Bf-109 Elec. Propeller Pitch control, .. how it works?

[IIIJG52_Otto_]

The electric propeller pitch control system in the Bf-109, is very different from the P-51, with which it is matched in DCS, according to somebody comments .

 

[Anatoli-Kagari9]

Otto,

 

I don't understand exactly your point: Are you saying that the Bf109K4 in DCS is using a model for the electric pitch trim controller that is similar to the one modelled in the P51d, and that it shouldn't?

 

Are you sure it is being modelled that way?

[Davis0079]

Very good video. I think you should link it over at ATAG.

[sobek]

with which it is matched in DCS

 

This is not true.

 

Try feathering your prop in the P-51.

 

Then try changing your prop pitch while the engine isn't running.

 

 

Both is possible in the Bf-109.

[Ala13_ManOWar]

Yeah, nobody gets the point Otto is talking about :P. What do you mean mate?

 

S!

[Art-J]

Maybe if we had a link to this "somebody's comments", we could understand what "matching" he was thinking about. I'd presume some misunderstanding here.

[Siegfried]

Are you saying DCS 109 prop pitch is wrong?

[IIIJG52_Otto_]

Maybe if we had a link to this "somebody's comments", we could understand what "matching" he was thinking about. I'd presume some misunderstanding here.

 

Are you saying DCS 109 prop pitch is wrong?

 

I do not know exactly at the moment .. but I've the doubt. :music_whistling:

At the moment, I intend to share the Bf-109 prop. pitch system video only, for everybody can see the difference.

 

Do you think that the behavior of Bf-109K4 propeller in windmilling, should be exactly the same as a P-51?? :huh:

[Art-J]

Interesting question. I don't know how the pitch regulator worked in real 109s in engine off (but not seized solid) conditions so I don't know what to think about behaviour of DCS one.

[IIIJG52_Otto_]

Interesting question. I don't know how the pitch regulator worked in real 109s in engine off (but not seized solid) conditions so I don't know what to think about behaviour of DCS one.

I agree , ... That´s one of my doubts, that I would want clearing in this thread.

[sobek]

I don't see anything in this video that would conflict with the implementation in DCS.

[IIIJG52_Otto_]

I don't see anything in this video that would conflict with the implementation in DCS.

 

Are you sure? .. How many take-offs have you done with the DCS:Bf-109K4 with propeller in manual pitch control? .. you feel it realistic when the engine grip? and the windmilling effect it´s well for you too?

[Anatoli-Kagari9]

Are you sure? .. How many take-offs have you done with the DCS:Bf-109K4 with propeller in manual pitch control? .. you feel it realistic when the engine grip? and the windmilling effect it´s well for you too?

 

Otto,

 

you mean how easily the engine seizures when set to manual prop pitch ?

 

Regarding windmill effects, can you be more explicit - I would really like to test it too Otto. Maybe you have a point, but it would help if you could give us some easier clues.

 

We all want it to get even better :)

[IIIJG52_Otto_]

Otto,

 

you mean how easily the engine seizures when set to manual prop pitch ?

 

Regarding windmill effects, can you be more explicit - I would really like to test it too Otto. Maybe you have a point, but it would help if you could give us some easier clues.

 

We all want it to get even better :)

 

See this video minute 0:21 The Bf-109K4 Should be able to do this?

Stop the engine, feathering the propeller, stop the propeller spin and then, re-start engine in windmilling changing the propeller pitch.??

 

 

At the moment, I can´t do it, In DCS:Bf-109K4 the airscrew no go back to spinning in windmilling, after complete stop, when changing the propeller pitch to medium pitch, or any pitch. ..even diving at 400-600 km/h.

 

But it's possible in-flight re-starting, cranking the engine with the command "signal starter crew" (in the air :music_whistling:)

Are both things correct? ..or we have a bug in the windmilling behavior?

 

...And if both are correct, would imply that the DB605 should have electric-inertia starter motor for in-flight restarting.. in according with the book of Jean-Claude MERMET "Messerschmitt Bf 109 G-1 to K-4 Engines & Fittings"-1999

in page 21 say:

""Incidentally, contrary to the accepted idea, the DB 605 was equipped

with an electric starter permitting in-flight restart."""

Edited March 29, 2015 by III/JG52_Otto_+

[Anatoli-Kagari9]

Ok Otto,

 

thx, now I got your point!

 

Will test it ans report back ;-)

[Anatoli-Kagari9]

Confirmed!

 

I believe your observations are right! And, I'd say it is wrong the way it is modeled right now...

 

Using the "free flight" situ, I turnd the engine OFF ( magnetos to OFF, as well as fuel pumps ), set the prop pitch to it's highest setting until the prop became feathered and stopped. Then, while descending at good speed, I turned the pumps and magnetos back ON and started decreasing prop pitch, but the prop never windmilled ? Strange indeed ...

[IIIJG52_Otto_]

Confirmed!

 

I believe your observations are right! And, I'd say it is wrong the way it is modeled right now...

 

Using the "free flight" situ, I turnd the engine OFF ( magnetos to OFF, as well as fuel pumps ), set the prop pitch to it's highest setting until the prop became feathered and stopped. Then, while descending at good speed, I turned the pumps and magnetos back ON and started decreasing prop pitch, but the prop never windmilled ? Strange indeed ...

 

Jcomm, ..a lot of thank for your help :thumbup:

[sobek]

Using the "free flight" situ, I turnd the engine OFF ( magnetos to OFF, as well as fuel pumps ), set the prop pitch to it's highest setting until the prop became feathered and stopped. Then, while descending at good speed, I turned the pumps and magnetos back ON and started decreasing prop pitch, but the prop never windmilled ? Strange indeed ...

 

A GA plane doesn't have a 36 liter 2000HP engine, so you can't simply extrapolate from that video (meaning the turnover torque for a stopped DB605 is considerably higher than for a 100-200HP engine). Besides, a turning prop is able to create *considerably* more torque than when it's stopped. The difference is so great that for engine failures in non featherable prop planes, it may be desireable for glide angle to slow the plane down to a near stall so the engine stops, at which point the prop will produce a lot less drag (and also torque).

Edited March 29, 2015 by sobek

[sobek]

But it's possible in-flight re-starting, cranking the engine with the command "signal starter crew" (in the air :music_whistling:)

 

If this does indeed work then it is a bug.

[IIIJG52_Otto_]

If this does indeed work then it is a bug.

No, I think no, .. due to the reason explained previously.

 

..... in according with the book of Jean-Claude MERMET "Messerschmitt Bf 109 G-1 to K-4 Engines & Fittings"-1999

in page 21 say:

""Incidentally, contrary to the accepted idea, the DB 605 was equipped

with an electric starter permitting in-flight restart."""

[Siegfried]

I think I told you in another thread that because of this bug, you can imagine that you have an electric motor in the engine start. At the end of the day is what you wanted, but now they are going to fix the bug and will leave you without "your electric motor".

[Yo-Yo]

A GA plane doesn't have a 36 liter 2000HP engine, so you can't simply extrapolate from that video (meaning the turnover torque for a stopped DB605 is considerably higher than for a 100-200HP engine). Besides, a turning prop is able to create *considerably* more torque than when it's stopped. The difference is so great that for engine failures in non featherable prop planes, it may be desireable for glide angle to slow the plane down to a near stall so the engine stops, at which point the prop will produce a lot less drag (and also torque).

 

It's not correct at least for Mustang size prop. The most energy-devastating is stopped prop, the lowest drag gives windmilling at low rpm, and it's actual for the speed of best gliding.

[sobek]

No, I think no, .. due to the reason explained previously.

 

Since voice control wasn't available in the 40ies, this being a bug is pretty much the only way to go. It would be a foul compromise to let it remain.

Edited March 30, 2015 by sobek

[sobek]

It's not correct at least for Mustang size prop. The most energy-devastating is stopped prop, the lowest drag gives windmilling at low rpm, and it's actual for the speed of best gliding.

 

Interesting.

 

Is that because while running down, the governor will try to set the prop to fine pitch?

 

How does that work out for torque?

Edited March 30, 2015 by sobek

[Yo-Yo]

Interesting.

 

Is that because while running down, the governor will try to set the prop to fine pitch?

 

How does that work out for torque?

 

The windmilling prop behaviour is not so simple and depends on speed and rpm. As you have engine down the prop will rotate at the desired rpm because the prop governor decreases pitch to keep rpm. It's not hard because cranking engine creates evenly distributed resistance moment (compression strokes are compensated with extension (power) strokes), and rotating prop creates much torque.

 

At moderate speed a high solidity factor propeller that has high absorbed power will create more drag than at windmilling as it freezes at fine pitch.

 

Starting the stopped prop is not easy or impossible sometimes because of high resistance of first compression strokes and relatively low moments created with the stopped prop.

Edited March 30, 2015 by Yo-Yo