wrote in :

Larry Dighera wrote:
On Wed, 9 Jan 2008 19:43:17 +0000 (UTC), Bertie the Bunyip
wrote in :

The rudder and the stab are both stil physically ( hydraulics)
attached to the flight controls.

Unless there are hydraulic cylinders attached to the flight controls
to activate the rudder and elevator (doubtful), there is going to be
a requirement for hydrolytic pressure from a pump to activate those
control surfaces. If that hydraulic pump can be controlled by the
hypothetical hacker through the computer system, vulnerability
exists, if the Dreamliner systems are similarly engineered.

Never seen a system where the hydraulic pump was controlled; valves,
yes, pumps, no.

What would one "control"?



The hydraulics are pressurised, just like on an earthmover or something.
Actuators on the surfaces move them. They're pumped up to 3,000psi in
just about every western airliner flying today.
In older "manual" anirplanes, like the 747, the pilot's controls move
the valves on the actuators ( power control units or PCU, actually).
With a FBW 'bus, the computer is in between the two, with the exception
of the stab trim, which moves the whole stab, like on a 'cub, and the
rudder, which works like any other hydraulic airplane. If the computers
all go tits up, the crew can disable the computers and fly the airplane
on the rudder and stab trim and the thrust levers can also be used
manually.
For certification, the 777 and 787 will have to have a similar
provision.


Bertie