The Weird and Wonderful Logic

A318/A319/A320/A321

Professional

Vol

8-03-2

10 July 2018

THE WEIRD AND WONDERFUL AIRBUS LOGIC

In the last few years we have seen many pilot who were used to Boeing (and more ‘standard’ logic) have

problems understanding the logic of Airbus. We’ll try to discuss the most confusing and often illogical

aspects in this document.

This is not a highly technical document and people accustomed to Airbus logic will not need it. In fact they

might find it lacking in detail or inconsistent. But if you are a real Airbus virgin you will appreciate the

information.

AUTOMATION

Almost everything that can be automated is automated and handled without any need for operator

intervention. You just tell the aircraft what you want and it will try to do it. This seems logical these days

but when Airbus started with this it was a strange concept. A fine example is the window anti-icing

systems. As they are fully automatic and we do not spend a lot of time on failures (as far as I could see a

serious problem resulting of a failure of the anti-icing system has never occurred in millions of flight hours)

we simply do not model them in our simulation. There is no need to. As far as a real pilot is aware they

simply take care of the icing issues without bothering the crew.

Airbus pilots call it ‘automagically’. You should not always try to understand the logic of the systems

(certainly not when you are busy), just accept that the aircraft will try to assist you in every stage of the

flight.

FLY BY WIRE

Of course this is the big one and the thing that set has Airbus Aircraft apart from others for a long time. It’s

a simple concept, the pilot talks to the computer and the computer talks to the aircraft, but it has a

profound effect on every aspect of the flight. It is best explained by a comparison. As the pilot in a Boeing

737 pulls hard on the yoke the aircraft will pitch up and it will keep pitching up until thing go horribly

wrong. If you do the same in an Airbus the computers would try to figure out what you actually wanted

and then try to get it done for you. As it will understand you want to go up fast it will allow you to pitch up

to a maximum (but still safe) angle and when you are running out of airspeed it will increase thrust to

TOGO (Go Around, the maximum amount of thrust possible). When even that does not keep enough air

going over the wings it will lower the nose to increase speed. The FBW systems also prevent the pilot from

doing silly things like stalling the aircraft or doing barrel rolls.

The controversy between FBW pilots and non FBW pilots will probably never end. There is a lot to be said

for each philosophy. While FBW will make flying inherently safer by preventing mistakes it also limits the

option a pilot has to get out of a bad situation. There is one fine example of a situation where the

automation helped. During the US Airways crash in the Hudson the pilot had to ditch with minimal ground

speed and minimal vertical speed. To do this he simply had to pull the control fully back. The aircraft knew

the weight of the aircraft and the environmental conditions so it knew the stall speed. It sensed the stick

being pulled back fully but as it had no running engines it simple selected the best option and that was to

slowly descend at a speed just above stall. In a Boeing the pilot would have to very carefully maintain that

minimal speed until touch down. That is difficult in a normal situation and nearly impossible in an

emergency.