View Full Version : 777 autopilot v a330 autopilot question

19th Aug 2007, 08:36
If you are sitting in the cruise in your A330 and the engine fails. Quite simply the autoplilot, if its on ,trims and controlls the rudder.
If you are in a 777 , is it true given the same situation that its up to the pilot to trim. This seems outdated ? Even with the TAC operative. What am I not seeing. I also understand that the only time the 777 autopilot actually controlls the rudder is during an autoland. The minute you change a vertical mode (on the go around)then its back to the pilot to trim the rudder (even with the other two autopilots engaged.) So it kinda says catch !!!!
Have I got this totally wrong. Just doing some light reading before my course.
Appreciate any inputs or corrections.

20th Aug 2007, 15:10
My tin hat is on but...

777, one of the worlds most advanced aircraft...dummed down to make it familiar to Boeing pilots.

TAC's flaw IMHO is that it relies on engines data to sense aysmmetric thrust. If no data available, say engine separation or such severe damage that the sensors have exited the rear of the engine too etc then TAC cannot function.

When it works it is brilliant because it works when flying manual too (even with feet away from the pedals (SIM demo during conversion) it contains the swing and you can fly happily hardly noticing a big difference from the both engines running case), but I think the Airbus method is more reliable using a rudder channel in the autopilot but limited in that it only works with autopilot in.
Which is best?

Personally...could I have a combination of both systems please.

(flown both 777 and Airbus and pleased not have had the need to test either system except in the SIM)

26th Aug 2007, 19:22
Many thanks Fil
It does appear that the 777 has been "dumbed down" a little. ah well I am sure it will have other qualities I will like. I was wandering about eating dinner without my table , but look forward to no pilot induced oscilations in strong crosswinds. I do prefer the ECL to the ECAM though.
Ultimately I will fly anything that gives the best lifestyle.Thats where the real love of flying will come back. thanks again.

26th Aug 2007, 21:22
The 767 was (is) that way, too. It can make things particularly interesting on an engine-out missed approach, so you may want to remember to have your feet firmly planted on the pedals and be ready with the rudder trim when you select any subsequent vertical mode.

Safe flying ...

26th Aug 2007, 22:15
Oh please, you're a pilot, fly your airplane! It's not a question of which autopilot is "dumbed down", it's these modern A/Ps dumbing down the pilots. I think all primary training should be done in old, ragwing taildraggers and all airliner approaches should be flown manually. Let the flaming begin! :E

Tight Slot
26th Aug 2007, 23:57
Ok "training" as you call it is always done on simple type A/C... then you get your ATP/ATPL. Think this guy just wants to know the diff between a 777 and the 330, whole new thing dont you think? I fly the A330 and cant comment on the Boeing, but the poster had a good question to ask as an airline pilot so dont knock him for asking.
Do you still start your car with a crank wheel?? Thought not, so Butt out

28th Aug 2007, 00:09
You're missing the point, bro. Yes, the old taildraggers are simple planes, but still not easy to fly. They have no engineering fixes for adverse yaw, etc, and the simple fact of being a taildragger makes them unstable on the ground. This teaches the new pilot to use the rudder properly right from day one, which skill transfers perfectly into any other aircraft with a rudder. (All of them)

Walker Texas Ranger
28th Aug 2007, 04:43
Well said Caboclo. It sounds like we both appreciate true stick and rudder flying. I feel that in the event of an engine failure it is extremely important to feel the airplane and give it what it wants to continue flying.

I support new technology and many of the advances made in aviation. However I feel that some of it has come to the point where it is dangerous. For example, whatever the A330 does with the rudders during an engine failure ultimately provides a crutch to the pilot which promotes lazines and complacency. A recipe for danger.

28th Aug 2007, 16:21
Hey Cabolco
Dont get too uptight mate. I think most of us concur and share your concerns that " stick skills" seem to be making way to automation. But you did jump on your high horse a little here. Part of being a professional pilot is trying to understand exactly what your machine is going to do and when . To fully understand your new machine technically and how it varies from your old one , also a huge part of being a jack of all trades and a master of one. I would rather rely on superior knowledge than have to fall back on superior skill ( to make up for the situation that my lack of knowledge put me in in the first place). A wise old captain once told me
" Son a professional pilot is made He is not born"

By the way I have over 800 hrs on taildraggers and clearly share your love for them. Safe flying :ok:

28th Aug 2007, 18:27
I'm frequently wrong, and haven't looked at the books for a hundred years, but the TAC operates with an engine failure in the cruise unless it's lost engine data, in which case you will probably get it back after running the cx list and resetting the TAC switch to re-initialise the system.

You will lose rudder control on a go-round (TAC off) when you select a lateral mode because the a/p had been trimming the rudder for the autoland. TAC on, it will still function and won't be a problem and you shouldn't have to use the foot rests.

22nd Oct 2007, 15:41
Here 'tis again fourgolds.

22nd Oct 2007, 16:26
TAC's flaw IMHO is that it relies on engines data to sense aysmmetric thrust. If no data available, say engine separation or such severe damage that the sensors have exited the rear of the engine too etc then TAC cannot function.Concorde had an "auto-rudder" function, that kicked in rudder in the case of an engine surge (which caused a very sudden and nasty yaw).
On the prototypes we had a separate auto-rudder computer, that used engine intake pressure sensor data. These turned out to be "somewhat" unreliable, although at least they stayed "in-situ" !
The whole lash-up was replaced on the preprod and production aircraft by a lateral accelerometer and a couple of circuit boards in the autostab. These fed straight into the PFCUs, so the function was independent of the autopilot.