Tech Log The very best in practical technical discussion on the web


Old 12th Jun 2009, 13:19
  #1261 (permalink)  
Join Date: Aug 2008
Location: Siófok
Age: 44
Posts: 18
ILS27LEFT: I tried to avoid unncessary posting there, since the thread is a bit chaotic as is, and if admins decided to keep it as thread and not as a temporary subforum where theories can be discussed in an organized way (and merged into a thread at later point, and moved back to this part of forum), I think it is easy to reduce their workload by posting less. Yet, your post makes me wonder, if it is a good decision or not.

First of all, you ignore some key thing. GPS wasn't lost, since the a/c knew its own coordinates.
GPS isn't useful to calculate airspeed, since you don't know about wings, so GPS signal has nothing to do with airspeed data.
(Even trying to track something that moves with the air would be better indicator for speed... but sadly it would be pretty hard to say the least)
Some people on a hungarian forum suggested, that if you have attitude data and EPR you can calculate the speed, but it would again ignore some of the effects of weather...
Some people suggested metal plates and various devices to determine airspeed, such devices aren't tested or installed, so it doesn't work.

While it is theoretically possible for a computer to calculate some estimated airspeed from various data, and try to help the pilot to keep the a/c in safe limits, it would require some pretty complex computer software, which isn't tested or installed yet. Worst of all: It isn't even implemented in a way that would let us use it on an Airbus FBW aircraft. And measuring if you are withing safe limits can be easier anyway.

The serious faults you speak about are consequences of each other. You also ignore what kind of "serious faults" we are speaking about. If you count the alternate law message, the autopilot and autothrottle messages, etc. as serious faults, not simple consequences of pitot icing, then it could make sense.

But you also gladly ignore the fact, that weather, etc. can be considered common, yet many flights cross the atlantic safely. Why? We can say, pilots try to avoid Thunderstorms. We can say, that the aircraft are certified and should be safe on such trips. We can also say there are many options to avoid such events.

About Coffin corner aviation: We can speak about Coffin Corner aviation for many pages, and about how various systems on the aircraft can determine what speed is safe, and how various factors like any "obstacle" under the aircraft (terrain, CB, traffic) can influence what can be safe, but it isn't that simple as you want to portray it.
Gergely Varju is offline  
Old 12th Jun 2009, 13:20
  #1262 (permalink)  
Join Date: May 2004
Location: Balmullo,Scotland
Posts: 922
Paul2412, It is not for the manufacturer ie Airbus to mandate a service bulletin and in fact they cannot in any case it is for the state of design to do this so only EASA would have been able to mandate a change from a SB to an AD. In earlier posts I have seen the term "mandatory service bulletin" used though manufactures often use this term only the state of design can change this from an optional SB to a mandatory airworthiness directive, so in summary from a legal standpoint Airbus did issue an SB but EASA never mandated it so I cannot see why there would be an issue as in reality AF really did not have to change anything as all service bulletins are optional until changed to an AD.
matkat is offline  
Old 12th Jun 2009, 13:22
  #1263 (permalink)  
Join Date: Mar 2002
Location: Florida
Posts: 5,473
If the VS failed in a downward compression direction as has been intimated in preceding writings, I would think that it is quite possible that this caused deformation and damage of the aft pressure bulkhead and the speculated subsequent pressurization failure.

Its really a chicken and the egg issue. For cascading failures you need to consider which direction they are progressing
lomapaseo is offline  
Old 12th Jun 2009, 13:24
  #1264 (permalink)  
Join Date: Jan 2008
Location: Kent
Age: 62
Posts: 215
Assuming that the accident came about because of extreme weather conditions (and that's still conjecture, I know), and given that other flights made the journey safely, at roughly the same time, I can only see the following possibilities:

1. AF447 was acting with the same caution as other operators, but experienced freak conditions (eg, lightning at a distance from the storm cell, or an unusually fast-developing cell).

2. AF447 was acting with the same caution as other operators, but did not have access to the same information about weather problems in front of them. (eg, inoperative weather radar).

3. AF447 was not acting with the same caution as other operators.

No.3 is the one that this community could usefully explore, I think.

Presumably, when approaching areas of difficult weather, there is a level of severity where the decision is to fly around the area rather than grit one's teeth and plunge through? This has to be the captain's decision, ultimately, but to what extent is the assessment affected by company expectations, or peer-group culture? How does the decision get made?

To what extent might exaggerated trust in the robustness of the airframe affect the decision? (Air France, Airbus, after all).

Please note: I'm not suggesting irresponsibility on the part of the operator or the crew. But I'd be interested to know how pilots here - who I assume are from a wide range of operators, of different ages, different locales - go about the business of deciding what to do about dodgy weather ahead.
overthewing is offline  
Old 12th Jun 2009, 13:27
  #1265 (permalink)  
Join Date: Mar 2007
Location: under the sea
Posts: 2,518
I discovered the following document on smart cockpit:
SmartCockpit - Airline training guides, Aviation, Operations, Safety

It is an Airbus presentation about Unreliable Airspeed from 2006.The document does not appear to be complete as some videos are missing but it does show that Airbus offer a backup speed scale rather like a traditional fast slow indicator. to cater for air data problems.
I wonder if the AF aircraft had this mod fitted?Has anybody got any experience of using this Airbus mod?
tubby linton is online now  
Old 12th Jun 2009, 13:34
  #1266 (permalink)  
Join Date: Sep 2007
Location: Melbourne
Posts: 180
Thanks for the constructive comments, guys.

As to why not make the changes mandatory instead of advisory, my guess is that there was an accountant sitting at the table. No disrespect to accountants - they're there to remind you that if you stop making a profit you'll end up on the dole.

My guess is that Airbus reasoned that all that had happened so far was that a few pilots (maybe ten crews, 6 Air France, 2 Air Caraibes, maybe 2 Qantas) pilots had got a fright - but they'd managed to recover and land safely.

An 'advisory' means that the airlines pay - if they care to. A 'mandatory' means that the manufacturers do.

I LIKE to think that in my own business - which was equally concerned with safety - I'd have been the 'White Knight' yelling for us to 'do the right thing.' I probably would have been in this case - but, as a director, you only have one vote, and I never got to be a CEO.

As to 'why use the rudder?,' the only things I ever flew were 'toy' aeroplanes and gliders. I never flew in bad visibility, leave alone thunderstorms. I'm pretty sure that, if I was in the circumstances those guys were probably facing, I'd have used anything within reach (even including sensitive parts of the guy in the other seat's anatomy) to regain control. I know one other thing, too - if I'd ever been thrown into say a 45-degree bank while losing height, I'd have remembered in particular that the rudder, geometrically speaking, was 'half of the elevator' in that attitude - and vice versa - and therefore I'd have made a balanced input of both..........

Maybe worth mentioning too that one accident I researched thoroughly (because I visited NYC shortly afterwards) was AA587. Believe it or not - because Airbus favour 'variable stop' rudder limiters (that is, the pedal travel is restricted instead of the rudder movement) a mere 1.2-inch pedal movement will produce full permissible rudder movement on an A300 doing only 250 knots.......

'Pilots aren't concert pianists,' you might say........

Last edited by RWA; 12th Jun 2009 at 13:49.
RWA is offline  
Old 12th Jun 2009, 13:41
  #1267 (permalink)  
Join Date: Aug 2006
Location: firmly on dry land
Age: 77
Posts: 1,537
From the first post on this thread:

Originally Posted by pattern_is_full View Post
this was a real aircraft carrying real people which really crashed in a real ocean due to some real cause - while flying in the vicinity of real weather.

. . . there is no jury to persuade, and a "convincing" argument will still carry no water if, in the end, it does not match up with the real event.
but many posts that try and bring people back to real events and reality with rational explanations are deleted.

"No Captain is going to . . . . Never say never....

At this point, almost anything is "possible", far fewer things are "probable" consistent with the limited evidence, and only one is "correct".
So, why, where we try and use real facts, including oceanographic data to either support or refute other posts are they deleted?
Wader2 is offline  
Old 12th Jun 2009, 13:48
  #1268 (permalink)  
Join Date: Jul 2002
Location: california
Posts: 35
Drowning ?

If they had NO water in the lungs, they didn't drown, did they !?!?
captainflame is offline  
Old 12th Jun 2009, 13:52
  #1269 (permalink)  
Join Date: Sep 2007
Location: Melbourne
Posts: 180
Yes, captainflame. The pathologists will likely tell us quite soon whether she hit the water in one piece, or broke up in the air.

But not WHY she did.....

Last edited by RWA; 12th Jun 2009 at 14:04.
RWA is offline  
Old 12th Jun 2009, 13:55
  #1270 (permalink)  
Join Date: Aug 2005
Location: fairly close to the colonial capitol
Age: 52
Posts: 1,692
Originally Posted by parabellum View Post
On the Boeing's that I have flown the only time you touch the rudder at cruise speeds is during the recovery from unusual attitudes, top rudder to compensate for extreme bank angle, other wise, once past, at the latest, 210kts, leave the rudder alone. It would appear that somewhere in the transition from general aviation to jets the lessons about the rudder, it's uses etc. and how to apply it are being forgotten.
At least in these threads.....among many other lessons.
vapilot2004 is offline  
Old 12th Jun 2009, 13:57
  #1271 (permalink)  
Join Date: Jul 2002
Location: california
Posts: 35
Rudder still attached...

I'm puzzled with the bit about in flight break off of the VS because the rudder is still nicely attached to it.

Seems to me that overloads there would have ripped it (the rudder) off too ? (see AA)

Where if VS broke off when hitting water, it's still attached. (see NWA and ANZ 320)
captainflame is offline  
Old 12th Jun 2009, 14:01
  #1272 (permalink)  
Join Date: Sep 2007
Location: Melbourne
Posts: 180
Right on cue - she broke up in the air.......

"Almost all of the bodies had multiple fractures, the paper reported. Investigators haven’t found water in the victims’ lungs, which would indicate drowning, Estado said. Bodies were found 85 kilometers (53 miles) apart, which may also indicate the Airbus A330-200 broke up before reaching the ocean, Estado reported."

Air France Probe Suggests Plane Broke Up in Air, Estado Says -
RWA is offline  
Old 12th Jun 2009, 14:17
  #1273 (permalink)  
Join Date: Oct 2004
Location: NY - USA
Age: 65
Posts: 65
Someone please tell me WHY, if true, there is an "Automatic" position on the Pitot Heat Switch on this, or any aircraft.
Avionics maintenance engineer here, specializing in air data systems.

The "automatic" mode is used to prevent electrically-heated sensors (pitot probes, AOA vanes, TAT probes etc.) from being switched "on" when the aircraft is on the ground.

The system is activated by the weight-on-wheels sensors, permitting electrical current flow to the probe heating elements only after the aircraft is airborne.

Without the cooling effect provided by airflow, the pitot probes in particular can reach a temperature of several hundred degrees in very short order, which can quickly cause the heating elements to burn out (at the very least), to say nothing of possible damage to surrounding aircraft structure.

A manual mode must be available, however, as there are occasions where it would be necessary to power the heaters on the ground - i.e. on a cold day where frozen precip (snow, sleet, freezing rain) is present.

A significant amount of electrical current flows through the heating elements when they are activated. If sensors detect no (or inadequate) current flow in a situation where the heater should be on, it will trigger a "fail" annunciator or EICAS message for the associated probe.

Many "vintage" Boeing aircraft (737, 727 etc.) had a switch-selectable ammeter so that the crew could actually see the amount of electrical current being delivered to each probe's heating element. More modern airframes depend solely on annuciators to detect heater failure.

However, none of these monitoring systems can detect a situation where the heater might be working perfectly, and yet unable to keep up with ice accretion in a particular environmental scenario due to a design flaw.

JR Barrett

Last edited by JRBarrett; 12th Jun 2009 at 14:39.
JRBarrett is offline  
Old 12th Jun 2009, 14:17
  #1274 (permalink)  
Join Date: Sep 2008
Location: Italy
Posts: 3
Similar design as A320

No. It is different, no FACs no ELACS
Just 3 PRIMS, 2 SECs, 2 RPTLs and 2 RTLs, 1 BCM for either Blue or yellow HYD.
elch is offline  
Old 12th Jun 2009, 14:27
  #1275 (permalink)  
Join Date: Jul 2008
Location: UK
Age: 66
Posts: 475
nice sentiment notpilotatall but doesn't match the real world.

The real world takes it for granted that "it won't happen to them" and due to some fantastic design and advances in technology they will most probably be right.
Safety Concerns is offline  
Old 12th Jun 2009, 14:44
  #1276 (permalink)  
Join Date: Jun 2009
Location: Bedford, UK
Age: 67
Posts: 1,275
Re: Overthewing, there is still the possibility that the conjecture is wrong and that the weather was not extreme to the point of loss of all hope of recovery. Need the recorders to know that and given the likelihood of wide dispersal, recovery of them will be a miracle. Lingering doubts will remain over the robustness of the systems until the environment is known.
Mr Optimistic is offline  
Old 12th Jun 2009, 14:56
  #1277 (permalink)  
Join Date: Sep 2008
Location: Italy
Posts: 3
Rudder and vma

When the upset recovery training came up we heavily contested the military derived rudder recovery usage ( sky rudder they said ). Best way to loose an aircraft by control inputs beyond FAR certification:

Code of Federal Regulations

Sec. 25.351

Subpart C--Structure
Flight Maneuver and Gust Conditions

Sec. 25.351

[Yaw maneuver] conditions.

[The airplane must be designed for loads resulting from yaw maneuver conditions specified in paragraphs (a) through (d) of this section at speeds from VMC to VD. Unbalanced aerodynamic moments about the center of gravity must be reacted in a rational or conservative manner considering the airplane inertia forces. In computing the tail loads the yawing velocity may be assumed to be zero.
(a) With the airplane in unaccelerated flight at zero yaw, it is assumed that the cockpit rudder control is suddenly displaced to achieve the resulting rudder deflection, as limited by:
(1) The control system on control surface stops; or
(2) A limit pilot force of 300 pounds from VMC to VA and 200 pounds from VC / MC to VD / MD, with a linear variation between VA and VC / MC.
(b) With the cockpit rudder control deflected so as always to maintain the maximum rudder deflection available within the limitations specified in paragraph (a) of this section, it is assumed that the airplane yaws to the overswing sideslip angle.
(c) With the airplane yawed to the static equilibrium sideslip angle, it is assumed that the cockpit rudder control is held so as to achieve the maximum rudder deflection available within the limitations specified in paragraph (a) of this section.
(d) With the airplane yawed to the static equilibrium sideslip angle of paragraph (c) of this section, it is assumed that the cockpit rudder control is suddenly returned to neutral.]

Amdt. 25-91, Eff. 7/29/97
elch is offline  
Old 12th Jun 2009, 15:03
  #1278 (permalink)  
Join Date: Aug 2008
Location: Siófok
Age: 44
Posts: 18
Safety Concerns: Sorry if it is a bit offtopic, etc. I agree with what you say, but I think it is a responsibilty of both our politicans and the self loading freight.

Why? Safe operation is mandatory, but if the management knows their aircraft isn't safe and people die, noone from the management is charged for it. No personal consequences for unsafe operations, but more premiums from extra profit if you ignore safety? It invites disaster to happen.

But the problem isn't here. If pax decides: if AF ignores SBs and some planes aren't that safe then we don't fly with them, because the contract is for a safe flight, etc. then AF wouldn't ignore SBs.

I am not sure how it works in your country, but in Hungary the generic population is less interested in which airline is safe, and more interested, if some package for a celebrity (who became one without any merit or real talent) was lost somehow. Or the "drama" or anything else, but not their safety.

Even if pax can raise stupid questions there, they vote with their money about safety, and their vote can determine the safety for pilots as well.

I don't want to start another Airbus - Boeing argument here. Probably we don't know what is better.

But most pax have an assumption about which is safer. Yet most of them ignore it when they can save an euro or two this way. If they ignore their assumption, they won't care about SBs they don't even know about.

And most companies simply do what customers want.

For them GSM on board, a few cents worth of discount, etc. are all more important than safety and this is why companies spend money to provide GMS service and not on reliable communication with ATC, following SBs, etc.

We decided to keep SLF discussion on this topic at minimum, since it is easier to moderate a single thread this way. If we would use the public exposure, would have a subforum, where SLF can learn and they would next vote for safety with their money? Then the picture would be different.

Our choices are part of the real world that makes ignoring SBs profitable. And even if it is a small part of picture, and our influence is pretty hard to notice, we should make sure our decisions contribute to safety and not to any future accident. Because if we don't follow this "example" then why would anyone else do it? But if many people decides even if his individual influence doesn't matter he stay security conscious that can have some effect.
Gergely Varju is offline  
Old 12th Jun 2009, 15:08
  #1279 (permalink)  
Join Date: Jun 2009
Location: Bedford, UK
Age: 67
Posts: 1,275
Public perception

Air transport needs to be considered so safe that safety isn't a purchasing choice. The DC 10 had a hard time in the '80's when it cropped up to often in the headlines. If, by unfortunate chance, another large loss was experienced whilst AF is still in the headlines I think public confidence in the industry would become an issue. So yes, safety is either irrelevant to choice or the only factor worth considering depending on public sentiment.
Mr Optimistic is offline  
Old 12th Jun 2009, 15:12
  #1280 (permalink)  
Join Date: Feb 2008
Location: Kemble - England
Posts: 12
However, none of these monitoring systems can detect a situation where the heater might be working perfectly, and yet unable to keep up with ice accretion in a particular environmental scenario due to a design flaw.

I find this hard to believe, as the aircraft clearly has to be certified for "flight into known icing" for a given specification. The entire airframe would have iced before the Pitot if the heater was actually working??????
Professorrah is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.