B777 pitch control
Joined: Jul 2007
Posts: 183
Likes: 0
From: Sandy Surroundings!
Because it is based on engine data to compute left and right thrust estimates, it is somewhat vulnerable to an engine failure that takes out the associated sensors. Just when TAC is most needed, it may not be available. For that reason 777 pilots must go through engine out training without TAC just in case.
Engine Separation 100%
Severe Engine Damage 10%
Engine Surge / Stall 1%
But, this sounds good :
On the 787 the equivalent of TAC is provided without such heavy reliance on engine data such that it is no longer necessary to train for an engine-out during takeoff without the ITAC (inertial sensor based TAC).
Joined: Feb 2009
Posts: 379
Likes: 0
From: Seattle
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.
Joined: Jun 2009
Posts: 801
Likes: 74
From: Germany
C*U patent
Reference with the figures
Aircraft-Pitch-axis-Stability-And-Command-Augmentation---Patent
Another read
franzl
Aircraft-Pitch-axis-Stability-And-Command-Augmentation---Patent
Another read
franzl
Last edited by RetiredF4; 6th December 2011 at 15:15.
Thread Starter
Joined: Mar 2005
Posts: 1,338
Likes: 1
From: Uh... Where was I?
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
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
Usual disclaimers apply!
Joined: Nov 1999
Posts: 843
Likes: 0
From: EGGW
In the B777, is the control column spring loaded to neutral?
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.
Last edited by gas path; 6th May 2012 at 22:44.
Thread Starter
Joined: Mar 2005
Posts: 1,338
Likes: 1
From: Uh... Where was I?
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 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?
Joined: Mar 2006
Posts: 2,632
Likes: 134
From: USA
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.
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?
