Oscillation issue

Hi everyone,

 

I am currently on a long flight from LFBD to KSEA (I am trying to complete one of the FS2020 challenges), and I am flying in my A320neo. I had a normal takeoff, I am flying on autopilot at 38,000 feet with a speed of 250 knots, and at the moment I am over the open ocean. The flaps are at zero, the landing gear is retracted, and the air brakes are not deployed. I have the weather set to clear skies with no wind.

 

Everything is going well, except that the aircraft keeps wagging its wings -- and a noticeable amount, at least 5 degrees up and down. (Well, maybe it is less than 5 degrees -- I am having trouble figuring that out -- but it is significant and annoying.) Understand that the plane is flying straight and true, following the flight plan, and altitude is holding perfectly steady. However, the oscillation is significant. I would not want to be a passenger or crew member on the plane.

 

Two questions, please:

 

• Why is this happening?
  
• How do I make it stop?
  

Thank you.

 

Stanley

Edited November 6, 2020 by Stanley777

I found turning the AP off for a few seconds, then re-engaging the AP and ensuring the correct manage modes are engaged seems to resolve the issue.

 

A kind of AP reset.

Thank you, Paxx. That seems to have solved it.

Hi everyone,

 

Since I am on the topic of my current flight, I notice another issue.

 

The nose is pitched up a bit -- not much, but a little bit. I suppose that would be a helpful flare for a landing -- actually, I would want just a bit more flare -- but if I were walking up the aisle from stern to bow, I would be going up a slight incline.

 

Is this normal?

 

Thank you.

 

Stanley

@Stanley777: Yes, that's completely normal. Not only the wings deliver the lift, also the body of the plane. Just a little bit – but it would be wasted uplift if it wouldn't be so.

 

Pino

Thank you, Pino, for your instructive answer.

Hi Pino and everyone else,

 

First, once again, thanks for your reply.

 

But actually, your answer leads me to ask another question.

 

You are saying that the body of the plane -- the fuselage, therefore, right? -- also delivers lift. To play devil's advocate, however, how can that be? The wings provide lift, and so does the horizontal stabilizer. But how can the fuselage, which of course has no wings, provide lift?

 

Can you, or anyone else, please answer my question.

 

Thank you.

 

Stanley

I just had the same thing tonight with the a320 on autopilot. I'll try what paxx said. Is this a bug in the program, or something we are doing wrong?

Turning the AP off and on again offers a temporary solution. After a few minutes the oscillation starts again.

Hi Elvensmith,

 

My situation was possibly different from yours and from others.

 

I had wind turned on as an experiment, and the wind was rocking the plane (as expected, of course).

 

So then, in mid-flight, I turned off the wind, but the rocking -- the wagging of the wings -- continued.

 

I then asked for help, and Paxx suggested disengaging the autopilot for a few seconds and then reengaging it. For me, that solved the problem completely.

 

Stanley

I just had the same thing tonight with the a320 on autopilot. I'll try what paxx said. Is this a bug in the program, or something we are doing wrong?

 

I use real weather and the oscillation seems to occur when the weather updates or when I fly into a "new" weather area.

Pretty sure it's a bug in the aircraft/AP.

 

Turning the AP off and on again offers a temporary solution. After a few minutes the oscillation starts again.

 

Yes, Ive had this happen too. Perhaps wait a few more seconds before re-engaging on the second try. Turning the AP off seems to allow the aircraft to reset itself trim-wise so the AP can fly it without "weird" data or limits that are causing the issue.

 

Im just guessing tho at this point. :)

Edited November 7, 2020 by Paxx

It's all to do with aerodynamics. Without getting too technical the fuselage is shaped like an aerofoil (view it side on) which adds to the overall lift factor of the airframe. On it's own it would be insufficient to support the aircraft but it's a bonus for the aeroplane builder.

Thank you, terrylawdinn, for your excellent answer.