Air France Flight 447

Mon Jun 8 00:13:53 CEST 2009

REPLY TO: D66 at nic.surfnet.nl

Ach ja,

Ze houden ook nog steeds net als wij vol dat we goed waren in de oorlog,
terwijl half Frankrijk (Vichy France) net als bijvoorbeeld het Amsterdam van
het uit Duitsland onwelkome meisje Anne Frank onwelgevallige medeburgers het
noodweer instuurden...

Fritz van Rikxoort

-----Original Message-----
From: owner-d66 at NIC.SURFNET.NL [mailto:owner-d66 at NIC.SURFNET.NL] On Behalf
Of ceesbink at xs4all.nl
Sent: Sunday, June 07, 2009 8:35 PM
To: D66 at NIC.SURFNET.NL
Subject: Air France Flight 447

REPLY TO: D66 at nic.surfnet.nl

Afgaande op de berichten had ik wel een mening gevormd wat er
waarschijnlijk gebeurd is, maar als je geen details hebt moet je je
gedeisd houden. De lacune die ik ervaarde was de hoogte van de storing, de
omtrek en de intensiteit was me al duidelijk geworden van beelden op CNN.

De onderstaande website heeft meer dan genoeg details over de
weersomstandigheden.

Ik had me al afgevraagd of het kan dat een piloot met 11.000+ vlieguren
deze weersomstandigheden niet zou opmerken, dat is me nu nog niet
duidelijk geworden.
Wel is me duidelijk geworden dat vlucht 447 geen schijn van kans had om
daar doorheen te komen. Tegen die krachten is geen enkel vliegtuig
opgewassen, en het vliegen door die storm had voorkomen moeten worden.

Met de grootste verbazing constateer ik dat de meteo van Franse kant nog
steeds volhoud dat er geen bijzondere weersomstandigheden waren.

Groet / Cees

http://www.weathergraphics.com/tim/af447/

Air France Flight 447:
A detailed meteorological analysis

by Tim Vasquez
Revised June 4, 2009

3. Summary of flight conditions
The satellite imagery indicates that numerous cumulonimbus towers rose to
at least 56,000 ft, and were embedded within extensive stratiform anvils
with tops ranging from 35,000 to 45,000 ft. This kind of configuration is
actually quite normal for equatorial storms due to the higher tropopause
height, but it emphasizes that the aircraft was certainly within the bulk
of an extensive cumulonimbus cloud field for a significant amount of time
and that storms could indeed have been a contributing factor to the crash.

[tekst en afbeeldingen stormintensiteit, omvang en plaats weggelaten]

4. Conclusions
I've edited this section Monday night to cut down on the speculation about
the accident chain, especially since I don't know a whole lot about A330
systems. The airliners.net board and other sites cover the aircraft, CRM,
and systems quite well. What I will try to do, however, is summarize what
the aircraft probably encountered based on the data and my own experience.

* Turbulence -- As of June 4, I still consider turbulence to be one of the
prime factors. Extensive reanalysis of upper level data supports
instability values of about 1100 J/kg, which is sufficient to be a danger
to airline operations. Though commercial aircraft benefit greatly from
airborne radar, these radar units detect mainly rain and hail. Updrafts,
particularly if they are strong, may form what are referred to as "weak
echo regions" and this can create highly turbulent areas which are not
detectable on radar. Another concern is the extensive upper-level dry air
shown on the SBFN sounding (not counting the anvil debris at 350-300 mb),
which may have contributed to enhanced evaporative cooling around the
margins of the anvil clouds and aggravated the turbulence experienced by
the flight around the periphery of the storm. It is worth considering that
cumulative periods of heavy turbulence crossing through the cluster may
have caused minor internal damage that progressed in some way into an
emergency.

* Icing -- With a flight level temperature of -40 deg C suggested by the
proximity sounding the A330 would have been flying mostly in rime ice and
possibly some clear ice and graupel. Unbelievably however I neglected to
mention the contribution of latent heat, which would immerse the aircraft
in -36 deg C air when crossing atop an updraft. Supercooled water is
usually rare at these temperatures (see here for an explanation) though a
couple of expert commenters below have presented different views on the
subject. And with -36 deg C this increases the risk of graupel, clear ice,
and supercooled water brought to FL350. This temperature of -36 deg C
represents the absolute maximum temperature that can be expected at FL350
since it is the highest equivalent potential temperature that can be
realistically constructed on the sounding.

* Lightning -- Due to the high cloud tops and freezing level at 16,000 ft,
there was extensive precipitation by cold rain process and it is likely
the MCS was electrified. I have read some claims that lightning detection
showed nothing occurring here, and I saw similar indications on the WWLL
lightning network, but I believe this is in contradiction with the
instability, cold cloud tops, extensive convection, and cold rain process
environment associated with this MCS. My belief is that the area is simply
too far away from the nearest sferic detection system (Ascension Island).
As far what a strike would do to the A330, I have to leave that to to the
avionics experts. Some answers might be found at
http://www.airliners.net/aviation-forums/.

* Precipitation -- A dual engine flameout due to precipitation or ice
ingestion is a noteworthy possibility as has been discussed on other sites
(specific to the A330 type too). Due to the high water vapor content in
the tropics, tropical weather systems can contain exceptionally high
values of precipitable water content. The plane, if at FL350, was
experiencing flight level temperatures of between -41 and -36 deg C.
Supercooled water is considered to be exceptionally rare or insigificant
at temperatures below -30 deg C, but if it does occur it does present the
possibility of aggravating airframe and engine icing. Overall the plane
was mostly in rime ice and possibly some graupel.

* Hail -- I got a few comments about hail. I am not entirely convinced
that structural hail damage is a factor, partly because I can't recall
hearing much about large damaging hail at altitude in my experience with
equatorial flight operations. This would require strong instability, which
I'm not yet sure we have, not only to grow the stones but to loft large
hailstones from the embryo "nursery" at FL200-250 up to flight level. A
value of 1067 J/kg CAPE is really on the fence but not out of the
question. I absolutely do not believe this would support the type of large
baseball-size type hail that would be expected to damage an airframe. The
other problem is the mounting body of evidence (see SPC studies)
suggesting well-sheared storms (this profile is weakly sheared) are the
ones conducive to structures that support hail growth. Finally, another
issue is airborne radars are highly sensitive to hail because of the
strong reflectivity of ice particles, making evasive action likely. The
"young updrafts" I pointed out earlier as a threat would not have provided
the residence times necessary yet to contain hailstones; their main threat
would be severe turbulence. I am not sure about the hail hypothesis, but I
believe there is a high probability of graupel, small ice pellets, or
small hail at FL350 in the storm complex (see Icing above). Finally one
consideration speed is the absolute maximum hailstone size theoretically
supported by a 23 m/s updraft (1067 J/kg CAPE) is about 4 cm; the relation
is given by Vt=AD^0.5, where D is the diameter in cm, A is an empirical
value (about 11.4), and Vt is the fall speed in m/s. If hailstones grow
larger than this their terminal fall speed exceeds the updraft speed.

Overall what we know for sure is weather was a factor and the flight
definitely crossed through a thunderstorm complex. There is a definite
correlation of weather with the crash. However the analysis indicates that
the weather is not anything particularly exceptional in terms of
instability or storm structure. It's my opinion that tropical storm
complexes identical to this one have probably been crossed hundreds of
times over the years by other flights without serious incident.

Still, in the main MCS alone, the A330 would have been flying through
significant turbulence and thunderstorm activity for about 75 miles (125
km), lasting about 12 minutes of flight time. Of course anything so far is
speculation until more evidence comes in, and for all we know the cause of
the downing could have been anything from turbulence to coincidental
problems like a cargo fire.

My own opinion of the crash cause, as of Monday night, based on the
complete lack of a HF radio call and consideration of all of the above,
suggests severe turbulence (see the BOAC 911 and BNF 250 tragedies)
combining in some unlikely way with
CRM/design/maintenance/procedural/other deficiencies to trigger a failure
cascade. We can almost certainly count on some unexpected surprises once
the CVR is recovered. Until then, all we can do is await the investigation
and hope that the world's flight operations stay safe until AFR447's
lessons are revealed.

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