Bugging study question, any help would be great!

[632Patch342]

I'm studying flight control systems and am researching the Airbus A320 since it was the first commercial aircraft to adopt a Fly-by-Wire (FBW) flight control system.

I have a question that has been bugging me, and I cannot seem to find an answer on the net.

If the two pilots both move their side sticks at the same time (perhaps in different directions) what does the aircraft do? How does the computers know which signal to take?

Its probably a simple answer for the people in the know (i.e. you guys), but there isn't much info on the net about it!

Cheers

[sinkingship]

It computs the difference, unless override is used (sidestick priority) in which will control.

[spannersatcx]

The 'computer' sums the inputs: left stick 5 degs right + right stick 5 degs right sum = 10 degs right. left stick 5 degs right + right stick 5 degs left sum = 0 degs.

[Capot]

I've strayed into here, well outside my comfort zone, and am very intrigued......

Surely, the logic is that if both pilots select 5 degrees right, then the correct command is 5 degrees right, not 10 degrees right, with a very high probability?

I can understand why a disagreement should be averaged, but not why an agreement should be doubled to a figure that neither pilot selected, and therefore is almost certainly wrong.

[spannersatcx]

you need to take it up with airbus as to why, but that's the way it works.

[cessna24]

When two inputs are made at the same time by both pilots, a GREEN caption light illuminates in front of the Capt/First officer {ANN-SIDE STICK PRIORTY}. If two inputs are made simultaneously then the input signals are summed for magnitude and direction. If the input signals are of the same direction then the Electrical Flight Control System computes a resultant which commands aircraft movement. If the two inputs are made of different directions then the EFCS will cancel out both inputs without any change to the flight path.
If priorty is required by, for example, the captain wants to gain control over the first officer, then a red button on the side stick would be pressed which controls the priority logic and the captain would have priority. He would see a green caption [ANN-SIDE STICK PRIORTY} followed by an aural warning of "Priority Left". The first officer would see a red caption {ANN-SIDE STICK PRIORTY} If the first officer decides he wants to override the captain, he would hold down the red button on the side stick which would override the whole system.

A bit detailed but hopefully of some help
{Not treading on your toes Spannersatcx}
c24

[subsonic69]

great

but with regards to side stick priority...

lets say both of them press the red button at the same time ( lets just say their timing is good ) ( or maybe theres like a nanosecond difference ) will the aircraft give priority to the captain's side (PRIORITY LEFT with a macho voice )?

or will it disregard the input made by the pilots and still continue with whoever is in control at that given moment.

sorry if im veering away from the main question.

( will have to try tom since i am off duty today )

[subsonic69]

thanks

thanks ASFKAP.

[Genghis the Engineer]

Originally Posted by 632Patch342

I'm studying flight control systems and am researching the Airbus A320 since it was the first commercial aircraft to adopt a Fly-by-Wire (FBW) flight control system.

Apart from Concorde of-course.

I have a question that has been bugging me, and I cannot seem to find an answer on the net.

If the two pilots both move their side sticks at the same time (perhaps in different directions) what does the aircraft do? How does the computers know which signal to take?

As previously said, the system is additive with an override function. That's the Airbus system, but do take account of the fact that other designers may well have taken a different approach to it.

Its probably a simple answer for the people in the know (i.e. you guys), but there isn't much info on the net about it!

Cheers

There are quite a few books however - try the national aerospace library at Farnborough. Or there are a few good review papers out there such as this, whose references will give you a good trail to follow.

G

[Bus429]

Didn't the Vulcan have some sort of integrated power pack/PCU flying control set up?
I remember from my days on the Bristol Britannia that it had FBW prop and throttle control (of sorts but the prop had a computer?)

[agazou]

Vulcan PCU

Vulcans had electric PCA's for elevons with huge power factor correctors for ea PCU