hi guys ,

 

hope you can help me with this .

 

I made a few flights , long and short with the 773 and everything works great but one thing i don't understand is the trim function.

I read the manuals , saw YouTube films read the manuals again and again.

 

How do i trim the plane on final approach ?

 

I m fully configured , autothrust on gear down ref speed  at 142 stable all the way down from beginning of the approach  flaps down , disengage the autopilot at 600AGLt  the speed stays fully stable as i can see with the fbw trim ref speed option  . speed is 142 and right beside it is the fbw mark .

Configuration and pitch stays the same until about 200feet AGL and from about  that moment  it look likes the plane stops descending and i almost can't get the nose down , resulting in floating above the runway, During the descent from the faf until about 200 AGL the speed stays the same 142 knots .

 

What am i missing here , the speed trim is  configured for 142 knots  because i disengaged the autopilot when i was stable on final approach  and speed stays stable so the trim has to be right for the remaing of the approach until touchdown .

 

Hope you can help ..

 

Best regards ,

 

Gérard

Try disconnecting AP and AT earlier as you state your fully configured and trimmed so you won't get any sudden movements, if you do at least you have control of the plane. Looks like the plane is trying to reach the final trim speed set that's why all of a sudden the nose pitched up trying to maintain the trim reference speed.

No in theory you don't need to touch the trim on final if the trim reference speed is correct. I get that Uncommanded pitch up as well at low altitude, as I have post up before as. And so far I have had no other feedback as to what caused it. And I don't use the AP.

 

I believe you had done nothing wrong. The only way to get around now is to anticipate it to happen and push the nose down to keep the aiming point constant.

I've had to trim the plane on final app when landing. Before sp1 I rarely had to trim, but on my first flight in the 77W, it threw me a loop. Disconnected the  AP at 1000ft and the plane started pitching down

 

Pierre W

hi guys ,

 

hope you can help me with this .

 

I made a few flights , long and short with the 773 and everything works great but one thing i don't understand is the trim function.

I read the manuals , saw YouTube films read the manuals again and again.

 

How do i trim the plane on final approach ?

 

I m fully configured , autothrust on gear down ref speed  at 142 stable all the way down from beginning of the approach  flaps down , disengage the autopilot at 600AGLt  the speed stays fully stable as i can see with the fbw trim ref speed option  . speed is 142 and right beside it is the fbw mark .

Configuration and pitch stays the same until about 200feet AGL and from about  that moment  it look likes the plane stops descending and i almost can't get the nose down , resulting in floating above the runway, During the descent from the faf until about 200 AGL the speed stays the same 142 knots .

 

What am i missing here , the speed trim is  configured for 142 knots  because i disengaged the autopilot when i was stable on final approach  and speed stays stable so the trim has to be right for the remaing of the approach until touchdown .

 

Hope you can help ..

 

Best regards ,

 

Gérard

Why not just hand fly the descent that what I do unless I'm busy doing other things(in college). To me the only time to use an autopilot is when your at cruise. If its a short hop(Less then two hours) I'll hand fly the whole way. Its a lot more fun and engaging that way.

The problem I reckon is not about hand flying or the use of AP. I only do raw data flying with PMDG 777, and I still get that Uncommanded pitch up on very short final. Although I just treat it as if I get a positive gust in real life no big deal. But ideally in a perfect environment like in FSX with NIL wind and turbulence. The airplane should be able to maintain a constant flight Path on final once in trimmed with constant airspeed. However that doesn't seem to be the case.

In theory, as mentioned above, no trim should be required.   Once trimmed, you just let the FBW system take care of the v/s during the descent for you by using the yoke and letting the FBW keep the pitch for you.

 

I also experience a little pitching up there, but I plan for that so what I would do is to come in about one dot lower and then correct for the pitching up and making sure that once I have sorted it out, I am in the glide slope again.   But I still fly the 200 at this stage, so not sure how bad it is in the -300ER.

 

Kind regards

hi guys thanks for your reactions ,

 

normaly i disengage the autopliot much sooner  but the last times i disengage the autopilot so late to be sure the speed is completely stable and correctly trimmed  but i think it wouldn't be a big difference if you disengage the autopilot sooner ,  because the plane was fully configured with the speed  being stable . If i disengaged the autopilot at say 1500  when fully configurd it's the same as long as you don't change your speed the trim should be the same  and you should'nt have to re trim only when you change your speed ,When on autopilot  , the autopilot is taking care for trimming the speed your flying , if you disengage the autopilot the trim is set for the speed wich the plane flew at time of disengaging the autopilot and you would only re trim when you change the speed , this is what I understand but my english is not my first language , maybe i read it wrong so please correct me if i m wrong .

If i disengage the autopilot at 1500  not fully configured , and changing the speed to ref speed than i have to re trim for speed changes .

 

What i do now is trim the nose down from about 300 -400 feet even when i don't change the speed , it wants to lower the nose wich i can compensate pulling the yoke , this way it stays on the glideslope , but this shouldn't be needed .you should be trimming the nose down when the speed is going up i think .

 

 

Best regards,

 

Gérard

 

 

but this shouldn't be needed .you should be trimming the nose down when the speed is going up i think .

 

I'm not sure what you're getting at here.  Trim and speed are both dependent, and independent.

 

For a given thrust setting (as in: you're not changing your thrust lever position at all):

To increase speed, you must trim the nose down.  To decrease speed, you trim the nose up.

 

For a given vertical speed (as in: speed is being managed by thrust):

To increase vertical speed, you must trim the nose down (related to final approach, anyway).  To decrease it, you trim the nose up.

 

 

 

Regardless:

Trim the 777 the exact same way you trim any other plane.  I'm not sure why people in the community are making this more difficult than it needs to be...

Hi Kyle ,

 

what i m trying to say is that just before touchdown from about 200 feet AGL it seems like the airplane won't descent further but instead increase the height even without incrasing thrust or trimming up the plane .

 

I just tried a approach into KIAH , runway 26Lstarting at 5000 feet at waypoint GRIEG  came from VANNN  for testing also at 5000 feet , 18 miles from touchdown on te glideslope ,   before intercepting the glideslope i was fully configured ,on ref speed 139 +5  knots , landing flaps 30 , gear down , autothrust on , autopilot on .

On the glideslope  ,fully stable , i disengaged the autopilot  and approach , fd off at about 4100 feet ,  let the autothrust on , plane  was perfectly trimmed  and was descending on the glideslope like the autopliot  and approach was on  , steady at 144 knots

 

It kept descending perfectly until about 300 feet AGL ,at speed 144 knots  than the nose was rising  a bit and the plane allmost didn't descent anymore  speed stayed the same 144 knots

Why did the plane ,s nose went up , this was without changing the thrust or airspeed  , at 100-150  feet the airplane started ballooning .

 

Wasn't the plane without touching the controls not supposed to continue the descent until it smacked on the runway , because i didn't change the thrust  , why did the plane starting to increase hight at about 300 feet , once again the plane was fully configured , perfectly trimmed , and without changing the speed or thrust so why was the height increasing  ??

 

Gérard

Tested with -200LR:

No weather set in FSX.

No AP, and no AT, full landing config through whole ILS.

Standard ILS 3* of glideslope

 

I slow down to VREF+5, trimmed aircraft and set 750ft/min descend. When stabilized, I left commands at ~3000ft AGL , and left aircraft on it's own all the way down to 40ft when I initiated flare. No corrections in between. Just a perfect approach, aircraft stayed at GS and LOC. No floating experienced at 200ft.

 

Maybe AP disconnection is the problem?

I used to get this problem in the NGX/74X.

 

At 200ft AGL the plane would float for 1 sec maybe 2, then sink rate would increase (a sort of down draft). I never isolated the cause, but I reckon it was a weather code glitch, and not aircraft related. I re-install windows and programs (fsx) periodically; haven't had the problem since I last did this.

 

Try a approach without a external weather provider AND use FSX to generate 'Clear Weather'. Try with the 777, then with another aircraft. Report findings.

 

Brian Nellis.

I've only seen this once so far, but it has nothing to do with pilot inputs. It goes from being stable and trimmed with constant IAS to just gradually pitching up out of nowhere.

 

Best regards,

Robin.

I'm not sure why people in the community are making this more difficult than it needs to be...

I can not look at your setup Kyle, so I dont know how well things are working on your end.

 

On my end though, this 777 trims NOTHING like a Cessna or 737!

 

So either you dont know how a real airplane flies (which I dont think is the case).

or

You think the 777 is now behaving as it should (as a conventional airplane) where it really is not

or

You are not having the issues I /others are having.

 

But I am sure we shall get to the bottom of this!

Can some of you experiencing difficulties record behavior with camera, to be able to see display and joystick?