Air France 447

[Mick F]

Compressor stall is a completely different kettle of fish Daniel. That relates to the compressor blades stalling in pretty much the same fashion that the wing of an aircraft stalls. Not stalling in the manner that Gerard has eluded to.

Mick

[Gerard M]

Thanks again for the explanation Mick. And if your really trying to confuse me with a wing stalling your doing an A grade job. (ok just joking clearly a wing can't stall...unless your being serious and if thats the case don't even bother trying to explain that one to me)

[Mick F]

Wings really do stall.

See here: http://www.eng.fsu.edu/~dommelen/res...l/airfoil.html

Mick

[Nigel C]

If an engine stalls, it stops working (no more energy being produced) and the vehicle it's in can't be propelled forward anymore.

If a wing stalls, it stops working (insufficient effective airflow over the wing to produce lift), and the body it's attached to (fuselage) can't maintain height anymore.

Make sense?

[Owen H]

Gerard,

I don't have the time now to go into too much detail, but no, Mick F is not joking.

"Stalling" in an aircraft is a very different concept from a car engine stalling, so you have to think of them in two seperate ways.

The similarity, as Nigel C has said, is that they both stop working, and that is where the similarity ends.

A stall (as quickly as I can put it at 5am) is basically where the smooth airflow over a lift surface (ie the wing) breaks down to a point where it becomes rough and separated, and stops producing lift. It is related to the "Angle of Attack"... the relative angle of the airflow. If this Angle of Attack gets too high, then the airflow breaks down, and the wing (or surface) stops producing lift. The most common time for this to happen is if the aircraft gets too slow (and we have minimum speeds to prevent this), although it can happen at very high airspeeds too. You'll have to wait for someone else, (or me to get back from work) to explain that one.

A compressor stall is caused in a similar way where the smooth airflow through the compressor is interrupted... something that the engine doesn't really like.

[Philip Argy]

When you fly a kite you need to get the right balance between angle of attack, trim and airspeed. When all is fine, the kite performs well. If the wind dies, the kite falls. If the kite is too high into the wind the airflow over the top of the kite stops and the kite falls. Those last two are the kind of aerodynamic stall that we talk about when we talk of an aircraft wing stalling.

For more explanation have a look at this Wikipedia entry:
http://en.wikipedia.org/wiki/Stall_(flight)

Another consequence of inadequate airspeed is that the flight control surfaces (rudder, elevators, ailerons) become ineffective, as they rely on air pushing against them to achieve their effect. Conversely, with very high airspeed, very tiny movements in control surfaces have a larger effect. Same in a boat - if you've ever tried to berth a low draft vessel at low speed, you lose steerage because the rudder has little water pressure to push the stern. That's why thrusters were invented.

As a digression, we have thrusters on rockets because in space there's no airflow. Most planes don't have thrusters. Harrier jump jets are a spectacular exception. They make a graceful transition from aerodynamic stall to thruster controlled descent, which involves simple but wonderful physics.

[Gerard M]

Once again i am extremely impressed and grateful for the information and explanations guys, much appreciated. Sorry if its like teaching a 7 year old uni grade maths.

Cheers
Gerard

[Philip Argy]

I really do hope that the black boxes are recovered, although I am not overly confident that they retained power or telemetry links for long enough to record the vital last moments

[Philip Argy]

Whilst the authenticity and veracity of the comments can't be vouched for, it seems to record most of the facts as we know them so far, with a few extra elements:
http://wikileaks.org/wiki/What_Air_F...t%2C_2008-2009

[Greg McDonald]

Latest:

THE Air France jetliner that crashed in the Atlantic a month ago with 228 people on board did not break up in mid-air, the French bureau leading the investigation says.

A month-long probe into the June 1 disaster also has found that defective air speed monitors on the Airbus 330 were "a factor but not the cause" of the crash, the worst in Air France's history.

"The plane was not destroyed while in flight," said Alain Bouillard from the BEA accident investigation agency as it released its first report on the crash of Flight 447 from Rio to Paris.

"The plane appears to have hit the surface of the water in flying position with a strong vertical acceleration," he said, adding that the Airbus came down in the water belly-first.

"The plane was intact at the time of impact," Mr Bouillard told a news conference at BEA headquarters in Le Bourget outside Paris.

There had been speculation that problems with the Airbus' airspeed sensors, or pitot tubes, may have caused the plane to stall or fly dangerously fast, causing a high-altitude breakup.

But investigators said that they had ruled out a mid-air breakup after carefully examining the 640 pieces of debris that have been recovered from the crash zone about 1000 kilometres off Brazil's coast.

The airliner's fin was discovered still attached to part of its base structure, further strengthening the view that the plane was all in one piece when it hit the water.

No inflated life jackets were found among the debris, said Mr Bouillard, adding that "the passengers were obviously not prepared for an emergency sea landing".

The lead investigator said the air speed sensors, or pitot probes, were "one of the factors but it's not the only one" that led to the crash as the plane flew through turbulence.

"It's a factor but not the cause," he said.

"We are still some distance away from establishing the causes of the accident."

French investigators have focused on the air speed sensors which fed inconsistent readings to the cockpit shortly before it plunged into the Atlantic.

No distress call was received from the pilots, but there was a series of 24 automated messages sent by the plane in the final minutes of the doomed flight, investigators say.

The BEA, along with Airbus and Air France, have repeatedly said there is as yet no firm evidence linking the speed monitors to the crash of the jetliner.

Air France nevertheless has upgraded all sensors on its long-haul fleet as a precautionary measure after protests from pilots.

The BEA was reporting on its first findings even though an intensive deep-sea search for the plane's flight recorders has yet to yield results.

Brazil decided on June 27 to call off the recovery operation but France has maintained its nuclear submarine, research vessel and other boats in the area on a final hunt for the black boxes.

The BEA has decided to continue the search for the flight recorders until July 10.

The homing beacons on the flight recorders emit signals for about one month after the crash and the BEA hopes that they will have a longer-than-usual shelf life.

French investigators complained that they had yet to see the results of autopsies being performed on the 51 bodies pulled from the disaster area, despite formal requests to Brazilian authorities.

Search and recovery efforts have been hampered by the fact that the crash zone has ocean depths of up to 6000 metres.

People from 32 different countries - including 72 French citizens and 59 Brazilians - were aboard the Airbus A330.