Handling dynamics with redesigned FBW Sytems

[Swen 1]

Back to topic...

 

 

You can see that the trim speed indicator is jumping and sometimes in the wrong direction...

 

Somebody here think that my hardware was faulty... I don't think so. If have tested so much with disconnected throttel also. If the plane was fly by AP and i disconnect AP the plane is stable. But if i try this by hand, i must fight against the engines and a faulty trimming.

 

In some cases i trim the aircraft and the indicator was not moving up or down.

[cmbaviator 5]

 

 

You can see that the trim speed indicator is jumping and sometimes in the wrong direction..

 

I can't see your video yet.

 

But when the indicator was jumping in the wrong direction, did you double tap quickly the trim switch ?

 

CMB

[Swen 1]

Yes i do.

[cmbaviator 5]

Yes i do.

 

Ok I guess that the trim indicator was within 5kts to the current airspeed of the 777, so by double tapping the trim, the "blid" trim enters in action , it will automatically set the trim reference speed to the current airspeed of the T7 provided that the indicator is with in 5 kts of your current Airspeed.

 

So no issue here

 

EDIT : " add no "

[Swen 1]

OK, if you can, watch my video to see my actions. Tell me that i'm wrong and all its normal, then this is ok. But for me its hard to trim level with speed on.

[cmbaviator 5]

OK, if you can, watch my video to see my actions. Tell me that i'm wrong and all its normal, then this is ok. But for me its hard to trim level with speed on.

 

 

Sorry I meant no issue here. sure I'll watvh your video but  need to wait 9 hours :(

[scandinavian13 5,192]

FWIW, we're getting a new build with some FBW tweaks in it.  I won't go into specifics, but we're looking at the issues.

 

The problem is that it seems some people are having a bunch of issues and some aren't.

[Swen 1]

Nice! Thanks for investigating!

[cmbaviator 5]

 

 

FWIW, we're getting a new build with some FBW tweaks in it.  I won't go into specifics, but we're looking at the issues

 

nice

 

 

 

The problem is that it seems some people are having a bunch of issues and some aren't.

 

weird :(

 

CMB

[hmsdreadnought 12]

So, I have the 200 only and have been flying it a lot the last few days. I'm not havinga any trouble on approach - the plane handles brilliantly in my opinion in this stage of flight.  But climb out and trimming for level flight is a different story.  I've been setting up 3-4 hour flights, so gross weight is in the 450-460 range,  Trimming out after cleaning up the plane is brutal with lots of sudden jerks up by the nose of the aircraft.  I"m also having to put tons of pressure on the yoke to keep the nose down - even with a very low trim setting for take off.

 

I also find trimming the plane for level flight, esp at lower altifudes really hard with lots of ups and downs before It finally settles in .

 

I've flow United's 777 simulator - at the Denver Avsim Conference - and I have so say that the sim feels jumpy and jerky to me.  The actual beast is smooth as silk and deceptively easy to fly (as in, after a few hours you are saying, "like, I could do this job today...).  I even pegged a 20 knot crosswind landing in the sim, didn't break anything, and i'm not a pilot.

 

My point is the jet is smooth as silk, and you don't really think about FBW. It's all very natural.

 

I'm thinking about it a lot with this product.

 

Colin Ware

Seattle

[Kimo 14]

Same issues here with the 200 SP1 trim/FBW.  

[cmbaviator 5]

let's wait for the fix, They said that they are working on a fix

[evaamo 549]

I noticed a strange behavior yesterday on the 300 that I had not noticed in the 200 SP1: right after cleaning up and leveling at 5000ft, I struggled to keep the aircraft level and the trim indicator on the pfd was moving in a very jumpy fashion, even as I was applying very gentle touches using both joystick buttons or the keyboard's numpad. Needless to say it wasn't just the fbw indicator that was jumpy, the aircraft just didn't "feel" smooth, as subjective as that might sound, I reckon. I will try again tonight and report back.

[kevinh 409]

Back to topic...

You can see that the trim speed indicator is jumping and sometimes in the wrong direction...

 

Somebody here think that my hardware was faulty... I don't think so. If have tested so much with disconnected throttel also. If the plane was fly by AP and i disconnect AP the plane is stable. But if i try this by hand, i must fight against the engines and a faulty trimming.

 

In some cases i trim the aircraft and the indicator was not moving up or down.

I don't see any problem with the trim in your video. You aren't giving it any time to settle at the new speed before moving it back again. You begin in trim, increase the trim speed, the elevators move nose down in response. All correct so far. Then, before the stab trim has even begun to follow up the elevator, you return the trim speed to the original value. The sim is actually now back in trim, but the pitch command has changed, presumably from your control input, so it's descending. Note, the speed is not changing so it's in trim. Instead of trimming again to correct pitch, bring the nose up to the level flight position with your controller and see if it maintains this. It probably will. If not make a small trim input and try again. If you are close enough to the trim speed a quick blip on the trim will set the speed exactly.

 

It's impossible to tell from the video when the trim speed is not responding to your inputs. As it's responding sometimes it must be something to do with your interface.

 

If you find the pitch attitude is not stabilising properly with your controller, try increasing the dead band for the pitch channel in the FMC CDU. The 1% default band might be too small.

 

If you have the trim speed display on trimming is really easy. Just set the FBW marker to the current speed. It's then in trim, exactly. If you want to trim like a 777 pilot, switch the trim speed display off and trim by feel. Use the one second trim per 10 knot speed difference as a rule of thumb to help. One thing I've found helps is to watch the yoke in the VC. Note where the neutral position is (i.e. no pitch input). Then see where the yoke moves to when you hold the speed with pitch. This gives some visual feedback about how far the yoke is from the trimmed position. I find the spring force from my stick isn't strong enough to judge trim accurately. When you are happy switch the trim speed display back on and see how close you got. It's quite satisfying to find you nailed it. If you didn't, try again until you are able to consistently get it trimmed within a few knots, at which point you can use the blip trim to set it exactly.

 

 

Ok I guess that the trim indicator was within 5kts to the current airspeed of the 777, so by double tapping the trim, the "blid" trim enters in action , it will automatically set the trim reference speed to the current airspeed of the T7 provided that the indicator is with in 5 kts of your current Airspeed.

Blip trim is a single momentary (i.e. brief) input. Not a double tap.

[kevinh 409]

FWIW, we're getting a new build with some FBW tweaks in it.  I won't go into specifics, but we're looking at the issues.

 

The problem is that it seems some people are having a bunch of issues and some aren't.

Good to know. The only serious fault I get with the FBW is a strong pitch up after banking level after a turn (less than 30 degrees bank). Everything goes OK entering the turn, altitude is maintained correctly without back pressure in the turn, but it goes a bit haywire in pitch as I roll level. Is this one of the known problems? I think I've seen it mentioned on the forum.

 

The other problem I have is more related to workload. On approach you have to change speed several times, that means several re-trims. Trimming is more difficult in the 777X than it should be and that makes things a bit lively at the busiest time of the flight. I haven't yet managed a good stabilised approach. FBW is supposed to make things easier. B)