Junkers Ju-52 1939 version, brakes not working, starting cold&dark

[Eelis61]

ISSUE DESCRIPTION

Description of the issue:

As title says, when starting cold&dark, brakes are not functioning although pedals are pivoting. Plane starts to roll after starting engines and cannot be stopped using brakes, both parking- and normal brakes, even chocks are not going to stop plane from rolling, they are moving with plane.

The Ju 52 has pneumatic brakes and need air pressure to operate. Originally, you would open one of the two valves labeled “Preßluft” and this would pressurize the system. In one of the recent updates, this seemed to get broken(?) and now the “Drukminderventil” switch is now pressurizing the system (if in conjunction with the right-hand Preßluft valve being open it will be at a lower pressure). HOWEVER, pressurizing the system is disabling the brakes, not enabling as it should. So, if pneumatic systen pressure gauge shows air pressure, the brakes will not operate and vice versa! (Thank you @NixonRedgrave for this finding)

FREQUENCY OF ISSUE

How often does this occur for you (Example: Just once, every time on sim load, intermittently)?

Every time starting cold&dark. This issue doesn’t happen when starting at runway ready for take-off.

REPRODUCTION STEPS

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

1. Just start Junkers Ju-52 1939 version cold&dark and start engines as they are supposed to start.

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?

No

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

DX11

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

Nvidia RTX 3060

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

MEDIA

Please add a screenshot or video of the issue occurring.

[Gugutoterell]

Having the same issue.

Parking brake non-op.

Brakes non-op.

Control bindings for both are working, as animations for parking brake and pedals will animate with control inputs.

I have checked for pneumatic pressure and ensured pneumatic system valves are on.

[GeeStoerty]

I just checked the 1939 version with manual step-by-step cold/dark startup and did not run into this issue.
Brakes and parking brake are animated and also working as intended.
On a second try using the ctrl-E startup it also worked fine.
Win11 Steam version (FS2024)

[Gugutoterell]

Really?! How strange!

Did you do this in 2020 or 2024?

Was there a specific livery you tried? (I used the one with the black/red. Maybe I need to try the default?)

EDIT:

The “1939” version is considered a different variant to those of the other liveries. You can see this in the Config section, as the 1939 is listed alone and has no other liveries when you click Livery. The other liveries are compiled under a different variant. When I first loaded C&D it has the default control profiles for it rather than all the ones I already had assigned to the Ju 52 via the other livery. This indicates a different variant, with potentially different config characteristics.

The parking brake and brakes work as expected in the “1939” variant, so it is strictly affecting the other variant that aren’t the “1939” livery.

[GeeStoerty]

FS2024; I used the silver 1939 variant (that only has the silver livery)

[Gugutoterell]

That is the reason. See my above Edit.

[GeeStoerty]

Hmm, for me also the 1939 “color livery” version, with black/red livery, work fine from c&d manual startup and ctrl-E startup.

Assigned controls:
Switch/button for:
Parking brakes on
Parking brakes off

Joystick lever:
Left brake axis + Right brake axis (1 lever only for both axis)

[Gugutoterell]

I’m lost then.

I tried the 1939 after seeing your post, saw that it worked, and then immediately switched back to the black/red and it did not work.

I will re-examine… again.

EDIT:

I figured it out.

The Ju 52 has pneumatic brakes and need air pressure to operate. Originally, you would open one of the two valves labeled “Preßluft” and this would pressurize the system. In one of the recent updates, this seemed to get broken(?) and now the “Drukminderventil” switch is now pressurizing the system (if in conjunction with the right-hand Preßluft valve being open it will be at a lower pressure).

HOWEVER, pressurizing the system is disabling the brakes!

So, if this gauge shows air pressure, the brakes will not operate!

So something here is screwy.

[Gugutoterell]

So, I’m a nerd.

I’ve been studying the written-in-German manual for the Ju 52 and the system is pretty well modeled here, however it is inverted.

Essentially, the Drukminderventil, as described in the manual, is utilized to adjust the outgoing pressure (pressure regulator) from the pressurized air bottle into the system. I don’t know if some Ju 52 had this as an on/off valve, as modeled here, but in the manual is is indicated that it would be rotated (like the other valves) to adjust the pressure to 6-7 kg/cm2. Perhaps this was simplified in later production models to an on/off pressure regulator, as modeled, that was self-adjusting.

So, you’d open the valve for the bottle, check the pressure, and adjust it as needed via the Drukminderventil (or in our model open the bottle valve and turn on the Drukminderventil to allow pressure regulated air into the system).

Anyhow, the system’s logic is clearly inverted as it’s behaving as though there is no pressure (no brakes) when the system is set to “on” and indicating the presence of pressure.

I love that this is modeled. It just needs the logic to be inverted!

(As an aside, this aircraft still looks so incredibly good even in 2024. It was my very first add-on purchase in 2020 and I still absolutely love it!)

[Eelis61]

So leaving the “Drukminderventil” = pressure reducing valve closed, thus not pressurizing the pneumatic operated brakes, enables brakes to work. Yes, verified that’s the workaround. And when you start on runway the valve is on and and gauge shows pressure, when you close the valve, gauge shows pressure decreasing to zero, as it should.

I might to adjust my bug report accordingly, thank you @NixonRedgrave ! I hope you don’t mind if I borrow your finding to the bug report?

Now, the chocks are just eyecandy, they don’t keep the plane in place, but are moving/dragging with plane. Oh well…

Thank you too @GeeStoerty !

-eelis-