AF 447

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plutocrat03
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AF 447

Postby plutocrat03 » Thu Jul 05, 2012 7:03 pm

As I am sifting thought the final report a question popped into my mind.

In a conventionally controlled aircraft, the position of the control yoke or stick gives feedback to the position of the control services. Full forward, elevator down etc. What indications are there in an Airbus cockpit to inform the pilot of the position of the control surfaces?

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jackhodgson
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Re: AF 447

Postby jackhodgson » Tue Jul 10, 2012 5:00 pm

A VERY good question.

// Jack

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cphillips103
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Re: AF 447

Postby cphillips103 » Wed Jul 11, 2012 9:49 pm

I have also been digging through the report. very detailed about all aspects. It's going to take awhile to fully digest, but the pilot voice transcripts pretty much spell it out.

The Airbus 330 doesn't have stick feedback. it also doesn't have feedback from the other pilot giving it input if both pilot's are manipulating their controls.

this creates a problem where one pilot could be turning the stick in a different direction from the other pilot without the pilot flying realizing it. in that situation, the fly-by-wire system averages the inputs.

as an example, one pilot is pushing their stick fully forward, while the other is fully aft. in that case the computer will average the two inputs. this is another reason to make sure pilots use positive exchange of controls. 'my airplane', or 'my controls', with the other pilot replying 'your airplane' or 'your controls". otherwise both pilots could be giving conflicting inputs.

I hope the BEA report makes the 'list' for the next podcast.

-cphillips103

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timothyettridge
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Re: AF 447

Postby timothyettridge » Thu Jul 12, 2012 11:18 am

As I've understood the reports, one of the main problems was that the FO in the left seat was unaware that the FO in the right seat was holding nearly full-back control inputs on the stick from almost all of the descent.

It seems unthinkable to me that this was considered acceptable programing for the fly-by-wire system.
Save space. Live on the edge.

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cphillips103
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Re: AF 447

Postby cphillips103 » Thu Jul 12, 2012 6:42 pm

Captain Sullenberger made an interesting comment that the amount of physical movement in the joystick from neutral to full aft is so small, it would be difficult for someone else to visiblly see the difference in position. You would really need to watch someone while they manipulated the stick. This is diffrent from a large Boeing yoke that would be obviously pulled back to the pilot's chest.

Here's the YouTube link.

http://www.youtube.com/watch?v=kERSSRJa ... ata_player


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