Yesterday I did a nice VFR flight in South America with the Baron G58. As always, I’m starting cold&dark and perform every required procedure to get started as mentioned in the POH. Starting/takeoff requirements are throttle and prop RPM full forward, so should be the mixture. Now I need to climb over a ridge with 13.0000-14.0000ft and the airport is located at 7500ft. So quite a climb before heading to a nice valley down to 10.000ft. Right after takeoff, after gear up etc., I adjust the mixture and lean, because I definitely need more power for the climb at given altitudes with min 1200ft/min to climb over the ridge.
Now my question: Is it possible, or is it advisable, to lean before takeoff at altitudes around 7000-8000ft or even higher? I feel like the engines are way more stable without full rich mixture, especially when performing a high performance climb to 14.000ft right after takeoff.
I noticed this recently as well when using a GA aircraft and taking off from a high-altitude runway and needing to get over some close mountains. So I did as you’re suggesting and leaned the aircraft prior to takeoff. I don’t see why it would be frowned upon to do that and it did help my climb. But the climb was slow as you’d expect. It was a struggle though to get over those mountains. In the end I found that my JF turbo-arrow aircraft was the best solution. The turbo really comes in handy in those situations.
Typically yes you would fully enrich the mixture for takeoff. Having a bit of extra fuel going in actually contributes to cooling slightly.
However, if at high elevation/density altitude for takeoff/landing then you can consider a slightly leaned setting to be equivalent to full rich in that scenario. The goal is to get optimal engine performance for departure or missed approach.
I noticed a while back that full rich can be too much even at sea level in MSFS, but perhaps this has been changed since.
At 7500 I would definitely lean a fair bit. On the Baron, open the lean page on the MFD of the G1000 and set the mixture to around 20-40 degrees rich of peak and you should be good for takeoff and climb. Really you can lean it however you like, by ear even. Never seen it happen in the sim, but IRL its good to keep an eye on the CHT when running really lean at high manifold pressures, they can start to get pretty toasty. Cowls help, they should be open for ground ops, takeoff, and climb. If you do notice the CHT getting hot, increase mixture and airspeed for better cooling and it’ll start dropping down.
If I understand what you wrote correctly, you absolutely HAVE TO lean for takeoff at that altitude. No way should mixtures be full forward for a takeoff at 7,500 feet MSL.
As @BubblyDruid56 says, yes, you should be leaning for takeoff at those altitudes. What you can do is lean the mixture until the engine coughs a little bit and then push the mixture in a little bit from there. You want to be just rich of peak for takeoff in those conditions. Not leaning for takeoff at high altitude is a good way to kill yourself. (in real life).
Coronos666,
Most manufactures recommend leaning the mixture prior to takeoff at elevations above 3000 ft - though in real life, you should always check the POH and follow their recommendations.
The best way to do this is to perform a full throttle runup of the engine(s,) and lean the mixture at full throttle to obtain max RPMs To do this, bring the mixture control back slowly, and watch your RPM. (Use RPM during the runup, even if it is a constant speed prop.) You should see the RPM increase as you lean the mixture. As you continue to lean the mixture, the RPM will start to drop. You should then enrichen the mixture again until you get back to max RPM - and you may want to enrichen it just at touch from there.
If you use the automatic lean option in the options menu, it will lean the mixture for you at your elevation, but you can usually squeeze just a little more power out of it by leaning it manually.
Again, it’s advisable to use this procedure at any elevation above 3000, but failure to do so at elevations above 6000 or so can result in your engine(s) not developing enough thrust to get you airborne or climbing once out of ground effect.
Also of note is that any aircraft that have Rotax or diesel, or turbine engines cannot be leaned.