@Handyman - cc:BOAC

The loss of cabin pressure message is incorrect.

According to a former A330 engineer, the ACARS data that was posted on French TV translates to the cabin pressure controller logging a warning/fault to the CMS of the aircraft altitude catching the cabin altitude.

hurricane hunters
 

Quoting: Gergely Varju
I think that impression of hurricane hunters should be set right. It's incorrect to think the planes in the hurricane hunter fleet merrily "go over" the storms of a full hurricane. The planes are limited by physics like any other, even if they might have more power for their weight and so on. They're not trying to avoid the "bad" weather. They go in low to study it. But if you want an account of why only hurricane hunters fly into storms. Forgive me if it's been seen before.
Hunting Hugo : Weather Underground (an account of flying into Hugo)
As Seen It All said, it's not a mission where they go out to take crazy risks. It really is a mission for those pilots and they're not going to go out there to risk the plane or the people anymore than a commercial pilot would like to. (but they will get into close scrapes as per the account above.)

Aircraft altitude catching cabin altitude? Let's see If I understand this right: The airplane was descending so fast it went through cabin altitude before reaching the water?

Whats the max rate for the cabin press system?

I guess you see where we are going.. isn't it?

While I don't doubt Mr. Vasquez's credentials, and I know he is being quoted third hand here, perhaps people should read the report on the four engine rollback of VH-JJP which was investigated in 1992 in Australia:

Appendix 1 of the report contains the Meteorological research of the warm air outflow from the top of the thunderstorm which caused the event.
The report is here:
http://www.atsb.gov.au/publications/...200286_001.pdf

It may be of interest to other jet pilots, so I reproduce here a relevant passage from Checkboard's and Yaw String's posts regarding 'warm air pools' - a new concept to me. It does not offer any advance on all the 'computer' glitches, I fear, but may explain the TAT changes quoted on various threads. It is from Appendix 1 to the report quoted.

The phenomenon is almost certainly the result of folding of stratospheric air back into the troposphere with concomitant warming as it descends. The most likely mechanism for this to occur is strong convection (and for the pilot, strong returns on his weather radar). It is reasonable to assume that, where there is strong thunderstorm activity, there is a fair likelihood that an area of anomalous warming will be present somewhere around the storm cell. The vertical extent of the anomaly is difficult to ascertain and is probably dependent on the strength of the outflow from the storm and its interaction with the environmental flow, but in this case, with the tropopause at 41000 feet, observations from the aircraft indicated that the warming stopped abruptly at 28000 feet. The horizontal distribution of the anomaly is most likely to be oncentrated in a zone of confluence between the environmental flow and the thunderstorm outflow, as that would be the area where maximum descent was occurring, associated with the largest perturbation of the tropopause. In this case the anomaly took place on the western flank of the main convective activity. It is unlikely that any anomalous warming would have occurred on the eastern side of the storm as there would have been no confluence and no tropopausal perturbation. The temperature anomaly was observed over a horizontal distance of approximately 60 nm. By comparison, the incident in 1979 took place within a distance of near 40 nm. It is appropriate to relate some of the pilots’ comments here. His normal practice (and it is understood that this is standard practice) when diverting around radar echoes was to ensure a buffer of 10 nm between the radar echo and the aircraft. As an extra safety margin on this occasion he diverted 30 nm from the strongest echo and in doing so encountered the phenomenon. Perhaps this is a reason why it is not encountered regularly by aircraft - most pilots (in maintaining the normal 10 nm buffer) may travel between the anomalous zone and the thunderstorm. It is estimated that in the ncident associated with tropical cyclone Kerry in Queensland, the aircraft encountered the temperature anomaly about 40 nm on the western flank of the main convection area. The BAe 146 pilot also commented that he had been flying in an area of innocuous radar returns - visible as a “green fuzz” on his radar screen. He noticed that the warming commenced as they flew along the boundary between the weak returns and the clear air. It is suggested that that boundary was an indication of the delineation between air masses of differing characteristics. Another interesting comment was that prior to the incident there had been an incredible display of St Elmo’s Fire, the best that he had ever seen. Whether this was a precursor to this type of event or merely coincidence is conjectural at this stage.

Disregarding, of course, the type involved etc etc, it is significant that the apparent rise in SAT caused a large degredation in the altitude/weight capability of the engines.

TAT temp increase
 

Re: the serious “a sudden and significant rise in the outside air temperature” (#608 R&N) and above.
Subsequent to the Australian report, the majority, if not all of the temperature rise was shown to be an apparent rise due to a frozen TAT probe – the probe indicated the ice temperature and not that of the atmosphere.
Following several other incidents BAe/Honeywell conducted tests in and near large Cbs to investigate the engine icing problem. As a result, the affected engine variant was modified.
The initial flight tests showed that the problem did not per se occur in the tops the Cbs, instead it was the water/ice concentrations in the out flow of these large storms (in the anvil) which presented a threat over a large area. The analogy is of smoke spreading out from a chimney.

The erroneous TAT in BAe146 aircraft was not deemed a significant risk. IIRC there was only an input to the TMS takeoff mode and a temp display in some FMS variants. Thus, the problem was documented and risks agreed with certification authorities; all engines were modified by AD.
At that time the industry did note similar problems with engines and TAT/pitot probes in other aircraft types, but (at that time) the safety concerns were not significant, certainly not in the same category as the multiple engine ‘rollbacks’ with the 146.
The TAT problem persisted, but industry follow-up identified differences between probe manufacturers and probe design, i.e. aspirated / non- aspirated versions.

I suspect that TAT is used in many modern computations and hence there are multiple sensors. Assuming that individual sensors do not ice at the same time / rate then disparities in temperature or in the parameters using TAT could trigger comparator alerts or even system lockout through data disagreement.
Many of the reported ACARs messages appear to represent this type of problem.

sp - "the probe indicated the ice temperature"- thus you are saying that ice that forms at -39C will be at a significantly higher temperture? I'm familiar with L Heat release at state change but cannot see how this can be? Surely also the measured TAT will decrease if the probe ices since there will be less airflow to 'halt'? We are looking to explain an overall 20deg rise or so.

Can someone remind me how/where SAT is derived on a/c? I've had a 'blank moment':)

I wouldn't mind seeing a citation for that statement, as it's the first I have heard it applied to the 146 case. You're not interpolating the Airbus AD backwards, are you?

any idea on how much the tops of CB's would be above the cruise lvl of the a/c
and was the wx radar collins or bendix

If you've missed it, this is as thorough as I have seen yet.

BOAC, I think that the theory is that the probe is heated, but not enough to handle the conditions. As the ice forms (at the atmospheric temperature, plus a bit of latent heat from the state change), that ice is then heated by the heating element of the probe.... or something like that.

The Rosemount SAT/TAS probe.
http://mozaic.aero.obs-mip.fr/web/fe...mage/inlet.jpg
(The lower sensor is the Rosemount probe housing - the other is an ozone detector, for the MOZAIC programme.)

Concerning one of the last ACARS messages,

Quote:

---

WN0906010214 213100206ADVISORY

---

Here's an excerpt of the A332 AMM about the Cabin Pressure System, I shortened some paragraphs:

A further mail from Tim Vasquez
 

Thanks Bert,

I have posted an update on the AF447 page clarifying my position
on the warming theory based on some new data. You may feel
free to relay this in whole if you wish. Hopefully it helps the
discussion.

Tim

On Mon, 8 Jun 2009 08:36:17 +0200, Bert van Horck wrote:
Dear Tim,


I have posted your comments on the open AF thread on the PPRUNE
forum. Several pilots have nevertheles come forward after this
posting confirming they have had temperature rises of in excess of
20 degrees C within Cb's.


Kind regards,


Bert

- I have always seen that as a TAT probe (probably aspirated) and the brain fade I am having is in remembering from 400 years ago where SAT is measured.:) In any of these supposed 'warm air' events, surely the clue would lie with the displayed SAT, not TAT? If that has increased too, then the air is warmer, if only TAT has increased.....?????

Bert -

A further mail from Tim Vasquez
Done

FBW

Checkboard “…interpolating the Airbus AD backwards…” absolutely not; the BAe/Honeywell work preceded the concerns on the ‘big jets’.
Links to the science relating to the TAT probe freezing are in http://www.pprune.org/tech-log/37578...ml#post4963257 ; most of this relates to engine core freezing, but the mechanism and atmospheric conditions are similar if not identical, for certain TAT probes.

BOAC, et al, as the TAT probe freezes the indicated temperature increases toward zero - ice temperature in a static airflow; because the airflow is blocked. The atmosphere - ambient air temperature is still cold.
In engine rollback incidents the TAT increase was a preceding or confirming characteristic seen on the FDR in the vast majority of events. Conversely there were TAT rises without engine malfunction. ( See slide 8)
In the very unusual conditions associated with large Cbs (probably only those which penetrate into the troposphere), the area in and around the anvil contains large quantities of minute ice crystals and often a high super cooled water content. In these conditions the TAT probe heater is progressively overcome by the high negative heat flow – melting ice crystals and water-flow off, such that further ice crystals accumulate in the probe throat (behind the heater). The melt water acts as glue for the ice crystals until the probe becomes blocked. IIRC the effect has been demonstrated in an icing tunnel.

With respect to the AF accident, it is of interest to establish how the various sensors use ‘temperature’, and particularly where there are multiple TAT inputs, how the systems (ADC/ ADIRS, Cabin, Rudder Lim) might cope with different values.
Assuming that multiple probes do not freeze identically; there will be different TAT values.
In a dual system, comparison can provide a comparator warning (systems still operative). However, with a triple input it may be possible to vote out an erroneous value; except in this instance the odd-one-out might be the true value and the voting system may have capability to shut down a ‘good’ system i.e ADC/ADIRS, etc.

Another issue is pitot icing. If the pitot system is also susceptible to icing in the same conditions, then conventionally the pressures existing at the time of blockage will be trapped. Thus there is no change in any of the input parameters with icing – whereas TAT will change with probe icing.
However, is has been suggested that the A330 pitot systems have a small leak path (drain) which will result in a pressure reduction to ambient (decreasing or fluctuating IAS). Thereafter the issues of value comparison and shut down are as above.

A bit premature on 447, but with the image of the complete R/VS assembly and the aerodynamic failures associated with its loss, the topic may be timely now. "Donated Failure". We have been addressing this concept for some time at my firm. Consider "crumple zone" where energy is dissipated by sequential failure of linear structural assemblies. "Ablative Cooling", where temps are dropped by sacrificing material in its melting or burning; "anomalous design" where systems have different capabilities but solve the same problems, Airbus and its "three different computers".

In Brief, if AA 587 had suffered a loss of its Rudder instead of the Rudder/Vertical Stabiliser together? Perhaps, though not demonstrable for AF447, the same?

A Rudder is a trimming device. Without it, flight is difficult but survivable. Without a VS, the game is over.

Had 587 been equipped with design limited hinges on its Rudder, well, you get the picture?

MD11 at Narita. Way too strong MLG and NLG caused the last bounce (when the NG failed to break off) and the subsequent "landing" on the mains, which broke both wings (but the gear "survived" on the right).

AF 447 may have had other issues, but if the VS separated first, instead of not at all (with a "donated failure" of the Rudder), ?? Will have to see.

A plainly incorrect statement - as it presumes that ice will be at zero (presumably Celsius) at any ambient temperature!!!

In any case - I am aware of the icing conditions and engine effects in the links you posted. You appear to think that that is the only possibility for engine rollback, and indeed dismiss high altitude temperature increases as misunderstood icing events. The science for high altitude warming is well understood - and there is no evidence that the JJP 146 event (certainly) was an icing event. Both events occur, both are rare.

Structural failure - hardly
 

IMHO,

Structural failure as a cause of this accident is highly unlikely. Especially unfounded speculation(s) regarding the v/stab and rudder on Airbus articles.

A lot more then a mere picture would be needed to provide sufficient data to support this. Everything else is out of scope for the "real world" situations like fleet operations with thousands of cycles.

Cheers

Regarding separation of the vertical fin:

The onboard computers that keep the pilot from 'overpowering' the rudder seem to get the job done while in 'Normal Law' on Airbus aircraft. But, when not in Normal Law for whatever reason, what indication does the pilot have to keep from exerting too much force through the rudder pedals to the rudder to keep it from departing the aircraft ?

I posted this question on another thread, but didn't get an answer. What model radar was Air France 447 using? The new digital Honeywell RDR-4000 is listed as an option on the A330, but I don't think the aircraft was new enough to have it. Does anyone know if Air France A330's are using the RDR-4000?

I didn't see a reply to this, but here's my simple take on this: The last thing you want when fighting for your life and asking for help, is to jam your radio. That is why military pilots are trained to turn off the parachute beacon ASAP. If you are transmitting on 121.5 (or 243.0), then you can't talk on it. If you can't turn it off (you're hurt or unconscious), then you want it to automatically turn on.

Hello everyone, this is my first post here, and i hope i got the right topic for this.

As seen recently in the news, there is a discussion about the un-overridable fly-by-wire technology in the Airbuses, compared to the overridable tech in the Boeing planes.

Now, most of you have a lot more experience in this topic than me, which is exactly why i am asking here.

Please correct me if i am wrong, but if i remember correctly, Airbus planes had (i think it was) three switches to disable all the flight support computers on board and override them manually.

Or am i really wrong on this one?

I'm just asking out of pure interest, would be glad if someone could help me with that issue :)

982500h
 

Sorry, but you are talking Vietnam war technology.
Modern a/c ELTs transmit on 406MHz which is nowhere near any voice band.
MAYDAY calls are made on 121.5MHz or any other available one. This is an ICAO approved procedure - not only a recommendation! And as stated before in post #22 in this forum, I find it utterly improbable and unacceptable that the crew didn't make it! I still believe that finding the reason for this will be a major contribution in establishing the cause for the disaster!
Pls do not mislead the uninformed...
:mad:

Other flights where no mayday was made before they perished:
Perpignan A320
UA585 Colorado Springs
Continental Connection Flight 3407, Buffalo NY
EgyptAir Flight 990
AirFlorida flight 90, 1982
Copa Airlines Flight 201, 1992

They all had time to key the mike. No value, unaffordable, counterproductive. Perhaps if you ever have an urgent crisis you'll understand. Perhaps not.

Amoung those who did: (radio calls)
USAir 427, 1994, ("Oh [unintelligible] Oh [expletive]" and "427 emergency")
Alaska Air Flight 261, 2000, ("Mayday")

I ignored flights where they crashed just short of the runway in bad weather, and a number of others which crashed just after takeoff. It wouldn't be fair to you to add these.

further update from Tim Vasquez
 

Tim has posted a further update on his MET site http://www.weathergraphics.com/tim/af447/ with a specific request for assistance from the pilot community.

Could somebody report this on R&N please? I have no access to it. Thx Bert

Update / June 9, 2009:

Myself (Ed: TIM) and Scott Bachmeier at University of Wisconsin/Space Science and Engineering Center are requesting that airline pilots who observed a significant warming episode at cruise altitude within the past 10 years and know the exact date/time and approximate location please drop us an e-mail with the story and include your credentials (which will remain anonymous). Unfortunately we must have an exact date and time in order to research the event. I have received a number of anecdotes from pilots who report encountering the phenomena, and while neither of us see evidence yet which supports this occurring in the Air France 447 storm cluster we believe it's a good idea to research this further rather than just dismissing it at this point. We appreciate your help.

Complete ACARS Messages
 

Regarding a search for AF447 ACARS messages, i found anywhere
(do not know where), that there should be a guy that holds all
received messages complete.
Is there anyone here, that have these original, not reformated messages
and can send it via private mail and attachment ?
(Or giving a hint, where it can be downloaded...)

ELT's transmit on 406 to talk to satellites for ID (and GPS if available) as per:

http://www.cospas-sarsat.org/Documen...ompleteDoc.pdf

It also includes a 121.5 option

The US FCC (and a lot of others) require 121.5 transmissions as before (but at a lower power) for final homing purposes.

You can find a clean file in R&N thread, or you can look at my post in Italian Forum, under relevant Thread. By the way, the ACARS messages which can be found is only maintenance ACARS without position reports.

Regards,
PapaEcho

EASA Issue SIB about Unreliable Airspeed Indications
 

Hi folks,
as you can see on EASA Airwothiness Directives section, under NON-MCAI, the European Authority have raised a Safety Information Bulletin (something like SAIB for FAA issue) regarding the Unreliable Airspeed Indications, where is required the operators and pilots to start assesment and recurrent training on Unreliable Airspeed Indications condition in order to identify and take corrective action as soon as experienced.

The direct link to this SIB is: EASA Airworthiness Directives Publishing Tool

In my opinion this SIB is a good system to throw media and press attentions out from construcotr and, why not, authority too.
So, now, if the aircraft we fly is not equipped with a satisfactory stand-alone stanby system, the problem is the pilot not trained and the operators poor training about that. :D Thanks guys, I will log on my Logbook anytime I will experience this type of accident stating in the notes "My company not provide training good enough & I'm a dm'ass because I'm not well trainee to read indications from my completely unreliable and failed instruments" :=

PapaEcho

At Boac.
 

Not sure if it's been answered as I'm just scanning the threads but SAT is calculated by the ADC as a function of TAT(measured by the TAT probe (when not iced up)) and Mach number(calculated by the ADC as a function of pressure(static and dynamic))

or at least that's what they told me when i were a lad.

Thanks FE - that was what I thought, but I wondered if there was some canny little thermocouple somewhere out of the airstream.

You are evidently unaware of the physical construction of a Rosemount TAT Probe and its heating system. The phenomenon of rising temperature is the result of the blockage of the air flow through the probe (and there is a flow - the air is not brought to a complete standstill) and subsequent heating of the detecting element by the probe's own anti-icing protection. It takes a lot of energy to raise the temperature of a probe that is air-blasted by air at -40C degrees C, to -5 degrees C, but with a blocked probe that is exactly what will happen. The ice will not penetrate into the sensor cavity and the sensor will be heated by radiant energy.

Greetings,
May the Crew and Passengers of this Flight Rest In Peace.
Why must we assume that it was ice that did provoque an unreliable Airpseed situation.
pitots and sensors are just calibrated tubes or holes, transmitting to the computors whatever is going through.
I think we could focus on the "whatever is going through"
If the recommandation to change the pitot tube had a sense of urgency, it would have been done OVERNIGHT :ouch:
Very often the Radar attracts Lightning, and is not the first time nor the last that the Radom will simply be blown away leaving a flat surface, which highly distrubs the Airflow to the pitots and probes, along with a big drag increase.
Severe turbulence CAN trigger flight controls to revert to DIRECT LAW (shake the controls in the simulator, and watch it happen) and all this happening in a giant storm.
It is easier to blame the technology and probably send the lawyers to try to get some juicy compensations :E, rather than looking at the reality and blame a Giant Thunderstorm. :=

"Very often the Radar attracts Lightning..."

Yeah, sure.

Like I told a line pilot once, "Oh, this is low power radar; it can't attract lightning." And that's the truth..

Greetings,
IONISATION is the attracting factor, not power.
:}

SLF questions here. I am not a pilot, but have over 30 years in the IT industry, most of that focused on user interface. My questions are;

On the 330, when the autopilot disengages, how is that communicated to the crew? Also, from the same perspective, how is the transition from Normal Law to Alternate or Direct Law communicated? Is it possible that when the flight, possibly unexpectedly, entered severe turbulence, that one or more of those cues may have been missed?

audio warning, if it was disabled with a system fault. I agree with what you say but it still rises alot of questions but all answer at the moment are hitting a :ugh: because we can only base these issue on facts.

Because it has happened before. Try checking the reason behind the 2002 Airworthiness Directive and the more recent focus on upgraded Pitot Probes that had not yet been fitted to the accident aircraft.

Lightning damage to radomes is very, very common and the results are not dramatic. Just a series of small holes in the paintwork.

Lets not forget about the bright red Master Warning light flashing in front of your eyes...