Position: Over KMCI (Kansas City)
Altitude: 33,000 feet
Mach: Seven-seven-five
Equipment: A321
Pax-on-Board: 183 + 3 jumpers
Airborne...
Holiday heavy with fuel, pax, bags, and cargo over the vast Midwest this morning. We have one pilot jumper stretched out full length on the cockpit floor in front of the circuit breaker panels; he is fast asleep covered with a light weight windbreaker. It is freezing on that floor, as well as noisy from the cooling fans in the Star Trek Bay underneath, but he is exhausted from flying a rigorous schedule today, make that yesterday.
My co-pilot, a thirty something whiz-kid, is reading a much used paperback he picked up in the pilot locker room. All is quiet at 0010 hrs local time. The radio frequency is quiet, too. There is no convective weather to deal with until arrival at the east coast. Fi-Fi's long fuselage will flex and twist a tiny bit from the very light turbulence we encounter at this altitude. Overall, a good ride.
Midnight meditations... I have had many emails generated from this blog requesting a read on the initial AF447 four page letter that the BEA released. Some of the comments from a few Wikipedia Warriors and Internet Oracles are unbelievable. I would pay good money to see these folks take a simulator ride re-creating the conditions of AF447.
It is not yet clear what those conditions were and will not be until the final accident report comes out in 2012. However, it appears that two young co-pilots lost control while the captain was resting. By the time the captain got back to the cockpit, they were probably doomed. It would take a substantial amount of altitude to recover a fully stalled A330 with a high angle of attack, a 15 degree pitch attitude, and 10,000 fpm descent rate.
Thinking about that gives me the creepy-crawlies.
What could possibly happen to cause such parameters? I am not buying into the theory that the two co-pilots did not know what they were doing. Air France pilots are some of the best on the planet. Obviously, they were presented with very confusing and conflicting data. And that is probably an understatement.
The aircraft gave up the protection of Normal Flight Laws and fell into Alternate Flight Laws which is a different ball game. The co-pilots did recognize that event. They were aware of conflicting data from the ADC (air data computers). But why did the two young bucks (quoting one of my retired Captain buds) start increasing pitch angle? Why didn't they ignore the bogus data and fall back on pitch and power? Why, why, why... ?
For one, I am intensely interested in the minuscule details of this event and will read the 200 plus page accident report when it is published.
This post written on the fly, so to speak. I am in the middle of a four day transcon trip. Fly all night and sleep all day... The vampire sched.
Life on the Line continues... Remember, when all else fails... Pitch and power.
56 comments:
Great post Dave. A lot of frustrating, unfair, uneducated things are being said about this flight crew. It's so easy to ask 'why' after the fact. Why didn't they.......? After this accident and the Aeroperu/Birgenair 757 accidents, I think it's safe to say pitot-static system failures are one of the most complex, confusing emergencies to deal with.
"I would pay good money to see these folks take a simulator ride re-creating the conditions of AF447."
One might expect airline chief pilots around the world with access to sufficiently capable simulators to have tried this already. Any idea how those went?
Cap'n:
I think everyone with any sort of a pilot's license is being bombarded with questions about AF447. Agreed, the real issues will emerge from the minutiae.
Meanwhile, how about Big Red Button that punches you out of everything except pitch, power and raw data?
...and when all else fails, may you be blessed with the clarity of vision to see that all else has failed.
Hoping your flights stay uneventful,
Frank
It really pisses me off when I read in the newspapers that so called experts basically blames the pilots for being unable to maintain pitch & power when facing unreliable data.
I think you really have to put yourself in their position, all of a sudden, out of nowhere the airplane starts giving you all kinds of warnings and hands control back to you.
I mean, the Airbus philosophy is basically "the computer is always right" (Air Transat Flight 236
comes to mind) and now it's disconnecting all systems and start telling the pilots they are wrong no matter what they do!
I'm sure some pilots would have been able to get out of this situation in the simulator, but when you're in there, you are expecting something to happen and you're mentally prepared it. I don't know but I doubt you're in the same mindset when you've been cruising on a routine flight for a few hours just like any other day.
"There but for the grace of God, go I" comes to mind.
Another good chapter for the book, Captain.
"...I would pay good money to see these folks take a simulator ride re-creating the conditions of AF447..."
So would I, If I had any. I think the "folks" would break first, but the simulator could be a close second.
i3simes: very correct!
fche: probably so, but I do not know that for a fact. No way a non-trained A330 pilot could survive this, no way. Especially if they did not know it was coming.
Frank van Haste: I like that! ...and when all else fails, may you be blessed with the clarity of vision to see that all else has failed. Amen!
Edwin: OK, this might be the comment of the year... Excellent! Just frigging excellent!
Captain Dave, Thanks for the brief comments regarding AF447. In some ways I think the industry would have been better served to hold off on the short report, but I'm sure the press has been pushing for the initial read of the recorders. I'll be looking forward to reading the whole report too.
Hey Frank - ..and when all else fails, may you be blessed with the clarity of vision to see that all else has failed. That is great, a new motto to live by.
I completely agree with you Dave. What happened to those poor guys was off the richer scale. The keyboard warriors are immensely frustrating, I suppose we have to factor all this palaver in these days...
I agree with your why why why Dave. Having read the BEA translation there are two things I find puzzling. Why does the stall warning not sound continuously until the stall has been fully overcome...is there a design reason for this. Also, when the PF lowered the nose briefly, the stall warning sounded...surely that's precisely when it shouldn't sound as he was beginning corrective action. Or maybe I'm way off base here.
What are Air France SOPs for Alternate Law high altitude stall recovery?
I remember in one of the previous posts here is mentioned how little airspeed margin there is at high altitude.
Coffin Corner?
I have two comments on the AF crash:
1) Your point is well taken that we don't know what was going on, but all indications are that they had a functioning attitude indicator. Can you, in your wildest speculation, even begin to posit a scenario where pulling up and reducing power is the right answer?
2) Most intelligent people aren't suggesting the AF pilots screwed up, but that they were failed by a system that adds more and more automation to the point where pilots become systems managers, and then in the rare case they find themselves back to a basic airplane, they are woefully out of practice in the art. That seems like a fair criticism to me, and I hope you address it at some point. The truth is that many people have lived through iced pitot tubes, but not many have lived through it in an Airbus (or experienced it, of course). I think THAT is really the crux of the matter.
Bottom line is blaming or not blaming the pilots is completely beside the point. I'm more worried about the fact that the airplane with that much automation suddenly turned into a partial panel instrument exercise. Even if it turns out those AF pilots weren't the best pilots in the world, and better ones would've gotten out of it, I don't care. I don't want to fly in airplanes that sometimes require the pilots to be the best in the world.
Dave, I strongly agree with your wise handling of this topic and with the wisdom in your readers' comments.
A lifetime of seeing misreported aviation news in the media has taught me to ignore it all until the final, official report is made public.
I'm sure journalists are given a headline including the words "pilot error" and told to write a story about it.
No doubt much has changed since 1986 when I retired from flying long-haul jets (B747-300). In my era, hand-flying at cruise altitudes was discouraged in the interests of passenger comfort. (Achieving smooth, accurate flight in the thin air was likened to milking a mouse; and the mindless auto-pilot's altitude-holding skills put us to shame).
Nor did we spend a lot of training time in high-altitude stall-recovery, or recovery from unusual attitudes on limited panel.
So when, without warning, a situation arises which needs those unpractised skills, it can be very daunting indeed.
Your "creepie-crawlies" aptly describes the sensations I experienced one night cruising in silky smooth cirrus. For no apparent reason, the altitude-hold clicked out followed by the conflicting indications of both airspeed and altitude increasing rapidly. We managed to get the beast back under control without waking the passengers, but it was a harrowing few minutes.
Is there more emphasis on training for these events in modern times?
...but if two young bucks pull back on the stick at the same time, you know what happens (dual input). Perhaps nothing happened because they were both pulling? But then again, why pull when in a stall?
Ryan
Dear Captain Dave, thanks for making your short "from the flighdeck" evaluation of this prelimiary report. For everyone, professional as well as amateurs just with some knowledge about flying, it is puzzling why the PF kept giving nose-up sidestick commands. It goes against everything they were supposed to learn about aerodynamics and stalls. I agree with you that something went wrong in there- BIG TIME. But isn't it that due to our sympathies with the pilots we would be too reluctant to accept that they froze in the moment of emergency? Is this possible at all with crew of 3? You mentioned several times that critics should try the situation in the simulator: more importan, of course, would be to know what professional pilots would be able to do in the same situation? Could the airframe have been saved and lives spared? I guess, we'll have to wait for the final report. May your flight stay uneventful. Istvan
One hopes that somebody can get hold of the FDR raw data and uses it somehow to make a sim ride of it and see if the airplane was recoverable.
I know that some time ago this was done after an Air NZ B767 had a problem landing somewhere in the Pacific (Nadi, Fiji I think it was) and the simulator crashed every time somebody tried to fly the conditions that the crew experienced on the real thing.
"Some of the comments from a few Wikipedia Warriors and Internet Oracles are unbelievable. I would pay good money to see these folks take a simulator ride re-creating the conditions of AF447."
Yep, I'm sure you would Captain Dave...
Having spent time with a bunch of phobics in the cockpit of a Boeing I-don't-know-what as it stood on the tar - being slightly buffeted by a moderate wind - in front of Cape Town International with that HORRIFIC alarm sounding, I can tell you I'm not up for the AF447 simulator experience!
Remembering all who perished on that tragic flight.
Bev
Cape Town
Remember guys, it wasnt just a partial panel situation, they were dealing with Atlantic Thunderstorm, and if you check the WX radar for that time, it was one heck of a Thunderstorm ... Moderate turbulence for sure, continuous updrafts and downdrafts, it is something serious.. Plus the Air Data disagreement... I had the chance of flying across the Atlantic on an A320 ferry Flight and it is a route to have respect... But like everyone said we need to wait for the final report to talk about with facts!
Great post again Captain Dave
Captain Dave:
I'm not a pilot, but I am curious: is it even remotely possible that it was AF447's computers that pulled the nose up, not the pilots? I understand Airbus systems are designed to prevent the pilots from doing anything really incredibly stupid; what if the aircraft's electronic brain lost its mind?
Finally catching up, after reading all your seven years worth of blog posts. Keep it up Captain!
About AF447...
Well, could vertigo have played a role in it? Would that explain pilots' nose up inputs?
They were inside CB clouds and there had been embedded thunderstorms. I.e. Heavy Turbulence and lightning inside Amidst that the pitot tube freezes up and they lose reliable information from ADC. The pilots are given the challenge of flying that beast with unreliable data, in an emergency situation inside turbulent clouds with lightninng all around them. They are trying to read the instruments whilst they are being bounced around.
I've been taught that the strobe lights inside the clouds can give you vertigo. Could the lightning inside heavy turbulent clouds in an emergency have made the AF pilot/s susceptible to vertigo?
Regarding AF 447, the initial report says "The trimmable horizontal stabilizer (THS) passed from 3 to 13 degrees nose-up in about 1 minute and remained in the latter position until the end of the flight." This was they were still in the vicinity of FL 380. Possible trim runaway?
Thanks Dave. Lots of folks have lots of questions about the demise of AF447 and, as you note, we just have to wait. The final report from BEA, with participation from Airbus, AF and others will tell us a lot more. I guess my rhetorical question about the Electric Airplanes and Normal Law vs. Alternate Law tends toward loss of reliable metrics. If Electric Airplane does not believe the data and the pilots have no relable alternate sources with which to hand fly, then what? I found the BEA summary and will read it, but with only a limited understanding of E.A. systems, I lot of it won't compute well. When the final report is issued, we will rely on your experience to translate it. Thanks for the update. -C.
An Addendum: I agree with several other posters that the vast majority of the popular press articles about AF447, including their reporting of the recent BEA summary are poorly onformed - at best. That's why we read you, Captain Dave! Thanks! -C.
Remember, when all else fails... Pitch and power.
Captain Dave, please would you explain what this means....as though for a pre-schooler.
Thanks.
Bev
Capt Dave,
I've been trying to find something on the www to try to get to grips with your last comment: Remember if all else fails pitch and power...
I stumbled across some info. on pitch and power, which lists some interesting-sounding books written on the subject - although I think they'd be beyond my grasp...
http://faaflighttest.us/pitchandpower.html
The information left me feeling pretty backward....tho' it served to up my respect for pilots (...if that is possible) who ferry humanity across the globe.
I don't think I like Pitout tubes...they bother me immensely...
Anyway, I don't think you +can+ assist me in understanding what you're talking about so....let go...
Great number of blogs for the merry month of May.
THANK YOU !
Bev
I saw this PBS NOVA tv program about AF447 and it seemed very good. As a pilot I'm used to cringing often when TV people play with airplanes. This show seemed up to the usual high standards of Nova.
http://www.pbs.org/wgbh/nova/space/crash-flight-447.html
Capt.Dave, Thanks for the input on AF447. Like most here, I've been pouring over what little info there is out there. I know little about modern aircraft or the computer systems that help fly them. Simulators are great but like Skeeter, I've experienced what it's like to have the bottom fall out of a perfectly fine plane on a normal flight. A P3A Orion, we were on our way to Hawaii, flying near our ceiling altitude of 30,000. Auto pilot was, of course, flying the a/c. Suddenly we were decending like a over loaded freight elevator and Weightless.Because we were not on station,the crew was in various places, not at their duty stations. All of us and everything that was not strapped down, paper, coffee cups, ashtrays full of cigerettes, pencils, charts, etc all in a very disorentated mess. The cockpit, was strapped in per standard procedure,as I assume you are too. We dropped nearly 5000 ft before they were able to regain control by disengaging the auto pilot. Now, everything that was up, came down. Scarey stuff. The autopilot did not get the blame, but it was decided wind shear was to blame. I guess, I'm taking the long way around to say, on top of everything else that Air France crew was dealing with, adding weightlessness to the mix must have made it much worse. One simulation that cant be duplicated in a trainer. If the Captain was out of the cockpit, he must have had a helluva time trying to get back as well.
Dave
This accident, and the initial report, are truly disturbing.
But it's also amazing that we have the data boxes, recovered from once hidden depths, and in time we'll all get to see that 200+ pager, the flight data and the cockpit voice recorder in full.
The holding statement, satisfying an initial craving to know something, has only raised more questions, making the craving worse.
All we know for sure is we need to know a lot more to understand what really happened that night to AF447.
Jonathan B said: Can you, in your wildest speculation, even begin to posit a scenario where pulling up and reducing power is the right answer?
Well, yes: if you believed you were in a dive. With your altimeter winding off at 10,000ft a minute, that's just what you might indeed do - pull back and pull up. And dare I suggest, even if you had your attitude indicator - you might not believe it, especially with Fifi tripping out, and a whirring altimeter getting your (perhaps undivided but confused) attention. They'd just zoomed climbed...they might just have easily thought they were in a zoom descent. There were storms around too remember.
Anyway, I confess, I don't know. Let's hope the report has the answers so we can all learn, and avoid this happening again.
Captain, as ever, I remain humbled by your meditations.
As a software engineer I find it hard to understand that you could (are allowed to) build a system (carrying people!) that will give up (Auto pilot disconnect) in the most critical (coffin corner) point due to some failing inputs (as it seems). It is well known that pitots and static ports can be blocked. It has happened before. I find it totally unacceptable that a modern aircraft can respond in such a way. Important inputs must be redundant (by different techniques) to a much higher level and it can’t be that hard to figure out which inputs are high priorities. I used to love flying and admired the modern aircrafts but this really breaks my trust.
Captain Dave, if the AF447 Captain wasn't in the cockpit at the time horror broke loose, where might he have been ?
Is it possible that the "young bucks", in the absence of the pilot, might not have had adequate training to deal with the situation ?
Bev
Bev: the most important single factor for a wing is "angle of attack" or AOA, the angle between the wing and the air flowing over it. At any combination of air conditions (primarily speed and density; density changes with altitude) there is a safe range of AOA. Within that range, if the airplane has enough power it flies, and if it has a little more power it climbs. If there isn't enough power it descends, and in the worst case it stops flying and falls -- that's a "stall".
The range depends on the total engine power available, which is always limited. Some military jets can climb straight up, but they aren't "flying" in that case, they're balancing on engine thrust like a rocket. An airliner doesn't have that much power because the engines would be too expensive and use too much fuel.
AOA is very difficult to see, feel, or measure, so Cap'n Dave and his fellows use pitch, the angle of the fuselage, which they can see and feel, and which is closely (though not simply) related to AOA. Cap'n Dave has a chart showing allowable pitch angles at various combinations of altitude, speed, and power. That chart is pointed at the top, because at high altitude the permissible range of pitch angles is very small.
The fundamental task of the pilot is to keep the combination of pitch and power within the safe range, where the airplane is flying, not falling. That's what the phrase "flying the airplane" means. At extreme altitudes, where the range is tiny, the task may be so exacting that no human being can do it, so the autopilot computer takes over.
In the Good Old Days pilots simply didn't go that high. Mother wants them to fly as high as possible, and so do you, because the airplane uses less fuel up high, keeping the cost of operation (and your ticket) down. Modern autopilots are sensitive and accurate enough to fly the airplane at extreme conditions. As a byproduct, they are also much "smoother" than hand-flying at any altitude, so Cap'n Dave and his fellows use the autopilot whenever possible to keep the airplane at its best performance point, which keeps fuel usage down. It also gives the passengers the nicest, smoothest, most stable ride possible.
The autopilot depends on sensors to determine the conditions to which it must respond. If the sensors become inaccurate, the autopilot will do the wrong things. If the computer determines that the sensors are wrong, the autopilot will turn itself off and tell the pilot "handle it, Cap'n". That can happen suddenly, and always happens in the most extreme and confusing conditions. Being ready and willing to "handle it" when the need arises is how Cap'n Dave makes his living.
What a helpless feeling they must have had...
do you think same would have happened during a day flight? would visibility,even assume limited in the storm, have improved the situation?
First rule of law regarding causes of aircraft accidents:
When pilots are dead, it was their fault.
Hi Dave -- Thanks for the writeups on AF447. I occasionally read pprune.org, and thought that this particular post (in reference to a Der Spiegel article) was instructive and worth sharing.
http://www.pprune.org/rumours-news/447730-af447-wreckage-found-62.html#post6486343
Take care, and thanks again!
hmmm ... When I watched the NOVA "crockumentory" earlier this year ...well it was so incredible the first viewing that I had to watch it again ... I was offended. Matter of fact, I was bothered by it immensely.
(thanks Bev ... I was at a loss for words there)
Kinda interesting how people can look at the exact same information and see totally different things ...
"when all else fails, pitch and power". Got it. I wont forget.
Thanks for your input there Warlock.
Much appreciated and it made for interesting reading.
Captain Dave had also tried to help.
Tho’ I think sometimes – even with the best of intentions of sundry authors – the poor pupil remains somewhat dejected at the back of the class and a tad shamed by her limitations….
BUT…….this is why I have such respect for folk like pilots who grasp all this complex stuff !
The brilliance behind all this phenomenal technology just blow my mind.
Just those little things that measure fluid flow velocity continue to trouble me and even increase my inability to set foot on any magnificent aircraft.
A while back Captain Dave made reference to E K Gann’s *Fate is the Hunter*.
I have finally managed to find it here in S.A. and it’s on its way to me…..
I CAN’T WAIT !!!
Excellent explanation warlocketx.
Dave, it's funny that you posted this Monday, because on Tuesday there was new information released and an interview with Captain Sully (the new Aviation Safety Expert, good pick) regarding the details.
Summarizing, Sully suggests that we're building our airplanes too complicated to fly when "things go awry"; that it's too hard to revert back to the basics (steam gauges I guess) when the smoke and mirrors go ca-put. I wonder what your opinion on this is?
Here is the interview:
http://www.businessinsider.com/sully-chesley-sullenberger-cbs-air-france-2011-6
Grayson
They were not the only ones on the same route from South America to Europe on that fatal night.
As far as my knowledge goes, they were the only ones to elect that DIRECT route through those dense clustered intertropical-onvergence-zone thunderstorms.
All the other flights at that time CIRCUMVENTED!
Had the Captain been on board, respectivel on flight deck:
would he have approved the decision?
Pitch and power in the absence of airspeed is a delicate balance at the best of times, fine in daylight with external references. But consider the scene when the crisis came. A pitch black windscreen in turbulent conditions, the lowest point of your circadian cycle in the wee small hours you are suddenly handed the surrender of the electric jet’s electronic pilot with conflicting airspeed numbers. My heart goes out to those guys and their passengers.
Dave, I really enjoy your writing. A new post from you is often one of the high points of my day.
All this talk about duplicating the conditions in the cockpit of AF447 in simulators is only valid to a point. There are a few things that no simulator can duplicate. They cannot duplicate the physical feel of dropping out of the sky at 11,000 feet per minute. And they cannot duplicate the mindset that dropping out of the sky at 11,000 feet per minute engenders in a human. When you are in a simulator, you know that, no matter what happens, the worst that will happen to you is that you get chewed out by somebody. When you feel that airplane start to fall, when all the loose crap in the cockpit starts to float by your eyes, when you know that you only have minutes, if that, to come up with a solution before you die...well, I think you do things a little differently that you would in a simulator.
Captain Chesley "Sully" Sullenberger reacted one way when the excrement hit the oscillating blade. I wonder how representative he is, though.
Anyhow, I do not want to disparage the men in the Air France cockpit. I am sure they did everything in their power to keep that aircraft in the air.
Pitch and power, captain. Pitch and power...
In an earlier post you commentated that a co-pilot doing a crossword was on the edge of what was allowed, where does reading a book come?
Jobrag
This "pitch and power" thing has got to me Captain Dave.
I watched a simulated version of Captain Sullenberg ditching in the Hudson and what astounded me was how high the nose of the aircraft was as he was descending toward the Hudson after bearing left after the bird strike....
That his plane remained airborne (and didn't fall to earth) with its nose so much higher than the tale was beyond me.
I would have thought the nose would have been lower than the tail section (in order to gain speed so as to stay airborne).
Nope.....there's the nose, way up there....
And why is the angle of the nose (in relation to the ground?) known as the AoA (Angle of Attack).
Why the word ATTACK ?
What IS it that's being "attacked"?
Warlock did a sterling job trying to help me....
And left me with yet more questions.
I hope I don't prove to much for you and Warlock ?!
Bev
Zoom up in to a 38,000 foot stall with a full boat and descend into a thunder storm.
Uh huh,yeh, uhhhh.
Whatcha gonna do?
Oh yes,don't forget, most of the instruments are showing conflicting information.
Well, hell, just go to the horizon son. Put that baby right there on the line,power at cruise or more.
Well yeah, but there's all this commotion . Overspeed and stall warnings.Which should we believe?
Back when I pulled the power back the stall warning came on again.
It's night.We're in a thunderstorm.
It's five minutes.
What a nightmare. God bless them.
Great post! I've been reading your blog with enjoyment for some time now and I've never left a comment. My thoughts to the families first of all.
I used to fly as an engineer on a cargo plane flying extended over water, sometimes near the equator. Unfortunately we could never get over any weather in our path especially these huge thunderstorms. Our altitude was always in the low twenties because we weighed too much to climb any higher. I especially did not like transiting these areas at night, as our weather radar was not up to snuff with systems they have now.
I saw the NOVA show about the crash and I would have to say they definitely did not even come close to displaying the level of turbulence that they would have experienced in that storm that had tops up to 55k feet. From my experience, simulators don't even come close either. Probably at the severe category or maybe some extreme?
No airspeed indicators. Probably had all the anti-icing equipment on, that would take more power from the engines. I'm not familiar with airbus systems but I suspect that their service ceiling would be affected with these systems on and would had made them slow with a high AOA if they tried to stay up there. These guys were trying to keep the aircraft upright in these updraft/down drafts without any airspeed indicators. I've seen my crew try to maintain control in a thunderstorm with a load of ice on our fuselage, let alone take away our airspeed indicators.
I think these guys fought for control all the way down and never gave up. I get upset when people that were not there try to assign blame so easily. Especially folks that don't fly. I can't believe statements made that other aircraft passed through that same area with no problems so AF 447 should have too. Weather changes! Holes around thunderstorms close up. Rapidly sometimes. Put them in the cockpit and ask them to read their inop indicators in severe turbulence and maintain control.
I enjoy your blog Captain Dave, keep up the great writing and fly safe.
Well spoken. I have been flying private planes for thirty years and I would in no way begin to second-guess these highly-trained professionals. Let's see what happened and all try to, dammit, learn something.
Grayson- My position on the A319-320-321 is that they are very easy to fly stick and rudder; as easy as a Cessna. Switching off the smoke and mirrors only requires the push of a couple of buttons. The problem is that the training is toward managing the smoke and mirrors. There is no time to fly stick and rudder in the simulator; we are overwhelmed with learning tasks mandated by every government agency in town. So, you have two young guys trying to pick their way through TRWs in IFR conditions and two of the mirrors start reflecting light the opposite direction. Uh-oh!
I have read and re-read this excellent post and all the stimulating comments with great interest. I am learning lots, and especially appreciate Warlocketz's information, primarily for Bev.
I can add no more than to express my great respect for the skilled and well-trained pilots who take on this huge responsibility for their passengers' lives. It is a testimony to them that events like this are so few.
Pilots: PLEASE correct anything I get wrong!
Bev: I see no one else has answered you last question. I THINK I understand what was going on enough to try to explain it.
At that point, Captain Sullenberger wasn't exactly trying to fly the airplane; he was setting up for a controlled crash into water! Capt. Sully was playing a three-dimensional balancing act: he needed to maintain the right amount of speed for a controlled landing. The best way to accomplish this when landing an unpowered aircraft is by controlling the pitch.
Complicating this all was the need to hit the water at a safe angle. Anyone who has ever done a belly flop off of a diving board knows that water can be HARD. Had Capt. Sully held the nose up too high when the A320 hit the water, it could have broken the tail off; if the nose were too low, it could have dug into the water and broken the airplane into pieces. Had he landed too fast, the airplane would have skipped across the water, creating all kinds of hazards; had he landed too slowly, the A320 would have stalled, and at some point dropped vertically in the water.
I suspect that Capt. Sully wasn't really thinking consciously about all these factors; most likely, he was relying on his many years of experience to guide the A320 into a safe water landing.
Bev,
It's not the angle of the nose -- that's pitch. Angle of attack is the angle the wing makes with the air flowing over it. What it's attacking is the air. The term was chosen a long time ago, and back then people were a lot more comfortable with military-related metaphors than they are now.
The higher the angle of attack, the more lift at a given speed, until AOA becomes greater than the power available. The more speed at a given angle of attack, the more lift. The airplane needs enough lift to counteract its weight, so at slow speeds the angle of attack must be high.
There are two ways to change the angle of attack: change the pitch angle (bring the nose up or down) or change the shape of the wing. The flaps, the big panels at the back of the wing that move for landing, change the shape of the wing so that the angle of attack is greater for a given pitch angle than normal. The pilot wants to go slowly for landing, so he wants a high angle of attack for lots of lift, but a high pitch angle would make it hard to see the runway, so he uses the flaps to increase the angle of attack without bringing the nose up too high.
Capt. Sullenberger had the nose high for two reasons. If you try to land on water with the nose down it might (in the ocean, almost certainly will) dig in and plunge the airplane to the bottom, so having the nose high is a good idea. He wanted a high angle of attack, because the airplane was going slowly and needed lots of lift to stay up, but using the flaps takes power, and with the engines off he didn't have any, so he used pitch instead.
Regards,
Ric
I am a the most amateur of pilots but had the following questions:
Has the Thunderstorm/turbulence been understated? If they just lost the airspeed indication why wouldn't they just keep the plane at the same attitude, why pull up or pull down? Were they battling updrafts and downdrafts? I think when the Autopilot disengaged it said that they "rolled to the right" was that the turbulence taking them that way? What I'm getting at is..if you were cruising at 35,000 ft. on a clear day and all of a sudden lost your airspeed indications, why panic and start pulling up or down? I think the understated fact here was the brutal weather causing speed and altitude/attitude variations? Does that sound right?
2) The Pitot tubes froze. That didn't happen on any of the other flights including another AF A330 in the area that night? Did they somehow fly into a worse area of weather than the other flights and why? The articles and BEA seem to somehow dismiss the storm aspect by saying they did a good job of trying to go around them. Based on the radar presented it looks like there was a very small window to avoid the "dark red" and maybe they just ran into the worse area compared to other Flights that night and had icing issues.
My bottom line question is :If it were not for the darkness/bad weather and lack of a real horizon, would they have ever stalled even if they had lost the airspeed indication?
If you read about Northwest Flight 8, they had almost the same thing happen to them, except they were in better weather during the daytime....
Just watched the Nova documentary on AF447. I immediately thought, why don't the designers incorporate a GPS backup. At least if they lost the Pitot system, GPS could still provide speed/altitude info!?!?!?
ZMP-ATC
May I Captain Dave.... ?
Artie See and Ric (Warlocketx) this is amazing stuff.
THANK YOU for your guidance there.
Makes me want to watch (yet again) that simulated version of Captain Sullenberger ditching.
I will of course....
And it sure underscores Captain Dave's great praise of Captain Sullenberger's accomplishment.
I will need to read and RE-READ what you have said about the AoA to try and get my head around it.
Just amazing !
Thank you.
Bev
Cape Town
@ Craig and Sheila: I'll try to come up with an explanation, although it might not be completely right. I'm not a pilot, I have a basic - but incomplete - understanding of how things work, and I'll try to explain this the best I can.
First of all, the GPS provides speed info (check the two pics in this post here) - in the first image you see two values, first the 240 which means air speed in knots and .71 which means the plane is flying at 71% of the speed of sound.
In the second image you see some more figures: the GS meaning ground speed is the speed over ground as recorded by the GPS, while the TAS (true air speed) is the airspeed corrected for altitude, as calculated by the plane. All values mentioned here except for GS are either directly linked to the airspeed provided by the pitot tubes or derived from that speed corrected for altitude as provided by the static ports (mach speed and TAS), so if either the pitot tubes or the static ports are blocked and give unreliable data, all of those speeds except for GS are unreliable as well.
So, we have GPS speed, but does this help? As you'll see, maybe it does, or maybe not.
(continued)
On the second row you see two values, 232/151 which means that at the altitude the plane is currently, the wind is blowing at 151 kts from (roughly) the southwest. That is more than half the speed of the plane itself! Now, depending on the direction the plane is flying, the 150 kts can be added to or substracted from the plane's speed, meaning that if the plane was flying with the wind straight from behind its speed (plus the speed of the airmass) would be of 390 kts and if it were flying against it it would have a relative speed of only 90 kts (think of swimming with and against the current).
Now the GPS, as I said, only provides ground speed, and the same GS can be obtained by flying at different airspeeds with different windspeeds (you can have the 90 kts mentioned earlier by flying @240 against 150, or @ 150 flying against 60, and the second would be too slow, meaning stall).
So, assuming you know the GS you had before the pitot failed, you can assume that maintaining the same GS means keeping more or less the same airspeed. But in that kind of storm, the wind speed can vary wildly, it can change direction and even reverse completely - so you just can't know for sure what your airspeed is - and if you're overspeeding or stalling, for that matter - based on GS alone.
A couple of questions to the pilots here:
1) flying so close to both the stall speed and the overspeed (maybe 40 or 50 kts apart), did it ever happen to you that a sudden change either in wind speed or wind direction push the plane either in overspeed regime or below the stall line?
2) is it possible that entering a storm the pressure could drop so brutally that there simply would not be enough air to support the plane and it would start falling?
For instance, the usual pressure at sea level is 1013 mb; fl 340 is 250 mb, and at fl 450 it's only 150 mb.
So is a drop of, let's say 50 mb, possible, making the plane act as if it suddenly climbed from fl 340 to fl 390 or even a 100 mb drop and subsequent "jump" to a fl 450 equivalent when its ceiling was let's say fl 380 and thus stall it?
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