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brucek

Can somebody explain mixture?

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I am using the CH yoke and was wondering exactly when I need to change the mixture. I assigned it to one of the levers next to the throttle but am unsure of when to use it. Thanks.

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Guest ExtraPilot

If you're using Flight Simulator 2004, you can find detailed, complete answers to the question about the mixture control (and many other questions about Flight Simulator and aviation) in the Learning Center that is installed on your hard drive when you set up Flight Simulator.Many other useful sources of information are available free (usually in PDF format) on the Web; for example:The Pilot's Handbook of Aeronautical KnowledgeThe Instrument Flying Handbook andThe Airplane Flying Handbookare all available on the FAA Web site at:http://afs600.faa.gov/srchFolder.asp?Categ...raininghandbookYou might also find it helpful to visit the AOPA Flight Training Web site (e.g., http://flighttraining.aopa.org/student_pilot/presolo/)and the Air Safety Foundation's Web site (http://www.aopa.org/asf/), which offers a variety of publications, online courses, and other resources, all free to anyone (you don't have to be an AOPA member to access this information).

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Guest JanniCash

This is covered in the learning center chapter "Controlling the Engine". And there is a whole lot more information than this (like what to do with the prop lever):As you climb into thinner air, lean the mixture until your exhaust gas temperature (EGT) peaks, then move the lever back a little bit. This will keep your engine at high performance in thin air and reduce your fuel consumption. When descending you have to enrich the mixture again or your engine will go out.Jan

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Guest Jimbofly

Brief explanation:An aircraft engine uses an optimal fuel/air mixture ration for best performance. This is usually between 1:15 to 1:16 fuel/air.When you climb, the air density decreases, and the actual air content per volume decreases. In order to maintain the optimal ratio, you generally need to lean the mixture a little (or a lot, depending on altitude) therefore reducing the amount of fuel being sucked into the engine via the venturi.The best way to remember: higher altitude, less air therefore less fuel.Not a precise explanation by a long shot, but I hope this helps.James

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Guest

Thank you all for the quick responses. My next question is where exactly the lean position is. Would it be when the lever is in the same position as the throttle would be when idle? Thanks again

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Guest Jimbofly

It's progressive lean. The further back (or out when in the Cessna) the lever the more lean the mixture.The optimal level depends on ambient air density and in general when you fly above 3000 feet you should start leaning the mixture. If you pull the mixture too far back the engine will cut out. If you pull it back near the point of cut-out the engine could overheat and detonate. Ideally you listen to the engine as you pull the lever back. Stop at the point where the engine sounds most powerful, and push it forward just a touch.James

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Guest av84fun

In FS9 you need to start leaning at 3000msl by default. There are two basic ways to determine correct leaning.1. As you lean, RPM should rise slightly and so will EGT (exhaust gas temperature). Continue to lean SLIGHTLY and SLOWLY until RPM and EGT peak. If you lean too aggressively, RPM will decrease and the engine will starve out and stall...in which case, just enrichen slightly and the engine will re-start.There is a long-raging debate ITRW about whether to lean rich of peak or lean of peak RPM/EGT and I don't want to get into THAT hornet's nest. But for simming purposes, the above is "good enough for government work."Best,Jim

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Guest Divergent Phugoid

Some excellent and accurate answers there. Especially regarding volume vs density.Regarding lean of peak arguments. Have a read of this from the suppliers of most pistons engines: Entitled "Experts" are everywhere to help you -- The "New" Old Leaning Technique". http://www.lycoming.textron.com/main.jsp?b...Tips/index.htmlWith regard to RLoperation. There is a myth that you mustn't lean below 3000'. This is incorrect. The correct mixture is the correct mixture for the conditions. The most common technique is to lean until the engine starts to run roughly and the richen slightly. Lean of peak EGT is the other method...if you have an EGT fitted. This basically mean you lean until you get the highest EGT and then you lean again until the needle drops back down a tad.Problems that you simply won't encounter in FS but are real world issues: When climbing, it is generally advised to fully richen as the fuel actually helps control the cylinders tempratures (fuel as a coolent!!). However, if you maintain too high a manifold pressure then the engine might suffer from detonation where the mixture ignites to early or too late and unevenly probably fatally injuring the engine.You should fully richen when descending too, for obvious reasons.

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Guest JanniCash

>There is a long-raging debate ITRW about whether to lean rich>of peak or lean of peak RPM/EGT and I don't want to get into>THAT hornet's nest. But for simming purposes, the above is>"good enough for government work."Since you can't damage the engine(s) in FS9 (they never overheat, implode or some such), I'd say a good compromise it "right on peak" :-)Jan

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Correct, at peak temperatures, the engine may overheat. The general rule is to lean to peak, then enrichen slightly. You can run at peak in real life, but just watch those temp gauages. Some planes don't have EGT guages at which point it's often done by sound of the engine or watching the guages for peak RPM.In the Warriors that I fly in in real life, there are RPM settings for cruise in the performance charts and you lean to that by two methods, best-economy and best-power. Best-economy is full throttle and you lean to the RPM. Best-power as I recall (haven't used it in a while) is throttling back to about 50 RPM above the desired RPM setting and then lean out to get the rest.In case you're wondering which lever is supposed to be which on your CH Yoke, the tulip shaped lever next to the throttle is the prop control, and the round bumpy one is the mixture control.----------------------------------------------------------------John MorganReal World: KGEG, UND Aerospace Spokane Satillite, Private ASEL 141.2 hrs, 314 landings, 46 inst. apprs.Virtual: MSFS 2004"There is a feeling about an airport that no other piece of ground can have. No matter what the name of the country on whose land it lies, an airport is a place you can see and touch that leads to a reality that can only be thought and felt." - The Bridge Across Forever: A Love Story by Richard Bach

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Guest av84fun

Oh boy...here we go! (: You are absolutely correct that most POHs recommend exactly what you state. But it is now becoming more widely accepted that there is NO scientific evidence that supports any particular advantage to using the rich of peak recommendations and that the only reason Lyc and Continental don't change them is for product liability reasons.They fear if they change, then every engine failure will be blamed on the new recommendation.Almost without question, the most significant research on this issue has been done by GAMI which, among other things, makes highly precice fuel injector nozzles.The problem with "factory" nozzles is that that are NOT tolerance matched so one nozzle will produce "X" fuel injection and another nozzle will produce "Y" injection at any given power setting. So, unless your aircraft has probes that monitor each cylinder, the temps from one monitored cylinder will bear no relationship to the temps in the other cyninders. Therefore, you are either rich or lean of peak on THAT cylinder ONLY and the others can be running at totally different temps so the process of leaning is basically a waste of time.But in addition to that, most engine gurus are coming to the conclusion that the only potentially damaging setting is PEAK...period. Rich of peak doesn't help anything except the profits of the oil companies and lean of peak doesn't hurt anyting but airspeed but with the benefit of fuel comsumption savings.The following is a quote from one of the head guys at GAMI."We are convinced that if done properly, there's no conceivable way that running an engine lean of peak can cause damage. The data simply doesn't support that lean of peak is, of itself, damaging." What GAMI recommends (other than buying their precision injector nozzles) is to stay away from PEAK...even momentarily...buy using what they call the Big Pull method i.e. you just pull the mixture knob continuously until a noticeable drop in airspeed takes place (obviously you don't YANK it but neither to you do the slight movement "progressive" leaning method either which is going to have you hit PEAK and stay there for several moments which is the WORST thing you can do).So you do the Big Pull which will cause you to PASS PEAK without pausing there until you see an airspeed drop...and of course, before engine roughness occurs and THAT is where you want to leave the mixture. They say that doing that will consistently get you 60 degrees + lean of peak.Here is a link to an article on this subject.http://www.avweb.com/news/reviews/182501-1.htmlBut as another poster pointed out, in the sim, there is no actual heat and the modeling of EGT/CHT, airspeed and engine roughness in proportion to leaning is all over the place but simming is all about trying to approximate reality so this subject seems appropriate for discussion here on this forum.IMHO, GAMI is THE authority on this subject so I have used the Big Pull ITRW and when I am simming for several years now. Absent a FADEC engine, I believe this is the way to go.Regards,Jim

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I haven't flown anything yet in the real world with an EGT gauge. Our Warriors IIIs and Cadets don't have them and neither did the Cessna 150s or 152s I've flown, so I'm used to the POH performance chart RPM settings. I should be in an Arrow next week or the week after and it has one. Gonna be taking my instrument ride next week then starting into my complex rating. Fuel-injection, retracable gear, and constant speed variable pitch prop, here I come. :-hah----------------------------------------------------------------John MorganReal World: KGEG, UND Aerospace Spokane Satillite, Private ASEL 141.2 hrs, 314 landings, 46 inst. apprs.Virtual: MSFS 2004"There is a feeling about an airport that no other piece of ground can have. No matter what the name of the country on whose land it lies, an airport is a place you can see and touch that leads to a reality that can only be thought and felt." - The Bridge Across Forever: A Love Story by Richard Bach

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Just one more bit on this thread: I learned to fly in Ft. Collins, CO. This relates to the "lean above 3000 ft" advice. We always leaned the engine during the run -up: set tach at 2000, did the mag check, carb heat check, and then leaned the engine by pulling back until the engine coughed, then up a notch from there (no EGT's on those old 172's). The point being: if you are taking off from a high altitude airport, lean before takeoff. My instructor showed me once what happens if we skipped that step. We did get into the air, but took most of the runway to do it as the engine was gasping for power from the way too rich mixture. Mike

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Guest

Thank you all for the help! Time to go flying the proper way

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Hi Mike,Are you still in CO? I fly out of Jeffco, and often do practice approaches to KFNL (no need to be worried by ATC as at Jeffco). I was taught the exact same way as you were regarding leaning the mixture, and also got the same lesson as you did about how sluggish the a/c is when using full rich mixture. (Also got the lesson about how sluggish the a/c is with carb heat on). They say that pilots learn from bad situations (hopefully not too bad!). I will always recall have balked a landing (porpoising) in an old N model 172 on a hot summer day here in CO (density alt was much higher than true alt). I left the carb heat on and flaps out at 40 degrees in my panic at having done the porpoise thing, found the a/c mushing in ground effect and then slowly noted this squeeling sound of the stall horn. That was shortly after soloing, and while I now do very rare porpoises :) and are less stressed on balked landings, I will never ever forget that moment! Seems rather stupid now years and many hours later, but it's burnt into the memory banks now.Bruce.

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