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Author Topic: Air France 447 - interesting article  (Read 6131 times)
ORD Don
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« on: December 09, 2011, 10:51:01 AM »




             
                   An interesting article from Popular Mechanics....


                   http://www.popularmechanics.com/technology/aviation/crashes/what-really-happened-aboard-air-france-447-6611877-2

       
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notaperfectpilot
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« Reply #1 on: December 09, 2011, 12:08:12 PM »

very interesting...I still cannot understand how you can have the stick all the way back for about 2 min. and still not realize that you are in a stall and dropping like a rock.
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joeyb747
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« Reply #2 on: December 11, 2011, 09:59:38 AM »

very interesting...I still cannot understand how you can have the stick all the way back for about 2 min. and still not realize that you are in a stall and dropping like a rock.

Like the "Unsinkable" Titanic, too much faith was placed in what the vehicle "can't" do...

From the article:

""You can't stall the airplane in normal law," says Godfrey Camilleri, a flight instructor who teaches Airbus 330 systems to US Airways pilots.

But once the computer lost its airspeed data, it disconnected the autopilot and switched from "normal law" to "alternate law," a regime with far fewer restrictions on what a pilot can do. "Once you're in alternate law, you can stall the airplane," Camilleri says."

"You can't stall the airplane in normal law...", meaning you can pull the stick all the way back and the airplane will pitch to a limit point and no further, it will not go to far and stall the wings...in NORMAL LAW. ALTERNATE LAW however, removes most of these such protections.

Check this out:

Normal Law, Protections, section:

"High Angle of Attack Protection (alpha):

*When alpha exceeds alpha prot, elevator control switches to alpha protection mode in which angle of attack is proportional to sidestick deflection.
*Alpha max will not be exceeded even if the pilot applies full aft deflection"

Alternate Law, Protections, section:

"*The airplane CAN be stalled in Alternate Law."

From:

http://www.airbusdriver.net/airbus_fltlaws.htm

This page is a great comparison of NORMAL LAW and ALTERNATE LAW.
« Last Edit: December 16, 2011, 09:27:58 PM by joeyb747 » Logged

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notaperfectpilot
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« Reply #3 on: December 12, 2011, 08:00:47 AM »

so, this guy had it engraved is his mind that with the fly-by-wire system working properly, he could NOT stall the airplane NO MATTER HOW FAR HE PULLED BACK ON THE STICK because the airplanes computer WOULD NOT let it stall, correct? In this case, the fly-by-wire system was NOT working the way it normally would because of the airspeed malfunctions, correct? So, since he did NOT know that the system was not operating the way it usually did, he thought it was impossible the stall the airplane . So, if I understand everything right, the FO did the RIGHT thing with the information that he had. Correct me if I am wrong.   
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ORD Don
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« Reply #4 on: December 12, 2011, 10:51:59 AM »






            I just realized that the link that I inserted for this thread is for Page 2 of the article. 

            The link below directs you to the beginning of the article.   Sorry........ huh


            http://www.popularmechanics.com/technology/aviation/crashes/what-really-happened-aboard-air-france-447-6611877
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Biff
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« Reply #5 on: December 12, 2011, 11:12:11 AM »

So, if I understand everything right, the FO did the RIGHT thing with the information that he had. Correct me if I am wrong.   

The information he had was that the aircraft was in alternate law.  He either missed that indication or didn't understand what it meant in regards to his stick input.
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Chadan
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« Reply #6 on: December 12, 2011, 11:24:10 AM »

The flight computer is essentially using Isaac Asimov's laws of robotics to keep the plane in the air. Pilots get conditioned to trust that the plane will fly within the flight envelope even when their inputs are unsafe or unrealistic and would cause the plane to stop flying. This trains pilots to trust the plane's systems as if they were playing a video game instead of using their skill and intuition.

The article did a reasonable job of explaining the psychology behind why Bonin did what he did. Having been trained that his plane is basically a video game, it looks like he used the joystick to tell the plane to "go up!". In natural law mode this is the correct and most effective action. But because the plane's computer switched to alternate law, the normal understanding of how the controls work was invalid. When the auto-pilot switches to manual mode, "pressing the UP button" will not necessarily translate to an increase in altitude as it does with autopilot engaged. Instead, the stick would have to be pushed forward to gain airspeed and produce lift so it can climb.

Perhaps future implementations of fly-by-wire systems could use two different types of controllers: a push-button or on-screen display for a pilot to maneuver the plane while in auto-pilot, and then the sidestick for "manual override". This switching between controls might help the pilot understand that the 'touch-screen' input is simply a video game, while the 'stick' will actually move the control surfaces.
« Last Edit: December 12, 2011, 11:37:49 AM by Chadan » Logged

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joeyb747
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« Reply #7 on: December 12, 2011, 01:02:08 PM »

...natural law...

...NORMAL LAW...   wink
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Chadan
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« Reply #8 on: December 12, 2011, 05:23:08 PM »

Thanks Joey  wink

My brother-in-law made an interesting observation:
Quote
I think driver's ed cars with the dual controls should average the inputs like this.
That would be highly entertaining.
From a distance.
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notaperfectpilot
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« Reply #9 on: December 12, 2011, 05:43:51 PM »

Quote
I think driver's ed cars with the dual controls should average the inputs like this.
That would be highly entertaining.
From a distance.

lol
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joeyb747
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« Reply #10 on: December 12, 2011, 06:12:29 PM »

Thanks Joey  wink

My brother-in-law made an interesting observation:
Quote
I think driver's ed cars with the dual controls should average the inputs like this.
That would be highly entertaining.
From a distance.
cheesy
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kumara6
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« Reply #11 on: December 13, 2011, 02:59:19 PM »

From:

http://www.airbusdriver.net/airbus_fltlaws.htm

This page is a great comparison of NORMAL LAW and ALTERNATE LAW.

Kind of a side note but...Two questions about things I saw on this site.
What is 50' RA?  50 feet what?  or degrees?  and when it says it's limited to 30 degrees of pitch, that doesn't mean AOA, right?  It's literally 30 degrees pitch angle, so it can't exceed that even if the AOA is only 10 degrees?

Thanks
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joeyb747
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« Reply #12 on: December 13, 2011, 03:10:12 PM »

From:

http://www.airbusdriver.net/airbus_fltlaws.htm

This page is a great comparison of NORMAL LAW and ALTERNATE LAW.

Kind of a side note but...Two questions about things I saw on this site.
What is 50' RA?  50 feet what?  or degrees?  and when it says it's limited to 30 degrees of pitch, that doesn't mean AOA, right?  It's literally 30 degrees pitch angle, so it can't exceed that even if the AOA is only 10 degrees?

Thanks

50' RA means 50 feet above the ground, or 50 feet Radar Altitude. And yes, 30 degrees of pitch means no more then 30 degrees nose up.
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