Tech Log The very best in practical technical discussion on the web


Old 5th Jun 2009, 09:30
  #81 (permalink)  
Join Date: Jun 2003
Location: UK
Posts: 153
Likes: 0
Received 0 Likes on 0 Posts
Article from today's New York Times, which links to above threads.

Investigators are pursuing a theory that excessive air speed -- potentially spurred by ice building up on electronic airspeed sensors -- contributed to the ocean crash of an Air France Airbus A330 amid heavy storms Monday, according to two industry officials familiar with the details.

The developments helped lead Airbus late Thursday to remind all airlines to follow certain backup procedures any time that pilots suspect their airspeed indicators are malfunctioning, according to the officials.

The Airbus announcement doesn't provide new details of the crash of Air France Flight 447. But it reflects the investigators' suspicion that the sensors -- also implicated in at least two other fatal airline crashes and numerous other incidents -- were involved, possibly as the first stage of a series of electrical and mechanical malfunctions aboard the jetliner. The reminder advises pilots to use backup devices including GPS systems to check their airspeed if readings from the primary indicators seem awry.

Investigators believe that the so-called pitot tubes may have iced up as the Air France plane with 228 people on board flew through a ferocious thunderstorm that could have included hail and violent updrafts, the two industry officials said.

Industry officials stressed it is too early to draw definitive conclusions from the scant data available, and theories of the crash could change in coming days. Investigators, for example, haven't ruled out the possibility of a fire or other electrical problems that could have led to the emergency. They also don't know what other actions the crew may have taken during roughly four minutes during which the plane apparently was going through a major storm.

The pitot devices have backup systems and are supposed to be heated to avoid icing. But tropical thunderstorms that develop in the area the plane was flying are full of ice at high altitudes, and air temperature at the plane's altitude is well below zero. A theory is that ice from the storm built up quickly on the tubes and could have led to the malfunction whether or not the heat was working properly.

If the tubes iced up, the pilots could have quickly seen sharp and rapid drops in their airspeed indicators, according to industry officials.

At this point, according to people familiar with the details, an international team of crash investigators as well as safety experts at Airbus are focused on a theory that malfunctioning airspeed indicators touched off a series of events that apparently made some flight controls, onboard computers and electrical systems go haywire.

According to people familiar with the thinking of the investigators, the potentially faulty readings could have prompted the crew of the Air France flight to mistakenly boost thrust from the plane's engines and increase speed as they went through what may have been extreme turbulence. As a result, the pilots may inadvertently have subjected the plane to increased structural stress.

It isn't known why other planes flying through such storms haven't suffered from such severe problems, but airline crashes often result from a chain of unusual events, not just a single trigger. Brazilian Air Force officials say three other jetliners flew in the general region around the same time; other airlines have reported no abnormalities in their planes' flights.

Investigators also are struggling to understand another big mystery: how the aircraft, equipped with its own weather-scanning radar, ended up engulfed in what is believed to be such extreme weather. The storm's exact force remains unclear, because the mid-Atlantic region isn't covered by precise ground-based weather radar.

Problems with pitot tubes have been implicated in many air accidents, and ice blockage wouldn't be unprecedented in commercial aviation.

Pitot-tube icing was suspected in the October 1997 crash of an Austral Lineas Aereas DC-9 in Uruguay that killed all 74 people onboard. Flight-data recorder readings showed anomalous airspeed readings and that the crew had adjusted settings in ways suggesting they thought they were flying much slower than the plane, built by McDonnell Douglas, was actually moving. Investigators concluded those settings caused the pilots to lose control of the plane, which plunged into swamps, according to the Aviation Safety Network, a crash database.

A Continental Airlines MD-82, also built by McDonnell-Douglas, skidded off the runway at New York's La Guardia Airport in March 1994 after the crew aborted their takeoff due to strange airspeed readings. Investigators from the National Transportation Safety Board later found the crew had failed to comply with checklist procedures to activate the pitot tub- heating system, allowing them to get clogged with ice or snow. Nobody was killed in the incident.

The NTSB cited similar issues with incidents during two flights of Boeing 717 jetliners in 2002 and 2005. Nobody was killed in those events, in which the planes encountered problems when the pitot tube heating system were temporarily inactive for reasons that were never determined.

In February 1996, a Boeing 757 crashed shortly after takeoff from the Dominican Republic, killing all 189 people onboard. Flight-data and cockpit recordings showed the crew got confused by conflicting speed readings and stalled the plane, which plunged into the ocean, according to Aviation Safety Network.

Investigators later concluded that wasps may have nested in the pitot tubes as the plane, operated by Turkish carrier Birgenair, sat grounded for several days. The tubes are supposed to be kept covered when a plane is parked, but a witness recalled seeing them exposed.

Wasp-nesting in pitot tubes was again cited in a March 2006 incident, where the crew of a Qantas Airways Ltd. Airbus A330 slammed on the brakes during takeoff from Brisbane, Australia. Nobody was injured, according to the Australian Transport Safety Board. Airbus is a unit of European Aeronautic Defence & Space Co.

The Air France jetliner was equipped with its own radar system, which normally suffices for letting pilots navigate through bad weather. But it doesn't always detect trouble, specialists say, or accurately depict the worst areas of turbulence. The signals can get absorbed by heavy rain or end up showing ground clutter, for example, preventing pilots from getting a clear picture of conditions in front of them.
backseatjock is offline  
Old 5th Jun 2009, 09:30
  #82 (permalink)  
Join Date: Mar 2009
Location: on the ragged edge
Posts: 80
Likes: 0
Received 0 Likes on 0 Posts
At this stage describe all the messages would be little bit useless, as what we need is the fault message from CMS related to these Wrn. In fact we need the full Current flight Report rather that the current leg report provided here.
Nevertheless, as I got the A330 AFR TSM in front of me, I do try to understand ,as you, what’s occurs during this flight, and despite my 17 years of experience (as line engineer) on this type of machine (A340/A330), I’ve still have difficulties to sort it out.
However for your perusal
228334 – FMGC
341234 – ADIRU
279334 – EFCS
341115 – PROBE – PITOT
That’s all the data, which could be helpful with what we have right now
The WRn messages are only 4 digits exploitable and the sixth one are mainly 00


Thanks, Greenman, you're the best. I have a sneaking suspicion this is the only acars report that will see the light of day.

Captain-Crunch is offline  
Old 5th Jun 2009, 09:42
  #83 (permalink)  
Join Date: Jan 2008
Location: VTBS
Posts: 27
Likes: 0
Received 0 Likes on 0 Posts
Furthermore, JAUH is right, ISIS it's 3422, but this kind of error exist sometime in the CMS.
However, starting again from this fault messasge,ISIS (22FN-10FC) SPEED OR MACH FUNCTION, with the red flag on the ISIS (I assume) it's lead me again to check the Stby Pitot Probe failure (9DA1, 9DA2, 9DA3)!
As the first fault recorded its also Pitot probe (341115), I would suspect severe icing (this only engage myself). When I mean Severe, I mean really severe, kind of Iceberg flying at FL 350

Last edited by greenspinner; 5th Jun 2009 at 12:00.
greenspinner is offline  
Old 5th Jun 2009, 09:45
  #84 (permalink)  
Join Date: Mar 2009
Location: on the ragged edge
Posts: 80
Likes: 0
Received 0 Likes on 0 Posts
Captain Crunch,

The transcript is wrong - FR0906010211 re: ISIS should start with 3422 not 3412
Thanks Jauh,

I've added a typo note. I'll PM selfin to try to correct it; but it may be too late.


Last edited by Captain-Crunch; 5th Jun 2009 at 10:05.
Captain-Crunch is offline  
Old 5th Jun 2009, 09:46
  #85 (permalink)  
Join Date: Jan 2008
Location: Denmark
Age: 79
Posts: 158
Likes: 0
Received 0 Likes on 0 Posts

As you have the TSM manual in front of you, I wonder if you are able to decode the failure codes associated with the flag warnings displayed on the CAPT and F/O PFDs related to ATA 34?



Last edited by grebllaw123d; 5th Jun 2009 at 10:07.
grebllaw123d is offline  
Old 5th Jun 2009, 10:02
  #86 (permalink)  
Join Date: Jan 2008
Location: UK
Posts: 13
Likes: 0
Received 0 Likes on 0 Posts

However, starting again from this fault messasge,ISIS (22FN-10FC) SPEED OR MACH FUNCTION, with the red flag on the ISIS (I assume) it's lead me again to check the Stby Pitot Probe failure (9DA1, 9DA2, 9DA3)!
I've posted JASC codes for some of the prefixes earlier, 3422 is directional gyro.
jauh is offline  
Old 5th Jun 2009, 10:08
  #87 (permalink)  
Join Date: Jul 2005
Location: エリア88
Posts: 1,031
Likes: 0
Received 0 Likes on 0 Posts
Investigators are pursuing a theory that excessive air speed -- potentially spurred by ice building up on electronic airspeed sensors
Speaking as someone who has flown in severe icing conditions, if this was possible on the Airbus (and I still find it total unbelievable!) then it should never have been certified for flight in icing conditions.

If this is the best theory that BEA can come up with then I fully understand why people are already questioning their ability to solve this accident and their neutrality.
Mercenary Pilot is offline  
Old 5th Jun 2009, 10:13
  #88 (permalink)  
Join Date: Apr 2002
Location: UK
Posts: 386
Likes: 0
Received 0 Likes on 0 Posts
This thread has a lot of relevance to me as a professional aviator. And fwiw I do try and learn from accidents/incidents. Also gaining a little more background info on some of the a/c subsystems & design can be relevant when the time comes to analyze what is going on with aircraft systems. (if there is any time).

I for one wish I had known about TAT Probe Icing (AND: possible EICAS messages) at high altitudes last year when we flew through high Cirrus upwind of a line squall south of Indonesia. St Elmo's fire was unreal.
The Thrust Lim/ Opt Crz & Max Crz / EPR ratings / TAT disappeared of the screens and FMC's, shortly followed by A/T disconnect.
Man Thrust for the next 3 minutes. No Engine Anti-Ice On cycling at this stage. So we related the A/T failure due to static around the EEC's.

After 3 minutes exited the high Cirrus et voila, A/T was able to be re-engaged and after checking Maint Page etc confirmed A/T was deemed satis for the remainder of the flight.

In hindsight it was confirmed to have been port icing.
And this was clear of an actual cell at 39000'
Shaka Zulu is offline  
Old 5th Jun 2009, 10:16
  #89 (permalink)  
Join Date: Feb 2007
Location: Lindum
Age: 47
Posts: 45
Likes: 0
Received 0 Likes on 0 Posts
Firstly, I am not a pilot, I am an aircraft engineer (without Airbus experience).

Secondly, I am not an ACARS expert and would be interested to find out the order of the faults.

What I can tell you is that the Rudder Travel Limiter, shown with a fault on the ACARS printout is designed to prevent excessive loading on the tail structure at high speeds.

As airspeed increases the amount of rudder travel permitted is limited. This is usually computed using inputs from the air data system to the flight control units.

I would be interested to find out from an Airbus Engineer exactly how this particular system works, and in particular how does the system fail safe if the RTL system was to fail at high speed/altitude?

Could it be possible that probe icing led to a lower computed airspeed which allowed the rudder travel limiting system to provide greater than necessary rudder travel?


Last edited by MLT; 5th Jun 2009 at 10:49.
MLT is offline  
Old 5th Jun 2009, 10:23
  #90 (permalink)  
Join Date: Mar 2009
Location: Prague
Age: 51
Posts: 60
Likes: 0
Received 0 Likes on 0 Posts
Nice job!
I am not 330 guy, but for decoding mesages is TSM (CFDS) right way only. If somebody put these mes. numbers into TSM "start troubleshooting" part of Airn@v software, get lot of information and possible causes immediately, includig power sources.Unfortunately my acces is limited to 320 only.
ISIS - not sure with this, but ISIS is connected to IRUs to provide optional heading information (compass scale on bottom of LCD display). If data bus or multiple IRUs fail, ISIS fault can be generated too.
Searching problems in ADR/sensor part of ADIRU system looks better for me.
LEVEL600 is offline  
Old 5th Jun 2009, 10:24
  #91 (permalink)  

Sun worshipper
Join Date: Dec 2001
Location: Paris
Posts: 494
Likes: 0
Received 0 Likes on 0 Posts
I just don't get it. What is the point of all this speculation, when basically, no-one knows what happened to this flight?
The big difference is that now the posters are having a discussion over some hard facts.
With the modest means they have (MEL, TSM, MM...) and a painful identification of a still broad spectrum of data, a better picture is beginning to reveal itself.
I'm hopeful that most of the ACARS data would be identified, we'll have a set of faults / failures that could at the very least eliminate a lot of the wild - or wise ass - guesses we saw too often on the previous thread.
As a matter of fact, I'm sure that quite a few already have a picture of the events.
Lemurian is offline  
Old 5th Jun 2009, 10:47
  #92 (permalink)  
Join Date: Apr 2005
Location: Stockholm Sweden
Age: 74
Posts: 569
Likes: 0
Received 0 Likes on 0 Posts
Looking at all the Messages the first thing that struck me was that except for the two 38 Vacuum Lav messages, all the others are to do with A/P and Nav. There are no other messages. No 24 or 29 failures. No 71 series.
At least this dismisses a lot of the theories running around.

24 Electrical
29 Hydraulic
71 Engines
Swedish Steve is offline  
Old 5th Jun 2009, 10:49
  #93 (permalink)  
Join Date: Oct 1999
Location: Two hundred baro
Posts: 160
Likes: 0
Received 0 Likes on 0 Posts
V1 ....oops: I also work in this profession, as a long-haul captain with 30 years of flying experience. So I well know the need to study the causes of accidents. The fact is, no-one knows yet what happened to AF447, and until we do, none of us is in any position to come to any conclusions as to how to avoid a repeat, save to perhaps treat cb's with a bit more respect in case this was the prime cause.
CAT1 is offline  
Old 5th Jun 2009, 11:07
  #94 (permalink)  
Join Date: Aug 2007
Location: Iceland
Age: 49
Posts: 1
Likes: 0
Received 0 Likes on 0 Posts
just few questions for the professionals from a humble PPL owner.
This message might well be deleted, but anyway no speculation intended here.

I find REALLY weird (and disturbing) that after more than 4 days they couldn't find any debris yet. I know that it's a vast area and the currents are probably strong and everything, but I'm also sure that the people involved in the search are professionals and know how to take into account all these factors.

So, my question is:
if the aircraft (or any debris) is not gonna be found, what is the most likely scenario then? I'm not talking about the cause of the accident, but the last serie of events.
A ditching followed by sinking? An extraordinarly powerful explosion that actually "disintegrated" the aircraft?

I repeat: no speculation or conspiracy intended here. Just probing alternative scenarios!

Thank you,
etabubu is offline  
Old 5th Jun 2009, 11:17
  #95 (permalink)  
Join Date: Jul 2008
Location: UK
Age: 69
Posts: 475
Likes: 0
Received 0 Likes on 0 Posts
just one point as many seem to believe that the thread is now becoming factual.

The released acars information appears not to be the actual information from the flight but from a search function performed on the ground. Unless my eyes are deceiving me the released pages are 28 + 29 from over 250 produced after performing a search from the 12/05 - 01/06.

That means information could be missing and that also means that this thread is actually no different from the original which has been closed. We may be witnessing a more professional response but the basic underlying information is not complete and that means we are speculating.
Safety Concerns is offline  
Old 5th Jun 2009, 11:39
  #96 (permalink)  
Join Date: Jul 2004
Location: Found in Toronto
Posts: 615
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Enkidelaplaya
Just keep to facts:

- the Air Comet pilot who said he saw a bright light wasn't on his normal path to Madrid but had to re-rout and go east (closer to the AF 447) due to bad weather. Yet, it is unsure if he was close enough to the missing Airbus. The Air Comet flight was 7° north and 49° west while the AF 447 was something like 30° west.
Un piloto dice que vio caer un 'destello de luz blanca' donde desapareció el avión francés | Mundo |
The Air Comet flight was over 2,000 km away. They could not have seen AF447. This is from the closed thread:

Great Circle Mapper

LIM (12°01'19"S 77°06'52"W) 07°00'00"N 49°00'00"W 2028 nm
07°00'00"N 49°00'00"W LIS (38°46'53"N 09°08'09"W) 2875 nm

RIO (22°54'S 43°14'W) CDG (49°00'35"N 02°32'52"E) 4950 nm

07°00'00"N 49°00'00"W 03°17'24"N 30°24'00"W 100° 1135 nm

That is too far to see anything other than a metor. (probably was a very big exploding meteor)

(with text added)

Last edited by Lost in Saigon; 5th Jun 2009 at 11:51.
Lost in Saigon is offline  
Old 5th Jun 2009, 11:41
  #97 (permalink)  
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,181
Likes: 0
Received 0 Likes on 0 Posts
While agreeing we don't know the real provenance of the ACARS message list, it appears to be in time sequence order, and people who routinely deal with ACARS stuff have suggested that the number of messages on these two pages is already large for a single flight. I see no evidence that it is, say, an ATA-restricted list and while it is an assumption, I think it is fair to assume that this is the complete list for AF447.
Mad (Flt) Scientist is offline  
Old 5th Jun 2009, 11:46
  #98 (permalink)  
Join Date: Jan 2008
Location: VTBS
Posts: 27
Likes: 0
Received 0 Likes on 0 Posts
Sorry, I was out off sight for a while, and I’ve got planes falling down here, but rather “smooth as Silk…”

Nevertheless, here after a breakdown of all the ATA messages related to the Current Leg Report provided.


22-30-00 – AUTOTHRUST
34-11-15 - PROBE – PITOT

for Grebllaw, 341200106 it’s ADIRU and last 2 digits 06 mean phase 06 (Cruise)
Trusting this will be of some interest
greenspinner is offline  
Old 5th Jun 2009, 12:00
  #99 (permalink)  
Join Date: Nov 2005
Location: No idea - what does the GPS say?
Age: 65
Posts: 62
Likes: 0
Received 0 Likes on 0 Posts
From today's Times

Air France Flight 447 'may have stalled at 35,000ft' - Times Online

The Air France jet that crashed into the Atlantic killing 228 may have stalled after pilots slowed down too much as they encountered turbulence, new information suggests.

Airbus is to send advice on flying in storms to operators of its A330 jets, Le Monde reported today. It would remind crews of the need to maintain adequate thrust from the engines and the correct attitude, or angle of flight, when entering heavy turbulence.

Pilots slow down aircraft when entering stormy zones of the type encountered by Air France Flight 447 early on Monday as it was flying from Rio to Paris.

The fact that the manufacturer of the aircraft is issuing new advice indicates that investigators have evidence that the aircraft slowed down too much, causing a high-altitude aerodynamic stall. This would explain why the aircraft apparently broke up at altitude over the Atlantic.

Airbus declined to comment on the report. A company official said: "Each time there is an accident, it is imperative for the manufacturer to inform all operators of the type of aircraft concerned of any specific procedures to put in place or any checks to carry out."

Jean Serrat, a retired airline pilot, told Agence-France Presse: "If the BEA [accident investigation bureau] is making a recommendation so early, it is because they know very well what happened. If they know what happened, they have a duty to make a recommendation, for safety reasons ... The first thing you do when you fly into turbulence is to reduce speed to counter its effects. If you reduce speed too much you stall."
MoateAir is offline  
Old 5th Jun 2009, 12:04
  #100 (permalink)  
Join Date: Mar 2009
Location: on the ragged edge
Posts: 80
Likes: 0
Received 0 Likes on 0 Posts
So, my question is:
if the aircraft (or any debris) is not gonna be found, what is the most likely scenario then? I'm not talking about the cause of the accident, but the last serie of events.
A ditching followed by sinking? An extraordinarly powerful explosion that actually "disintegrated" the aircraft?
Until the flight data recorder and CAM recording is found and played back, and decoded nobody can answer you. But we can make educated guesses. There is no evidence right now of an explosion. The pressurization message was the last received at 14 past the hour. In an explosion, you most likely would loose the pressure vessel immediately like UAL747 HNL, like TWA800. If the airplane fell off it's knifepoint (and at FL350 with that much fuel and pax aboard; it is sitting on a knifepoint), it isn't likely to come apart at high altitude. What most reporters in the press don't understand is that you can have a high speed stall above MMO that will drop you tens of thousands of feet, just as bad as a low speed stall will. (PJ2's Coffin Corner weight/alt point) You might not recover, if ever, until say (example only) 8,000 feet. At this point, "Lost in Saigon" and my theory goes, you are close to the cabin altitude of say 6,000 feet and will have pressurization problems when the two meet, "Catching the Cabin" (and that might be reported by acars.) That's if the wings or tail didn't come off already and rupture the pressure vessel from exceeding design limits in the dive. Many jet upsets have resulted in major structural damage. Recently an Adam Air 737 came apart in the dive in Indonesia (coincidentally near the equator also and as a result of the autopilot letting go, and the crew's inability to fly partial panel.)

But to answer CAT I, most of us don't want to wait years for the accident report which may or may not be revealing. When the ORD AA DC-10 facts came out, most of us didn't wait for the report. We V2 plus a bunch right after lift off. The government training to yank it back to V2 was dangerous and unnecessary and the pilot population deduced this for themselves: for all we know it saved someone somewhere.

Maybe as a result of our discussion, pilots will start clicking the autopilot off at altitude and get an idea of how it feels in the real airplane on a nice day. It's absurd, imho, for your first experience hand flying at FL350 to be on a dark and stormy night with half of the instruments not working and a flashlight clamped in your teeth.

Or, Maybe as a result of these postings, Air France will take note of crewmembers complaints of no dispatchers and no graphical weather updates available to the crew enroute and do something about it.

Stranger things have happened in Aviation.
Captain-Crunch is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.