Spitfire jumps forward on engine startup on P3Dv4.3

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Daube
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Spitfire jumps forward on engine startup on P3Dv4.3

Post Daube »

Hi all,

I'm having a frequent issue with the Spitfire in P3Dv4.3, and it's becoming quite annoying.
When I start the engine, the plane wants to move forward as if it were at full power.
If my parking brakes or chocks are set, the plane will nose down and break its prop (and other engine parts).
I would like to know how I should proceed to prevent this.
I fly in multiplayer with two other guys using the Spitfire, and they also have the same issue, on the Mk.I or on both the MK.IIa and b.

This happens no matter if the RPM lever to 100% or 0%.
This happens no matter if the throttle lever is set to 0% (engine will just cough, then I advance the throttle and it starts) or at normal startup position (throttle just a bit forward, like 10%)
For the moment, we took the habit of starting the Spit with the stick full backwards and parking brake OFF, so our planes will all move forward 10 to 15 meters on startup until we manage to stop them without breaking the prop...

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Lewis - A2A
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Re: Spitfire jumps forward on engine startup on P3Dv4.3

Post Lewis - A2A »

Hello,

please check the throttle positions and power settings on your Default flight

thanks,
Lewis - A2A
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Nick - A2A
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Re: Spitfire jumps forward on engine startup on P3Dv4.3

Post Nick - A2A »

Hi Daube,

Just to add to Lewis's comments, it may also be worth cycling any hardware axes such as your throttle a couple of times before startup just to make sure everything is synced correctly.

Also, does your default scenario in Prepar3D use one of the default P3D aircraft? Modifying the default flight so it loads a complex add-on such as the Spit may cause issues.

Thanks,
Nick

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Daube
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Re: Spitfire jumps forward on engine startup on P3Dv4.3

Post Daube »

My default flight is set to Cold&Dark with the default Baron (because that plane has all necessary controls and switches).
Throttle, RPM and mixture are all set to zero.

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Lewis - A2A
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Re: Spitfire jumps forward on engine startup on P3Dv4.3

Post Lewis - A2A »

Can you please cycle the hardware before loading the Spitfire, it could be that the throttle is sitting at a setting that is giving power.

thanks,
Lewis - A2A
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Daube
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Re: Spitfire jumps forward on engine startup on P3Dv4.3

Post Daube »

I have tried to cycle the controls and put them back to original position, before trying to start.
It reduced a little bit but the problem still exists.

I made another experiment, following these steps:
- set RPM to 100%
- throttle to "just about to stop pressing the gear horn button" (if that makes any sense :) )
- primer pumping 10 times
- magnetos ON
- trigger engine start.
- engine starts successfully, plane moves a bit forward but not too much. Engine at idle, stable.
- magnetos OFF
- wait for prop full stop
- magnetos ON
- trigger engine start
- engine starts and planes goes forward. If parking break is set, tail wheel will make a small jump, in the best case.

I'm just surprised by the strength of the engine/prop upon startup. It pulls the plane more strongly than I expected, and I wonder if this is really supposed to happen at all at that precise moment. The prop is just starting to spin, engine at very low RPM, so I'm not sure the prop would have enough pulling strength to move the plane so much...

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Oracle427
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Re: Spitfire jumps forward on engine startup on P3Dv4.3

Post Oracle427 »

Considering the power to weight ratio of the Spitfire, I would be surprised if it didn't launch forward violently with a open throttle.
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Daube
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Re: Spitfire jumps forward on engine startup on P3Dv4.3

Post Daube »

Open throttle ?
You mean 100 % ?
My throttle is not at 100%
The RPM is at 100%. Throttle (or power) is set to something around 10% I guess, just enough for the engine to start.

Concerning the RPM lever, if I set it to 0% for startup, it actually makes the problem even worse.

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Lewis - A2A
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Re: Spitfire jumps forward on engine startup on P3Dv4.3

Post Lewis - A2A »

Which prop on which model are you trying?

thanks,
Lewis
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Daube
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Re: Spitfire jumps forward on engine startup on P3Dv4.3

Post Daube »

I'm using the 3 blades constant speed on the Mk.IIa. Same problem on the Mk.IIb.
And if I'm not mistaken, same problem on the 3 blades 2 speed of the Mk.Ia.

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Daube
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Re: Spitfire jumps forward on engine startup on P3Dv4.3

Post Daube »

Just did a new test.
Took the Mk.Ia with metal 3 blades 2 speeds prop.
If I let the prop on the "coarse 0%" for startup, the aircraft jumps forward. Much less if the prop is on "fine 100%".

Then, after engine start, I switched the magnetos to OFF and waited for the prop full stop.
Then switched to wooden 2 blades prop.
Started the engine again, with parking brake set: the plane bent over on startup and broke the prop.

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Lewis - A2A
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Re: Spitfire jumps forward on engine startup on P3Dv4.3

Post Lewis - A2A »

Hello Daube, what happens if you don't have your controls plugged in and just use mouse or shift + 3 auto start?

thanks,
Lewis
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bladerunner900
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Re: Spitfire jumps forward on engine startup on P3Dv4.3

Post bladerunner900 »

If I kill the mags. with an open throttle, the next time I start that particular Mark, the throttle will be open and if the brakes or chocks are on, she will tip over and break the prop.

My solution is to close the throttle and let the prop slow to idle and cut the fuel. As she starts to splutter then kill the mags. Next time I load that particular Mark it will be sitting there on the tarmac, engine cut. Before starting up, I quickly open and close the throttle just to be sure. This seems to do the trick for me for all three Marks.

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Daube
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Re: Spitfire jumps forward on engine startup on P3Dv4.3

Post Daube »

Lewis - A2A wrote:Hello Daube, what happens if you don't have your controls plugged in and just use mouse or shift + 3 auto start?

thanks,
Lewis
I will give it a try, but honnestly I don't think this is linked to my controls.
My joystick is a simple MS Sidewinder FFB, and it has only one axis for the throttle, with no interferences or erratic movements.
The throttle lever in the cockpit reacts correctly to my inputs, and doesn't move by itself.
The position of the lever in the virtual cockpit is correct when I start the engine.
But I will try anyways.

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Daube
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Re: Spitfire jumps forward on engine startup on P3Dv4.3

Post Daube »

bladerunner900 wrote:If I kill the mags. with an open throttle, the next time I start that particular Mark, the throttle will be open and if the brakes or chocks are on, she will tip over and break the prop.

My solution is to close the throttle and let the prop slow to idle and cut the fuel. As she starts to splutter then kill the mags. Next time I load that particular Mark it will be sitting there on the tarmac, engine cut. Before starting up, I quickly open and close the throttle just to be sure. This seems to do the trick for me for all three Marks.

Steve.
What do you mean by "open throttle", how much % more or less ?
When I kill the engine for my test, the throttle is just open enough to maintain idle, so probably something around 10%. The engine runs and the plane doesn't move forward, I don't need to set the parking brakes.
And then I don't touch the throttle anymore. I just kill the engine with the mags, and set the mags back ON, then trigger the start switch.

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