Since a lot of this has been coming up I thought many people might like to know the basics of how the auto-thrust system is used. Some of this information could be slightly inaccurate so if a real pilot wants to correct anything here, that would be great. The auto-pilot setting for autothrust (A/T) has a lot of modes. You don’t specifically set the mode so much as a combination of settings can affect the mode that it’s in. The modes are the following (this is fairly generic and probably not exactly how the 777 system works):
A/T by itself will simply hold a specified airspeed by adjusting the Thrust Levers.
A/T + FL/CH + V/S + Alititude Hold: (Auto-Thrust + Flight Level Change + Vertical Speed + Altitude Hold) climb or descend to the set altitude by the set vertical speed at the specified airspeed. The thrust levers are maniplated by the system. Generally once the altitude is attained, V/S and FL/CH will turn off.
A/T + “V/S”: The same as the above but with no set altitude.
A/T + Thrust Hold: I looked at the 777 main control panel and I couldn’t find the setting for Thrust Hold, however it seems to be referred to in various things on the internet and I just don’t know what to look for. This setting is normally used for takeoff (maybe landing?) where the pilot sets an airspeed and a thrust (via the thrust levers) and the airspeed is regulated by pitching the aircraft up or down.
A/T + Thrust Hold + FL/CH + Altitude Hold: This setting is similar to the one above, but without setting a vertical speed. The indicated airspeed is controlled via pitching the aircraft up or down until the specified altitude is reached. I believe once the altitude is reached FL/CH mode is switched off as well as Thrust Hold.
This is my best guess as to what the 5 modes the NTSB says the 777 has. If any pilots could correct anything I’m missing or that is simply wrong, that would be great.
Switching between modes is really not intuitive because you’re fiddling with settings and it’s hard to know what button press is actually going to tell the system to do something. If you’re interested in how confusing it can actually be, I’d recommend installing the x-plane trial and trying to mess with these settings.
If you want to give it a go, the beginner’s tutorial for x-plane & the 777 has you do a visual landing on 28L @ KSFO
A/T by itself will simply hold a specified airspeed by adjusting the Thrust Levers.
A/T + FL/CH + V/S + Alititude Hold: (Auto-Thrust + Flight Level Change + Vertical Speed + Altitude Hold) climb or descend to the set altitude by the set vertical speed at the specified airspeed. The thrust levers are maniplated by the system. Generally once the altitude is attained, V/S and FL/CH will turn off.
A/T + “V/S”: The same as the above but with no set altitude.
A/T + Thrust Hold: I looked at the 777 main control panel and I couldn’t find the setting for Thrust Hold, however it seems to be referred to in various things on the internet and I just don’t know what to look for. This setting is normally used for takeoff (maybe landing?) where the pilot sets an airspeed and a thrust (via the thrust levers) and the airspeed is regulated by pitching the aircraft up or down.
A/T + Thrust Hold + FL/CH + Altitude Hold: This setting is similar to the one above, but without setting a vertical speed. The indicated airspeed is controlled via pitching the aircraft up or down until the specified altitude is reached. I believe once the altitude is reached FL/CH mode is switched off as well as Thrust Hold.
This is my best guess as to what the 5 modes the NTSB says the 777 has. If any pilots could correct anything I’m missing or that is simply wrong, that would be great.
Switching between modes is really not intuitive because you’re fiddling with settings and it’s hard to know what button press is actually going to tell the system to do something. If you’re interested in how confusing it can actually be, I’d recommend installing the x-plane trial and trying to mess with these settings.
If you want to give it a go, the beginner’s tutorial for x-plane & the 777 has you do a visual landing on 28L @ KSFO
http://wiki.x-plane.com/777_beginners_tutorial#Landing_the_7...