B707-320C - Pitch Oscillations

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ISSUE DESCRIPTION

Description of the issue: Seeing a lot of pitch oscillations while on autopilot during flight. In the climb, at cruise, in descent, various phases. The trim wheel keeps going back and forth (and makes a really annoying noise) and you can see the plane porpoising in external view. Another user reported here: Boeing 707 pitch oscillations - General Discussion - iniBuilds Forum

FREQUENCY OF ISSUE

How often does this occur for you (Example: Just once, every time on sim load, intermittently)? Pretty much all the time when on autopilot, with various amplitudes. Frequency of roughly 1 oscillation per 3-4 seconds.

REPRODUCTION STEPS

Please list clear steps you took in order to help our test team reproduce the same issue:

  1. Fly on autopilot

YOUR SETTINGS

If the issue still occurs with no mods and add-ons, please continue to report your issue. If not, please move this post to the User Support Hub.

What peripherals are you using, if relevant:

[PC Only] Are you using Developer Mode or have you made any changes to it?

[PC, MSFS 2020 Only] Are you using DX11 or DX12?

[PC Only] What GPU (Graphics Card) do you use?

[PC Only] What other relevant PC specs can you share?

MEDIA

Please add a screenshot or video of the issue occurring.

2

I’ve flown two 1.5 hr flights using the autopilot & have not encountered this on my PC, as long as my speed and altitude are within the flight parameters of the aircraft.

I did find that too little speed, or two high an altitude for the aircraft’s weight & loading distribution can cause porpoising as the aircraft tries to maintain level flight at the extreme edge of its’ flight parameters.

3

ive been flying at FL350 at mach .85 for the last 8 hours and have had it porpoising for the entire flight. my GW is 210k lbs. CG is also perfectly in balance

4

If it helps, when I experienced this I was climbing out, fairly heavy (maybe 80-90% loaded). It happened from under 10000 all the way up to the 300s. 250kts till 10, then 290 transitioning to about mach .7. The trim wheel was cranking forward then back all the way up, super loud and annoying. Wonder if this sound could be temporarily disabled as a bandaid fix; that’s honestly the worst part about the porpoising. The actual movement is not super noticeable in cockpit view but that sound is horrible.

5

Also here, no porpoising seen in a three hour flight.

8

I just loaded up into the 707 and took off with no payload at all. climbed to FL330 and the plane has been porpoising/oscillating since 26,000 feet. however, the oscillations are noticeably less intense than on my previous flights with payload

9

I have noticed them as well.
They seem more pronounced at higher altitudes.

10

I too had the same with a full passenger load and no cargo.

11

Same issue here, got to cruise FL380, aircraft throughout climb and cruise kept oscillating. Pitch trim wheel sounds keep going off even though the trim wheel doesn’t physically move, this makes it very unenjoyable to fly. I would suggest to the developers to lower the sensitivity of the trim wheel noise i.e. only when trim changes a certain significant number when the wheel actually turns?

12

Currently cruising above the Atlantic ocean at FL390, doing Mach .83, current total weight is 225,000lbs and it is oscillating. The trim keeps moving back and fort at increments and I can hear the trim wheel going very often.

Edit: Whether I am flying .80 or .86 doesn’t seem to make any difference.

13

Did another test while flying at mach .90 at 33,000 feet and 190,000 lbs A.U.W. Oscillations are still present, although they are less pronounced

14

Well, this is just weird. I’d like to say that I experienced no porpoising because I’m just a better tubeliner pilot than you’all & know what I’m doing, but that is complete nonsense as I rarely fly tubeliners! :grin:

What I will say is that in my first flight - when I I experienced porpoising at around 40,000 ft - I just hit Ctrl-E at the start of the flight, used the default payload, totally ignored the checklists and flight engineer, and took off without paying attention to anything that might have been required. I was busy checking out the passenger cabin & and only found out that I was at 40K ft when the porpoising started.

For my second flight - having watched the 707 livestream with WT - I took a bit more care over loading the aircraft & used the flight engineer to complete all the various checklists. I had zero porposing on this flight.

So, are the above facts relevent? I have no idea. It’ll be up to the dev teams to determine that. :thinking:

15

What i will say for mine is the third time I flew the 707, i took extra care with the checklists as well as used the AFE. Also loaded no payload just about 40,000 pounds of fuel. Still porpoising, but just not as extreme

16

I’ve done both, originally with FE assistance, and later with none.
I had porpoising in both cases, although it did smooth out somewhat with a slight speed increase.

17

I had something I wouldn’t necessarily call porpoising, but could definitely be described as instability, in my flight last night. Cruising at FL380. I think there’s something funky going on at high-ish altitudes.

19

For me the plane is not porpoising TBH it flies very well. The trim wheel is stable when in cruise but it sounds like its moving. I have tried to lower the enviornment and cockpit sounds but the problem of the noise does not stem from there. It would be better if the sound will be removed entirely or reduce to like 10% volume.

20

My trim wheel is moving and making a noise, it never makes a noise if it’s not moving. These may be separate issues.

21

It definitely will make a noise, most do when changing trim is activated.

22

@Rogerdodger4424 said that his was making noise while not moving. I said that might be a separate issue from the oscillations.

23

Are you sure the trim wheel is not moving.
It is common for it to be doing so in cruise as atmosphere and heading changes occur.