View Full Version : Mixture/Pitch - How to use them???
01-30-2004, 12:40 PM
Can anyone help me,
How do I correctly use the Mixture or Pitch control in prop aircraft, I've read the FS manuals about it, and it doesn't seem to be very explanitive.
Any help, or links would be appreciated...
Thanks in advance
01-30-2004, 04:25 PM
Mixture - shift+ctrl+ F1/F4 lean enrich. Usually, you lean your mixture when you climb out in a reciprocating engine aircraft, like a cessna or piper. Sometimes, after 3000 ftMSL is when you start leaning, other times, not until 5k, or even @ 2k, depends...Im not really a constant speed prop weirdo so you'd have to ask the other complex rated pilots here about the pitch controls....
oh, and make sure automixture is not enabled, change the realism settings....
01-30-2004, 09:59 PM
For mixture, as you gain altitude you lean it to the point - a) where rpms are at the maximum - b) the engine starts to run rough then move forward to smooth it out - c) the EGT (exhaust gas temperature) is at the maximum safe level (if your plane is equipped with a gauge for reading EGT).
For plane with constant speed props, my understanding is that you just want to keep the prop speed at the top of the green. But I'm certainly no expert.
01-31-2004, 08:51 AM
Since others have explained mixture, I'll try to explain the prop control.
In an aircraft with a constant speed propeller, the prop govener adjusts the pitch of the prop to maintain whatever rpm you have set using the prop control. So if you're flying along straight and level, and you push the nose down, the govener will increase the prop's pitch so that the engine stays at it's set RPM. If you raise the nose the govener will decrease the pitch to maintain the set RPM.
You still use the throttle to control power, which is set by using the manifold pressure (MP) gauge. This gauge usually reads inches of mercury.
I'll use the default Baron for examples here. For takeoff you set the props full forward, and use full power. I was taught that at 500' AGL to set the climb power, some say 1000', but it doesn't really matter. The climb power setting in the Baron is 25" MP and 2500 RPM. You set this by first reducing the throttle until the MP gaige reads 25", then pull the prop lever out until you get 2500 RPM.
As you climb the MP will drop, about 1" per 1000ft, so you have to keep pushing the throttle in to keep 25" MP. If you're climbing to a high altitude, eventually you'll have the throttle all the way in and not be able to maintain 25" MP. This is normal, just keep the throttle full open.
The opposite happens when descending, and you need to watch the MP gauge and keep pulling the throttle out. A general rule is not to have your MP setting higher than RPM.
Once you reach your cruise altitude, give the aircraft time to accelerate to speed then set the cruise power setting. You usually do this by the aircraft's performance charts, but MS doesn't give us these. A good setting for speed and fuel economy is 23" MP and 2300 RPM for cruise. When reducing power, you always reduce the throttle, then the props. When adding power, do the opposite, props then throttle ( remember throttle down, prop up).
If your at a high altitude and you have the throttle full open and are below 23" MP, just leave the throttle full open reduce the RPMs. If you're cruising at 10,000ft, you probably would only be able to get 20" MP at full throttle. At this altitude, I'd probably set 2400 RPM.
In high performance aircraft you also will usually (but not always) have cowl flaps. Those are usually open when on the ground and during climb. When you level off and set cruise power, close the cowl flaps. Leave them closed during your descent, but when you land you need to open them to let the engine cool while taxiing. After parking, you should close them.
To make things even more complicated with high performance aircraft, it's usually not a good idea to do large reductions in power. This can "shock cool" the engine and crack the cylinder heads. This won't happen in FS though, so you can ignore this. If you want to try to keep it real you can try this, but it takes a bit of planning and practice.
When reducing power in high performan aircraft, usually 1" MP per minute is recommended. Some people say 2" every 2 minutes, but I always did 1"/1min. You need to plan your descent and power reduction before you get to your destination airport.
In the baron, I try to be at 15" MP (bottom of green arc) by the time I reach the pattern altitude. You need to figure how much altitude and how many inches of power you need to reduce. If your cruising at 23" MP at 5000ft, and your destination airport is at sea level, you know you need to lose 8" MP and 4000ft. Reducing 1" per minute it will take you 8 minutes to go from 23" to 15" MP. Descending at 500 ft. per min will also take you 8 minutes to reach pattern altitude.
I usually start my power reductions before I start descending. You know you're going to pick up speed in the descent, so give yourself some extra time. I don't try to be exact with a calculator, I just gustimate it. The GPS helps too, it shows you time to destination with your current ground speed, so about 12 minutes out, I start reducing power 1" per minute. At 20" MP, I start descending 500-700fpm, and continue reducing the power 1" every minute until I'm at 15" MP. Just leave your RPMs set to whatever you had in cruise. 15" MP will be enough power to fly the pattern.
By now the engine has cooled enough and you can make minor power adjustments for landing and forget the 1" per minute thing. On base leg I do what's called a GUMPS check. G is for gas, make sure the fuel selector is on the fullest tank or both if you have a both setting. U is for undercarrage, make sure your gear is down. M is mixture, if below 3000ft it should be full rich. P is for props, push the prop lever full forward in case you have to go around you've already got it set. S is seat belts, but that doesn't apply is FS.
01-31-2004, 10:00 AM
Will FS9 cause an engine to "run rough"? Or do we rely on A and C only...in the sim?
01-31-2004, 10:02 AM
Thanks a bunch, Jim.
That's a copy and paste post if I ever saw one.
01-31-2004, 02:47 PM
In FS you wont hear or feel the engine running rough, but you'll see a drop in RPM. The best way is with the EGT if your plane is equipped with one. Different aircraft have different recommended mixture settings, most light Cessna aircraft recommend 50° rich of peak. The lines on the Cessnas I flew were in 25° incriments, so when the EGT peaks, richen (push the mixture control in) until the needle goes 2 lines cooler. That was just reccommended, you can run it at peak EGT, which gives lower better fuel burn, but higher engine temps.
Without an EGT, I was taught to lean until peak RPM, then richen it with two twists of the mixture knob. In the real planes you turn the mixture nob, in FS you'll just have to guess. :)
01-31-2004, 11:18 PM
Absolute excellent advice . . . right on the money! Couldn't have said it better myself, and probably wouldn't have. <G>
As mentioned below, that is for sure, a sticky paste if I have every seen one. I haven't flown a piston engined aircraft for quite some time, but you pretty much covered it by the numbers. Great job!
Clayton T.Dopke (Clay)
Major, USAF (retired)
02-01-2004, 08:04 AM
Jim, a real pilot with real experience provided an excellent post.
I would also recommend obtaining something akin to a POH (Pilot Operating Handbook). These are sometimes available at sites like Flightsim, virtual airlines, sites with specific interest in a given craft, etc.
For example, I've been "monkeying" with the DC-3 ever since FS2000. The Bill Rambow (and I'm embarassed I can't remember the other two guys names) C-47/DC-3/R4D Dakota operated rather close to the real McCoy and had a lot of good info with it. Then, very recently, I joined DCAirways (www.dcairways.com) and found tons of good info about flying the DC-3, including dynamite info on what the recommended settings are for throttle, prop and mixture during ascent, descent, approach, cruise, etc. Great stuff.
I also remember years ago finding a POH for the 747 at a virtual airlines that specialized in flying the big iron.
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