Ask Captain Lim ~ All about Aviation

Dear Capt Lim

Firstly, thank you for your effort into answering questions of passengers that lie beyond the common queries like what meal will be served? which movie will be shown? I have got a few questions regarding the flight deck controls that may be of interest not only for myself but other aviation enthusiasts as well.

1) Since Boeing built its first fly-by-wire aircraft, the Boeing 777, but yet equipped it with a conventional control column, I have asked myself whether the control columns still move - in contrast to 747, 767 planes etc. - when the autopilot is engaged and the autopilot triggers the ailerons and elevators. Does it also indicate turbulences by generated shaking? Does it shake when the plane is in a stall? - obviously almost never on commercial flights.

2) Airbus plane on short final, Captain flying, autopilot disengaged: what would happen if the First Officer puts the side-stick at the same moment of a Captain steering command to the opposite of the Captain's input - of course a stupid action. Which command would the flight control computers carry out? Thank you for your time on this.

Chris

Hi Chris,

You appear to be knowledgeable about flying because you seems to be familiar with some of the airplane operations which I am not so!

Even though the control of the Boeing 777 is based on fly-by-wire concept, it still has all the characteristics of the conventional control column. Yes, the control column still moves in the normal sense just like the Boeing 747, 757, 767 etc. Fly-by-wire merely got rid of the conventional cables and uses electrical wires/signals and hydraulics to move the controls. The control column does not generate any shaking when it encounters turbulence. Of course, any turbulence encountered would be felt everywhere. Many other airplanes have stick-shakers as a warning prior to stalling but the Boeing 777 will not stall when the autopilot is engaged. When it senses the approach to a stall, the power would come on automatically to recover the unsafe condition. In fact, there are also many fail safe functions in the flight envelope of the Boeing 777 in the pitch, speed and banking mode.

I have not flown a side stick control column such as that of the new Airbuses. However, regarding your question, there is an overriding authority switch which allow the last person to have priority over the flight controls. If the Captain have the overriding authority switch on, then the First Officer opposite action has no effect at all. However, if the First Officer engages the overriding authority switch first, then he would override the Captain. So the computer will react accordingly to the overriding authority switch, even though both steering command are takes place at the same time.