Throttle, RPM & Mixture Adjustments and Reaction

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Jotayhen
Posts: 27
Joined: Mon Mar 06, 2017 4:54 pm
Throttle, RPM & Mixture Adjustments and Reaction

Post by Jotayhen » Tue May 30, 2017 11:27 am

First, I compliment the Milviz team for a fine product. I am very much enjoying the new Beaver. I also understand and appreciate the fact that there are issues right now with the Beaver and that those issues are being resolved as we speak. Overall, this is a very nice rendition of an iconic bush aircraft that will only get better!

Having said that, I would like to go on record with some issues that I believe should be examined by the team. As power is applied and the manifold pressure increases the sound file correctly responds however as the throttle is retarded and the manifold pressure correspondingly decreases, the sound file remains at previous levels of intensity.

Prop RPM adjustments appear to be correctly modeled but throttle adjustments need to be further examined.

Mixture adjustments do not appear to affect the applicable engine sound file and so it is really not possible to effectively lean this radial engine "by ear" at this time. Additionally I do not see where mixture adjustments affect manifold pressure readings on the appropriate gauge and so I believe I am unable to effectively adjust these settings, Finally, increases in altitude do appear to cause a reduction in manifold pressure and that decrease is reported by the MP gauge, adjustments to the mixture do not seem to mitigate this decrease in any way.

Just a few observations to add to the list and be considered in the future. Thanks again for giving us a wonderful new Beaver!

MatzeH84
Posts: 51
Joined: Sat Aug 03, 2013 2:04 am
Re: Throttle, RPM & Mixture Adjustments and Reaction

Post by MatzeH84 » Tue May 30, 2017 10:25 pm

I'd second the most of your observations, however it is normal that you lose manifold pressure as you climb.
If I interprete the engine parameters correctly, the supercharger is able to provide METO power up to 5000ft, above that you would naturally lose about 1 inch per 1000ft just as in every un-supercharged aircraft.
By adjusting the mixture you just match the amount of fuel to the amount of air.. Nothing more, nothing less. It can't compensate for the loss of air pressure. To do that, you would need another supercharger and / or turbocharger

Jotayhen
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Joined: Mon Mar 06, 2017 4:54 pm
Re: Throttle, RPM & Mixture Adjustments and Reaction

Post by Jotayhen » Wed May 31, 2017 2:07 am

I agree, Matthias. I did not make myself clear apparently. I was referring to the effect upon the engine of properly balancing the ratio of fuel to air by retarding the mixture lever as you gain altitude beyond the ability of the turbocharger to continue to maintain optimum air pressure and the expected audio file reaction to these actions by the pilot.

CAPFlyer
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Location: Wichita Falls, Texas, USA
Re: Throttle, RPM & Mixture Adjustments and Reaction

Post by CAPFlyer » Thu Jun 01, 2017 11:50 pm

There's no change in sound pitch. Maybe a slight change in sound volume, but with a constant speed prop, pulling back the throttle within the governed range will *NOT* change the pitch of the engine, only the volume and only marginally. Setting the mixture will have no appreciable effect on the volume or pitch of the engine while in the governed range beyond rough-running, however with a radial, rough-running is much more subtle than with a horizontally-opposed engine as a misfiring cylinder is "dampened" by the other cylinders operating normally, masking the issue until it gets severe.

The proper way to lean an aircraft with a constant speed propeller is with temperature - either via the CHT or EGT gauge (if equipped). This is why the manual very specifically states that the engine is to be leaned to 50* Rich of Peak during cruise operation. If you wish, you may lean the engine manually during climb to peak, that's fine, but again, it's done with the CHT gauge on the Beaver.

Jotayhen
Posts: 27
Joined: Mon Mar 06, 2017 4:54 pm
Re: Throttle, RPM & Mixture Adjustments and Reaction

Post by Jotayhen » Fri Jun 02, 2017 11:15 am

Thanks, CAPFlyer! I appreciate the great information. I will act accordingly. Great to have folks here with the necessary knowledge and the willingness to share when these types of questions arise. Thanks again!

sunjunkiesi
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Joined: Fri Mar 03, 2017 2:03 pm
Re: Throttle, RPM & Mixture Adjustments and Reaction

Post by sunjunkiesi » Sat Jun 03, 2017 2:33 pm

CAPFlyer wrote: 50* Rich of Peak during cruise operation.
This is what I also understand, however here are my observations of how that works in this beaver...

The maximum "peak" I can achieve is about 40degrees higher than full rich. The CHT will not drop to 50 below peak before the engine cuts out.

For reference, I tried to check the fuel flows out, and whilst I do appreciate that simulated will never be the same as real world, the fuel consumption figures are WAY out. With the fuel at full rich, I am getting a burn of over 30gph, at peak 27.2, and nominally under peak 25.2. This is with 1650/29@2000ft. The manual states this should be 19.8gph.

Given these two situations, I would suggest that the whole mixture side of things is wrong somewhere along the lines.

Still a fantastic aircraft though. I love it. If it's meant to be a study sim as originally suggested, it would be nice to get such fundamentals ironed out.

Krazycolin
Site Admin
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Joined: Mon Sep 08, 2008 4:18 pm
Re: Throttle, RPM & Mixture Adjustments and Reaction

Post by Krazycolin » Sat Jun 03, 2017 3:16 pm

We never "suggested" this was a study sim. Please show me this...

Which manual did you check?

Chuck Jodry
Posts: 442
Joined: Mon Dec 20, 2010 4:30 pm
Re: Throttle, RPM & Mixture Adjustments and Reaction

Post by Chuck Jodry » Sat Jun 03, 2017 5:53 pm

Thank You for the observation on fuel burn rates , we have a modification ready for assessment being tested , a copy of it is available in the attached aircraft.cfg for the base version.
Attachments
aircraft.zip
(6.6 KiB) Downloaded 74 times

sunjunkiesi
Posts: 94
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Re: Throttle, RPM & Mixture Adjustments and Reaction

Post by sunjunkiesi » Sat Jun 03, 2017 7:40 pm

Krazycolin wrote:We never "suggested" this was a study sim. Please show me this...

Which manual did you check?
I thought it was originally stated as a study sim, of that I am 99% sure. If I am wrong then I apologise. :oops: It's a shame if it isn't, as you are so close...

Which manual do you think I checked? The one that comes with your aircraft, or some random manual that I found on the street somewhere? Lol - I reckon you have been working too hard on getting this beaver released, and maybe you need some sleep matey... :roll:

Great work on the plane, it's awesome and I love it. I was only hoping to clarify the fuel burn/mixture scenario. If it's not something you can fix I can just about live with it :lol:

Krazycolin
Site Admin
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Re: Throttle, RPM & Mixture Adjustments and Reaction

Post by Krazycolin » Sat Jun 03, 2017 8:45 pm

So far, we've never called any of our products study level though... we've come close.

sunjunkiesi
Posts: 94
Joined: Fri Mar 03, 2017 2:03 pm
Re: Throttle, RPM & Mixture Adjustments and Reaction

Post by sunjunkiesi » Sat Jun 03, 2017 11:55 pm

You sure have... 8-)

Just to mention a couple more issues with the engine management system. The checklists tell us to check the MP at barometric pressure to give rpm of 2100. In reality, barometric pressure usually redlines the rpm. :shock: This would be a nice checklist feature if it worked properly. Likewise the check prop lever operations don't respond realistically.

I reckon if you get the engine right, you are basically there on a study sim of this aircraft. I am quite sure that this is the hardest part, but it would really put this aircraft into a different league.
:ugeek:
Cheers!

Taguilo
Posts: 658
Joined: Sun May 11, 2014 11:49 am
Re: Throttle, RPM & Mixture Adjustments and Reaction

Post by Taguilo » Sun Jun 04, 2017 3:03 am

sunjunkiesi wrote:
CAPFlyer wrote: 50* Rich of Peak during cruise operation.
The maximum "peak" I can achieve is about 40degrees higher than full rich. The CHT will not drop to 50 below peak before the engine cuts out.
With your test values 1650/29@2000ft, ISA conditions, CarbHeat Off, CHT is ~ 196 C full rich, If you lean it, peak will be at ~219 C with lever ~ 60 % of full rich position.
Now you use the 50 F (10 C) decrease temp, increasing mixture...and you will end with the lever slightly below full rich, which would be the "recommended lean mixture" for that altitude.
So, going after a good leaning method, just remain with CHT needle in the blue area, and within that area, below ~ 200-205 C (400 F), if you want to maintain your engine healthy. (you can apply Carb Heat to cool it down some degrees if you still need power and temp approaches green sector).
sunjunkiesi wrote: The checklists tell us to check the MP at barometric pressure to give rpm of 2100. In reality, barometric pressure usually redlines the rpm
That's correct, RPMs are 5-6 % high, but also working Oil Temp is 10 C higher than normal and Oil press ~10 psi lower, meaning this engine has fought many battles and an overhaul is not far away. Prop governor's slight overspeed must be considered then.
sunjunkiesi wrote: Likewise the check prop lever operations don't respond realistically.
I did Magnetos check and prop behaves as expected (~40 RPM drop) . Which ones are you talking about?

Tom

sunjunkiesi
Posts: 94
Joined: Fri Mar 03, 2017 2:03 pm
Re: Throttle, RPM & Mixture Adjustments and Reaction

Post by sunjunkiesi » Sun Jun 04, 2017 8:05 am

I tip my hat to you Taguilo - many thanks. I can't fault your post. My bad completely, I didn't notice the CHT gauge was in C and the manual in F either. :oops:

I love this aircraft.
EDIT - sorry I forgot to say the prop lever cycle from high rpm to full decrease check that is in the warmup section seems to just suddenly kick in at the lower limit of the lever travel, where I would have expected a smoother reduction of rpm as the governor catches up with itself. Perhaps I have got this wrong too, and is deliberately modelled. :roll:


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