Maybe not as vulnerable as some might think. Boeing recommends the following possibilities of TAC disengagement :

Engine Separation 100%

Severe Engine Damage 10%

Engine Surge / Stall 1%

But, this sounds good :

Questions Welcome
 

Microburst2002 - I welcome any questions or clarifications you may want. A trend that concerns me is more and more pilots who don't know enough of the details of what they are operating every day. Even worse are those who don't care to learn more about their rides. You are strongly bucking both of those trends so fire away with any questions that I might be able to help with.

C*U patent
 

Reference with the figures

Aircraft-Pitch-axis-Stability-And-Command-Augmentation---Patent


Another read

franzl

Airbus fbw, Boeing fbw and F-18 fbw
 

Thanks FCeng84
Time to recover this thread!

I have been looking at these subjects again, and I have some questions. I have read a bit about the B777 FCS, as well as that of the F-18. I have even found that Airbus fbw family uses a C* law, blending some pitch rate demand at low speeds, too. However in the FCOM only load factor is mentioned.

I am most interested in the difference between the pilot-FCS interfaces.

In the Airbus the stick as absolutely no other force than that of the springs. It is spring loaded to neutral.

In the F-18 it is the same, I think, but I am not 100% sure. In normal flight it uses a C* law, too. At low speeds during approach it uses an Angle of Attack demand, (similar to that of the Airbus when in the alpha-prot range, I suppose) with a trimmable neutral stick reference angle of attack, for "on speed" trimming.

The 777 is proving the most difficult to understand. My first question is:

In the B777, is the control column spring loaded to neutral?

thanks

Yep. Feel and centreing mechanism under the floor...Ailerons
Column balance weights....Elevators.
There is elevator feel units, under the flt deck floor. Similar to other Boeings, artificial feel provided by a typical cam and roller. The artificial feel being modified as well by electric actuators with changing airspeed.

In the patent of the C*U an airspeed sensitive control column feel is mentioned.

I wonder how does it work, exactly. (similar to the artificial feel of a typical airliner such as a 767)? I deem that it is not like the Airbus sidestick, which feels always the same no matter what the speed is.

Also I have seen that there is a short period damping signal included in the system, so that keeping the column deflected will have a much different effect than on an airbus, and very similar to a conventional airplane.

In the bus, the elevators and THS would give the command g load continually, until reaching a limit triggering the corresponding protection (AoA or high speed).

In the 777 it seems that the pitch rate will soon become zero, and the flight path become 1g at a different speed and angle of attack, similarly to a conventional airplane. Am I right?

I don't fly anything near the size or complexity of a 777, but I have had the chance to look through the manuals. Part of the problem is that he manuals themselves are not sufficiently detailed.

A lot of it seems to leave out the details of what's going on to make the system work. Do you have any idea why the manufacturer has decided to take this direction?