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AF447 wreckage found

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AF447 wreckage found

Old 21st Jul 2011, 16:54
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BOAC:
No, I still back my call (elsewhere) for properly trained and capable pilots who have the innate ability to sift the wheat from the chaff and an FCS that they can understand and use . In my opinion, 'automation' has still way to go.
BOAC, I'm with you 100%. I still think that the best way to avoid accidents is to have properly trained and capable pilots in the cockpit flying an ("honest") aircraft easy to understand and very straightforward to handle. Maybe you're right to have a feminine word for airplane... Like women, they seem to have their days... (in our lexicon we have a male word for airplane).
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Old 21st Jul 2011, 17:03
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@RWA

THS overview...
Pitch control is through 2 independent elevators and a trimmable hydraulic stabiliser (THS). These surfaces are normally driven by PRIM 1 by the green hydraulic jacks and THS motor 1. If all 3 PRIMs are lost, electrical control of the THS is lost; actuation is available through the manual pitch trim wheel control. 2 electrically controlled hydraulic servo jacks are fitted to each elevator having 3 modes: active in which the jack is positioned is electrically controlled, damping where the jack follows surface movement and centring where the jack is hydraulically maintained neutral. In normal operation, one jack is active, one is damping. If both servo-jacks fail, they default to the centring mode. Some manoeuvres cause the second jack to become active. The stabiliser is actuated by a screw jack driven by 2 hydraulic motors controlled by 1 of 3 electric motors or the mechanical trim wheel. The right elevator uses GRN & YLO hyd, left uses BLU & GRN. The THS uses BLU & YLO.

If a failure occurs in PRIM 1, assoc hyd system or hyd jacks, control is transferred to PRIM 2 for the elevator via the BLU and YLO jacks and the THS via motor 2. If both PRIM 1 & 2 are inop, control is transferred to SEC 1 for the elevator and PRIM 3, motor 3 for the THS. If all 3 PRIMs are inop, the elevator is controlled by SEC 1 and electrical control of the THS is lost.
See below BEA report quotes with my own bold and underscore for emphasis.

It has been stated by posters that in ALT LAW under some conditions the auto trim feature on THS can be inhibited and pilot should utilize manual trim as required.

At 2 h 10 min 51 , the stall warning was triggered again. The thrust levers were positioned
in the TO/GA detent and the PF maintained nose-up inputs. The recorded angle of attack, of
around 6 degrees at the triggering of the stall warning, continued to increase. 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.


After the autopilot disengagement:
  • the airplane climbed to 38,000 ft,
  • the stall warning was triggered and the airplane stalled,
  • the inputs made by the PF were mainly nose-up,
  • the descent lasted 3 min 30, during which the airplane remained stalled. The angle of
  • attack increased and remained above 35 degrees,
  • the engines were operating and always responded to crew commands.
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Old 21st Jul 2011, 17:15
  #2103 (permalink)  
 
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BOAC

Perhaps they missed this

ABNORMAL ATTITUDE LAWS

An abnormal attitude law in pitch and roll is provided if the aircraft is in flight and in any of these conditions :
— Pitch attitude > 50 nose up or 30 nose down
— Bank angle > 125 
— Angle of attack>30or<10
— Speed>440ktor<60kt
— Mach>0.96or<0.1
The law in pitch is the alternate law without protection (except load factor protection) and without auto trim. In roll it is a full authority direct law with yaw alternate.
After recovery, the flight controls laws are:
in pitch : alternate law
in roll : direct law with yaw alternate law
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Old 21st Jul 2011, 17:23
  #2104 (permalink)  
RWA
 
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I see what you're getting at, xcitation. But the BEA report goes on to say:-

"At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have no valid indications". At that moment, the thrust levers were in the IDLE detent and the engines’ N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs. In the following moments, the angle of attack decreased, the speeds became valid again and the stall warning sounded again."


So if the THS responded to the 'nose-up inputs,' why did it not also respond to the nose-down ones, and instead remain at full nose-up?

While the aeroplane (and the pilots) still had more than 10,000 feet of altitude in hand? Allowing plenty of time for the pilots to level out, climb back to height, and continue on their way?
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Old 21st Jul 2011, 18:00
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Any chance the stabilizer jammed or otherwise stayed in full up position (by design) like Ci Nagoya crash?

Accident Database: Accident Synopsis 04261994





excerpts from Ladkins report on the Ci TAipei Crash pertaining to the Ci Nagoya crash (both crashes the same type of aircraft)

The Crash of Flight CI676, a China Airlines Airbus A300, Taipei, Taiwan, Monday 16 February, 1998: What We Know So Far


"[02.19]

On 26 April 1994, an Airbus A300-600 crashed tail-first while trying to land at the airport in Nagoya, Japan. The co-pilot, who was flying, had inadvertently triggered the Take-off/Go-around (TOGA) switch on the engine power levers. This caused the Flight Director (an advisory device on the Attitude Indicator) to switch to GO-AROUND mode, and increased thrust on the engines. The autopilots were subsequently engaged, with GO-AROUND mode still engaged. The co-pilot applied heavy nose-down forces to the control column under the Captain's instructions, and continued to do so. The autopilot on this A300 did not disengage under these forces, specifically because of its design. Thus it attempted to counteract the nose-down attitude of the aircraft by putting in nose-up trim on the Horizontal Stabiliser (the moveable, horizontal part of the tailplane, the empennage), causing an abnormal out-of-trim situation. The copilot and the autopilot were thus fighting each other. The captain took over control, judged that landing would be difficult, and opted for a go-around. The abnormal nose-up trim caused the aircraft to pitch up drastically, losing airspeed very quickly, stall, and impact the ground tail-first. The final report from the Japanese authorities singled out 12 causal factors. I quote in full from the report. My comments are in parentheses with the form "[..... PBL]"

While the aircraft was making an ILS approach to Runway 34 of Nagoya Airport, under manual control by the F/O [First Officer PBL], the F/O inadvertently activated the GO [GO-AROUND PBL] lever [positioned on the thrust levers PBL], which changed the FD (Flight Director) to GO AROUND mode and caused a thrust increase. This made the aircraft deviate above its normal glide path.

The APs [Autopilots PBL] were subsequently engaged, with GO AROUND mode still engaged. Under these conditions the F/O continued pushing the control wheel in accordance with the CAP's [Captain's PBL] instructions. As a result of this, the THS (Horizontal Stabilizer) [the horizontal part of the tailplane, the empennage PBL] moved to its full nose-up position and caused an abnormal out-of-trim situation.

The crew continued approach, unaware of the abnormal situation. The AOA increased, the Alpha Floor function [a particular automatic control function intended for situations in which a high angle-of-attack (AOA), the incidence of the wings to the air, is very high. A high AOA leads to a stall PBL] was activated and the pitch angle increased.
It is considered that, at this time, the CAP (who had now taken the controls), judged that landing would be difficult and opted for go-around. The aircraft began to climb steeply with a high pitch angle attitude. The CAP and the F/O did not carry out an effective recovery operation, and the aircraft stalled and crashed.

The AAIC [Japanese Air Accident Investigation Commission PBL] determined that the following factors, as a chain or a combination thereof, caused the accident:

The F/O inadvertently triggered the Go lever It is considered that the design of the GO lever contributed to it: normal operation of the thrust lever allows the possibility of an inadvertent triggering of the GO lever.
The crew engaged the APs while GO AROUND mode was still engaged, and continued approach.
The F/O continued pushing the control wheel in accordance with the CAP's instructions, despite its strong resistive force, in order to continue the approach.
The movement of the THS conflicted with that of the elevators, causing an abnormal out-of-trim situation.
There was no warning and recognition function to alert the crew directly and actively to the onset of the abnormal out-of-trim condition.
The CAP and F/O did not sufficiently understand the FD mode change and the AP override function. It is considered that unclear descriptions of the AFS (Automatic Flight System) in the FCOM (Flight Crew Operating Manual) prepared by the aircraft manufacturer contributed to this.
The CAP's judgment of the flight situation while continuing approach was inadequate, control take-over was delayed, and appropriate actions were not taken.
The Alpha-Floor function was activated; this was incompatible with the abnormal out-of-trim situation, and generated a large pitch-up moment. This narrowed the range of selection for recovery operations and reduced the time allowance for such operations.
The CAP's and F/O's awareness of the flight conditions, after the PlC took over the controls and during their recovery operation, was inadequate respectively.
Crew coordination between the CAP and the F/O was inadequate.
The modification prescribed in Service Bulletin SB A300-22-6021 had not been incorporated into the aircraft.
The aircraft manufacturer did not categorise the SB A300-22-6021 as "Mandatory", which would have given it the highest priority. The airworthiness authority of the nation of design and manufacture did not issue promptly an airworthiness directive pertaining to implementation of the above SB.
It should be fairly clear that most of these causal factors pertain to the crew's actions and understanding of the aircraft systems. However, contributing were unclear manual descriptions (also a factor in the Lufthansa Warsaw A320 crash in 1993 and the Birgenair Puerto Plata B757 crash in 1996), and the placement and design of the GO-AROUND lever on the thrust levers. Also that China Airlines had not performed a recommended modification to the aircraft.

The modification has to do with pilot inputs to the con......."

Remote but was there any failure between man and machine that locked the rear stabilizer in full up by any chance on AF 447 ?

Last edited by armchairpilot94116; 21st Jul 2011 at 18:14.
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Old 21st Jul 2011, 18:25
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NO Thunderstorms???

BOAC

"wallybird - I would ask you to carefully read both the current and old threads on this topic? Your fixation on 'thunderstorms' is out of place based on what we are told by BEA. There is also no firm 'evidence' of any 'thunderstorms' on their route.

There is no evidence that they 'penetrated' or flew near a 'thunderstorm'."


BOAC

Forget the threads. Read AF447: A Meteorological Analysis.

EVERY professional pilot KNOWS that a line of thunderstorms lay in the flight path of this flight. And every one I know stated "Why didn't they deviate?"

Some may be benign. Others may not.




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Old 21st Jul 2011, 18:30
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Turbine D

"Nearly all are not thunderstorms..."

Unfortunately, some are! And this one proved deadly.
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Old 21st Jul 2011, 18:38
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armchairpilot94116

Having taken shelter under my nomex umbrella, I would like to say how delightful it would be to discuss the mechanical architecture of the THS (and elevators). Without prejudice, a discussion of the power supplies, articulation geometry and other would be a fantastic foundation for understanding the ultimate upshot of the explanation for the lack of ND re: THS on the way down. For the moment, PE is the working theory.

Fine, no bad. Lacking airstream damping consistent with cruise speed, did the jack overspeed? Did it, not encountering a back lash from the THS, shift thrust faces on its screw and lock? For the partisans: No offense, none intended, and save your energy for later, eh?
 
Old 21st Jul 2011, 18:56
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It was not a thunderstorm it was a convective system, there was not any reported lightning by a satellite and sensors that monitors the presence of lightning. Read the first BEA report, again. Read Tim Vasquez's update, again.

Hint: From Tim:
* Lightning -- Though in earlier versions of this study I had identified lightning as occurring in this mesoscale convective system, recent evidence from spaceborne and sferic sensors indicate that this system contained little or no lightning. Soundings do indicate moderate levels of instability, but there are indications in the literature that cumulonimbus clouds in oceanic equatorial regions entrain considerable quantities of drier, cooler air that dampen upward vertical motion in the lower portions of the storm, and in some way this reduces charge separation 2. In any case it does look fairly likely that we can rule out a lightning strike as being a factor in the A330 crash. That said, it should be emphasized that lightning is modulated by distribution of ice and water fields within a cloud and is influenced by updraft strength, and is not simply a function of the storm's severity or predisposition for turbulence. Whether the aircraft was struck is the main item of concern, and it appears no such event occurred.
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Old 21st Jul 2011, 19:11
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Curious: How much of the tail (THS and elevators and all that is connected to them) section was recovered from the underwater grave?

May need to go back a thread or two and check out the various photographs.
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Old 21st Jul 2011, 19:19
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Just as some CVR may be upsetting to the families, likewise some pics of the empennage may be upsetting to Airbus?

I found nothing, save Machaca's excellent pic of the 330 innards complete with jackscrew and RCU.........

There was that "Unidentified" pile of debris to the Northeast in the debris field, I always took that to be the tail feathers. No comment from BEA re: (that I can recall).

MLA. Interesting. Wasn't a spoiler located and recovered in the initial search? Wasn't it one of "4,5,6?" Could the 'g' have been =>2 on the climb? Could a spoiler anomaly have been the result of overstress at initial NURL? Thus far, ACARS is unable and BEA unmoved, to address mechanicals? ~500knots and a manual input initiating an extreme ascent?

Food for thought?

Last edited by bearfoil; 21st Jul 2011 at 19:34.
 
Old 21st Jul 2011, 19:44
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Bear, on your behalf, I will slightly misquote a CINCPACFLT signal, circa 1944 ...Where is the reason for the loss of the spoiler? The world wonders.
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Old 21st Jul 2011, 19:50
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Just to add that I believe the sensor for Spoiler deflection is mounted on the actuator, not on the control surface. lonewolf?
 
Old 21st Jul 2011, 20:02
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iceman50
ABNORMAL ATTITUDE LAWS

An abnormal attitude law in pitch and roll is provided if the aircraft is in flight and in any of these conditions :
— Pitch attitude > 50° nose up or 30° nose down
— Bank angle > 125°
Angle of attack > 30° or < 10°
— Speed > 440kt or < 60kt
— Mach > 0.96 or < 0.1
The law in pitch is the alternate law without protection (except load factor protection) and without auto trim. In roll it is a full authority direct law with yaw alternate.
After recovery, the flight controls laws are:
in pitch : alternate law
in roll : direct law with yaw alternate law
The conditions described above, due to the "any" in the first sentence, are assumed to be "mutually exclusive" and any one or a combination will trigger ABNORMAL ATTITUDE LAW.

Not so, and the FCOM has unintentionally lead everyone astray.

Due to the discrepancy in the airspeed measurement, all three ADRs were rejected by the FCC, which left either of the inertial input criteria:-

— Pitch attitude > 50° nose up or 30° nose down
— Bank angle > 125°

to be met. This didn't happen.
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Old 21st Jul 2011, 20:16
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@RWA

So if the THS responded to the 'nose-up inputs,' why did it not also respond to the nose-down ones, and instead remain at full nose-up?
Good question.
To be specific I think your question is how do we reconcile this contradiction in BEA report:
At 2 h 10 min 51
...13 degrees nose-up in about 1 minute and
remained in the latter position until the end of the flight.
and then
At 2 h 12 min 02
...PF made pitch-down inputs. In the following moments, the angle of attack decreased, the speeds became valid again and the stall warning sounded again.
IMHO the BEA are making a generalization saying THS stayed at +13 deg, or else how do we explain the pitch down inputs followed by a change in AoA. In which case this appears to be rather sloppy writing or a poor translation from the french original. What they should have said "...remained [mostly] in the latter position...".
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Old 21st Jul 2011, 20:26
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Cool

Hi,

At 2 h 10 min 51
...13 degrees nose-up in about 1 minute and
remained in the latter position until the end of the flight.
IMHO the BEA are making a generalization saying THS stayed at +13 deg, or else how do we explain the pitch down inputs followed by a change in AoA. In which case this appears to be rather sloppy writing or a poor translation from the french original. What they should have said "...remained [mostly] in the latter position...".
The french note tell EXACTLY the same

Le plan horizontal réglable (PHR) passe de 3 à
13 degrés à cabrer en 1 minute environ ; il restera dans cette dernière position jusqu'à
la fin du vol.
It's a very affirmative statement from BEA and let no gap for interpretation.
So it stay on 13° to the end despite some elevators command to dive
Some justified this because the elevators commands to dive are too short .........
This must certainly be show better on the FDR than on the CVR

Last edited by jcjeant; 21st Jul 2011 at 20:37.
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Old 21st Jul 2011, 20:35
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And yet, when describing Pilot input, they use a squishy "..mainly NU inputs...."

sauce for the goose? Commercial hypocrisy?

Or, were the PF inputs limited to independent elevators only (to include Roll?) Because the THS couldn't/wouldn't "move"?
 
Old 21st Jul 2011, 22:09
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Thanks Lonewolf 50, thanks for a sensible reply to my question, I realise I am getting a bit off subject.
"I have to fight like hell is to overcome any feeling of seat of the pants, since in IMC it can give me the leans and kill me via the classic death spiral"
I personally have flown in non visibility situations both without and with instrument training (the former nearly killing myself!) thus I appreciate how 'seat of the pants' flying does more harm than good in certain situations. Questions are often posed about the lack of basic 'flying' training of commercial pilots and it may be argued that in some situations a 'boffin' might do better than a 'flyer'?
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Old 22nd Jul 2011, 00:45
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Turbine D

"Whether the aircraft was struck is the main item of concern, and it appears no such event occurred."

All that refers to is the fact that the plane was probably not struck by lightning.

It still confirms the fact that strong updrafts were probable as well as turbulence and that alone was enough to cause the pilots to lose control of the airplane. Which they did.
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Old 22nd Jul 2011, 01:28
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w7, you seem a bit warped.
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