AF 447 Search to resume

[Rockhound]

CONF,
Sorry but I don't understand your post. Could you elaborate pls?
Rockhound

[Chronus]

Various news sources have reported twelve other flights in the vicinity or similar routing to the ill fated AF447. Is there any information on these other flights and whether any PIREPS were issued. Did they encounter any severe wx and did they alter course or change level for avoidance. Given wx encounter appears to be the favourite I would have thought some focus on this would be a reasonable expectation.

[NeoFit]

Rockhound

It's seems CONF isn't yet here.
Perhaps a beginning of answer:
http://www.bea.aero/docspa/2008/d-la...081127e.en.pdf

[SPA83]

2h10mn34 : last position known
2h14mn : the A330 is diving through 5000ft (ADVISORY CABIN VERTICAL SPEED) with a vertical speed around 10000ft/mn
So, the upset could have occurred at 2h11mn, 30sec after the last position known. Did they try to find AF447 just below that position ?

[mm43]

MCScott in post #1496 (his/her first) which was delayed and may have been missed, ends by stating -

- It is easy to identify accidents related to failures of automated flight systems, or the misuse thereof. It is impossible to track accidents avoided by such systems. The overall statistics, which seem to show fewer and fewer accidents per air mile traveled, suggest that [if] automation is either a net safety benefit, or it is being overwhelmed by other safety improvements. I have no data to say one way or another.

So that is the crux of the matter. It is only when something gets completely outside the "envelope" that the statistic is generated. In the safety manual, there is no such thing as a "near miss", as a "near miss" is an accident that was avoided through timely and proper intervention. The human ~ automation interface is where the problem actually lies. In other words, how far can you let automation extend the envelope without placing the human in the loop?

BTW, the brackets around the "if" in the quote are mine, and apologies to MCScott "if" it was intended otherwise.

mm43

[infrequentflyer789]

Originally Posted by CONF iture

What about this one ?



Amazing, it didn't really happen in the middle of the Atlantic, but that's the only photo we have seen so far ... Some know how to control the information.

I posted another one earlier in the thread

http://www.pprune.org/rumours-news/395105-af-447-search-resume-post5553191.html

but I agree with you - there is very little in the way of images of the 888T crash in the reports or anywhere else I can find.

[mm43]

Chronus;

Various news sources have reported twelve other flights in the vicinity or similar routing to the ill fated AF447. Is there any information on these other flights and whether any PIREPS were issued.

There is extensive discussion on the above throughout this thread, but the following will provide you with most of what you ask:-

Tracks of other aircraft crossing the ITCZ

You will need to be using the Firefox 3.6 browser to view the page correctly.

SPA83;

2h14mn : the A330 is diving through 5000ft (ADVISORY CABIN VERTICAL SPEED) with a vertical speed around 10000ft/mn

The Cabin Vertical Speed Advisory could also have been caused by engine roll-back, a precursor to flame-out, so the position you are suggesting is just one of many possibilities. Likewise the lack of any further ACARS messages could be due to the SATCOM buss not being powered.

mm43

[MCScott]

mm43,

Thanks for correcting my grammatical error (the extraneous "if"). I'd reread the post a couple of times, but, as the author, I completely missed it. I think there's an analogy here to the possibility of pilot over-familiarity with their current situation leading to oversight of obvious inconsistency. But I won't go there

In any case, your observation about the importance of human - automation interface has sparked further thoughts, which I don't have time to put down now, but will expand upon tomorrow.

[Walking Bird]

BBC Scenario

There is one thing that puzzles me all the time after watching the BBC documentary. They describe a scenario of pitot icing due to supercooled water that freezes all pitot tubes upon contact.This would mean that the a/c passed through an area that contained supercooled water droplets. But would not the whole outside structure (not only pitot tubes) of the a/c be subjected to instantly freezing of these droplets?
And what happens then with the handling characteristics of the a/c and its weight.I feel that this degradation of the flying capabilities of the a/c combined with the increased weight from icing would be a much bigger problem for the pilots than the failing airspeed indication.Perhaps somebody can comment on this...


WB

[mm43]

Airspeed - The Pitot Pressure versus Suction Conundrum!

The blindingly obvious can itself be blinding! (anon)

EDIT:: Due to Copyright restriction, the image associated with this post has been deleted.

Yes, the stagnation point and compressibility associated with the Pram side also exist with the opposite sign on the Pvac side, but a properly designed tube will track equally the Pt ~ Ps difference, be it on the pressure or suction sides.

Nothing is new, and this idea came to me when examining the usage of a venturi variometer in high performance gliders.

mm43

[HazelNuts39]

venturi

mm43;

That reminds me of my post in july 2009 on the AF447 thread.

HN39

[Yiorgos]

venturi choke?

A venturi may be OK in a glider but it will choke way before M 0.82 (cruise Mach No for A330).

(hint: airflow is accelerated within a venturi)

And icing will also change it's geometry and lead to erroneous readings.

[mm43]

HN39;

I vaguely remember your posting - now you mention it. The solution looks on the surface to be relatively simple, either as a combo pitot/venturi replacement for each existing pitot, or as a standalone monitor.

If the ADIRUs were to monitor all pitots for agreement and likewise compare the venturi Pt ~ Ps, then you would have doubled your redundancy and half of the tubes would be detecting the IAS in a different manner than the other half. A small but significant improvement over the current situation.

mm43

[mm43]

Originally posted by Yiorgos ...
A venturi may be OK in a glider but it will choke way before M 0.82 (cruise Mach No for A330).

(hint: airflow is accelerated within a venturi)

And icing will also change it's geometry and lead to erroneous readings.

There is no choke point involved. The device is not a venturi in the true sense of the word, but rather a blocked tube passing through a fluid/gas. To my mind the positive pressure rise on one side will be matched by the negative pressure on the other side. The surrounding fluid/gas pressure is the Static and the differences mentioned are the Dynamic pressures. Bernoulli's equation applies in both cases.

Perhaps the name Venturi has been used erroneously, and the title of the post should have been -

"Airspeed - The Pitot Pressure versus Suction Conundrum"

mm43

[CorkStudentPilot]

I agree with everyone that posted about the Pitot!!

I think this crash is going to be something along the lines of Aeroperu 603
and Birgenair 301. The biggest culprit is darkness!

let say the pitot was blocked the aircraft on board computer would have picked up on the problem, when it noticed the difference in airspeed and altitude between the two sets of instruments!! that then triggered the ACARS message!!

both pilots would have gotten confused by the different readdings and flown the aircraft into the ocean!!! (CFIT)

Just my opinion (Sorry if thats what like everyone said, i didnt read the other posts)

[HazelNuts39]

"off-spin"

Originally Posted by mm43

Bernoulli's equation applies in both cases.

mm43;
Just another "off-spin": Perhaps the inventor of this device misunderstood Bernouilli's equation?

HN39

[Yiorgos]

mm43:
To my mind the positive pressure rise on one side will be matched by the negative pressure on the other side

I don't see where this assumption is based. The idea of using the pressure drop behind an obstruction, as opposed to the pressure increase in front of it, may have some merit though.

If the device is blow-through and based on the bernoulli equation an immediate comment is that the bernoulli equation is valid only for incompressible flow i.e ~< 0.3M.

If the device is not blow-through, then the front part is essentially a very crude pitot tube, with all associated issues the engineers that have been developing the pitot tubes the last 2-300 years have faced still unresolved.

[grity]

AoA tube

That reminds me of my post in july 2009 on the AF447 thread.
HN39

HN39 you must not rotate the tube, the pressure differenz between the two presure holes will be in significant corelation to a fixed AoA......

one qustion is, can it be icing the pressure hole at 1 or 5 o'clock ?

grity

[mm43]

Originally posted by Yiorgos ...
The idea of using the pressure drop behind an obstruction, as opposed to the pressure increase in front of it, may have some merit though.

That is the whole point of the exercise. The dynamic pressure drop should equal the pressure increase on the pitot side. Will Bernoulli's equation cater for this? I suspect it will.

Originally posted by HN39 ...
Just another "off-spin": Perhaps the inventor of this device misunderstood Bernouilli's equation?

Not quite an "under-arm bowl": He may well have done!

mm43

[HazelNuts39]

Bernouilli

Originally Posted by Yiorgos

the bernoulli equation is valid only for incompressible flow i.e ~< 0.3M.

Yes, incompressible and inviscid. However, it is used over a wide range of conditions as a first approximation to the solution of a problem of flow. Care must be taken to account for the effects of viscosity and compressibility, where these effects become significant.

HN39