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AF447

Old 8th Jun 2009, 17:32
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Originally Posted by Bleve
My experience is that some pilots don't fully understand the true significance of a sudden outside air temperature rise
You are not even avare of how thrutfully you have spoken.

Originally Posted by Quantz
Flying from Buenos Aires we overflew Rio de Janeiro and followed the same route that AF474 was flying when the accident happened. Crossing the ITCZ at FL370 with moderate to heavy turbulence in a 1-2 minutes period we experienced a sudden increase in air temperature, from -48ēC to -19ēC.
Using my faithful Felsenthal MB-2A (it gives very good results for troposphere which start diverging above tropopause but not by much), I estimate that your density altitude would jump from appx 37600 to 40100 ft, provided there were actual temperature rise.

Originally Posted by Capt Kremin
I was crossing the ITCZ a few years ago at FL390 and flew into a green radar return. The OAT before entering was -56C. In a few seconds it had risen to -28C. We received a message from out FMC that we were cruising above Max Flight level. The ride however was smooth and the aircraft, a 767, coped well. Flying out of the cloud brought an instantaneous reduction in Temp back to -56C.
Tim Vasquez may be a fine meteorologist, but he doesn't know everything.
And that makes density alt jump from 38900 to 42300 ft. Now ask yourself whether your wings would support at your new density altitude and whether your engines would give you enough trust to serenely cruise along. Tim Vasquez knows enough to state with confidence that thermal bubbles with 20-30 K higher temp than surroundings are thermodynamically severely improbable or, in layman's terms, impossible.

Congratulations fellows, you have witnessed very rare phenomenon. What you've seen was false excessive TAT reading, probably caused by TAT probe blockage, probably caused by ice cristals in cirruses. All we currently have about it is anectodal evidence that suggests that it happens very, very seldom. Being shy an rare beast we know very little about its habits and habitat apart that it occurs in temperatures below -40°C where it's assumed that ice is too dry to stick to anything. We can only guess that under certain circumstances it can thrive on pitot probes too.


Regarding the AF447: we don't know yet if it actually entered the CB or not so asking why did it enter the CB is pointless. Our only hope of finding out what exactly happened is recovering the CVR and FDR in good shape. And very, very, very thin hope it is. Oh, and IR needs TAS input to keep itself upright.

Photos show the composite tailfin with rudder still attached. Obviously it floats so currents have moved away it from the original splashdown point. Also apparent lack of damage on the side and leading edge has some implications but I don't intend to be the first one to write it down on the PPRuNe.
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Old 8th Jun 2009, 17:33
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Err, excuse my ignorance but if were looking at an unreliable airspeed caused by pitot malfunction, can we not measure airspeed by GPS???
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Old 8th Jun 2009, 17:36
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Here is an update from Tim Vasquez on the topic of "sudden upper tropospheric warming" (quoted in full with his permission):

Update / June 8, 2009:

It was brought to my attention (thanks Bill S.) that an episode of sudden upper tropospheric warming has been quantified in the peer-reviewed literature (see here, PDF). Though I had ruled out sudden warming in earlier updates, I had only been considering buoyant cumulonimbus ascent, in which case a 30-degree rise in the cloud would be unprecedented and indeed unsupportable by the theta-e profiles in the air mass feeding the storm, though if it did occur the vertical velocities and turbulence potential would be astronomical.

Though stratospheric "warm sinks" and "cold domes" have been a part of forecasting for years, this paper proposes a very intense, small-scale, convectively driven downdraft mechanism caused by the penetration of a mesoscale convective system into the stratosphere. The paper identifies a scale of about 75 km in width and an anomaly of 18 Celsius degrees. Any forced downward motion from the stratosphere like this will cause very strong adiabatic warming and associated drying, characterized by a profound lack of high cloud layers and low radiance on water vapor imagery (which by a stroke of luck is most sensitive to the upper troposphere). Since a mesoscale signature like this is well within the sampling capability of the GOES and METEOSAT platforms, I immediately reviewed the water vapor loop (SSEC). However it does not appear to show any anomalous subsident signatures. The area to the north of the MCS appears to show normal synoptic-scale subsidence within the trade wind inversion and the A330 is not believed to have made it this far north anyway.

I do have grave doubts a warm, mesoscale subsident area would be enough to significantly disrupt the A330 flight, and occurring in clear air there is a good chance any failure would be recoverable. I will however continue pondering this idea, will work this topic into the study, and will be glad to entertain other thoughts in this direction. The mystery continues.

-- Tim Vasquez
Weather Graphics / Norman, Oklahoma
from Air France 447 - AFR447 - A detailed meteorological analysis - Satellite and weather data

FBW
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Old 8th Jun 2009, 17:37
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Err, excuse my ignorance but if were looking at an unreliable airspeed caused by pitot malfunction, can we not measure airspeed by GPS???
No. Airspeed is the speed at which you are moving relative to the surrounding air (which is probably also moving itself.) GPS measures the speed you are moving relative to the Earths surface (ground speed,) or more properly the speed you are moving relative to a selection of satellites in orbit.
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Old 8th Jun 2009, 17:45
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Clearly this is the case as one can see the solid white line at the bottom of the fin located just above where it is attached to the fuselage. This and the lug image looks frightenly like AA587. The question is when the fin departed in this case.
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Old 8th Jun 2009, 17:47
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FDR & CVR mounts

I assume that one of the reasons (other than listening capabilities) that France has dispatched a sub is to use radar/sonar to map the floor to look for large pieces of wreckage.

There is some hope that the aft section of the fuselage may remain in fairly large chunks so, rather than just searching for the FDR & CDRs, they are looking for the much larger pieces of the aft fuselage.

I would hope the US Navy would be aiding with their undersea maps of this area to help the search for anomalies.
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Old 8th Jun 2009, 17:48
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I doubt the ISIS (3-in-1 Standby Instrument) was fully lost: only the Airspeed part as the Attitude is a separate electric gyro powered by the DC Essential or Hot Battery Bus. ISIS Altitude is raw data from the standby static vents (does not go through Air Data Modules) - While pitot icing is likely I feel it is unlikely that the static vents iced up too. So ISIS attitude and ALT should have been reasonable. At the very least ISIS Attitude should have been good
These are also my thoughts.

At the very least altitude & attitude should have been available to our crew. Power & pitch would be the NNOP per the unreliable airspeed drill.

Has anyone ever ran this in the sim at altitude? I have set up for lower altitudes. It was no picnic. I can't imagine the challenges the real life situation would entail above FL300.
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Old 8th Jun 2009, 17:58
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Does the A330 have an emergency Yaw Damper for use at altitude, or doesnt the 330 have dutch roll issues at height?

How does the aircraft respond in alternate law and is there any requirement for an emergency descent to assist the yeaw damper in Alternate law?
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Old 8th Jun 2009, 17:59
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Aal587

Images from the NTSB's investigation into AAL587's crash are here:

NTSB - American Airlines Flight 587
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Old 8th Jun 2009, 18:09
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Has anyone ever ran this in the sim at altitude? I have set up for lower altitudes. It was no picnic. I can't imagine the challenges the real life situation would entail above FL300.
I'll only make this comment. Years ago I was flying a Jet Commander at FL41.0 weaving around the tops of a line of thunderstorms using radar and visual clues. We were passing between the tops of two cells and were hit by lighting which caused both the DC and AC generators to trip of line along with the battery buss.

All I had left was the standby attitude indicator and the co-pilot's airspeed indicator and altimeter. Shortly after this electrical failure we entered IMC and encountered light to moderate turbulence. It was very difficult to fly the aircraft, it seemed as if it was a hour before we came out the other side of the line, but in reality it was only about fifteen minutes.

In summation, it is not easy flying on standby instruments at high Flight Levels, no matter the size of the aircraft.

I just hope they find the boxes.
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Old 8th Jun 2009, 18:20
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Hot towers

About the temperature, this reminded me a troubled NOAA Hurricane Hunter flight to Hurricane Felix in September 2007 who measured temperatures at 10,000 feet 25ē C warmer than normal for that altitude. I suppose there are some similarities between hurricane convective hottowers (tropical cumulonimbus) with a strong convective complex in ITCZ.

The pressure at the bottom of the eye had hit 934 mb, and the temperature outside, a balmy 77 degrees at 10,000 feet. This is about 24 degrees warmer than the atmosphere normally is at that altitude, and a phenomenally warm eye for a hurricane. N42RF then punched into the northwest eyewall. Flight level winds hit 175 mph, and small hail lashed the airplane as lighting continued to flash. Then, the crew hit what Hurricane Hunters fear most--a powerful updraft followed a few seconds later by an equally powerful downdraft. The resulting extreme turbulence and wind shear likely made the aircraft impossible to control. Four G's of acceleration battered the airplane, pushing the aircraft close to its design limit of 6 G's. Although no one was injured and no obvious damage to the airplane occurred, the aircraft commander wisely aborted the mission and N42RF returned safely to St. Croix.

Wunder Blog : Weather Underground
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Old 8th Jun 2009, 18:22
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Seeing the photograph of the fin being recovered made me look again at one of the failure messages sent by the ACARS:
272302006 F/CTL RUD TRV LIM FAULT
IF the failure was corrupting speed data and the rudder travels had gone into low speed(full deflection) mode it would have been very easy to rip the fin off the aircraft.

Last edited by tubby linton; 8th Jun 2009 at 18:39.
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Old 8th Jun 2009, 18:24
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The vertical stabilizer looks very similar to that of the A300 from AA587. This is not especially surprising because these stabilizer are built to break there. The composite structur is attached with several bolts just on top of the rear fuselage. You also will be not surprised when the engines will be found broken off the wings somewhere at the pilon.

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Old 8th Jun 2009, 18:28
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and another (A310) rudder

and there is of course this:

Air Transat loses A310 rudder inflight
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Old 8th Jun 2009, 18:50
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@DC ATE:

You are with doubts that the flight had the required uplift of fuel including 3% Route Reserve. I would call this at least a big speculation, now I do not know what the ETOPS requirements of AF are (reserves may vary from operator to operator depending on certification of the authority envolved). But I am damn sure, that they had all legal requirements fulfilled.

Concerning Abnormal Airspeed Indication Procedure, I am Boeing driver, do not know much about Busses, but one thing catches my attention:
I cannot imagine that the high altitude cruising attitude of a bus is much different to other types. Makes my think that max 3,5° would be the value to start with and about 95% N1. Felt kinda uneasy people posting here that You go to 5° Pitch. You are at max altitude remember.

Reading a lot posts claiming problems at high altitude, I always tended and will go on so, to ignore too high levels in CFPs (company flight plans), never encountered any stability problem and at the end of my flights the fuel bill was not higher as if beeing flying the sometimes unrealistic high levels.
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Old 8th Jun 2009, 18:52
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these stabilizer are built to break there.
Some big BS here. There is no intended break line whatsoever.



As pointed out in a more in-depth article here http://www.pprune.org/tech-log/37634...ml#post4982977 , there is no hard fact that tells us neither in-flight breakup nor steep dive.

The cabin pressure advisory ACARS message can just as well result from erroneous data from the ADR parts of the ADIRUs - which we already know to have failed.
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Old 8th Jun 2009, 19:01
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there is no hard fact that tells us neither in-flight breakup nor steep dive.
I still believe that the lack of finding a large debris field lends support to the airplane entering the water mostly intact. Had a total failure occured at altitude, and even with a tight pattern of entry, a considerable amount of items would be floating, and by now, distributed over an extremely wide area. This simply has not been the case.
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Old 8th Jun 2009, 19:06
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Back to pitots tubes

Sorry to come back quite lately on a matter that was raised pages ago.
I just needed to access some resources to recover data.
  • EASA AD F-2002-586R01 requires all Thales Avionics pitot probes P/N C16195AA with S/N lower than 4760 to be inspected to detect the presence of burr that may block the drain holes and as a consequence obstruct the air intake of the probe. After S/N 4761, Thales Avionics has performed the cleaning of the drain hole during the manufacturing process.
    This AD refers Airbus SB A320-34-1263 and Thales Avionics VSB C16195A-34-002.
  • SB A320-34-1354 (first published in March 2006) proposes to change Thales Avionics pitot probes P/N C16195AA by pitot probes P/N C16195BA .
QUOTE
  • REASON/DESCRIPTION/OPERATIONAL CONSEQUENCES Operators have reported airspeed discrepancies while flying under heavy precipitations or in freezing weather conditions. In such an icy and turbulent atmosphere, the aircraft air data parameters may be severely degraded, even though the probe heaters work properly. It appears that the characteristics of such an environment could exceed the weather specifications for which the pitot probes are currently certified. This Service Bulletin replaces the existing pitot probes (FINs 9DA1, 9DA2 and 9DA3) by new probes which are mechanically and electrically interchangeable. Accomplishment of Service Bulletin will improve the resistance against water ingress under severe conditions resulting in improved airspeed behavior. In addition, this new pitot probe introduces a new external protection layer to prevent corrosion.
UNQUOTE
  • SB A330-34-3071 (first published in September 2007) proposes to change Thales Avionics pitot probes P/N C16195AA by pitot probes P/N C16195BA.
QUOTE
  • REASON/DESCRIPTION/OPERATIONAL CONSEQUENCES A320 aircraft family operators have reported airspeed discrepancies while flying under heavy precipitations. A new Pitot probe has been designed to improve A320 aircraft airspeed behavior with these specific weather conditions. A few similar discrepancies had also been reported by A330/A340 aircraft operators and AIRBUS now proposes this Pitot probes improvement for Long Range (LR) aircraft. This Service Bulletin proposes the replacement of the three Pitot probes PN C16195AA (FINs 9DA1, 9DA2 and 9DA3) by new probes PN C16195BA. Accomplishment of this Service Bulletin will improve the resistance against water ingress under severe conditions resulting in improved airspeed behavior. In addition, this new Pitot probe introduces a new external protection layer to prevent corrosion.
UNQUOTE
Please note that both of these SBs are RECOMMENDED only, meaning that it's up to the operators to decide upon the embodiement on their fleets.

To conclude, P/N C16195 has been improved by Thales Avionics to cope with some minor (because no AD was raised to cover those two SBs) in-service issues.

Therefore, the various retrofit campains that have been mentioned in the previous pages are led on a volontary basis by the operators.
  • No TFU on A330 airspeed discrepancies has been published by Airbus meaning that, even if some incidents have occured (see Air Caraībes above), it was not on a widespread basis and/or no major safety issue was identified.
Hope this clarifies.
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Old 8th Jun 2009, 19:07
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Sequence of ACARS items

I found it very interesting to read the Euro Cockpit site, that Milka posted in posting #610.
I would think some people involved with Airbus technic are manifested there.

The main message: The fault msg about the pitots was the first and everything thereafter a consequence.

To the somehow more precise map of the SAR search area:

Did anybody notice the positions "AF447 ultima reporte" and ACRS 0214Z. They are 27 NM apart or 3,5 minutes with a presumed GS of 470kt.

Am writing this, because I do not understand the term 'AF447 last report', it is more or less the point wher ACARS transmitted the first patch of msgs.
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Old 8th Jun 2009, 19:07
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I respectfully need to disagree. Take a quick look at post 648. At the bottom center of the fin, you will see a little 'hook'. This is part of the center attachment point (the bottom half is gone) and a bolt would have run through it.

Now google "AA587 and photographs". Close inspection of those photos will show that the damage is remarkably similar.

This suggests perhaps that the loss of the rudder limiter allowed the rudder too much motion and ripped the fin off, during transition throught the storm. If it did, then the result is probably the same as AA587
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