Pilot53

777 FBW

9 posts in this topic

When handflying the 777 it seems like the fbw function that hold altitude when banking within 30 degrees disconnects anytime you make a slight pitch movement with the yoke.  For example, if properly trimmed and i bank left and center the yoke the aircraft will hold altitude, but if I try to add back pressure to initiate a shallow climb the aircraft will loose altitude as if the fbw system had been switched off, Returning the yoke to neutral pitch will then also increase the rate of descent.  Just wondering if the real 777 behaves this way or if it is maybe a bug?

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15 hours ago, Pilot53 said:

but if I try to add back pressure to initiate a shallow climb the aircraft will loose altitude as if the fbw system had been switched off,

Try adding power for the shallow climb and climb on the excess thrust.

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Hi,

Remember that the FBW of the T7 is a trim for speed, no trim for pitch. If you start climbing a little without adding thrust, you will loose speed and the aircraft will nose down.

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This is all being done with the autothrottle, speed is constant and has nothing to do with what I am describing, sorry should have specified that.   What I am saying is the aircraft maintains level flight in the turn until the yoke is moved, even if I add slight backpressure with constant speed the aircraft will start to descend.  Its like moving the yoke switches off the fbw system.

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15 hours ago, Pilot53 said:

What I am saying is the aircraft maintains level flight in the turn until the yoke is moved, even if I add slight backpressure with constant speed the aircraft will start to descend.  Its like moving the yoke switches off the fbw system.

It does in a manner, I don't recall the exact bank angles (you can search the forum for discussions on FBW and last year a very informative thread was active) involved but at shallow bank the system will maintain altitude for you but as you exceed that value then you need to become a pilot again and fly the airplane just like a big Cessna.  A 25 deg bank is going to require enough back pressure to maintain altitude, if you are descending either reduce bank or increase back pressure.

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I dont think my point is getting across...  It maintains altitude in the bank until the controls are moved again. then suddenly drops like the fbw has been switched off.  Im just wondering if the 777 should behave this way.

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1 hour ago, Pilot53 said:

then suddenly drops like the fbw has been switched off.

If you are expecting the FBW to hold altitude when bank exceeds xx degrees then you are wrong. That is the point. Increase your back pressure or decrease bank.

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12 minutes ago, downscc said:

If you are expecting the FBW to hold altitude when bank exceeds xx degrees then you are wrong. That is the point. Increase your back pressure or decrease bank.

No, again you are missing the point.  Fbw holds altitude in the bank, less than 30 degrees is the spec.  Say we are holding 20 degrees of bank, fbw is holding altitude fine.  Now we dont change the bank angle, but we briefly tap the controls but not enough to change pitch or bank.  The aircraft then starts to descend as if fbw was switched off.

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Hi,

Have you tried to play with the null zone settings in the CDU (cf. Intro manual page 0.00.171)? Also, have you configured your hardware through fsuipc or P3D/FSX? PMDG recommends not to use fsuipc for the controls.

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