Hacker News new | ask | show | jobs
by gcp 5296 days ago
Once you are at stall there is a protection in alternate mode (if I remember properly) that will pitch down the plane to help getting a recover speed (not like normal law that will prevent you from performing stall and over speed maneuvers), BUT that protection can be overridden (unfortunately in this case) by side stick input.

So ironically, the correct advice is not to "fly the plane", but "DONT fly the plane" and let it fix itself.

(This is what I would have expected from a reasonably designed automated system, anyway)

I don´t think you could engage the autopilot in such situation even in normal law(I´ll try at my next simulator).

Can you clarify whether going from alternate to normal law requires a specific action, or is it automatic?

1 comments

Well, yes in this case , but if you have obstacles ahead maybe your best option is keeping the plane close to the stall in order to climb, so you need to fly the plane. That is the reason most of this protections must have an override.

The modes are automatic, if you have all the flight computers and inputs available it will be at normal mode, if you begin loosing computers or inputs (like speed) it no longer has the capability to have that protections active so it downgrades itself, if there is a recovery of some sort (computer reset or working again pitot) it will upgrade the mode to normal by itself. The only action that can be taken is resetting computers or trying to recover a system. In fact when we want to practice alternate or direct law in the simulators, we just disconnect some flight computers. It is not that different flying in alternate or direct law than it is flying normal mode (just a bit more dizzy), unless you try something like pulling the control all the way back for 3 minutes.

Here there is a resume of the airbus flight laws:

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

Pd. mechanical backup, THAT is difficult to fly!. edit: typo