Aces High Bulletin Board
General Forums => The O' Club => Topic started by: rogwar on May 27, 2011, 10:19:03 AM
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Definitely interesting read. Reminds me of tape over the static port on that Peruvian 757 several years ago. And flying such an electric plane as well.
http://www.flightglobal.com/articles/2011/05/27/357307/af447-stalled-but-crew-maintained-nose-up-attitude.html
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Straight down stall.... looks like it hit tail first at 107 kt ground speed.
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I had a pitot freeze on approach, in the middle of a snow storm. Speed decreased rapidly, so I starting droping the nose more and more thinking I was caught in a nasty downdraft. After a couple of seconds nothing made sense with my instruments, but I figured out that if my airspeed was really 80kts, I'd be already stalked big time so I decided to ignore my speedo and resume my approach at a power settingthat I knew would work and go from there.
I fly steam gauges, so I'm used to troubleshoot yet got disoriented for a couple of secs till I could make sense of it. On a full glass cockpit, I think it could be way worse because you naturally trust computers more.
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Sounds like PBS and NOVA nailed it with their documentary last year, even without the data recorders they pieced it together from the ACARS data. Only "new" bit of info is that the Captain wasn't on the flight deck when it all started going bad. Pitots froze, autothrust shut down, pilot failed to follow SOP (5° nose up, 85% throttle) for no airspeed data, and was confused by conflicting data, plane climbed into a stall. :(
What's baffling now is it seems like the pilot in control never realized they where in a stall condition, as he kept fighting to keep the nose up instead of pushing over, the report says he even set the horizontal stab to 13° UP? :headscratch:
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maybe he "felt" the loss in altitude and thought it was from loss of elevator input not stall.
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In real IFR conditions it is easy to lose the physical sense of flying the bird. Pilots are hammered time and time again to trust the instruments when IFR because your inner ear can and will often betray you. Vertigo will tell the pilot one thing and they are trained to trust the instruments anytime there is a conflict between the way they feel and the instruments.
In VFR it's easy to see the instruments are lying to you. In IFR with no vision of the horizon to orient yourself the pilots will rely on training. It's very easy to criticise the flight crew from the ground and safety of the keyboard. It's another thing to have experienced vertigo in flight.
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Same happened to Kenedy.
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In real IFR conditions it is easy to lose the physical sense of flying the bird. Pilots are hammered time and time again to trust the instruments when IFR because your inner ear can and will often betray you. Vertigo will tell the pilot one thing and they are trained to trust the instruments anytime there is a conflict between the way they feel and the instruments.
In VFR it's easy to see the instruments are lying to you. In IFR with no vision of the horizon to orient yourself the pilots will rely on training. It's very easy to criticise the flight crew from the ground and safety of the keyboard. It's another thing to have experienced vertigo in flight.
What do IFR and VFR mean?
-Penguin
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In real IFR conditions it is easy to lose the physical sense of flying the bird. Pilots are hammered time and time again to trust the instruments when IFR because your inner ear can and will often betray you. Vertigo will tell the pilot one thing and they are trained to trust the instruments anytime there is a conflict between the way they feel and the instruments.
In VFR it's easy to see the instruments are lying to you. In IFR with no vision of the horizon to orient yourself the pilots will rely on training. It's very easy to criticise the flight crew from the ground and safety of the keyboard. It's another thing to have experienced vertigo in flight.
Bingo. I'm no grizzly seasoned veteran pilot but I spent enough time under the hood doing IFR training to know that what the seat of the pants "feeling" is telling you may, and often is, totally different from what's actually going on.
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IFR Instrument Flight Rules
VFR Visual Flight Rules
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What do IFR and VFR mean?
-Penguin
IFR - Instrument Flight Rules, where there is little or no visibilty outside of the cockpit (fog, clouds, rain, etc), you fly and navigate by instruments
VFR - Visual Flight Rules - you can see outside, you fly and navigate primarily by visual reference
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Oh, I see. Why does your inner ear often 'lie', though? Is it because of changing cabin pressure or perhaps a lack of sensitivity?
-Penguin
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Your inner ear can be fooled into telling your sense of balance you are doing things that are not really happening. Just think how those arcade rollercosters work. They tilt you a few degrees to the left and stop but your inner ear combined with the image you see on a tv screen are telling you that you are doing a full barrel roll to the left. The five senses are more powerful than a lot of people think, if they weren't you wouldn't hear stories on these forums about guys getting motion sick sitting at their computer desks flying AH while using TrackIR.
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Not a pilot, but the first reports always blame the pilots. The truth comes out latter. I don;t buy that two pilots could not figure out they were in a stall especially after the alarms went off. Nor that they never tried nose down since nose up was not working. Easier to blame the dead man than having to deal with the consequences of a faulty design, computer, maintenance, etc
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Not a pilot, but the first reports always blame the pilots. The truth comes out latter. I don;t buy that two pilots could not figure out they were in a stall especially after the alarms went off. Nor that they never tried nose down since nose up was not working. Easier to blame the dead man than having to deal with the consequences of a faulty design, computer, maintenance, etc
Except that all of this data is taken directly from the black boxes. The only thing the black boxes don't tell you is why those control inputs were made--i.e. what were the humans thinking? So, perhaps its ok, just this once, to keep the conspiracy theories out of this one.
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Except that all of this data is taken directly from the black boxes. The only thing the black boxes don't tell you is why those control inputs were made--i.e. what were the humans thinking? So, perhaps its ok, just this once, to keep the conspiracy theories out of this one.
:lol That is exactly what I am saying. The recordings don't tell you why they did what they did.
Check this one out. It was initially blamed on the pilots (Helios Airways Flight 522). Do some search and see for yourself how many accidents have been blamed on the pilots initially. It is just cheaper for the airlines and the airplane makers.
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My Hometrailer is more Safe than the Most modern Plane.
Hometrailer are speedlimit to 80kmh in Europe I dont have a cruisecontrol if I go over 80kmh I have to pay Alot
Thats why I use GPS, when I go over 80kmh the Navigationsystem warn me.
Even if my Speedgauge Fail I can read in my GPS the speed
WHY Modern planes dont have this?
Who Beleve that Terorist can Hijack Helicopter and Break into Nuclearplants (2hours for Supergau)
Who knews that people with 14 Carpetknifes killed about 3000 people in about 3 hours?
Go on stupid I phone generation...
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Airplanes have GPS that tell you groundspeed, which is the speed of point a to b, but airspeed is what matters when talking about stalling. You can't know the airspeed from a GPS.
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Airplanes have GPS that tell you groundspeed, which is the speed of point a to b, but airspeed is what matters when talking about stalling. You can't know the airspeed from a GPS.
GPS can derive altitude though, might be a dumb question but why hasn't anyone built a system to derive airspeed in the event of a pitot failure from GPS - even if it's just a backup?
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You have to have been there to understand. Back when I was a new pilot, I was judgemental. How could they lose control? Then I got a job as a skydive pilot. My job was to get the customers to altitude and drop them. Easy you think, yes it is when the sun shines. In the USA there's a rule, no dropping in cloud. That wouldn't work in Europe. So I found myself in cloud, often with ice building up and high ground nearby. More than once, I'm in the middle of an icing cloud near a hill nearby. You have no idea of the tension.
I have a GARMIN 430 and it's yelling 'Terrain, terrain'. The only thing you have in your favour is local knowledge.
Take away the local knowledge and you are doomed.
At times, I've lost it, the only thing that saves me is the fact that I'm know where I am and I know that wings level and a descent or climb will save my ass.
But consider an airline pilot, whose life is all numbers somwhere off Africa. Suddenly it all goes crazy. What do you do?
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GPS can derive altitude though, might be a dumb question but why hasn't anyone built a system to derive airspeed in the event of a pitot failure from GPS - even if it's just a backup?
Because it would have to know the exact winds at the point in space at that time.
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:lol That is exactly what I am saying. The recordings don't tell you why they did what they did.
Check this one out. It was initially blamed on the pilots (Helios Airways Flight 522). Do some search and see for yourself how many accidents have been blamed on the pilots initially. It is just cheaper for the airlines and the airplane makers.
Who else besides the Pilots CAN you blame this one one?
Facts are:
-They flew into a storm they should NOT have (it's still unknown why they chose to fly into that monster storm)
-They lost airspeed data.
-They have an SOP to follow in the event of loss of airspeed data. (the same Airbus model had had several previous pitot icing incidents, all ended safely)
-They DID NOT follow that procedure, which lead to an extreme AOA near the flight ceiling, and stall, from which they did not and/or could not recover.
Other factors are probably the fact that they where getting bombarded with system warnings incipient to the pitot failures, and they where likely getting bounced around like crazy in that storm.
I'm not ragging on pilots at all, I trust them with my life every time I fly without a second thought, just like I trust the mechanics, and controllers with my life as well every time I fly. But the facts are that nearly all commercial aviation accidents are attributed to "Human Factors" whether those humans are the pilots the mechanics/techs or a combination of both.
When maintained and operated within the proper parameters the machines themselves are very, very safe.... ...the weakest link in aviation safety is the human being, that's just the way it is. Fortunately incidents like this are very, very rare, and flying is still safer then just about anything else I do everyday.
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Because it would have to know the exact winds at the point in space at that time.
yup but there must be a "something is better than nothing" point reach.
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Except that all of this data is taken directly from the black boxes. The only thing the black boxes don't tell you is why those control inputs were made--i.e. what were the humans thinking? So, perhaps its ok, just this once, to keep the conspiracy theories out of this one.
did they not find the cockpit voice recorder also?
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did they not find the cockpit voice recorder also?
Yes, from the report from the French it seems like there wasn't a lot of voice chatter though. Talks about one of them calling for the Captain to come back (he was on routine rest period), FO acknowledging taking manual control, Captain acknowledging taking control from FO when he gets back... reading off the altitude tape as they drop.... that's about it.
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Who else besides the Pilots CAN you blame this one one?
Facts are:
-They flew into a storm they should NOT have (it's still unknown why they chose to fly into that monster storm)
-They lost airspeed data.
-They have an SOP to follow in the event of loss of airspeed data. (the same Airbus model had had several previous pitot icing incidents, all ended safely)
-They DID NOT follow that procedure, which lead to an extreme AOA near the flight ceiling, and stall, from which they did not and/or could not recover.
Other factors are probably the fact that they where getting bombarded with system warnings incipient to the pitot failures, and they where likely getting bounced around like crazy in that storm.
I'm not ragging on pilots at all, I trust them with my life every time I fly without a second thought, just like I trust the mechanics, and controllers with my life as well every time I fly. But the facts are that nearly all commercial aviation accidents are attributed to "Human Factors" whether those humans are the pilots the mechanics/techs or a combination of both.
When maintained and operated within the proper parameters the machines themselves are very, very safe.... ...the weakest link in aviation safety is the human being, that's just the way it is. Fortunately incidents like this are very, very rare, and flying is still safer then just about anything else I do everyday.
Where is golfer when you need him :lol
These guys are not your average hotshot that will break every rule and fly in clouds in kite. They are highly trained professionals in a real plane flying at 35,000feet. There is some time to react up there. Those maybe the facts as you say, but if there was a malfunction and they were getting the wrong information from the plane they might have responded the wrong way. It would not be their fault even though the facts would state so.
Do a simple search and see for yourself how many times the pilots have been blamed initially. I am not saying it can;t be their fault. Just saying it is a little too early to claim they know exactly what happened. Initially the said they wont have anything to tell us until sometime in July. King of fast dont you think? Normally these investigation dion't take a month to come to a conclusion.
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... :noid
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GPS can derive altitude though, might be a dumb question but why hasn't anyone built a system to derive airspeed in the event of a pitot failure from GPS - even if it's just a backup?
It exists. Even Tupac family 172 can derive that information from the Garmin unit that his dad is installing in their airplane. Dig a little into the GPS or FMS functions in most airplanes and you'll find a GPS derived altitude quite simply.
In the simulator I've been given frozen pitot tubes (L, R and Standby) which make your airspeed indicators act more like altimeters. What will happen is during initial climb is you'll have what you perceive to be a boost of performance with your airspeed trending up and increasing your pitch angle to take advantage of the performance. Once you get past a certain point of what is normal your brain starts clicking and you know the airplane doesn't perform like that so you begin to look at what's going on. GPS derived groundspeed is displayed in my current airplane and cross checking that to show that the 300kts being indicated isn't correct. In that case setting your pitch to where it needs to be-ish (TLAR, That Looks About Right) and the thrust levers where they typically are was the recovery. Eventually finding clear air and letting the pitot heats do their job will let the ice eventually melt or sublimate (or in the simulator, the instructor or check airman will clear the malfunction) and off you go.
For a professional flight crew to take a happily flying and trimmed airplane with 7 miles of sky between them and the ocean to their deaths in about 3 minutes is a big deal. The weather they were in was no joke, they were at night, in a low of their bodies rest rhythms and not expecting anything like this while fat dumb and happy in cruise.
While it's easy to say it won't happen to me, I'd like to know what happened to them with some factual reporting and analysis so I can prevent it. The updated findings can be found here:
http://www.cbsnews.com/htdocs/pdf/point.enquete.af447.27mai2011.en.pdf
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Thanks for that link. Looks like they were piloting a darn stall all the way to the water.
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My question is, how did they not know they were stalling? Instrument failures or not, surely they must have felt the plane buffeting?
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IFR - Instrument Flight Rules, where there is little or no visibilty outside of the cockpit (fog, clouds, rain, etc), you fly and navigate by instruments
VFR - Visual Flight Rules - you can see outside, you fly and navigate primarily by visual reference
IFR and VFR have nothing to do with being able to see...they are definitions of the rules used to conduct the flight.
IMC and VMC (Instrument or Visual Meterological Conditions) relate to visibility and/or ceiling/cloud conditions.
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I'm obviously not a pilot either, but I've experienced a similar type of stall in Falcon 4. The plane will repeatedly oscillate up and down at AoA's well above the 25* limit on the F-16, while you fall toward the ground. The only way to get out of them is to override the Flight Control System and rock your way out of it with elevator. I'm not sure how well an airbus would fare with such harsh inputs though?
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I can't see them mushing in all the way down without realizing it.
There had to be some sort of overspeed to airframe failure at some point.
More time to reduce the data and testing in same type plane will eventually yield the answer.
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I can't see them mushing in all the way down without realizing it.
There had to be some sort of overspeed to airframe failure at some point.
More time to reduce the data and testing in same type plane will eventually yield the answer.
disorientation. listening to your senses, rather than trusting your instruments.
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I saw a crash the other day, and it was a complete and absolute pilot's mistake. Stall.
However, 3-4 minutes of mushing down at some 100 kts is really funny. You'd have thought that there was plenty of time to nose-down and gather some speed.
Was there downstream? It is nasty, experienced it once as a right-seater with an old hand on the controls of a Cessna 172m, and in what looked like harmless weather, it took full power just to maintain altitude.
But....the airliners like the airbus have a lot bigger envelope. And the aircraft sort of corrects stall, look here:
http://www.youtube.com/watch?v=IKBABNL-DDM&feature=related
Is there a possible explanation in that video?
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i think there was mention of the auto pilot being turned off.
if the crew got it into a stall, and it was night(i don't remember what time this happened), over the water, there is nothing. nothing at ALL for reference.
had something happened that allowed the aircraft to get into a stall, and the crew got a little "behind the curve" in correcting....now they're going to go on what they feel, rather than what their instruments tell them.
all that being said, i've obviously not flown anything that big, and am just speculating.
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My question is, how did they not know they were stalling? Instrument failures or not, surely they must have felt the plane buffeting?
A swept wing transport jet isn't a 172. They don't behave the same way.
Whether they seemed to expect stall/AoA protection in alternate law for their flight controls I don't know. What was going through their heads I don't know. I can say it can be disorienting and confusing when you're in a lull to have your whole world go to hell while you're clipping a rock-your-world thunderstorm like they were. I imagine their responses are going to be studied in further depth to help understand the why's of this accident. It's easy to get fixated and I've seen pilots do it when something abnormal happens. From your weekend warrior in a bonanza to a professional aviator with what you'd consider a lot of experience. It's not that common and usually it just takes a little kick start to get their scan moving again but it's happened.
Many times actually recognizing what failure has occurred can be more difficult than actually dealing with the failure. Getting a bunch of CAS messages (Crew Alerting System, depending on your acronym, Awareness) at night, in a thunderstorm, during a circadian low and troubleshooting just as the airplane gives up and says "you got it" because it doesn't know what to believe isn't easy especially for the first couple seconds while you're absorbing all the information. After that you start flying and then fixing. Should it have been managed? Sure. Why wasn't it? I'd like to know. I don't know what else this crew saw, felt or thought to led them down the road they were on but I'd like to. I hope we learn.
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I said that. To clear up, - a swept wing airliner on full power has hundreds of knots between stall and top cruising speed or VNE. A Cessna 172 has only 50 knots or so between maximum level speed and the stall.
Hundreds of knots, ponder on that.
The average speed in the descent would be very near a hundred knots, or some 10.000 fpm. It means nothing untill one knows what the actual curve was like during the descent.
And the aircraft landing on the sea in a nose-up position would be how an aircraft would normally be landed on water. But did it fall into the water with the nose-up, or make an emergency landing?
Dunno.
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I said that. To clear up, - a swept wing airliner on full power has hundreds of knots between stall and top cruising speed or VNE.
That's correct for flight down low but not at altitude. The margin between overspeed and stall can get down to 40 knots in normal cruise and less until they eventually meet. This is depicted in a flight envelope and where they begin to converge is known as "coffin corner" because the aircraft has such a tight margin between overspeed and stall.
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Further reports on the subject will be most interesting.
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That's correct for flight down low but not at altitude. The margin between overspeed and stall can get down to 40 knots in normal cruise and less until they eventually meet. This is depicted in a flight envelope and where they begin to converge is known as "coffin corner" because the aircraft has such a tight margin between overspeed and stall.
this i never knew.
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http://en.wikipedia.org/wiki/Coffin_corner_(aviation)
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this i never knew.
To expand a little (just a little) the maximum altitudes for a given weight will change based on temperature in relation to standard (ISA +/-) but some airplanes at certain weights just can't go above a certain altitude. At Brand X airline we had a performance manual in each aircraft's library that would be referenced for our max altitude at a given weight. The airplanes FMS/FMC can compute your maximum altitude and the airplane will get there but depending on the programming would not provide any buffet margin meaning any burble of air that adds even momentarily a higher wing loading could result in a stall. We'd reference this book which had 1.3G charts meaning those weights and altitudes had a built in margin that was 1.3x stall speed for the given circumstances. This will keep the high and low speed envelopes wide enough with reasonable safety but you can see how if you're heavy and in cruise that flying into a thunderstorm with it's associated turbulence could potentially lead to a stall condition. My current airplane doesn't have these charts anywhere but we do have two engine cruise charts for a constant speed and long range cruise which one can only assume have these margins built in. Seeing what the AoA (Angle of Attack) is and the low speed awareness (LSA) cue projected on the primary flight display (PFD) when we're curising tells me there's a comfortable margin.
I usually don't cruise around unless the airplane will maintain .4 AoA or less but in smooth air for longer range (think holding on an arrival when going fast and burning lots of fuel doesn't help anything) can increase it to .5 or .6 with a comfortable margin. At .8 the stall warning system (stick shaker in this airplanes case) will begin to shake telling you "hey dummy, get me out of here" while the airplane is still flying until 1.0 AoA as displayed on the indicator when the stall occurs. The point is yes the margin between stall and overspeed can and does get fairly slim especially when operating near the aircraft's ceiling for that given weight.
These guys losing reliable airspeed, combined with a potential legitimate stalled condition and it happening RFN (right friggin now) can be extremely disorienting especially initially. They seemed to be talking all the way down and were stable enough for (at least my take was) the captain to take his seat back and have control up until impact with the water. More information and analysis of the data is required but I'm anxiously awaiting to learn something from this.
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I'm anxiously awaiting to learn something from this.
So am I, thanks for the link, it makes horrifying reading.
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You need a very high altitude for that margin. (Coffin corner), and since the aircraft did not go "mach" which would have broken it up in the air, we have to look at a possible stall. But stalling all the way to SL leaves you nowhere near the coffin corner.
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You need a very high altitude for that margin. (Coffin corner), and since the aircraft did not go "mach" which would have broken it up in the air, we have to look at a possible stall. But stalling all the way to SL leaves you nowhere near the coffin corner.
A "very high altitude" is relative. All you need is to be at the maximum altitude for any given weight which is less than the aircraft's maximum certified ceiling especially in the case of heavy airliners. In my little business jet we can get to 43,000 most days but if the temperature is higher than standard and we departed at max takeoff weight it's possible that 40,000' is our maximum altitude. You can definitely see the narrow window between overspeed and stall condition with the low speed awareness really creeping up. Our maximum certified altitude is 51,000 and I've never been higher than 47,000 since there aren't really any practical situations to ever go to 51,000 in this particular airplane.
Also a momentary overspeed condition will not make an airplane break apart.