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AF447 wreckage found

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AF447 wreckage found

Old 12th Jun 2011, 07:26
  #1621 (permalink)  
 
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BEA published facts found, not conclusions, that is why no reason given for AF447.
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Old 12th Jun 2011, 07:39
  #1622 (permalink)  
RWA
 
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So why no reason for the 2008 A320 accident at Perpignan either, opherben?

In the final report?
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Old 12th Jun 2011, 09:18
  #1623 (permalink)  
 
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GYS

When you fly an ILS and you get a little high, you don't pull the power, you put your nose down.
Disagree... If you can show me a training manual clearly stating the opposite, please post it here, but for now I will extract from the Student Guide to my first Jet:

(This is actually for the PAR, but the same technique used for an ILS).

In practice either technique works to an extent, but the 2 are intertwined.

NoD
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Old 12th Jun 2011, 10:54
  #1624 (permalink)  
 
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Angel

Keep it simple:

Pitch attitude IS speed control:
On a glider you adjust your speed with your pitch attitude.
On a 747 without any thrust you have a veeery big glider. Again you adjust your speed with your pitch attitude. (Altitude is "just" a time factor)

The bonus by power/thrust: You are now able to maintain your altitude - even climb (in most situations) So power/thrust IS altitude control!!!

By the way - ain't we just a little of topic??
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Old 12th Jun 2011, 11:04
  #1625 (permalink)  
 
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complexman:
I am an aircraft engineer with nearly two decades of experience in the industry. I am not a pilot. What I find SHOCKING is that many professional pilots in this thread disagree so strongly on such basic issues as flight dynamics or what a variation of throttle will do to you in level flight. This is really scary. I know quite a lot about airframe design as well as flight control system design having done both for many years. But this thread is proving that as automation proceeds flying IS going to become more and more dangerous. And if that were not enough, they've now started to make airplanes from plastic!
complexman:
We have a saying in my country, that goes like this:
"Presunção e água benta, cada um toma a que quer..."
(Presumption and holy water, each one takes whatever...)

What I find really scary is the way engineers are designing flying machines that are so complex that even made them think that they have created an aircraft "against pilot's mistakes".
Man/machine interface was relegated to a status of "get used to it". Adapt yourself to your new role: flight management.
Fortunately for us, things are not all black and white. Engineers are not perfect, nor are we pilots...
But one thing is for sure, pilots are open to debate, open to new ideas, open to other professional classe's meddling and scrutinizing opinions.
In favor of flight safety, we do need to continue to open ourselves to our own scrutiny and open ourselves to other's opinions. I have learned a lot in this forum. There are a lot of great professionals with whom I love to exchange ideas and comments.
What we don't need is that sort of sleaze and arrogance, especially when coming from someone who should behave as an invited guest and therefore adopt more urban manners.
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Old 12th Jun 2011, 11:13
  #1626 (permalink)  
 
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Quote, "With the greatest respect to some: On Approach,

1) light aircraft use pitch for speed

2) Heavy Jets use thrust for speed

Too many light aircraft pilots here who obviously have no experience in heavy aircraft operations "


By George,
I beg to differ. Since you are on the thrust curve backside, adding thrust will not necessarily regain target airspeed, but lowering attitude will. No different from light aircraft.

The differentiation of light from heavy aircraft flying technique is an error in understanding aircraft flight mechanics and resulting handling qualities, even if the chief flight instructor taught this way. What matters are design parameters like wing loading, thrust over weight, lift over drag, and the CL vs Alpha and thrust vs airpseed curves. The B747 at any landing weight isn't substantially different in approach handling qualities from a Cessna 206, even though the Boeing wing is swept, and has more tires and Lbs. Their greatest handling qualities differences are in the flight control system mechanical characteristics, irrelevant to the above quoted issue.
The writer served as chief experimental test pilot since the 70's.
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Old 12th Jun 2011, 11:34
  #1627 (permalink)  
 
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Cool

Hi,

Pitch and attitude ....

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Old 12th Jun 2011, 11:56
  #1628 (permalink)  
 
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For those questioning the auto-trim on the airbus - this is a function of the FBW system.

On a conventional aeroplane (PA28 or 737) the pilot pitches up using the control column and manually trims the pressure off using the trim wheel or electric trim switch (same thing).

On the airbus this happens automatically. The pilot pitches the aeroplane up with sidestick inputs and the computer trims off the resulting "pressure" (you can still see the trim wheel rotating back during this process).

If the pilot applies sufficient back stick for a sufficient amount of time then the trim will wind fully back to the stop. This is what happened during the deceleration phase of the Perpignan Accident and almost certainly what happened during the Air France 447 tragedy.

In some conditions the auto-trim disconnects (abnormal attitude and direct law) and the trim setting and therefore wheel and stabiliser will remain in that final position until either

a) auto-trim is restored

or

b) the pilot moves the trim wheel manually!
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Old 12th Jun 2011, 15:27
  #1629 (permalink)  
RWA
 
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Man Flex

If the pilot applies sufficient back stick for a sufficient amount of time then the trim will wind fully back to the stop. This is what happened during the deceleration phase of the Perpignan Accident and almost certainly what happened during the Air France 447 tragedy.
Fair enough, Man Flex - except that I can't recall (unless I missed it) any reference to the Perpignan pilot applying 'up stick'? Please correct me if I'm wrong?

And secondly, the ('vestigial)' BEA 'note' about AF447 does indeed refer to the PF applying 'up stick' in the early stages of the accident -but it ALSO says, in the next paragraph:-


"The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb. The PF made nose-down control inputs and alternately left and right roll inputs. The vertical speed, which had reached 7,000 ft/min, dropped to 700 ft/min and the roll varied between 12 degrees right and 10 degrees left. The speed displayed on the left side increased sharply to 215 kt (Mach 0.68). The airplane was then at an altitude of about 37,500 ft and the recorded angle of attack was around 4 degrees."

So it appears, on the face of it, that the PF 'did the right thing,' recovered control, and restored the aeroplane to a stable flightpath and a sensible attitude? But - important point - the THS didn't respond?


On the airbus this happens automatically. The pilot pitches the aeroplane up with sidestick inputs and the computer trims off the resulting "pressure" (you can still see the trim wheel rotating back during this process).



If the pilot applies sufficient back stick for a sufficient amount of time then the trim will wind fully back to the stop. This is what happened during the deceleration phase of the Perpignan Accident and almost certainly what happened during the Air France 447 tragedy.


In some conditions the auto-trim disconnects (abnormal attitude and direct law) and the trim setting and therefore wheel and stabiliser will remain in that final position until either



a) auto-trim is restored



or




b) the pilot moves the trim wheel manually!



Entirely acceptable in after-dinner parlour games. But NOT, IMO, on airliners travelling at around 400 knots at well under 10,000 feet......


OK, I'll stick my neck out. I think that it's high time that aviation (Airbus, but also Boeing if appropriate) adopted a principle called 'failsafe.' At one time (I'm actually ancient enough to know ) it was new to my own industry - but it was a 'blinding light' at the time, and (in my own experience) started saving lives within months.......



What it would have amounted to, in aviation terms, is that the 'systems' should have reverted to neutral settings after they signed off - so that the autotrim, for example, would not have just signed off and left the THS at an unheard-of 13 degrees up or so, but would have reduced the angle to a conventional setting (say 3 degrees up or so).



But even that 'begs the question' of how long the THS actually TAKES to adjust. From the BEA 'note,' it appears to have taken the best part of a minute to go from 3 degrees to 13 degrees - presumably it would have taken most of another minute to go back from 13 degrees to any sort of reasonable angle? Considering that the whole accident happened within not much more than three minutes, that still wouldn't have given the pilots much chance?



OK - as just a 'seat of the pants' amateur pilot from many years ago (who mainly flew sailplanes because I couldn't afford powered aeroplanes) I'll stick my neck out.



And say that, in my (genuinely-humble) opinion, both manufacturers should actively consider whether such 'new' features as slow-acting, but enormously powerful THS's - as opposed to old-fashioned, under-powered, but quick-acting trim-tabs -are 'a step too far'.........


Last edited by RWA; 12th Jun 2011 at 15:37.
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Old 12th Jun 2011, 16:58
  #1630 (permalink)  
 
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RWA,

I don't know you're experience but you are one of few posters here asking the right questions.

In the Perpignan Accident the autopilot was disconnected in level flight and the aeroplane decelerated. The pilot would require to applying increasing nose up attitude to maintain level flight. The auto-trim would react correspondingly.

I see your point about the pitch down inputs made by the Air France F/O. I personally believe that these were token gestures to reduce the rate of climb. If the aeroplane has reached a pitch attitude of 10 degrees nose up then the trim would be wound back. The fact that the trim wound all the way back does, in my opinion imply that the F/O's inputs were predominately nose-up and as I say his inputs would have to be sufficient to allow this to happen. I don't think for one second that the THS acted alone or there was a failure.

What it would have amounted to, in aviation terms, is that the 'systems' should have reverted to neutral settings after they signed off - so that the autotrim, for example, would not have just signed off and left the THS at an unheard-of 13 degrees up or so, but would have reduced the angle to a conventional setting (say 3 degrees up or so).
I completely agree and a very valid point. I believe that in both accidents both crews failed to appreciate that auto-trim was no longer available and it was necessary for them to move the trim wheel.

In my opinion and from all that I have read, the aeroplane responded as it was designed to do in accordance with the pilot inputs that were made.

Why he made those inputs are yet to be explained.
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Old 12th Jun 2011, 22:46
  #1631 (permalink)  
 
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RWA
Agree with your post as well as Man Flex; Have discussed the THS with a few colleagues & I don't see what benefit there is in allowing the THS to remain in a position (that would most likely render the aircraft unflyable) without manual re-trim following reversion to alternate law.
Indeed, (and without knowing the typical range of THS movement during the cruise phase of flight), I can't see why the autotrimming isn't limited to a degree or two beyond the "normal" cruise range, with a warning that it is reaching the limits of its "normal" travel. I doubt that more extreme manoeuvres such as TCAS RA or Terrain avoidance would be hindered significantly by such a limit.
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Old 13th Jun 2011, 00:58
  #1632 (permalink)  
 
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Some of the descriptions of Airbus's propensity to stall are inaccurate and, in my opinion, incorrect.

***************************
330 testflight in Toulouse stalled due to pilot mishandling leading to an unrecoverable stall. Two experienced pilots. Still some debate if the aircraft would have been able to save, still debates about the electronics/protections handling.

320 Perpignan stalled due to THS behavior. Normal pilots. Still some debate about the recovery possibility or not.

Qantas Perth. Aircraft apparently didn't obey pilot orders, recovery succeeded. Still debating about the real reason of the electronic/protections behavior.
**************************
I recently reviewed flight test accidents in FBW airplanes.

The circumstances in the A330 in Toulouuse was caused by deviating from the desired entry conditions and engaging the autopilot with full thrust then shutting one down. Unfortunately during the brief interval between A/P engagement and engine shutdown the autopilot entered altitude capture mode because the selected altitude had been left too low. Because of the nature of altitude capture, the airplane tried to maintain too steep a climb gradient. Some of the envelope protections were not available in altitude capture.

The A320 in Peripignan had two alpha probes frozen effectively outvoting the third (correct) probe. The test card was to verify alpha protection. Clearly with two indications at low values, alpha protection mode was never going to activate. Nevertheless, the crew continued down to the stall to see if it would finally activate (it didn't). During the stall, airflow differences between the various probes cause a transition to direct law. Unfortunately the test was flown at much too low an altitude for recovery.

This paper was presented at the Flight Test Safety Workshop last month.

The A-330 north of Perth is one of the very few in-service, civil flight by wire accidents (several serious injuries). In my opinion, this was a result of a poor voting scheme for a failed sensor. I say "In my opinion" as the formal report has not been released yet.

This was discussed in a 2009 paper at the International Society of Air Safety Investigators. At that time, only three FBW-caused accidents had been reported with no fatalities. AF-447 was not included because the cause wasn't known (and actually still isn't)

I think we should wait for the report to come out. After all, they've only had the flight and cockpit voice recorder data for a few weeks now.


Goldfish
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Old 13th Jun 2011, 01:05
  #1633 (permalink)  
 
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Would the crew have a "Man Pitch Trim" annunciation in the FMA?
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Old 13th Jun 2011, 02:00
  #1634 (permalink)  
 
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Cool

Hi,

Goldfish85
320 Perpignan stalled due to THS behavior. Normal pilots. Still some debate about the recovery possibility or not.
From the BEA report Perpignan

Captain

Flying hours:
• 12,709 flying hours of which 7,038 on type.
• 128 hours in the previous three months, all on type.
• 14 hours in the previous thirty days, all on type.
• No flying hours in the previous 24 hours.


Co-Pilot

Flying hours:
• 11,660 flying hours of which 5,529 on type.
• 192 hours in the previous three months, all on type.
• 18 hours in the previous thirty days, all on type.
• No flying hours in the previous 24 hours.
Maybe not very very experienced ... but certainly more than those of the AF447

The crew of Toulouse test flight:

Nicholas Warner, chief test pilot and captain. 7,713 flying hours experience.
Michel Cais co-pilot. 9,558 flying hours experience.
Jean Pierre Petit engineer. 6,225 flying hours experience.
Very more experienced ? .. maybe as test pilots ......

Last edited by jcjeant; 13th Jun 2011 at 02:19.
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Old 13th Jun 2011, 03:21
  #1635 (permalink)  
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Many thanks for your open-minded approach, Man Flex. It 'spurred me on' to have another read of the Perpignan report which I linked to earlier. I'm afraid that the paragraph immediately preceding the part I quoted does indeed say that the 'systems,' for reasons best known to themselves, did apparently ignore the pilot's nosedown inputs and leave the THS at 'full up':-

When the stall warning sounded, the Captain reacted by placing the thrust levers in the TO/GA detent and by pitching the aeroplane down, in accordance with procedures. The nose-down input was not however sufficient for the automatic compensation system to vary the position of the horizontal stabilizer, which had been progressively deflected to the pitch-up stop by this system during the deceleration. The Captain controlled a left roll movement, caused by the stall. The aeroplane’s high angle of attack and the roll movements generated asymmetry, and a speed variation between ADR 1 and 2 appeared. This increasing divergence caused a rejection of the three ADRs by the FAC then the ELAC. The flight control system then passed into direct law. It is likely that the crew did not notice this due to the emergency situation and the aural stall warning that covered the warning of a change of flight control laws. The Air New Zealand pilot, by saying “alpha floor, we’re in manual” likely considered that the alpha floor function had triggered and that in fact the autopilot had disconnected.

Golden Rivit, the same paragraph also largely answers your question. As far as I know (Airbus pilots please amplify) when the systems go into 'direct law' a message appears saying "USE MAN. PITCH TRIM" - I don't know whether there is an aural warning as well. But the BEA report concludes that this could well have been 'masked' by all the other warnings that would have been going off by that time.

Man Flex, have to 'come to the defence' of the AF447 pilot. He did indeed apply nosedown stick and get the aeroplane practically level, at Mach 0.68, and at an AoA of only four degrees (that is, near enough 'normal flight'). I'm afraid that it looks increasingly likely that the AF447 THS, like the Perpignan one, ignored the pilot's 'nosedown inputs,' and stayed at full up. Which could very well have both caused and maintained the stall?

The PF made nose-down control inputs and alternately left and right roll inputs. The vertical speed, which had reached 7,000 ft/min, dropped to 700 ft/min and the roll varied between 12 degrees right and 10 degrees left. The speed displayed on the left side increased sharply to 215 kt (Mach 0.68). The airplane was then at an altitude of about 37,500 ft and the recorded angle of attack was around 4 degrees.

Anyone know more about that 'automatic compensation system' that the Perpignan report mentions?

Last edited by RWA; 13th Jun 2011 at 04:24.
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Old 13th Jun 2011, 03:28
  #1636 (permalink)  
 
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Thank you Basil for what I consider to be the best post so far on this topic. I too have flown the 320 and agree with all you say. I will forever state that they should never have entered the CB in the first place given the circumstances (heavy, high, turbulence). I still feel that the radar was not working. So far there has been no conformation that it was. Why else would trained pilots fly through the red area of a CB ? (see the satellite Wx photo). Something that most of you don't know is that Airbus issued a NOTAM reminding pilots not to depart with inop radar if there was reported CBs enroute. This was sent out some time after the 447 crash. Got me thinking !!
I blame the government watchdogs like the FAA, and others like them, for not paying attention to the type of training required on these new computer driven 'planes. There are a number of items we never covered during our training in the sim. With one day of so called "practice" and then a nerve racking check ride that that was full of surprises, I don't see how any pilot gets any benefit from these stupid sim sessions.
Hope we get more info from the two data recorders soon.
Glad to be retired from a crazy industry such as this.
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Old 13th Jun 2011, 04:04
  #1637 (permalink)  
 
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With the Captain on a break ...and two f/o's in charge ...what would be the likely seating arrangement ?

I would imagine the less experienced f/o (800 on type) would be in the RHS as PF and the more experienced f/o in the LHS..

However after the proverbial hit the fan there was a change over of PF..and
this would lead to the f/o in the LHS trying to recover it..with no real experience of operating from that seat ?

is this a possible scenario?
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Old 13th Jun 2011, 04:48
  #1638 (permalink)  
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It is my understanding that a typed Pilot must fly in the Seat which he occupies in his regular role, Captain LHS, F/O, RHS, and relief in either. This puts the F/O in the RHS the one whose panel reads are not recorded. In the ITCZ, my guess is that the F/O is PF. Stand to be corrected.
 
Old 13th Jun 2011, 05:26
  #1639 (permalink)  
 
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jcjeant wrote :
From the BEA report Perpignan
Crew maybe not very very experienced ... but certainly more than those of the AF447
.............
The crew of Toulouse test flight:
Very more experienced ? .. maybe as test pilots ......

What a lot of confusion regarding flight hours !

It's hard to admit for a lot in the industry, but flight hours don't have the same value, depending on the background... Even if it doesn't prevent them for having accidents (see Toulouse Airbus crew, also british Trident stall in the 60's, dozens of others...) hours in a flight test environment have thirty (or more ?) time the value of hours in an airline environnment, with nothing happening in cruise, and landings always identical - if not in external conditions, but for sure in performing. Comparing flight hours of both sides is like mixing strawberries with potatoes.
Maybe there will be an understanding of all this after ?
The Perpignan crew was conducting an acceptance flight, and they had no training for that, period. To call them test pilots is totally unappropriate. I know that in the companies (including mine) you have supposed experienced pilots, calling themselves "test pilots" when they just perform "out-of-maintenance" check flights ....

One day airline pilots will have to admit that their hours don't have big value, compared to other backgrounds ... but as flying big jets is supposed to be the pinnacle of careers, its' not going to happen soon, I'm afraid.

So jcjeant .. please document yourself a little bit about flight testing, ask people or read books...
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Old 13th Jun 2011, 06:21
  #1640 (permalink)  
 
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Bubbers44 wrote, "I know we are drifting off topic but I don't understand why the pitch for glideslope and power for airspeed is so hard to comprehend. All autopilots work this way. "

Repeating wrong technique isn't going to make it right. I explained why on the previous page.

The comparison here of autopilot to human is wrong, in that an autopilot is designed to make corrections a number of times a second, which makes speed instability a non factor in flying an approach. The aircraft longitudinal time constant is significantly longer, making autopilot control effective, however a human burdened with multiple tasks, is unable to effectively cope, because of our inherent time constant, especially during multi-tasking workload.

Last edited by opherben; 13th Jun 2011 at 06:36.
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