News French plane lost over Atlantic

[Keatah]

I think that with a Boeing fbw system the crew would have had more time to fly the aircraft. The FBW system in Boeing is quite different than that of Airbus.

First of all, let us establish that the big jets always need hydraulics to actuate their control surfaces. And that the FBW takes pilot input from the stick and sends it to the hydraulics to move the control surfaces.

In an Airbus you have a series of control laws and algorithms to help ensure the plane stays within the flight envelope, there are varying degrees and levels of exactly how much the pilot input is modified before it reaches the hydraulic actuators. This system cannot be fully disabled.

In a Boeing there is basically the same setup with one difference, the pilot can cut out ALL of the control laws and modifiers. If he wanted to do so, he could jam full left rudder against the stop, at high cruising speed, and cause the plane to break-up. Or perhaps command full reverse thrust immediately after takeoff, resulting in a crash, too.

Basically, on Airbus the computer has the last say what the control surfaces do. With Boeing it is the captain and co-pilot - all computer algorithms are turned off.

I found this article which would more elegantly explain that.
http://www.fortunecity.com/marina/invincible/249/yokevsti.htm
I have some cool .pdf's that really get into the nuts and bolts and I'll post them up soon.

 

[Linguofreak]

As much as I do agree that it's better to let the pilot have the final say on what happens with the controls, I don't think it would have made a difference here. Severe turbulence plus icing conditions can ruin your day. Period.

 

[garyw]

Not wanting to dwell too much on speculation I don't think any system can help if you lose the pitot tube system. If this does turn out to be the cause it won't be the first time that a plane was lost due to pitot tube problems.

Imagine yourself trying to fly a plane through turbulence when the speed displayed on the PFD doesn't match with that of the Co-Pilots. Imagine getting error messages about flying too fast whilst having a stick shaker going - confusing enough during normal flight. Add a dark night & poor weather distorting your visiblity and you'd have no chance of recovery.

[ame="http://en.wikipedia.org/wiki/Birgenair_Flight_301"]This article[/ame] makes intersting reading about the problems of blocked pitot/static tube systems.

 

[FADEC]

I think that with a Boeing fbw system the crew would have had more time to fly the aircraft. The FBW system in Boeing is quite different than that of Airbus.

First of all, let us establish that the big jets always need hydraulics to actuate their control surfaces. And that the FBW takes pilot input from the stick and sends it to the hydraulics to move the control surfaces.

In an Airbus you have a series of control laws and algorithms to help ensure the plane stays within the flight envelope, there are varying degrees and levels of exactly how much the pilot input is modified before it reaches the hydraulic actuators. This system cannot be fully disabled.

In a Boeing there is basically the same setup with one difference, the pilot can cut out ALL of the control laws and modifiers. If he wanted to do so, he could jam full left rudder against the stop, at high cruising speed, and cause the plane to break-up. Or perhaps command full reverse thrust immediately after takeoff, resulting in a crash, too.

Basically, on Airbus the computer has the last say what the control surfaces do. With Boeing it is the captain and co-pilot - all computer algorithms are turned off.

Blocked pitot tubes make all systems equally same useless in such cases. Wrong measurements make the air data computers literally go gaga. Boeing aircraft also have crashed due to blocked pitot tubes. Pilots react as wrong just as computers do if there are wrong measurements and indications.

You actually can fully disable the flight envelope protection and flight augmentation on an Airbus by the way. You have to switch off all 7 flight control computers (the buttons are unguarded and easily reachable on the overhead panel), but then you will also lose direct law which makes fly-by-wire useless and the aircraft uncontrollable. This is in fact a bad design in my opinion.

 

[Cairan]

I like the idea of a standby pitot and static port being deployed from a sheltered location on the plane, and why not mandate that airliners must use pitots provided by two different manufacturers between the pilot/co-pilot systems and the third standby. What good does triple redundancy do to you if there is a design flaw in the instrument which all fail in the same exact way.

We've seen the rationale behind that with the BFS vs PASS on the Space Shuttle. I think both Airbus and Boeing should look hard at making the standby systems as much separate from the primary flight instruments as possible as far as hardware and software goes.

 

[Urwumpe]

I like the idea of a standby pitot and static port being deployed from a sheltered location on the plane, and why not mandate that airliners must use pitots provided by two different manufacturers between the pilot/co-pilot systems and the third standby. What good does triple redundancy do to you if there is a design flaw in the instrument which all fail in the same exact way.

We've seen the rationale behind that with the BFS vs PASS on the Space Shuttle. I think both Airbus and Boeing should look hard at making the standby systems as much separate from the primary flight instruments as possible as far as hardware and software goes.

You have already 3 probes on an aircraft in different locations. Usually it is already bad enough if one fails. That all three can fail at the same time is a design error of the probes that had to be fixed.

Too much redundancy is also bad.

Also: A new Shuttle would never have a BFS again. The BFS was done in a time when computers had been just in the making and software errors very likely. FBW was a completely new idea then, and the Shuttle actually the second plane in the world to make use of it.

Today you have completely different tools in programming that permit you to exclude software errors as origin of danger. Software does still fail - but how it fails can be controlled differently, it simply costs more to program the software, but it costs still less as a separate project.

 

[Wishbone]

Have to agree with both of you
Common-mode failure is unlikely with well-designed and well-tested sensors. Re: software - reckon BFS was and still is a good idea, despite the limitations we have discovered since then.

 

[Screamer]

Not wanting to dwell too much on speculation I don't think any system can help if you lose the pitot tube system. If this does turn out to be the cause it won't be the first time that a plane was lost due to pitot tube problems.

Imagine yourself trying to fly a plane through turbulence when the speed displayed on the PFD doesn't match with that of the Co-Pilots. Imagine getting error messages about flying too fast whilst having a stick shaker going - confusing enough during normal flight. Add a dark night & poor weather distorting your visiblity and you'd have no chance of recovery.

This article makes intersting reading about the problems of blocked pitot/static tube systems.

It reminds me of a documentary I watch on National Geographic Channel.
It was a series of Aircraft Investigations. I can't remember the flight's name, but the plane was park inside a hanger when a wasp decided to make a nest in one of the pitot tube's. When the plane was flying, all sort of troubles emerge like airspeed and altitude conflicts. The pilots lost there situational awareness, and the plane crash!!!

 

[Linguofreak]

It reminds me of a documentary I watch on National Geographic Channel.
It was a series of Aircraft Investigations. I can't remember the flight's name, but the plane was park inside a hanger when a wasp decided to make a nest in one of the pitot tube's. When the plane was flying, all sort of troubles emerge like airspeed and altitude conflicts. The pilots lost there situational awareness, and the plane crash!!!

Actually, in that incident, they don't *know* what blocked the pitot tubes. They suspect that it was probably an insect nest, but they don't know for sure.

 

[Keatah]

I scan this thread from time to time, and if it hasn't been discussed before.. Why not transmit black box data to the ground? It is certainly possible.

Just transmit it to the ground, the ground only need keep it for the duration of the flight. So no excuse about costs of data archiving. Certainly a few hard disks could easily handle the world's traffic easily.

Or have the black boxes transmit their data by sonar or short range radio. That would eliminate having to find them!

 

[tl8]

I scan this thread from time to time, and if it hasn't been discussed before.. Why not transmit black box data to the ground? It is certainly possible.

Just transmit it to the ground, the ground only need keep it for the duration of the flight. So no excuse about costs of data archiving. Certainly a few hard disks could easily handle the world's traffic easily.

Or have the black boxes transmit their data by sonar or short range radio. That would eliminate having to find them!

There was infact an article in IEEE that had this propsal. And the problem is bandwidth. There are a lot of flights and a lot of data to transmit.

Secondly radio links don't have much. Long overwater flights are already hard to communicate with, (They use a lower frequency link to get more distance). Satillites help, but they too have limited data transmission.

Finally, who is going to pay for it?
There are very few plane crashes (compared to road anyway) and most times they can get the black boxes. The airlines probably don't want to pay for gound equipment. Also who is going to run it? Currently each country has its own investigational team. I can see problems with data access.

 

[Keatah]

Swastica pitot tube..

Why not have a retractable pitot tube? One that can be deployed from a trap-door. It could be kept warm and ice-free inside the body of the plane till needed.

OR better yet, a set of rotating tubes. Like a Swastica pinwheel, half in the fuselage, half out. And rotate it when one gets blocked, or rotate it on a regular schedule. This way you always have an unblocked tube.

 

[Turbinator]

How the real rules look like: http://www.smartcockpit.com/plane/airbus/A330/

Where was this website before?!
Thanks for posting this, it is something I have been looking for for a while.

 

[Keatah]

One important file they don't have online..
View attachment 7119

 

[Urwumpe]

Why not have a retractable pitot tube? One that can be deployed from a trap-door. It could be kept warm and ice-free inside the body of the plane till needed.

As well as to the other one: Usually the heaters should keep the pitot tube ice-free. The rotation or trapdoor assembly wouldn't prevent the formation of ice, without heaters, and it all adds additional mechanical systems that can fail. For example you could have ice blocking the mechanism, then you need again heaters for keeping the mechanism ice-free.

In this case, it isn't even sure that the failure was caused by ice. The air data system failed and the cause was likely pitot tubes of a single manufacturer, which had been discovered to be inadequate. It is likely to be ice, but why and how, that is unknown.

 

[Ripley]

Flight recorders found.
So they say in Italy...

http://translate.google.it/translat...le_nere_volo_air_france-14847755/?ref=HREC1-7

 

[Keatah]

As well as to the other one: Usually the heaters should keep the pitot tube ice-free. The rotation or trapdoor assembly wouldn't prevent the formation of ice, without heaters, and it all adds additional mechanical systems that can fail. For example you could have ice blocking the mechanism, then you need again heaters for keeping the mechanism ice-free.

In this case, it isn't even sure that the failure was caused by ice. The air data system failed and the cause was likely pitot tubes of a single manufacturer, which had been discovered to be inadequate. It is likely to be ice, but why and how, that is unknown.

We're talking a mechanism the size of a laptop or netbook. That can easily be kept ice-free, and you build the motor and gearbox strong enough to crack any ice. After all, ice-cracking devices are used on the leading edges of some regional turboprops.

This would be intended as a backup mechanism to the existing standard pitot tubes. I can't see how enough ice would build-up on a flush surface. And what ice that did accumulate would be cracked when the door opens.

The trapdoor idea is only for emergency usage and the mechanism would be simple enough, I don't see mechanical complexity as an issue. Cost, yes. Typical cost-cutting corporate structure is the cause of so many accidents.

If indeed ice caused the crash of 447, well then, wouldn't you like to be a pilot that could press a button and get a fresh hot unobstructed air data probe going? And if THAT one froze up, well, you'd know what the problem is and could work around it.

If the heaters are inadequate for these probes, then they need to be re-designed. It's really that simple. Let's wait till we get the (ntsb) report before further speculation.

 

[Urwumpe]

We're talking a mechanism the size of a laptop or netbook. That can easily be kept ice-free, and you build the motor and gearbox strong enough to crack any ice. After all, ice-cracking devices are used on the leading edges of some regional turboprops.

Again - the heaters on the pitot tube should do this job.

With the electricity needed for such mechanic toys, you could easily triple the heater power of a good pitot tube.

Also, remember the amount of accidents that happen despite such mechanisms - these permit flying in adverse weather, but they have limits. If the weather becomes really bad, you shouldn't be in it.

Also, if I would be pilot and suddenly see all three air data systems failing at once, I would want two things:

1. The reference data for stable flight by engines and inertial attitude alone, and that ASAP
2. A good prayer

Both is around already. The reference data can be displayed instantly if a software module is installed, that was then optional and which is today part of the base Airbus software.

 

[Linguofreak]

Typical cost-cutting corporate structure is the cause of so many accidents.

If it's a factor here, it's a factor in that the pitot tubes were inadequately heated, not that the aircraft lacked a complex and heavy backup system.

---------- Post added at 13:26 ---------- Previous post was at 13:19 ----------

Flight recorders found.
So they say in Italy...

http://translate.google.it/translat...le_nere_volo_air_france-14847755/?ref=HREC1-7

From the news I'm seeing the tail section of the aircraft has been found, and should contain the flight recorders, but the flight recorders themselves have not yet been confirmed to still be in the tail section (there's a chance they could have been dislodged in the crash).

 

[Keatah]

Again - the heaters on the pitot tube should do this job.

With the electricity needed for such mechanic toys, you could easily triple the heater power of a good pitot tube.

Also, remember the amount of accidents that happen despite such mechanisms - these permit flying in adverse weather, but they have limits. If the weather becomes really bad, you shouldn't be in it.

Also, if I would be pilot and suddenly see all three air data systems failing at once, I would want two things:

1. The reference data for stable flight by engines and inertial attitude alone, and that ASAP
2. A good prayer

Both is around already. The reference data can be displayed instantly if a software module is installed, that was then optional and which is today part of the base Airbus software.

1st, let us see if the heaters did their job, when the report comes out.
I am suggesting this as a backup device. It should consume no current when stowed in the un-used position.

It is fact, pilots will continue to fly through bad weather, with passengers, as long as there are corporate bottom lines to be met.

What is troublesome is the cascading system failures texted back to the maintenance facility.

Anyways, here is a tv show about this, its all speculation, but nevertheless good entertainment!