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wipeout01

Doubts about Cruise performance tables for the A36 Bonanza (LEAN / RICH)

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Hi, I have several cruise performances but I really don't know very well how to deal with them.

I post the charts as follows:

RICH - 25.0 IN.HG (OR FULL THROTTLE) 2100 RPM - CRUISE RICH MIXTURE

RICH-2100%20RPM_zpswcrhxm3f.jpg

LEAN - 25.0 IN.HG (OR FULL THROTTLE) 2100 RPM - CRUISE LEAN MIXTURE

LEAN%202100%20RPM_zpso3hkuluk.jpg

LEAN - 21.0 IN.HG (OR FULL THROTTLE) 2100 RPM - CRUISE LEAN MIXTURE

LEAN%202100%20RPM-2_zpssszzhcol.jpg

RICH - 21.0 IN.HG (OR FULL THROTTLE) 2100 RPM - CRUISE RICH MIXTURE

RICH-2100%20RPM-2_zpshcfwyode.jpg

LEAN - 23.0 IN.HG (OR FULL THROTTLE) 2300 RPM - CRUISE LEAN MIXTURE

LEAN%202300%20RPM_zps6z4y6xxb.jpg

RICH - 25.0 IN.HG (OR FULL THROTTLE) 2500 RPM - CRUISE RICH MIXTURE
RICH-2500%20RPM_zpsyqryj5zd.jpg

LEAN - 25.0 IN.HG (OR FULL THROTTLE) 2500 RPM - CRUISE LEAN MIXTURE
LEAN-2500%20RPM_zpskzn7sqti.jpg

Okay, I have seral doubts inside. First, I'd like to say what I know how to do. I know how to lean the mixture and how to get the EGT peak by monitoring the EGT instrument (Exhaust Gas Temperature).
I also know how to match the altitude and the temperature in the charts
, so if I fly to 10000 feet and I have 69 Fº for the outside temp... I know I would have to look first the altitudes in the table 10000 feet and then the temp... so I find the range 10000 feet -8 Fº TO 10000 feet 28 Fº so accoring my exterior tempo, I find in that range the proper speed as indicated in the table.
I know how to do all that.

However, here I have several charts for cruise performances.
I see LEAN MIXTURE CHARTS and RICH MIXTURE CHARTS.

My first doubt is about what criteria should I apply to decide if I use a LEAN MIXTURE CHART or a RICH MIXTURE CHART.

What I think...if I am flying 9000 feet... normally at that altitude I would have the red lever almost back, to a 23%, so it is clear my mixture is lean. In that case I think I should apply LEAN MIXTURE CHART?
In the opposite case... I am descending, I am close to the runway and my MIXTURE IS FULL RICH... in that case I guess I must use the RICH MIXTURE CHARTS.
Is that correct?

That was my first doubt.

My second doubt is about the title of the charts...

RICH - 25.0 IN.HG (OR FULL THROTTLE) 2100 RPM - CRUISE RICH MIXTURE
LEAN - 25.0 IN.HG (OR FULL THROTTLE) 2100 RPM - CRUISE LEAN MIXTURE
LEAN - 21.0 IN.HG (OR FULL THROTTLE) 2100 RPM - CRUISE LEAN MIXTURE
RICH - 21.0 IN.HG (OR FULL THROTTLE) 2100 RPM - CRUISE RICH MIXTURE
LEAN - 23.0 IN.HG (OR FULL THROTTLE) 2300 RPM - CRUISE LEAN MIXTURE
RICH - 25.0 IN.HG (OR FULL THROTTLE) 2500 RPM - CRUISE RICH MIXTURE
LEAN - 25.0 IN.HG (OR FULL THROTTLE) 2500 RPM - CRUISE LEAN MIXTURE

I see there are charts for Inches of Mercury IN.HG.
Okay, that is what I use to calibrate the altimeter.
Then I see (OR FULL THROTTLE)...
And finally the RPM... 2100... 2300... 2500..

I am very confused with this.

Let's take an example... the first chart...
RICH - 25.0 IN.HG (OR FULL THROTTLE) 2100 RPM - CRUISE RICH MIXTURE

I don't know if I understand this well or not...
I should use this chart if my altimeter is calibrated to 25.0 IN.HG or more and my RPM is 2100 maximum.
Is that right? or am I wrong?
Please, could you help me about how must I understand this?

Cheers

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Hi...

 

Yep - it can be a little confusing - to start off with - "complex" aircraft have two primary gauges to indicate performance - the Tachometer which indicates propeller RPM a the Manifold Pressure which correlates to your IN HG... Keep in mind that the purpose of a complex aircrafts setup is to maintain a constant RPM on the prop to be the most efficient for a given flight regime... Kind of like why we have gears on a car...

 

The Rich and Lean charts are all in reference to the "Peak" Exhaust Gas Temperature which is very important in both simple and complex aircraft as reference point for the engines performance... If you look closely at the charts (always read all the notes included) - they actually give your a temperature in relation to "Peak"... Running LEAN of Peak is simply a fuel saving measure to save you money (Avgas runs about $6.00 a gallon by me) or extend your range a bit - for my use in the FS - I would just ignore it... I always run RICH of Peak because it buys you a few extra knots...

 

In order to find "Peak" you gradually lean your engine at a given altitude - until you find the spot where the EGT needle peaks - you have to move the mixture (red) lever slowly - that's your reference point and some gauges include a pointer to mark it... If you change altitudes - you should find "Peak" again... We don't really care what temperature Peak is - just that we know where it is...

 

Typically when getting to your cruise level you set the Throttle first for Manifold Pressure - then the Prop (blue) lever for RPM - then lean... If you want to increase power - the Prop (blue) lever should be moved first - then increase the throttle... In most cases the Throttle and Prop should combinations are recommended to run "Squared" - meaning if you are running 25 inches Manifold Pressure - you want 2500 RPM - - 23/23 24/24 etc etc etc... You want to avoid situations where the Manifold Pressure exceeds RPM...

 

The Inches of Mercury corresponds to your "Manifold Pressure" gauge...

 

Keep in mind as altitude increases - the maximum manifold pressure the engine runs at will decrease... That's why the tables mention wide open throttle as you'd never be able to maintain the pressure...

 

If it were me - I'd just use the RICH chart for "Recommended Cruise" all the time in FS... I seldom fly to the absolute edge of range and I'm not trying to save money...

 

Finally - keep in mind while all these charts are great - they may not even come close to reflecting actuall values you'll see from the model... If you want the best most realistic performance FS can offer from a GA plane - stick to the A2A Skyhawk, Cherokee, Skylane, or Comanche (truly wish they would tackle a Beech)...

 

Hope this helps some...

 

Regards,

Scott

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Hi Scott,
First thing I'm happy to talk with a real pilot like you, and also because you explain the things extremely easy to understand, so that is really nice instead so much technical vocabulary.

Okay.

Let's see if I catch you...

*** PLEASE, CORRECT ME IF YOU FIND SOMETHING WRONG ***


I am using plain words, with examples, not technical stuff. More easy to understand.

- Tachometer indicate RPM (also I have a digital display showing me the RPM in the Bonanza A36 and an analog gauge for the RPM)

See both instruments here: MANIFOLD PRESSURE AND RPM GAUGES
manifoldpressureandrpmgauge_zps2hugjvql.

- Inches of Mercury IN.HG related to performance (and not the altimeter, this is different), we have an instrument called MANIFOLD PRESSURE, which show us the IN.HG inches of mercury, according our RPM and how we push forward or backward the throttle (more gas, less gas).

See the instrument here, you can find IN.HG
MANIFOLDPRESSUREINCHESOFMERCURYINHG_zpsd

- Peak EGT is, as I said, having the EGT needle in its higher position, moving forward or rearward the red lever. The goal is that moving the red lever, we have the needle from the EGT gauge instrument in its higher position always. That mean our mixture is correctly configured. Correctly enriched or leaned.

See the EGT gauge here:
egtgauge_zps27rq5zn2.jpg

For common sense I assume that if we have the red lever very much rearward, we have a lean mixture, and if we have it very much forward we have a rich mixture.


NOW... with all this in mind.

1) To use a CRUISE PERFORMANCE CHART, we always need to find the EGT peak first. If we don't have the EGT peak, we shouldn't use any performance chart. So first, we have to do the EGT peak, moving rearward or forward the red lever, to maintain the EGT guage needle in its higher possition.

2) WHEN RICH OR LEAN? That is a question of range autonomy and money. If you run RICH, you will get a more expensive flight and less autonomy (more extra knots). If you use (run) LEAN, you will get more miles, more autonomy and a more cheap flight. USING LEAN CHARTS OR RICH CHARTS DO NOT DEPEND ON HOW WE HAVE CONFIGURED THE RED LEVER, IT DEPENDS ON HOW WE WANT TO FLY, IF WE WANT TO FLY IN AN ECONOMY CRUISE WITH MORE AUTONOMY OR IN A FASTER CRUISE, MORE SPORTY, MORE EXPENSIVE TO THE POCKET.

3) WHEN REACHING THE CRUISE LEVEL, TO CONFIGURE A NICE REGIME, THE ORDER IS:

* First, black lever, throttle for speed and we will get our INCHES OF MERCURY ACCORDING OUR PERFORMANCE IN.HG IN THE MANIFOLD PRESSURE INSTRUMENT.

* Second, blue lever, the rpm, like the gauges in a car, to have the engine rested. RPM also affect to the speed, so the key is finding the perfect combinations between both levers (black throttle, blue rpm). WITH THIS, WE WILL GET THE RPM WE HAVE CONFIGURED OUR AIRCRAFT.

FOR THE PERFECT COMBINATION BETWEEN MANIFOLD PRESSURE IN.HG (INCHES OF MERCURY) AND RPM, WE NEED TO MAINTAIN THE SAME RELATION.

THAT IS 2500 RPM ---> 25 IN.HG (RELATION 25/25)
THAT IS 2300 RPM ---> 23 IN.HG (RELATION 23/23)
THAT IS 2100 RPM ---> 21 IN.HG (RELATION 21/21)

**** MANIFOLD PRESSURE SHOULD NOT EXCEED RPM **** In other words, we should have a higher value in the MANIFOLD PRESSURE INSTRUMENT, WHILST WE HAVE A LOWER VALUE IN THE RPM INSTRUMENT.

* Third, red lever, enrich or lean mixture, calculating the EGT peak.

4) WHEN USING A CHART, RICH OR LEAN, HAVE IN MIND WE NEED TO CALCULATE THE EGT PEAK FIRST, THEN, DECIDE IF WE WANT AN ECONOMY FLIGHT (IN THIS CASE USE LEAN) OR AN SPORTY FLIGHT (IN THAT CASE USE RICH) AND...

REMEMBER THE VALUES FROM THE MANIFOLD PRESSURE GAUGE AND THE RPM GAUGE

For example:
If we have 2100 RPM and 25.0 IN.HG in our manifold pressure instrument, and we want an economy flight... our chart would be this one:

LEAN - 25.0 IN.HG (OR FULL THROTTLE) 2100 RPM - CRUISE LEAN MIXTURE


LEAN%202100%20RPM_zpso3hkuluk.jpg


Is this okay?

Cheers

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Hi,

 

I see you've invested quite a bit of time into figuring this out. I used to fly IO520's and 550's, and can understand your confusion.

 

Firstly, one thing that caught my eye, right off the bat:

 

 


THAT IS 2500 RPM ---> 25 IN.HG (RELATION 25/25)
THAT IS 2300 RPM ---> 23 IN.HG (RELATION 23/23)
THAT IS 2100 RPM ---> 21 IN.HG (RELATION 21/21)

**** MANIFOLD PRESSURE SHOULD NOT EXCEED RPM **** In other words, we should have a higher value in the MANIFOLD PRESSURE INSTRUMENT, WHILST WE HAVE A LOWER VALUE IN THE RPM INSTRUMENT.

 

This is false. The relationship between MP and RPM is essentially how much stress you are putting on the engine, and how much stress the engine can take. We would normally cruise with 26" and 2300 RPM. At one point it was 2100 RPM and 29" (turbocharged). 

 

The factor determining this setting is the fuel setting. (Red knob). Are you going to run lean? or are you going to run rich?

 

Side note:

P3D and FSX do a very poor job of modeling engine performance. Especially when it comes to pistons and turboprops. In the sim, when you lean the mixture, you'll notice that your fuel flow goes up, then drops back down after that fuel flow has peaked for the altitude you're at. Completely false and as far from reality as the kardashians. In real life, with the IO520/550 engines, when you climb (in a non turbocharged airplane) the manifold pressure will drop. This is due to the drop in air density as we get higher (you probably know this already). What happens to the fuel flow (FF) is, with that decrease in manifold pressure, the fuel flow is reduced to match the setting you had it at. i.e. if you were climbing at 90% MP at sea level, then set the FF for its climb setting, let's say 85%, as your manifold pressure drops, your FF will drop in relation to the MP. You would probably then add more fuel by enriching the mixture to keep the climb power in. So, take what I say with a grain of salt when relating this to the virtual world because this particular sim is limited in its ability to mimic reality. 

 

 

 

In the real world, if you are choosing to run LOP (lean of peak), you need to have a damn accurate EDM (Engine digital monitor). This way you can see what is going on in each cylinder. If you use the conventional EGT gauge, you are getting a totally impoverished account of what is happening in the engine. Usually, those EGT gauges have a single probe in the hottest cylinder. The other thing you'll need are balanced fuel injector nozzles. This allows a precise amount of fuel (in relation to the compression ratio, airflow, and average temperature of each cylinder) to enter each cylinder. The charts you have up there are a bit archaic. When running LOP you are doing 4 primary things to the aircraft:

1) You are reducing the amount of fuel going to the engine

2) Lowering the temperature of each combustion cycle (because each "bang" will take longer, the temperature is greatly reduced)

3) Reducing wear and tear on the engine and crankshaft. 

4) Reducing the overall power output of the engine (which will make you fly slower)

 

Seeing as how we don't have control of the type of equipment we put into our engines in the virtual world, we are extremely limited in seeing what is actually going on inside of the engine.

 

Now, let's use the equipment we have available to illustrate the issue. If you fly at the same altitude every day in the same temperature, your EGT will probably be pretty predictable. But seeing as how that never happens, your EGT will change. Your peak EGT depends on a few factors, your MP setting, your altitude, and your RPM. Let's say you're at 7,000' cruising at 2100 RPM and 25" of MP. You find your peak EGT. Now you WAIT at peak for everything to stabilize. At this point, ignore your Fuel Flow because the sim does a terrible job of modeling it. If you want to run LOP (Save gas and fly slower), pull the mixture knob  out slowly. Once you start getting a rough running engine, enrich the mixture slightly so you have a smooth running engine again. The sim doesn't model the relationship between ROP/LOP and the cylinder head temperatures (CHT). But, in real life, you would see your CHT start to drop (this is good for prolonging the engine's life). 

 

If you choose to fly ROP (faster, more power, screw fuel) you use the same technique to find your starting point. However, you then increase the mixture. It'll take a little longer to get a rough running engine, but that's not what we're looking for, we're looking for 1) 50* (two ticks of the EGT marks) 2) 100* (four ticks) 3)125* (five ticks).

 

Option 1 will give you a good airspeed to fuel use ratio. Option 2 will give you the best amount of power at the cost of fuel. Option 3 will give you fowled magnetos. In the real world, you could compare your CHTs from using LOP vs ROP and notice significantly lower temps when using LOP. 

 

So, when do you choose to use LOP or ROP? It's really up to you. Do you want to fly far or fast? 

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I concur with Andrew. In addition in real world we prefer to lean engine right after the start while running rich only on runup, take off, and landing

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Personally I wouldn't focus too much on those charts: don't look at the charts before leaning the mixture and think 'this is what I have to do or get done' but look at the charts after leaning the mixture to check if things are kind of operating as expected. Or use them during the planning phase to figure out an approximate ETA if you want to.

 

I never use those charts (for simming): I set the mixture around 20 to 50 degrees rich of peak during cruise and that's it. Whatever speed or power that results in simply is what I am getting. During regular cruise my throttle is always full forward and (depending on the engine) I set squared settings (24 RPM and 24 HG, if the altitude allows it, although lately with my turbo Lancair it's more like 34 HG and 24 RPM  :wink: ).

 

In other words: don't chase the charts and try to get the exact speeds etc. as you see on them: they are there for reference so you know what you can expect. Don't focus too much on them and don't let them lead you. In the end there is nothing you can do to get the numbers you see on them on your gauges: first of all that will never ever happen and secondly it all depends on the weather and circumstances. I think you are making them too important.  :wink: So to answer the question "I really don't know very well how to deal with them": just use them as reference to see what you may expect and if things are working correctly. Again, as I said, I never look at charts like those anymore and simply accept what the plane is giving me.

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