How do I lean the mixture on a single prop?

[oneleg]

In this case, it's Just Flight's PA-28R Turbo Arrow III. I mostly fly below 7000 feet.

This is the Arrow's instrument panel.

[PhrogPhlyer]

Per the 1988 Arrow POH:

 

4.27 CRUISE (4.5j)

Following level-off for cruise, the airplane should be trimmed.

 

The cruising speed of the Arrow is determined by many factors, including power setting, altitude, temperature, loading and equipment installed in the airplane.

 

The normal maximum cruising power is 75% of the rated horsepower of the engine. When selecting cruising rpm below 2400, limiting manifold pressure for continuous operation, as specified by the appropriate AvcoLycoming Operator's Manual, should be observed.

 

To obtain the desired power, set the manifold pressure and rpm according to the power setting table in this manual.

 

Use of the mixture control in cruising flight reduces fuel consumption significantly, especially at higher altitudes. The mixture should be leaned during cruising operation when 75% power or less is being used. Ifanydoubt exists as to the amount of power being used, the mixture should be in the full RICH position for all operations.

 

To lean the mixture, disengage the lock and pull the mixture control ( until the engine becomes rough, indicating that the lean mixture limit has been reached in the leaner cylinders. Then enrich the mixture by pushing the control towards the instrument panel until engine operation becomes smooth. The fuel flow meter will give a close approximation of the fuel being consumed. The low side of the power setting, as shown on the fuel flow meter, indicates best economy for that percent of power while the high side indicates best power.

[oneleg]

2 hours ago, PhrogPhlyer said:

To lean the mixture, disengage the lock and pull the mixture control ( until the engine becomes rough,

Thank you. How does one know when the engine becomes 'rough'. I don't think when it's 'sputtering'.   It seems to me sputtering or violent shaking risks turning off the engine? 

[PhrogPhlyer]

29 minutes ago, oneleg said:

How does one know when the engine becomes 'rough'.

Just like when driving a car, by sound and vibration. Anything other than a smooth purr is running rough. A combination of objective and subjective.

It's one of those things that can't be verbally explained, rather something you learn by demonstration and/or experience.

[oneleg]

Ahhh, like porn. I get it. Lol.

"When Supreme Court Justice Potter Stewart was asked to describe his test for obscenity in 1964, he responded: "I know it when I see it.""

I know it when I see it - Wikipedia

[jgf]

4 hours ago, PhrogPhlyer said:

Just like when driving a car, by sound and vibration. Anything other than a smooth purr is running rough. A combination of objective and subjective.

It's one of those things that can't be verbally explained, rather something you learn by demonstration and/or experience.

 

Ages ago I broached this question and was told, "adjust for highest EGT reading".  Well, I rarely noticed any definite change in that, plus many aircraft do not have an EGT gauge.  So when I got the message, "engine is losing power", I just let the sim adjust it, watching all the engine gauges as it did ...and again noted nothing useful.  By experimentation I discovered what you've recommended - lean the mixture til the engine runs rough, then back off til it's running smoothly again.  But is there any way to know when the mixture needs to be leaned other than waiting for the "losing power" message?

[nsproles]

Set your power settings as described above, then slowly pull the mixture control back to lean the mixture while observing the RPM.  You will see the RPM gradually increase to a maximum then decrease from that maximum.  When the RPM start to decrease, push the mixture back in until it gets to the maximum RPM you observed before the decrease.  Some say that you should continue enriching a little from lean, but as always happens, some say do not.  You will probably need to use the propeller lever to re-adjust your RPM a tad.  Also, as mentioned above, some aircraft have EGT gauges for this but I have not seen it work well in MSFS.  Are you aware that you should also adjust mixture for every 3000 feet of climb?  The result is that by the time you get to your cruising altitude, your mixture setting should already be close to correct.  At your regular cruising altitude of 7000 feet for example, you would have already leaned it at least twice.

An interesting aside.  In WWII the RAF Bomber Command operated almost exclusively at night, so they could easily see the colour of the exhaust gases coming from the exhaust manifolds.  They adjusted mixture by observing the colour of the exhaust gases from their engines.  They even had a little colour chart to compare with the the colour of the exhaust gases, but after a while the pilot or flight engineer could do it by just looking.  

[oneleg]

1 hour ago, jgf said:

lean the mixture til the engine runs rough, the

 

1 hour ago, nsproles said:

You will see the RPM gradually increase to a maximum then decrease from that maximum.  When the RPM start to decrease, push the mixture back in until it gets to the maximum RPM you observed before the decrease. 

Wishing Just Flight or a 3rd party dev would make something like this available to the PA-28R (CHT is cylinder head temperature):

 

[PhrogPhlyer]

8 hours ago, jgf said:

adjust for highest EGT reading

For EGT, most aircraft I've flown recommend 2 or 3 degrees below max EGT.

 

8 hours ago, jgf said:

But is there any way to know when the mixture needs to be leaned other than waiting for the "losing power" message?

Without tactile/aural indications, I don't believe so.

[PhrogPhlyer]

8 hours ago, nsproles said:

observing the colour of the exhaust gases from their engines. 

When flying a T-28C, the Wright 1820 would exhibit a nice soft blue "flame" from the exhaust stacks. Red/yellow was definitely running hot.

Of note, approximately 2% of total thrust was from the exhaust.

[nsproles]

This video explains the science around why the mixture needs to be leaned.  It also provides a nice practical demonstration of Exhaust Gas Temperature and Cylinder Head Temperature in use in a real aircraft in flight.

https://youtu.be/Yq0XW8K5CrU

 

[nsproles]

This  video is about running mixture rich or lean of peak. https://youtu.be/C0-X_Flz4C8

Manufacturers will provide power tables etc. but there is a lot of room for individual operators to tweak them for particular conditions.  For example, in the video, the fact that the aircraft has large tyres affects how he adjusts mixture.  How applicable all this is to MSFS aircraft would be interesting and it could be a measure of how close developers are to providing a model to the real aircraft.

[Rupert]

On 6/13/2023 at 8:47 AM, PhrogPhlyer said:

When flying a T-28C, the Wright 1820 would exhibit a nice soft blue "flame" from the exhaust stacks. Red/yellow was definitely running hot.

Of note, approximately 2% of total thrust was from the exhaust.

+1

[snave]

31 minutes ago, Rupert said:

+1

How it works in FSX is slightly different. You lean until it runs rough, then slightly richen the mixture. The actual amount varies according to the piston engine. Use whatever instruments you have to optimise your fuel flow. In most cases pay more attention to Exhaust Gas Temperature than cylnder head temp, but have regard NOT to exceed acceptable limits for BOTH.

In the case referred to, the Warrior is optimised by fuel flow