Brake by wire
12-01-2014, 07:37 PM
#1
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Joined APC: Oct 2014
Position: CEO pax Area ( Boeing BBJ)
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Brake by wire
Can anyone explain the following about a brake by wire system
1) is it safer/ how does it work?
2) easy transition into from a simple hyd brake system?
3)Is there any special training required?
Any info given will be much appreciated.
1) is it safer/ how does it work?
2) easy transition into from a simple hyd brake system?
3)Is there any special training required?
Any info given will be much appreciated.
12-02-2014, 08:45 AM
#2
Gets Weekends Off
Joined APC: Dec 2009
Position: B77FO
Posts: 105
Brake by wire
I'll bite. It's very safe and reliable.
1 . Generally there is a computer that measures input and varies hydraulic pressure to the brakes. Then you have a alt. hydraulic system to the brakes as a backup. And as a last resort due to hydraulic failure there is normally a form of accumulator braking although you will only get so many applications of the brakes.
2. As far as transition. It's not noticeable.
3. Nothing beyond learning a new aircraft.
1 . Generally there is a computer that measures input and varies hydraulic pressure to the brakes. Then you have a alt. hydraulic system to the brakes as a backup. And as a last resort due to hydraulic failure there is normally a form of accumulator braking although you will only get so many applications of the brakes.
2. As far as transition. It's not noticeable.
3. Nothing beyond learning a new aircraft.
12-02-2014, 09:09 AM
#3
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I'm told , and this makes sense to me. Speed is directly proportional to braking efficiency...meaning Vref braking efficiency will be , lets say 15% and as speed decreases , braking efficiency increases, depressing the brake pedals fully after planting the aircraft on the ground the BBW system will not allow full brakes to be applied. The system is controlled by a Brake Control Unit (BCU) which receives speed data from the wheel speed xducers and brake pedal position from the pedal xducer . The BCU interprets this then sends a signal to the Brake Control Valves ( BCV) allowing only the amount of HYD pressure needed. As speed decreases the BCU will allow increased HYD pressure thru the BCV to increase braking . Sound correct gentlemen and ladies?
12-02-2014, 02:03 PM
#4
"Yinzer an'at"
Joined APC: Jun 2012
Position: Sittin at the puter
Posts: 186
Originally Posted by B1RD
I'm told , and this makes sense to me. Speed is directly proportional to braking efficiency...meaning Vref braking efficiency will be , lets say 15% and as speed decreases , braking efficiency increases, depressing the brake pedals fully after planting the aircraft on the ground the BBW system will not allow full brakes to be applied. The system is controlled by a Brake Control Unit (BCU) which receives speed data from the wheel speed xducers and brake pedal position from the pedal xducer . The BCU interprets this then sends a signal to the Brake Control Valves ( BCV) allowing only the amount of HYD pressure needed. As speed decreases the BCU will allow increased HYD pressure thru the BCV to increase braking . Sound correct gentlemen and ladies?
That is very generic. It depends upon the system. This sounds like an FAA system question. Boeing does it one way and Airbus another.
Brake by wire is a computer primary system with a manual or standard back up. There are valves, BSCU's (2 of them), and other stuff. You press on the pedals and something happens. If it doesn't, the system is supposed to shift automatically to the second system, via the shuttle valve. If that doesn't work you turn the BRK/NW STRG switch off and press the pedals again. If still nothing happens you use short repeated applications of the parking brake.
There are some diagrams; discussions and a few questions in training and that's about the extent of the education on Brake by wire. This is how Airbus does it. Works good last's a long time not many problems.
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