B757 (RB211) Engine Ctrl & A/T
Thread Starter
Join Date: Aug 2002
Location: East Coast
Posts: 40
Likes: 0
Received 0 Likes
on
0 Posts
B757 (RB211) Engine Ctrl & A/T
I have a copy of the Big Boeings FMC user guide and occasionally go thru it as it is a pretty good read. But before I raise a red flag...maybe someone in here can shed some light on what the writer may be trying to say.
In the section of the book where the CRZ function is being discuseed, there are references to the A/T and Engine Control systems on various jets. Here is the text in question:
Second generation airplanes, such as the B-747 while incorporating an autothrottle system were still unable to operate at maximum range cruise due to inherent inefficiences of the autothrottle system. The automatic system operated the fuel controller through the same linkage used by the thottle levers in the cockpit.
The B767-200 and the RB211 version of the 757 permit the fuel controller to change engine thrust through a pre-determined range without without back-driving the throttles. Although the system is still hydromechanical, more precise control is possible. Finally with the advent of the true FBW system found on the B-747, B-767-300 and the P&W version of the B-757, almost flawless control of the engines is possible.
My question is, when they say the RR 757 and 767-200 "permit the fuel controller to change engine thrust through a pre-determined range without without back-driving the throttles", is it possible that they are talking about the EEC functions?? The way it is worded sounds sort of like they are saying that the A/T in the B757 (RR) doesn't backdrive the throttles...which it very well does.
In the section of the book where the CRZ function is being discuseed, there are references to the A/T and Engine Control systems on various jets. Here is the text in question:
Second generation airplanes, such as the B-747 while incorporating an autothrottle system were still unable to operate at maximum range cruise due to inherent inefficiences of the autothrottle system. The automatic system operated the fuel controller through the same linkage used by the thottle levers in the cockpit.
The B767-200 and the RB211 version of the 757 permit the fuel controller to change engine thrust through a pre-determined range without without back-driving the throttles. Although the system is still hydromechanical, more precise control is possible. Finally with the advent of the true FBW system found on the B-747, B-767-300 and the P&W version of the B-757, almost flawless control of the engines is possible.
My question is, when they say the RR 757 and 767-200 "permit the fuel controller to change engine thrust through a pre-determined range without without back-driving the throttles", is it possible that they are talking about the EEC functions?? The way it is worded sounds sort of like they are saying that the A/T in the B757 (RR) doesn't backdrive the throttles...which it very well does.
Join Date: May 2003
Location: The Roman Empire
Posts: 831
Likes: 0
Received 0 Likes
on
0 Posts
On the 737 classic the thottle position asks for a certain amount of thrust, in poor words, but that thrust is refined electronically by the PMC at the variation of the external conditions.
These refinements don't cause the throttles to move.
So probably on the older big birds they didn't have such electronic refinement.
Your manuals refer to EEC, I think.
Last generation 737 don't have hydromechanical system with electronic refinement, but full FADEC.
These refinements don't cause the throttles to move.
So probably on the older big birds they didn't have such electronic refinement.
Your manuals refer to EEC, I think.
Last generation 737 don't have hydromechanical system with electronic refinement, but full FADEC.
