News French plane lost over Atlantic

[SiberianTiger]

There are reports of the black boxes being recovered.

 

[doggie015]

Update: The nearly impossible happened, the french nuclear submarine in the region picked up the weak sonar signals of the Black boxes and is now triangulating the position.

As sonar signals are not moving in a straight line in the ocean, this will be a bit more complex as finding the boxes over radio signals, but that they received the weak signals is already a good sign, the submarine must be very close to the target.

Why are they denying this? http://www.guardian.co.uk/world/2009/jun/23/france-plane-crash-black-boxes

 

[Hielor]

Why are they denying this? http://www.guardian.co.uk/world/2009/jun/23/france-plane-crash-black-boxes

Perhaps because they didn't actually find the black boxes? It's not necessarily a conspiracy...

 

[Urwumpe]

They are resuming searching for the black boxes months after the crash!

http://www.nytimes.com/2010/02/18/world/europe/18plane.html

 

[Bj]

They are resuming searching for the black boxes months after the crash!

http://www.nytimes.com/2010/02/18/world/europe/18plane.html

Well that's interesting. I wonder if the black box would actually work? After all it has been underwater, and at great depth for 8 months.

 

[Urwumpe]

Well that's interesting. I wonder if the black box would actually work? After all it has been underwater, and at great depth for 8 months.

Likely yes. It shouldn't be corroded away in such depths.

 

[Andy44]

Interesting article on this here: http://www.spiegel.de/international/world/0,1518,679980,00.html

Some of the comments are interesting, too, and put things in a little better perspective.

 

[Urwumpe]

I don't think so, many comments read pretty poor to me, only globetrodden is doing a pretty good criticism there.

But he is wrong on the fuel loading - while the flight plan and fuel estimates are really done by specialists in advance, the captain has the last word on them. I know that the flight planning is always done by the pilots before entering the plane, including the fuel calculations, since they have to include last minute changes in weather and route. They have the responsibility for everything related to the executions of the flight - from the technical state of the vehicle before lift-off to the ability of the cabin crew to do their work.

The latest strike of the Lufthansa pilots was a good reason in TV to show their work again. And it is a really hard job, in the rather good paying by highly challenging European airliner world just the same as in the USA, where the expectations are lower like the payment at first.

 

[Sky Captain]

I have few questions
Why there is no other means of getting airspeed data if pitot tubes are so prone to failure? A GPS system would give a groundspeed and vertical speed which together with throttle setting should allow to guess airspeed with reasonable accuracy.

From the Spiegel article it seems the plane stalled and fell out of the sky. Are`t recovery from stall among the first things pilots are taught?

It seems that ability to override the flight computer and go to full manual control in emergency might be a good safety feature.

 

[Hielor]

A GPS system would give a groundspeed and vertical speed which together with throttle setting should allow to guess airspeed with reasonable accuracy.

Not even remotely true.

Wind.

 

[Urwumpe]

A GPS system would give a groundspeed and vertical speed which together with throttle setting should allow to guess airspeed with reasonable accuracy.

No, not at all. especially the throttle is pretty unreliable to measure speed with. GPS does not give you any kind of exact velocity reading, the error is pretty huge, especially at high speeds. Also the updates come pretty rarely. The same with the vertical speed.

Currently GPS is still too bad for navigation in airspace, the best possible error magnitude with GPS + WAAS + LAAS is still bigger than needed for replacing ILS Cat II for example.

Also, GPS does not give you indicated airspeed, or even allows calculating it. Indicated airspeed includes measurement bias, temperature, local air pressure and such, all the information that affects the aerodynamics. Which is why the pitot probes are so important.

And then, if this is not bad enough: Every recent jet engines has its own air data system, often with small pitot probes on the engine fairing.

 

[garyw]

From the Spiegel article it seems the plane stalled and fell out of the sky. Are`t recovery from stall among the first things pilots are taught?

I believe it is part of the pilot syllabus but it's not something that airline pilots would practise in a simulator.

Now, try a spin recovery at night, in cloud, with a storm raging around you and your airspeed indicators giving false readings (which you might not even be aware of). it's quite possible to go into a spin and not even realise it.

 

[Sky Captain]

So there is NO other technology that would allow to get airspeed data? Not even something that would give approximate value as a backup in case pitot tubes fail? An approximate airspeed data still should be better than no airspeed data at all.

---------- Post added at 12:04 PM ---------- Previous post was at 12:00 PM ----------

I believe it is part of the pilot syllabus but it's not something that airline pilots would practise in a simulator.

Now, try a spin recovery at night, in cloud, with a storm raging around you and your airspeed indicators giving false readings (which you might not even be aware of). it's quite possible to go into a spin and not even realise it.

Well yea the turbulence and frequent lightning flashes together with malfunctioning instruments could make pilots loose orientation.

 

[Urwumpe]

So there is NO other technology that would allow to get airspeed data? Not even something that would give approximate value as a backup in case pitot tubes fail? An approximate airspeed data still should be better than no airspeed data at all.

GPS gives you ground speed. Now you are in the upper atmosphere, have a unknown wind speed around you, likely the wind changes quickly while you travel through the thunderstorms.

How much actual airspeed do you have now? If you are in the jet stream and in the same direction as it, a ground speed of 300 knots would actually mean you are already deep in the stall without knowing it.

 

[garyw]

What about the INS - Would that provide any sort of speed readout or would turbulence upset the platform too much?

 

[Urwumpe]

What about the INS - Would that provide any sort of speed readout or would turbulence upset the platform too much?

Same problem as GPS - it produces ground speed. It can't tell if an acceleration is caused by wind or vehicle performance. It will always tell you roughly where you are (including drift. Large and small accelerations are bad) and how fast your position on Earth changes.

You can't measure the air speed with it. Even radar wouldn't help you.

 

[Sky Captain]

GPS gives you ground speed. Now you are in the upper atmosphere, have a unknown wind speed around you, likely the wind changes quickly while you travel through the thunderstorms.

How much actual airspeed do you have now? If you are in the jet stream and in the same direction as it, a ground speed of 300 knots would actually mean you are already deep in the stall without knowing it.

What if you also take engine throttle setting into account. For example throttle is set so the aircraft should cruise at ~500 knots airspeed. The GPS measures ground speed of 700 knots so it should be obvious there is ~200 knot tailwind.
However I agree in a highly turbulent thunderstorm with winds rapidly changing direction and speed this method would be very inaccurate.

Also the pilots should avoid at all costs flying into powerful thunderstorms no matter what beancounters say about delays and unplanned refueling stops.

 

[Urwumpe]

What if you also take engine throttle setting into account. For example throttle is set so the aircraft should cruise at ~500 knots airspeed.

That would be too nice to be true - and it is: The thrust of the engines depends a lot on the ambient atmospheric conditions, at a set power level. and the velocity you can hold with that thrust depends on aircraft drag. Which depends also on the current air conditions. And you rarely reach a stable equilibrium, you could have strong wobbles in both altitude and airspeed at constant thrust.

Airspeed hold uses the air data as velocity reference, not the throttle.

And 500 knots indicated airspeed would be a tiny bit fast...

 

[Sky Captain]

What then a pilot should do if a pitot tube fails to prevent plane from falling out of the sky?

 

[tl8]

What then a pilot should do if a pitot tube fails to prevent plane from falling out of the sky?

Pray, hence why there is generally a number of pitot tubes

I may be wrong but maybe the RAT could help with airspeed but I think that is unlikely