Question: On the sidesticks of Airbus aircraft, there is a Priority Takeover button. [Wikipedia](http://en.wikipedia.org/wiki/Side-stick) has this to say:

> 
> In typical Airbus side-stick implementations, the sticks are independent. The plane's computer either aggregates multiple inputs or a pilot can press a "priority button" to lock out inputs from the other side-stick.
> 
> 
> 

On US flight 1549, [the CVR transcript](https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR1003.pdf) shows that Sully hit the Priority T/O button, after the co-pilot (Skiles) handed over control of the aircraft:

> 
> *15:27:23.2* - **Sully:** My aircraft.
> 
> 
> *15:27:24.0* - **Skiles:** Your aircraft.
> 
> 
> *15:27:26.5* - **FWC:** Priority left.
> 
> 
> 

I'm curious as to why there's a need for this button at all?

Here's a short video on YouTube, demonstrating this:

Answer: 
It's been several years since I worked at United's flight training center, but if my memory serves me, it is there in case the system is receiving input that the pilot wants to exclude. As was explained to me, an example of this would be the other pilot becoming incapacitated, with their body leaning against the sidestick. In this case, one would want to use the Priority Takeover button to eliminate the other pilot's input.

In Captain Sullenberger's case, it is likely that he wanted to ensure that First Officer Skiles wasn't providing any control inputs that would work against his control inputs. 

Now, it is also my understanding that such functionality is not useful in a "hostile takeover" event, since the other pilot can also attempt a priority takeover (or use physical force, due to the close proximity of the two pilots).
A prime reason for this is the fact that the Airbus sidesticks are not connected mechanically, unlike the center control columns of other aircraft. In the event of conflicting inputs from both pilots, such a condition would not be readily apparent. With mechanically connected columns, conflicting input is not possible, without both pilots being aware that the other was trying to do something different. 

As Jay Carr mentioned, this was one of the reasons that led to the AF447 crash - conflicting stick inputs, and apparently neither pilot was aware of that situation, as they would have been with mechanically connected columns. That was an avoidable accident, on several levels. 

It's surprising that Airbus came up with dual disconnected sidesticks and didn't consider the possibility of conflicting inputs, certainly didn't do a very good job of alerting the pilots that such a condition existed. In retrospect, the computer should be screaming bloody murder at the pilots if it detects both sidesticks in use simultaneously - a situation that should never happen.