As my British friend, Trevor says, "Hang about!" (translation: wait a minute) Gotta love those Brits!
The previous post on AF 447 has generated a lot of comments in a short period of time. Some of these comments need (in my opinion) to be addressed. Remember, generally speaking, that I do not go negative, I will keep this post within those parameters.
Airbus Industries does not make bad aircraft. They are robust and safe flying machines. Admittedly, they have a reputation for being complex. Of course, my Boeing buddies and I like to kid each other about our flying machines, but there are no major design flaws in the Airbus. The rumored quirkiness can usually be traced back to the pilot not understanding the system completely. Over the years, there have been a few changes in electrical design components and fuel system plumbing, but what aircraft has not? I have no complaints about Fi-Fi... She is a fine aircraft.
The AF 447 pilots did nothing wrong by taking off and flying toward Paris. Dealing with weather is part of our job. The crew cannot always fly around a line of storms, as (usually) there is not enough fuel to take major course line deviations. Sometimes, you have to pick your way through the weather with radar and eyeballs. Hopefully, the flight data boxes will be found and an answer to this tragedy will be forthcoming.
There is a report out that conflicting airspeed values were present at the time the A330 met it's demise. I have seen talking heads wondering if the pitot system was rendered inop by ice.
Also, they conjecture computer problems (which somehow the maintenance folks missed or were told by the evil CEO not to repair because of cost) may have generated airspeed instrument differences which caused the auto-pilot to disconnect.
Another report states that twelve other airliners flew through the same area without weather related problems. That leads the lay person to believe that it must be aircraft related. As any private pilot candidate is taught early on during training, there is no guarantee that a following aircraft can cross the same area of problematic weather successfully.
All of the data-link messages that this A330 broadcast before the end could have been caused by an encounter with a thunderstorm. The airspeed would flucuate wildly in severe turbulence causing the auto-pilot to disconnect, which in itself, is no big deal, because Fi-Fi handles very well with stick and rudder. Notice the could have in first sentence. That sounds just like a talking head!
The pitot system is well protected against icing. I am not sure, however, if it could be overwhelmed by super cooled water droplets present in thunderstorms. That possibility sounds incredible to me.
I still believe this accident was caused by an encounter with thunderstorm related high altitude weather. Every nasty weather condition that a pilot fears or should fear, is part of a thunderstorm and it is all contained in a small volume of atmosphere.
Life on the Line continues...
35 comments:
i always appreciate your comments and commentary on disasters such as this.
Dave, I'm very new to your blog, and instantly hooked. I happened upon your site trying to satisfy my curiosity about AF 447.
Your approach and demeanor is exactly the temperament I hope is endeared by the person occupying the left seat up front on my frequent business flights. You are truly a credit to your profession and all who aspire to join your profession. Keep it on the center line Dave. Thanks so much for what you do.
Hi Dave, I'm a fellow pilot flying the cargo on the MD11. The autopilot disconnect might have occured for various reasons:
A: Wrong speed reported.
1) A pitot heating system powering one of the tubes malfunctioned, or 2) the pitot tubes were clogged. Scenario #2 caused a crash of a Boeing 767 operated by Birgenair into the Atlantic ocean. Or else,
3) Winds aloft pushed the aircraft well above or below the secure air speed restrictions at relevant crz level, where procedure calls for a manual disconnect (the MD11 is a little slow in adjusting to overspeed situations, I prefer disenganging the A/T and manually controlling the thrust)
I am thinking #3. Of course it's just a guess, but who isn't taking those right now.
Here's my opinion on the proceeding events, and the order in which they might have taken place:
1-Heavy headwinds. We both know this slows us down fast and throws us in the trouble zone. An underspeed profile can only be corrected by descending to a lower altitude. Say they went to a FL in between 230 and 280.
2-Hail strikes the engines dead. Alternatively, fuel freezing problems?
Electricity drops, the Airbus deploys it's auxillary wind power generator.
3-Cabin Pressure drops.
Emergency descend to safe altitude.
4-Preperations for ditching the aircraft.
I am really nervous about all of the above. I might be dead wrong with each and everything I wrote here, but my hopes are we will find out what really happened on this flight one day.
Best regards
As always, thanks for the level headed viewpoint. It seems fairly certain that Thor could have batted that A330 out of the sky like a balsa wood toy. I do hope that they find the black boxes as that will answer the technical questions and point to the cause. They will certainly answer many of the open questions.
Out in the middle of the Atlantic there isn't much in the way of weather radar or much else to help fill in the gaps if the black boxes aren't found.
Dave, I appreciate your response to all of the questions you've been bombarded with since the BBC linked your blog to all of us.
For me, and probably for most of us, there is a certain something about the mysterious tragic loss of an aircraft mid-flight. Its actually very macabre when you think about it.
I'd also like to say, you've managed the crazies pretty patiently, and you've proved an excellent source of information.
Cheers,
Scott
revthought- thanks
jay-Thor! I like that...
Patrick Rizzo- yep, you are probably in the ball park. What a friggin nightmare.
Mr. Phil- thanks
Dave, long time reader. As always your blog is insightful. I have a family friend that flies A320 for a major and I'm always amazed by the level of professionalism that is brought to the table by commercial pilots.
I do find it amazing that there is all this speculation and without adequate data as to what may have happened, we simply do not know what happened in the final minutes. Hopefully they find the Flight Data Recorder to provide some lessons learned as to how to continually improve flying for all.
It also interesting how people are trying to address sensors, fly by wire systems, etc. Aircraft are complex entities as we all know and I assume there is always a balance between how much automation an aircraft designer provides to ease up a pilots workflow and how much does a designer force a pilot to contend with.
This is stuff I wrestle with all day in my line of work (engineering usability for non aircraft related systems) and it would be interesting to hear your opinion as to how the Airbus helps provide a safer and more positive user experience vs a more "hands on" aircraft. I have heard positive comments on the layout of the Airbus cockpit in that it does provide a pretty good view of the world.
Thanks Dave, insightful as always.
I've heard some people comment that there's some similarity between the ACARS messages sent by AF447 and the sequence of events in the Qantas flight last year that had a Flight Control Computer malfunction. Both flights were A330s. The source of this information is questionable at best, so I'm not taking it very seriously.
Nevertheless, I'd love to hear your opinion on the possibility that these incidents are even remotely related. What do you think?
Icing in the pitot probes or static ports from super cooled rain seems likely to me. Everything else appears to be a cascading of problems from unusual attitudes trying to fight the loss of Pitot ports. In chronological order this was one of the first things reported by ACARS at 0210Z:
02:10Z:
Autothrust off
Autopilot off
FBW alternate law
Rudder Travel Limiter Fault
TCAS fault due to antenna fault
Flight Envelope Computation warning
All pitot static ports lost
02:11Z:
Failure of all three ADIRUs
Failure of gyros of ISIS (attitude information lost)
02:12Z:
ADIRUs Air Data disagree
02:13Z:
Flight Management,
Guidance and Envelope Computer fault
PRIM 1 fault
SEC 1 fault
02:14Z:
Cabin Pressure Controller fault (cabin vertical speed)
Simon_G
Dave - As always, a great post. I like that you've been commenting on comments. Where is the BBC link to your blog?! I know that publicity can be a double-edged sword, but I think most of us will continue to show the love no matter what!
Dave, thank again for your insights you share on your Blog. I trusted what I read on your Blog more then the stuff I hear on the news. It seems people are just jumping to conclusions on happen with so little information.
Dave,
When I saw comments disappear I feared you had reached your limit and pulled the plug. As a regular reader, I'm glad to see this is not the case.
I enjoy your blog and trust your regular, loyal readers will help to keep your heart in the blogging game.
I'm sure Ernie Gann had his frustrations as well...
Cheers,
Bob in Minnesota
Thanks for the great blog!
Of course we have to wait till at least some of the data has been confirmed, but it is really comforting to read something from someone who really KNOWS something. As there are not so many pilots around... especially the writing ones. Do go on!
Dave...thanks. I have an infinite amount of respect for the Viking God of Thunder. Unlike a former BA Captain turned talking head who said to Sky Networks it's all because of ETOPS, implying that four engines would've carried them through. Not sure which Boeing he flew for BA but you can snuff four as quickly as two in a big enough cell. It's in every 744 sim drill.
Your maturity and professionalism is evident from the manner in which you have handled the recent influx of "off topic visitors" to you blog. Please be aware that your "regular" visitors appreciate your insights and information, and we commend you for "keeping on". We all benefit. Thanks!
Thakns Dave for the topical and very interesting comments as always.
Dave .... on CNN they report that almost all air accidents came from pilots who have at least once failed at simulator test if not more. Is it common for an airline pilot to fail these simulator tests at least once in their flying career?
Snip from comment by Tim
"We hear all too often how Airlines PROFIT from crashes, because the airframes are aged, and insured for FAR more that were paid for them. (This is widely reported to be the case with AA#11 and AA#77, lost on 9/11)"
Hmmmm, it was also "widely reported" that the US government were responsible for the 9/11 attacks - because it is widely reported does not make it so - it simply means that there is some speculation in most cases.
I add my thoughts and prayers for all those on AF447 and to their loved ones.
Dave, as mdavis said, "Your 'regular' visitors appreciate your insights and information, and we commend you for 'keeping on'."
I think we all enjoy the questions readers ask, and look forward to learning from your answers and further comment.
I have come to realise just what an interesting little community we have become here on FL390. We sometimes get to know one another a little better by checking out each other's blogs as names become familiar.
When a new post appears, it's kind of like - ah good, Captain Dave's on the flight deck and we can board for another destination and adventure. You fly the blog and we fill the seats and chat - and the flightdeck, its wonders, and the view are shared with us. (There's even the odd, obstreperous passenger on board!)
Thanks for opening your world to us Dave, and may you keep safe and long continue writing.
Until this dreadful disaster I had no idea that aircraft sent automatic maintenance messages via satellite telemetry.
Which got me thinking; instead of downloading the last thirty minutes or so of flight information to the Flight Recorders, is there scope for the introduction of a system whereby the aircraft downloads flight data via satellites to a database?
That way, if the aircraft went down in unreachable areas, we'd all know what happened PDQ.
I know there is a lot of information, and bandwidth might not be readily available, but it was only a few years ago that Bill Gates was opining that no-one needed more than 640k of memory.
Times change and this might just be the answer to a lot of problems.
Ah well, that's my tuppence worth (coupla dimes to you lot with the funny accents :) )
Patrick
Dave,
I've attempted to avoid almost all media coverage of this tragic incident, however, on the rare occasion I'm forced to view or read the coverage, it never fails to range from simply inane to outrageous and brings a certain sense of truth to the lyrics of Don Henley's famous song. At times like these I'm relieved I can visit this blog and read your measured, balanced, and professionally reasoned thoughts.
Wishing you continued safety on the line.
Hi Dave and others,
I just read the news that AF pilot unions have recommended their members not to fly A330/340 that have the same speeds sensors as the crashed A330.
I'm very supriced to hear this news because I would expect that pilots know best that all kinds of "news" concerning the reasons for the accident are merely speculation right now.
If there really were significant problems with the sensors in the A330/340 (remember AF already changed these sensors in its A320 - as recommended by Airbus quite some time ago) the pilots should have acted beforehand and start a publicity stunt right now....
What do you guys think on this news?
Very interesting take on the weather
http://www.weathergraphics.com/tim/af447/
Dave - Once again, I appreciate your professionalism and candor.
A statement in a newspaper article caught my eye and am interested in your comments. It said "At cruising speed at high altitude, a plane has to fly within a fairly small margin of speed...If speed drops just a little, the plane can lose lift. If the speed is too high, it causes instability over the control surfaces." The article also implied that hand flying at cruise speed was very difficult.
The small speed range is very true for U2s flying above FL600, but it seems counterintuitive for commerical aviation.
Cheers,
David
Miles O'Brien, in http://trueslant.com/milesobrien/2009/06/08/the-coffin-corner-and-a-mesoscale-maw/ , states that modern jetliners such as Air France 447 commonly cruise within a narrow 25-knot speed window called the "Coffin Corner". Scary stuff for passengers, if true. And on top of that, you say that you're usually piloting with a tiny fuel margin. I'd be interested in your comments.
Miles O'brien is wrong on the 25 kt speed envelope.
Dave has never called his fuel reserve "tiny." It's never as large as the Capt. would like. We all want unlimited fuel.
Hey Tim! I think I resent this stereotype:
"Many folks, ESPECIALLY middle America, believe if FOX news reports it, it's BIBLE Truth."
Give us scandinavian folks in middleoftheroadfyloverland a little more credit than that, will ya? LOL!
Tim G in MN
Tim...regarding any bomb threats, my wife worked for three air carriers during her airline career. Believe me when I say that bomb threats are almost as regular as the stock report. That doesn't mean that they're not taken seriously, they are taken very seriously, it's just that it's a regular occurrence on any large carrier. Someone once missed the flight my wife used to manage and actually called in a bomb threat under the belief that the plane would turn around and he'd be able to board it then. They ended up landing in Turkey to clear the aircraft, an expensive proposition since Istanbul was an offline city for that carrier. (Meaning no ground or support staff to assist at the airport.)
As for airline executives, yeah well it's kind of hard to love a group who, as a whole, have taken air travel (particularly in the U.S.) from it's glamourous and exciting past to not much more than a Greyhound bus with wings today. That sounds harsh and I mean no disrespect to Dave or any of the workers who I know are working hard to keep the shiny side down but it is a fact. It wouldn't surprise me if some carriers put quarter boxes on the toilets in their continued disdain for their passengers (and to help pay those fat exec bonuses).
My only bit of consternation with AF 447 that raises the hair on the back of my neck is how AF keeps repeating that the black boxes may never be found. While that may be true I'd rather they set that expectation and then say what they're doing to try to recover them. As it reads to me it's as if they don't even want to search for them. Or I'm mis-reading French reserve, hard to tell.
(Sorry Dave to have used up so much space. Feel free to edit, delete as you see fit. As always, blue skies Captain!)
Dave, Here is what I would like to know. How do you prevent your oft-used stubby #2 pencil lead from staining your shirt pocket? Do you use a pocket protector? Or is the famed stubby #2 pencil really a mechanical pencil with retractable point?
david- hand flying at altitude is not that difficult. My minimum envelope between overspeed and stall buffet is 50 knots hand flying or 30 knots on auto-pilot. If it is turbulent I will descend to increase the margin. Even 25 knots is OK in smooth air.
tim- I think the crew inadvertantly flew into a thunderstorm and suffered structural failure. Flying into a big storm will cause huge airspeed fluctuations, auto-pilot disconnect, inertial reference malfunctions and on it goes. Flying at turbulence penetration speed will not protect you in a thunderstorm.
jeff- that is correct. Our fuel reserve is never as much as I would like, but since they sign the paychecks...
ron- I keep my pencil stub in a side pocket on the flight bag along with a 20 year old hand calculator. It drives my young co-pilots crazy.
wdfarmer- 25 kts would be OK in smooth air. I routinely fly at 30 knots with auto-pilot/ 50 knots hand flying. Our fuel reserve depends on weight and weather, always 45 minutes in good weather.
tim- I might be mistaken, but I believe the crew told the ATC controller that they were about to enter an area of thunderstorms. They probably flew into a radar shadow, or were struck by lightning which knocked out their radar. Thunderstorms are very dangerous to aircraft, even big ones.
No, I do not believe AF was in anyway negligent over the pitot tubes, air data computers. I am quite sure they were working OK when they flew into the storm. This whole media blitz over the pitot tubes is kind of like looking into a politicians background. If you look hard enough you will find dirt.
I doubt they will recover the black boxes because of the depth and terrain of the ocean floor, however I might be proven wrong on this...
Tim: No problem, just wanted to distinguish Lutherland from Bible Belt.
Thanks!
Tim G in MN
Just came across an "ancient" DC-8 pilot's report who climbed away between thunderstorms. He said something like "We encountered the most violent jolt I have ever experienced in over 20,000 hours of flying. It was like sitting on the end of a huge tuning fork that had been struck violently. Not an instrument on any panel was readable to their full scale but appeared as white blurs against their dark background. From that point on, we had no idea of attitude, altitude, airspeed or heading. Violent buffeting, ripping, tearing, rending crashing sounds. Briefcases, manuals, ashtrays, suitcases, pencils, cigarettes flying about like unguided missiles...and so on....
Guess it's better to put the seatbelts on, when captain Dave tells us to do so.
@Dave...they told mother view text message that they were entering a "dark cell" (per BBC News). They were out of range from ATC except via HF which would've been useless in such a storm.
@Tim...since we still fly on her furlough benefits I won't say who it was. :-) It wasn't QF but the seriousness is the same everywhere.
I also agree with Dave, I don't think AF is negligent. And European courts tend to not be as "plaintiff friendly" as U.S. courts. The concept of risk and personal responsibility are looked at different in Europe. Only if there was a cover-up or if they were truly negligent (i.e. deferring maintenance on a safety item) would the courts get involved. And then there would also be jail terms for the executives. If the airframe broke up due to the forces of nature there isn't any legal liability. You can't sue nature.
Think about this, if a catering truck striking an aircraft doorframe too hard can take an aircraft OOS by damaging the pressure seal what about a storm producing 10,000 fpm updrafts? Planes are sturdy but I don't know of any item manmade or natural that can withstand sudden and drastic changes in speed and/or pressure. None.
I'm truly saddened by the thought of the forces those passengers and crew endured those final minutes. It had to be horrific and hellish.
As for the pitot tube replacement, AF will say that Airbus didn't make it an emergency order. And Airbus will say that the JAA didn't require an emergency order, both of which are, in hindsight, perhaps unfortunate but also true. In this case I don't think it matters whether they lost pitot and ADIRUs. Or if it would've been different with the replacement pitot. Right now those are just symptoms rather than a root cause. All of which is why I pray that they find the FDR and CVR even if I know it's a long shot.
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