The Weird and Wonderful Logic

A318/A319/A320/A321

Professional

Vol

8-03-3

10 July 2018

Another very important aspect of FBW is that when the pilot does not give any input the aircraft will stay

on its current flight path. Best explained with an example. Take an Airbus up to 5000 feet, bank it a bit and

let go of the side stick. Then go have diner. When you come back the aircraft will still be at the same bank

and making large circles in the sky. A non FBW aircraft would be flying a straight course and it would level

out. This may sound not too important, but consider what happens when you extend the gear. That

increases drag and because they are positioned below the CoG they will cause a pitch down movement the

pilot has to correct. In an FBW aircraft this would happen automatically and the aircraft would not pitch

down.

In very simple terms: When you point a FBW aircraft somewhere it will go there as long as it has enough

energy.

DARK COCKPIT CONCEPT

Airbus understood that the modern cockpit crew has a huge amount of information to process. To help

with that the cockpit is designed with the ‘dark cockpit concept’. Basically it means that if a system is

running normalll there is no indication. No green light, no pressure indication, just nothing. Only when

there is an abnormality will the system try to draw your attention. Even when there is a problem and the

systems were able to sort things out it might not be shown until the flight is over! These days Boeing also

adheres to this concept in the 777 and to some degree in the MD11.

Of course some control do need to give some feedback and this is done in green (all okay) and blue (still

okay).

THRUST LEVERS THAT ARE MODE SELECTORS

The thrust levers might be big and obvious things in the Airbus cockpit but they are hardly used. In a

standard flight the pilot only touches them a few times:

• TAXI: the thrust levers behave like normal Thrust Levers.

• TAKE-OFF: Pilot advances the thrust levers to the FLEX or TOGA indent.

• AFTER TAKE-OFF: Pilot puts Thrust Lever on CLIMB indent.

And now comes the funny part. It stays in climb setting the whole flight until a few seconds before

landing! To remind the pilot he need to do something with those levers the aircraft even tells him exactly

what to do with the ‘retard…retard’ call. So the Airbus cruises, descends and lands with the Thrust Lever

set in the CLB (Climb) setting.

• AFTER LANDING: Pilot closes Thrust Lever and activates reverse thrust.

So in the air the thrust Levers are used to select the FADEC (the computer that controls the thrust output

of the engines) mode and not the amount of thrust they provide.