View Full Version : Fly-by-wire elements in the 747-8?
Less Hair
17th Feb 2010, 08:44
Boeing's latest 747-8 will incorporate a partial FBW control. My question is: What exactly is controlled by that new system? I know about the roll spoilers. How about the ailerons, speedbrakes and stuff? Will these systems have any mechanical backup? How about artificial feel? Are there any new FBW-"laws" or protections? How about system or elec failures? Can't find any details yet. Thanks for any link that's a little more detailed.
Spoilers as you said plus the O/B ailerons are FBW
Speedbrakes should be as well, I'd say the spoiler mixer and aileron programmer in the wheel wells have been replaced by something new leaving the I/B aileron as the only mechanical roll control and therefore can double as mechanical backup rather than a couple of spoilers like on the 777.
Artificial feel for the roll control is a simple spring and the output is reduced by locking out the O/B aileron at high speed.
I don't think there are any new FBW-"laws" or protections however the -8 will be "tweaked" to fly like a -400.
Elec failures - with 4 engine generators I doubt they'll have any problems, the -400 is no problem with spoiler or O/B aileron issues.
A RAT has been added, I believe it's due to the wind milling speed of the GEnx-2B which are considerably bigger and only have 18 fan blades which may be the cause. I think the RAT is purely for hydraulics sys 3 from memory.