PPRuNe Forums

PPRuNe Forums (https://www.pprune.org/)
-   Tech Log (https://www.pprune.org/tech-log-15/)
-   -   AF447 (https://www.pprune.org/tech-log/376433-af447.html)

greenspinner 5th Jun 2009 13:18

Lemurian,
With the only data we have right now, and as per these data the only concrete things we can say now is that Icing is the most probable cause.
But as I said in my previous threads, it must be really severe Icing condition, like an Iceberg at FL 350 :sad:

FlyingCroc 5th Jun 2009 13:22

Iceberg?
 
A hell of a storm! :eek: Check this out on Tim's webpage.
Air France 447 - AFR447 - A detailed meteorological analysis - Satellite and weather data

http://www.weathergraphics.com/tim/a...7-cloudsat.jpg

Boxkite Montgolfier 5th Jun 2009 13:22

MR8

It is inconceivable to me that experienced pilots would not have searched exhaustively for wx returns at extreme radar range when approaching the notified presence of ITCZ activity. It is reported that a turbulence report was made 10 minutes prior to the ACARs download.
Pitot probe failures, if true, will have have made safe penetration and control very problematic. Thanks to many for a very informed debate, finally!

MR8 5th Jun 2009 13:26

Wytnucls - I'm sorry, but you are wrong! If you do that in the current scenario, you will STALL.

The 5 degrees nose up is when you are in CLIMB above THRUST RED ALT and above FL100.

The checklist clearly states further:

When at, or above MSA or Circuit Altitude - level off for trouble shooting.

Initial pitch/thrust for FL200 - FL 350 above 190t is 3.5degrees/70.9%N1 - and that is NOT a MEMORY item.

If you would go to 5 degrees, you will fall out of the air before you clear the weather.

MR8

Wossname 5th Jun 2009 13:37

Hand Flying @ Hi-FL
 
P51Guy & Parabellum - My questions were in response to Captain Crunch's assertions that seemed to suggest that a) aircrew should not wait years until an enquiry reaches a conclusion, but should act more proactively (his V2 example). Secondly, in his experience, it seems that pilots are less able/experienced in hand flying at altitude, therefore, less prepared to deal with hazardous, low-frequency conditions.

While I realize that sims can only throw so much into the mix, the idea that perhaps increased automation along with enhanced safety envelopes is also bringing a concurrent degradation in 'real' flying skills, is a worrying one.

I'm sure that Airbus don't know what brought down the AF lads, even if they have narrowed down the possibilities, but perhaps they felt it prudent to remind operators and crews of previous directives.

Cap'n Crunch, thanks for your candor.

Regards,

SaturnV 5th Jun 2009 13:44

MD100,

In the closed thread, Snaproll posted these speeds:
http://www.pprune.org/4969395-post571.html


According to the QRH and based on a weight around 210t:

(speeds are approximate)

Green Dot (minimum clean speed): 245 kts

Turbulence penetration speed: 260 kts

Vls w/ 0.3g buffett margin: 235 kts

Speeds are all indicated so no ISA deviation necessary.
Not much margin.

c130jbloke 5th Jun 2009 13:49

Recovery op sitrep
 
Sorry to shunt this one onto a new aspect, but does anybody know if the crash site and / or a floating debris field has been located and confirmed yet ?

I have tried the usual news sites, but I cannot make it out and the area in question is pretty big for a search which is just adding to the mystery of what happened.

Apologies if this is a bone question.

C130JB

ChristySweet 5th Jun 2009 13:51

Please excuse this layman's intrusion and posting mainstream media but this article has some info on the weather that is pertinent and seems to have been sourced to knowledgeable persons who are on the same page as the discussion here.

Air France jet's flight-control system under scrutiny - Los Angeles Times

>>>>>>>>>>>

"...Meanwhile, new analysis of the weather in the vicinity at the time of the crash appears to cast doubt on earlier reports that the plane encountered severe thunderstorms, lightning and wind gusts. Though there were storms, they were almost certainly less intense than those sometimes encountered above the United States, and lightning was at least 150 miles away, said Greg Forbes, severe-weather expert for the Weather Channel.

Forbes said an examination of weather data for Sunday, including satellite images, indicated updrafts of perhaps 20 mph, far from the initial reports of 100 mph.

"I wouldn't expect it to be enough to break apart the plane," Forbes said.

.....

"Air France executives said the plane had sent out a series of messages indicating technical failures, confirming news reports in Brazil and data that U.S. aviation experts had already gained access to.

A series of serious electronic breakdowns occurred on the Airbus over a four-minute period before the jet plunged into the sea, said Robert Ditchey, an aeronautical engineer, pilot and former airline executive.

The sequence started with an autopilot failure and a loss of the air data inertial reference unit, a system of gyroscopes and electronics that provides information on speed, direction and position. That system has been involved in two previous incidents that caused Airbus jetliners to plunge out of control, though the pilots were able to recover.

The automated messages then indicate that a fault occurred in one of the computers for the major control surfaces on the rear of the plane. Such a failure would have compounded the problems, particularly if the pilots were flying through even moderate turbulence.

The last message indicates that multiple failures were occurring, including pressurization of the cabin. Such a message would have reflected either a loss of the plane's pressurization equipment or a breach of the fuselage, resulting in rapid decompression."

>>>>>>>>>>

Blacksheep 5th Jun 2009 13:54

From reading the ACARS data and discussions with others in our unit, it certainly does seem that Cb penetration followed by sensor failures and loss of control is the most likely scenario.

Rather worryingly, from a number of comments, it appears that many pilots do not use their Wx radar properly.


Radar is not simply something that you switch on in the hope that significant returns will pop up - the display must be seen to even test and start using it
Spot on!

The radar detects water droplets only. It does not, indeed cannot, detect ice. The turbulence mode only detects turbulence that contains water droplets; if there is no rain in the turbulent air, the turbulence remains invisible. On a dark night, if there is no rain in the top of a Cb it is invisible. The Wx radar must be operated in pitch to scan various altitudes ahead: the beam covers a taller column at greater range than at close range and you can pick up the rain that appears lower down in the column that may indicate the presence of a Cb full of ice towering up above it.


Forgive me, a couple of dumb questions for my own edification. Firstly, if we don't know what caused AF to go down until the report comes out, what steps should crew take to avoid the same fate?
Cbs may sprout up in your face very quickly - while working in equatorial climes for decades I have regularly observed Cbs build up from virtually nothing to monsters towering up to 30,000+ feet in the space of fifteen to twenty minutes. This makes it especially important to actively manipulate the Wx radar tilt when flying in known areas of Cb activity and learn to interpret what you see. Do not imagine that what you see is what you get with Wx radar; the truth is, you have to work it and interpret. Honeywell and Rockwell Collins both produce useful pocket sized pilot guides on the subject.

Contact the Flight Ops Support people through these links and since you're pilots, try asking for a freebie:

Honeywell

Rockwell Collins

Lost in Saigon 5th Jun 2009 13:56

AS of Friday June 05/09 the official stance seems to be that NONE of the debris found belongs to AF447. It is entirely possible that they are not even in the right area. They were only searching that area because the last ACARS message was received at the approximate time they would have been in that area.

I would imagine that they are now re-thinking their search. It is possible the aircraft flew in some direction for a considerable time before being lost.

theamrad 5th Jun 2009 13:57


Maybe as a result of our discussion, pilots will start clicking the autopilot off at altitude and get an idea of how it feels in the real airplane on a nice day. It's absurd, imho, for your first experience hand flying at FL350 to be on a dark and stormy night with half of the instruments not working and a flashlight clamped in your teeth.

I concur.

Thanks to the more Airbus avionics orientated guys for trying to make more sense of the ACARS messages for everyone.



If all speed displays are off by more than 16 kts and reliable ADR cannot be identified, switch ADR 1 and 2 off and fly pitch and N1 setting as per the 'Unreliable Speed Indication' paper checklist.


Question concerning Airbus FADEC:
Notwithstanding Safety Concerns warning, and given the earlier posts trying to explain the ACARS messages. I presume with no sign of degraded engine performance and no loss of engine indications, and that PFD flags concerned only airspeed (and possibly alt) – attitude reference was still available. I presume with A/TH disconnected – the throttles allow the setting of a specific n1(from the unreliable speed chart etc), subject to FADEC derived limits??
Also – do the FADEC units derive their main sensed data from their own dedicated sensors – or is some derived externally (ADIRU’s etc)?


p51guy - I think you are mistaken. The pitch/power tables are very rudimentary. When flying close to the coffin corner at altitude and in HEAVY turbulence, you don't stand a chance, not even if you're a stick & rudder ace.

With an unknown airspeed teetering between or exceeding beyond the upper and lower bounds of MMO and min manoeuvring !! And not everyone has the comparitive luxury of even a GPS derived ground speed which isn't dependent on a primary display.

clivewatson 5th Jun 2009 14:25

Blacksheep - it's clear that you understand the point I was trying to make!

MR8 and greenspinner - thanks for the clarification. Yes, I accept that the radar may have been left in a dimmed condition, but I am surprised that several Airbus drivers have complained that this can easily be missed by crew.

Even if you skip the radar taxi check on a cavok day (which I can understand), there is no excuse for not carrying out a function test when you decide to use the equipment to detect weather (one falcon written off after flight into CB due to crew being unaware that the radar red did not paint).

Even if you skip this test, how on earth do you start to scan for weather if you can't see a screen because it happens to be dimmed? Surely you don't simply set a tilt angle and hope for the best? Please tell me that you don't!

Blacksheep 5th Jun 2009 14:35


The only way anyone will know for sure what happened is when the FDR and the CVR are brought up from the bottom of the ocean.
They might tell us waht happened but they won't tell us why. Even the best accident investigations rely heavily on data "interpretation" - another word for speculation. For the time being we have ACARS Data that tells us a great deal of what system failures occurred and these data at least permit our speculation to point towards a reasonable conclusion concerning the root cause.

Regarding the difference between Mmo and stall speed at high altitude, Mmo is set low in certification to ensure that the aircraft is kept clear of the edge of the envelope. There is disagreement between the authorities as to where it should properly be set - for example, the B767 Mmo is 0.84 by UKCAA rules and 0.86 by the FAA rules. The book figures are not clearly defined knife-edges.

Caudillo 5th Jun 2009 14:38


I have no intention of speculating of the possible cause/s of this tragic accident, but I would like to ask a question that relates to the Airbus radar.

Several posters have mentioned that it is possible to have the radar "dimmed" and that this may not be noticed by the crew.

What I don't understand is how it is possible to select, test, tilt and operate the radar if it is dimmed to an extent that it prevents seeing any image or returns. Surely, in order to start any kind of scan using the radar, the image must be visible so that tilt and intensity scans can be seen and set up for the phase of flight.

Radar is not simply something that you switch on in the hope that significant returns will pop up - the display must be seen to even test and start using it - unless Airbus have some fancy system that I have not yet come accross.

Can Airbus pilots please explain the "dimming" problem that several have mentioned
Clive you're quite right. To try to give you an idea of how it works (or doesn't) In front is your ND - Nav Display, which is to the side of the PFD - Primary Flight Display, which contains horizon, altitude, speed, mode annunciators (FMAs) etc. On the ND you can toggle between overlays of weather, of GPWS terrain data, or nothing.

The dimming function doesn't refer to the operation of the weather radar itself, it simply changes the brightness of the selected overlay on your ND. So if you have is pointed right down, and turned to full brightness you be presented with a huge swathe of primary colours, mainly red. Much like the contrast of brightness on your TV you can then adjust the brightness of that colour to what is the most comfortable or least distracting. The actual functions of the weather radar itself are as I'm sure you can imagine, controlled on the weather radar panel elsewhere.

In my own experience I have found the weather radar on my Airbus fallible. A day or two before the Air France accident I flew through an area of numberous isolated CBs. All well defined in daylight in an otherwise clear blue sky and easy to spot and count by eye. Try as I might, scanning up and down with the radar for my own amusement, by my reckoning only 50% produced a return. When it did come, it was very good but for some reason others produced not a sausage. Not a problem on a day like that, but it gave me pause for thought should the same scenario be repeated with the addition of turbulence, night and embedded CBs. I do not think that a weather radar need be inoperative in order for you to fly into something.

AMF 5th Jun 2009 14:48


backseatjock Article from today's New York Times, which links to above threads.

Investigators are pursuing a theory that excessive air speed -- potentially spurred by ice building up on electronic airspeed sensors -- contributed to the ocean crash of an Air France Airbus A330 amid heavy storms Monday, according to two industry officials familiar with the details............
.........................
If the tubes iced up, the pilots could have quickly seen sharp and rapid drops in their airspeed indicators, according to industry officials.
I'm not sure why anyone has to presuppose iced-up pitot tubes or that the cockpit airpeed indications were erroneous. Sharp and rapid decreases or increases in airspeed while within or above a CB that produces violent atmospheric shearing and/or updrafts/downdrafts are going to occur. All the cockpit indications may have been absolutely correct and shown the true picture of the situation if they were in one of the magnitude the weather picture indicates they may have been; that any aircraft's capablity to counter such very real and extremely dynamic atmospheric forces may not be enough (especially at high altitude and heavy weight where aerodynamic and performance are seriously degraded compared to even 10,000 feet lower).

To me the most telling and glaring ACARS message is the first one...Autopilot Disengament....not the flurry of messages that come a few minutes later. Something caused this. The autopilot's inability to hold altitude or being buffeted past it's pitch or roll limits will cause the AP to disengage. Given the context of where they were and the pilot's own message to his company a few minutes prior regarding turbulence, this has to be considered and from this moment the pilots were hand-flying with various flight control limiting protections against aerodymamic excesses removed.

If an aircraft also enters into an extreme updraft (such as those found inside or above a rapidly developing CB) the Autothrottle would begin to close when the airspeed rapidly rose, or the pilots might disengage it if the ATs aren't reacting as swiftly as the pilots need or want.

And if, while in an extreme updraft, the A/P disengages due to the inability to hold the selected altitude and the pilots do what we're normally trained and told to do in that abnormal situation...attempt to maintain pitch and wings level in order not to exceed AOA and load factor limits and control the speed if with thrust while letting the aircraft ride the updraft to a higher altitude (or to a lower one in the case of a downdraft)...that aircraft is going up.

But if the aircraft is already flying at it's maximum enroute altitude near the top of it's operating envelope for that loaded weight when an extreme updraft encounter begins, it could suddenly find itself higher than it should be...a thousand feet higher?...higher still?.... and therefore in a very perilous situation when it exits the updraft. If it's still being buffeted while at that higher altitude, engines spooled back due to the A/T or pilot's prior attempt to counter the indicated (and very real, not "erroneous") acceleration towards overspeed due to the shear accompanying the updraft, but now suddenly the airspeed is rapidly decaying and excess available engine thrust to stop and reverse decaying trend even more limited becaue of altitude, the situation is downright hairy.

Did this happen to this particular flight? Only the FDR will tell. But what can be said is that it's a very real and possible scenario for any heavily-loaded aircraft near to top of it's current operating envelope if it enters or flies just above a quickly developing CB.

Recovering or attempting to recover from this scenario while descending (and you MUST descend to recover) through the severe or extreme conditions inside or around the CB itself could easily result in a cascade of failures and/or failures of electronic self-monitors and sensors within the aircraft, especially if one or more engines flame out.

That "aerodynamics lost" situation is a KNOWN and ALWAYS-present threat in high-altitude flying that we mitigate through choice of crusing altitudes, routes, and actions to get ourselves away from near the edge of the performance envelope if conditions change or develop that could put us outside what was previously comfortable. It's present even with no thunderstorms within 1000 miles. If you pass into or are pushed by extreme and sudden atmospheric forces (like are found in or around CBs) into an aerodynamically unviable situation/jet upset, very few air data indications in the cockpit will be reading correctly even on a clear, sunny day after that occurs.

There's no need to pre-suppose any pitot or probe heat failures or erroneous readings as a cause for the worst happening, and icing severe enough to overcome working pitot heat would normally be found at lower levels (which would of course hamper recovery, assuming other essential structures and powerplants are still working).

And similarily, there's no need to presume a worst-possible-moment, made-for-a-disaster movie script lightning strike that coincidentally knocks out the one component you really need in a CB-avoidance situation...the radar. What can't be seen can't be avoided, and radar still has limitations even while in good working order, especially when it comes to painting the kind of young, developing cell that creates severe-to-extreme updrafts within itself up to thousands of feet above it's visible (by eye or radar) top.

Once again, mitigating the chance of encountering airborne threats is what we do, but the smaller the eye of the needle you thread while picking your way through CBs...especially in a very dynamic steady-state or developing area...the smaller the chance of mitigating it at all. The small or "soft-looking" as-seen-on-radar area you believe is the best route can quickly close up, especially if you're also seeking to avoid being directly over developing cells where the worst turb can be found. And at FL350 and heavy, any pilot should be avoiding that particular spot for that reason, because if a cell is buildng at 10,000 fpm it's a trap for envelopement. Get closed-in, and it's guaranteed your world is going to be rocked, so perhaps the only way to mitigate the threat is to quit worrying about deviating around individual cells and take the 200 or 300-mile deviation around the whole, cursed area.

To me, combined with the pilot's earlier message, the A/P disengaging first with no coinciding source/power failure messages is the biggest red flag of all. What are the possible reasons for it to do so while it's still powered and functioning? Just because it's not controlling the airplane anymore doesn't mean it isn't functioning, or that it only thinks it's being asked to do something it can't due to erroneous Air Data, iced-up sensor input. It's disengament was probably the exact thing it was designed to do under certain conditions, and unfortunately there's the very real possibility that atmospheric conditions outside the aircraft could have been dictating the show into an entenable position from that point on, or perhaps it was even at that point already.

I truly believe many are overcomplicating this. Not every aircraft accident is an overly-complicated series of many technical-issue, swiss-cheese holes. The Laws of Aerodynamics represent one, rather large one when you're mixing it with CBs.

Blacksheep 5th Jun 2009 14:50


When it did come, it was very good but for some reason others produced not a sausage.
Most likely there was no rain in them. Weather radar can only detect water droplets. If there's no water droplets in a cloud pattern, there's no return. Wx Radar isn't magic, it has to be used actively and the results interpreted, but sometimes you just don't get the data you expect.

On one occasion I was called to an aircraft departing in heavy tropical rain that returned to the stand with a weather radar defect. The pilot complained that his display was completely red. I turned the range up to 130 miles and it showed the presence of a heavy rain cell extending out to about 60 miles from the coast.

After he'd been gone the regulation thirty minutes I was able to go home for a change of clothes. :ugh:

clearedtocross 5th Jun 2009 14:51

ACARS timestamps
 
Does anyone know if the timestamps shown on the list are transmitted (e.g. originated in the aircraft) or added at the receiver? It might make a whole difference to the timeing of the events.
Generally fault lists are time-stamped at the originator. However, in a low bandwith situation like transmission of data on a HF-link, time and date might not be transmitted as they are not crucial for maintenance purposes. Then, serialized and delayed, the string of events in the list might be stretched or even out of order of occurence.

blackmail 5th Jun 2009 15:00

AF447
 
c.tocross,

4 minutes.
bm.

incontrol6 5th Jun 2009 15:03

Re: FADEC question. With A/TH disconnect, FADEC will command N1 based on throttle, per pre-defined power curves for flight condition (altitude, TAT, Mach). ADC is prime input for inlet TAT/Mach, but local engine sensors exist as backup.

Dysag 5th Jun 2009 15:04

clearedtocross
 
Your question was already answered in post 61: "ACARS maintenance messages are time stamped according to the event and have nothing to do with the transmission time". You must be getting old.

TripleBravo 5th Jun 2009 15:07

P2J, thanks for your insights.

Here is (partly) the actual ATA chapters from the AMM A330 of AF (actually and currently valid for MSN660, April 1, 2009):

34-10 Air Data / Inertial Reference System (ADIRS)
34-11 Sensors, Power Supply and Switching
34-11-00 Sensors, Power Supply and Switching
34-11-15 Probe - Pitot
34-11-16 Probe - Static
34-11-17 ADM (Air Data Module)
34-11-18 Sensor - Total Temperature
34-11-19 Sensor - Angle of Attack
34-12 Air Data / Inertial Reference System (ADIRS)

And yes,
21 Air Conditioning
21-31 Pressure Control and Monitoring

Rockhound 5th Jun 2009 15:13

Blacksheep,
But what do clouds consist of, if not of water or ice particles? OK, the wx radar will not pick up up/downdrafts or other forms of CAT inside them, but surely it would detect dense cloud. Or am I missing something?
Rockhound

Will Fraser 5th Jun 2009 15:15

There is a pattern to AF and ABI press releases (warnings). Without the boxes, they initially (AF) reported the cause as 'Lightning'. Then the PR was 'maintain airspeed', (this interesting because the implication is the pilots were 'behind'). Now the investigators are reporting 'no 447 debris', just other 'junk'.

It doesn't take a genius to conclude that the line is not only hoping for, but trying to lay the foundation for, pilot error.

How convenient, predictable, and deceitful.

For an aircraft that makes much of its automation, to the exclusion of the necessity for brilliant airmanship, only to see such aircraft dump the flight on the humans when it can't keep up seems, what, ironic??

A33Zab 5th Jun 2009 15:19

Engine FADEC Question
 
theamrad:


Question concerning Airbus FADEC:
Notwithstanding Safety Concerns warning, and given the earlier posts trying to explain the ACARS messages. I presume with no sign of degraded engine performance and no loss of engine indications, and that PFD flags concerned only airspeed (and possibly alt) – attitude reference was still available. I presume with A/TH disconnected – the throttles allow the setting of a specific n1(from the unreliable speed chart etc), subject to FADEC derived limits??
Also – do the FADEC units derive their main sensed data from their own dedicated sensors – or is some derived externally (ADIRU’s etc)?

GE CF6-80E1 - FADEC (ECU) is selfpowered by engine alternator when N2 > 12%.

As far as I know:
ADIRU input is used for N1 Limiting / Thrustsetting.
When A/THR is off,
Fuel Metering is proportional to T(hrust) L(ever) A(ngle)
with structural and thermal protections from its own ' Engine mounted' sensors.

A330 GE Engine Testrunner.

Admiral346 5th Jun 2009 15:23

Rockhound,

the radar will not show "dense clouds".

Radar reflects best of water in the liquid state, very lightly of ice (hardly detectable) and not at all off of vapour.

As stated above, you need to actively scan the sky by moving tilt up and down, to hit the part of the cloud that contains the liquid water.

And the airbus I flew had a Turbulence mode on the radar, a rather unreliable gadget that was supposed to indicate areas of turbulence (in magenta), but usually did so inside a cell. And as one doesn't fly into the cell knowing that turbulence exists inside, the information was generally useless.
Don't ask me how the technical part of that radar worked, I have forgotten and don't have access to the manuals anymore...

Nic

PS: And, Rockhound, there is no CAT inside a cloud - ever. CAT stands for CLEAR air turbulence and is the term for turbulence OUTSIDE of clouds. Everybody who flies knows it is ALWAYS turbulent inside cumuliform clouds, it's just the nature of these things, it is how they are created...

Rockhound 5th Jun 2009 15:34

Thanks, Nic. I shall now retreat back under my rock.
Rockhound

Boxkite Montgolfier 5th Jun 2009 15:36

AMF

I am struggling a little with your concept.
If the Ap disconnect was inadvertent, would the pilots not re-engage immedietly to preserve protection integrity?
If deliberate, which I am doubtful, attention scan and workload is necessarily more demanding. Not recommended and of very doubtful assistance in a very hostile environment. I am still inclined to problems with AD sensors, for whatever reason, being causative .
I am very grateful to the many informative posts which appear to be managed in a more enlightened manner. Downloaded Weather actuals for AF447 are particularly revealing together with ACARS intepretation.
Thanks to all.
Clearly we are all hopeful that search mechanisms are reliable and successful not only for possible debris but also ultimately for FDR and CVR.

Will Fraser 5th Jun 2009 15:48

Boxkite Montgolfier- If your language is French, would you explain your comment re a/p 'inadvertent disconnect'. Because to me that implies 'accidental'. Please tell me you didn't mean 'accidental.'

CaptJ 5th Jun 2009 15:49

A330 vs A340 at FL350
 
Given the sensitivity on this forum I hesitate to ask this question (Sensitivity I don't agree with BTW, there are always idiots and you can't sanction for them)

We have much discussion about the fact the A330 was likely to have been operating out of it's comfort zone at FL350 at this point in the flight. Pretty much in Coffin corner.

So the question is "Given the same route and passenger/freight loading would the A340-300 be operating with a greater speed margin at FL350"?.
I sort of expect it would, being a longer range aircraft, but hard information has been surprisingly hard to find.
(This question is prompted by the IB flight going through at FL370)

regards

Futura Rider 5th Jun 2009 15:49

It seems as though Airbus is suggesting, through their "airspeed" warning to pilots, that they think one of the links in the chain of events that led to the loss of AF447 is the pilots flying in severe/extreme turb. with the autothrottles engaged instead of flying the recommended turbulence power setting with the A/T off?

clearedtocross 5th Jun 2009 15:51

Dysag
 
If you know for sure that events on ACARS are timestamped and transmitted with the message, then that answers my question nicely.
If you just quote what others have heard, said or posted, then your remark is not really helpful. I am might be getting older, yes, however a career in computer engineering has left me to take nothing for granted, most certainly not a sequence of fault messages created by a cluster of dying computers and then transmitted serially through a small bandwith expensive communication line.
cheers, oldie

zekettledrum 5th Jun 2009 15:51

The reports regarding debris seem to be completely contradicting each other. The Brazilian Air Force has been quoted as saying they have not collected anything which belonged to AF447, yet the French Air Force are quoted as saying that life vests and chunks of the plane and baggage containers have been collected.

Will Fraser 5th Jun 2009 15:52

Futura Rider- This is a blunder by ABI. In attempting to finger the crew, they forget that the a/p was flying the a/c, and that after the disengage, the pilots goofed by not maintaining proper speeds. AS IF. Any release by AF or ABI will have this complexion: 'Airbus cupable? mais non'


Starbear 5th Jun 2009 15:54

Nuclear sub to join hunt for jet
 
Hopefully, this might be the first bit of good news. Just surprised it hadn't been mentioned or suggested by authorities before now. BBC


Lost in Saigon 5th Jun 2009 15:55


Originally Posted by CaptJ (Post 4976714)


(This question is prompted by the IB flight going through at FL370)

Aircraft flying at higher altitudes can simply mean they are carrying fewer passengers and cargo.

avspook 5th Jun 2009 16:01

WXR Operation
 
The weather radar system will collect returns from precipitation to activate and acquire a paint the precipitation has to be moving and measurable by Doppler Effect. The higher the Doppler Effect the faster the precip is moving allowing the different colours to be displayed.

It will not pick up hail very well as it is a 'stealthy' circular shape allowing only a single point on the spherical hail to provide a return.

The radar range is affected by the time the radar beam travels out to target & returns so for the same measurable display the radar gain has to be increased as the returning signal is weaker. (STC Sensitivity Time Control)

IF the beam is entirely reflected by Extreme precipitation the backside display of the weather Can look clear (Black) the crew temptation would be to cut across the thin line of 'bad' weather to reach the calm beyond.

What is actually beyond is Hell.
Updated radars detect this as A PAC alert (Path attenuation Compensation) Along with The TURB Mode & PWS these are calculated figures within the radar.

They are best guess logic only but best guess based on years of experience and engineering & meteorological calculation.

The radar pic presented to the crew Has to be interpreted; the same display in Iowa has to be treated differently than in Hong Kong.

As a side note this is the second Airbus down with what pre investigation appears to be erroneous sensor data (ANZ A320 AOA - admittedly with apparent crew contribution)

theamrad 5th Jun 2009 16:01

Incontrol6 and A33ZAB - thanks for confirming/clarifying that point

Although I don't to speculate in AF447's case specifically - wouldn't failure of a FADEC sensed value, from an AD source for example, causing 'reversion' to an alternate/backup mode generate an ECAM and/or ACARS message. (Such as 744 ÉICAS message ENG 1 EEC MODE, for example).

AMF 5th Jun 2009 16:01


Boxkite Montgolfier AMF

I am struggling a little with your concept.
If the Ap disconnect was inadvertent, would the pilots not re-engage immedietly to preserve protection integrity?
Boxkite,

Among other ways, most autopilots will disengage themselves if the aircraft begins rolling or pitching due to outside forces to outside pre-defined limit built into the autopilot itself.

The same is true if it's set to hold a particular altitude but outside forces or decaying airspeed/high AOA approaching a stall exceeds the autopilot's ability to maintain that altitude. Therefore, it's set to disengage by design, accompanied by a warning to the pilots that essentially tells them "you're flying the airplane now".

It should also be mentioned that most generic procedures for inadvertent CB penetration call for de-selecting the Altitude Hold function of the Autopilot even if it remains engaged to allow variations in altitude occur due to extreme updrafts and downdrafts. This is so the AP doesn't keep running pitch control/trim servos to max limits in the futile attempt of trying to maintain a selected altitude which could result in overstress and/or far out-of-trim situations. Perhaps someone here could post what the A330 QRH/AFM procedure calls for with regard to Alt Hold if encountering a CB/Severe Turb?

These limits are designed into autopilots so it doesn't try and overstress the aircraft or keep trying to fly it when the wing stops flying, so through engineering they limit how far it can respond with control surface deflections. In the closed thread, others have posted what those particular pitch, roll, etc. limits are for the Airbus 330-200 aircraft. In severe or extreme turbulence, it's very possible the aircraft was pitching or rolling up to, and beyond, one or more of these internal trip points.

And an autopilot will lock-out engagement (or re-engagement) if you're handflying flying outside of these built-in parameters. So if violent pitching or rolling was/is occuring, you can select engagement as many times as you want but it won't because it needs to see all the parameters met for its engagement first.

Hope that clears up your question, and explains my line of thinking as to why it's the big, red flag of this event.

avspook 5th Jun 2009 16:05

G- Switch or manually activated 121.5/243/406 MHZ type

Lost in Saigon 5th Jun 2009 16:06


Originally Posted by zekettledrum (Post 4976721)
The reports regarding debris seem to be completely contradicting each other. The Brazilian Air Force has been quoted as saying they have not collected anything which belonged to AF447, yet the French Air Force are quoted as saying that life vests and chunks of the plane and baggage containers have been collected.

I believe it was the Brazilians who found life vests and a WOODEN cargo pallet. Two things that boats usually carry. They are now saying that they don't belong to AF447.

Unless you can provide an official press release from The French Air Force saying otherwise, it appears that nothing has been found yet.


All times are GMT. The time now is 21:28.


Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.