) released by the plane.


Within a few minutes after release, kerosene spreads on the sea surface as a very thin layer of the order of 1
m (actually between 0.05 and 5 m; the uncertainty is large). After 30 hours kerosene will have evaporated and dispersed[26] almost completely: with an initial amount of 50 m3 there would remain (with a 10 knots wind) roughly 0.5 m3 for a SAR detection. The estimated area of the spot on Figure A7_1 is approximately 0.5 km2 and that would correspond to a layer 1m thick at most. Knowing that some 43 000 kg of kerosene were still in the plane tanks after its 3h 40 mn flight (Rio to LKP), thus roughly 54 m3 (kerosene density is 0.8 kg dm-3), it is not impossible that this pollution spot may be the remnant of a kerosene release by the plane (be it voluntary or not). Of course it is difficult to tell which quantity is precisely involved (it may vary between 3 m3 and the whole 54 m3).

A last point concerns the wind drag on the spot as a whole: generally, 3% to 4% of the wind speed is assumed for oil (CEDRE, 2004). On Figures 25 and 27 we took 0% and 2% respectively (kerosene is light and volatile and has possibly a smaller wind drag than oil). The greater the windage the nearer the back tracked position to LKP since winds were northerly, but the nearest to the plane track is obtained with a 2% wind drag (whence our choice). Over only 30h we could expect a small distance between positions estimated with a 1% drag difference: there is however a 5 km distance (slanted in a SW-NE direction, see Figure A5_2) because the wind was strong then.


We have been unable, however, to relate this pollution spot to any impact point of the plane as determined from the debris and bodies found and the velocity fields estimated (whatever the methods). But, all our calculations, are based on the assumption that the plane hit the sea surface intact (following BEA expertise of the recovered plane remains).


NOTE:[26] breaking waves can drive small droplets into the water column. This process is called dispersion (Lehr & al., 2002)
-------------------------------------

This "oil-slick" can not be discounted, bearing in mind that the modeling which resulted in the Phase 3 Search Area, has so far not provided a result. My initial reaction to this information was that if it wasn't kerosene, it could possibly have been a short-lived algae bloom. Those blooms are more likely to be found in coastal waters where land based run-offs provide nutrients to trigger them.

Machinbird and GreatBear have both postulated (with different reasons) that the crash spot may be closer in to the LKP than had been assumed. Obviously, further research and modeling may bring this oil-slick and its location into sharper focus.

EDIT:: "...
experts were not able to understand its origin" - that alone is cause for further investigation?????

mm43



Last edited by mm43; 11th Aug 2010 at 22:28.
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