Some of course are self-explanatory but others are a bit more vague. The mixture setting is one of the most vital and also one of the least understood. Just because you may be learning to fly at the coast you should not be drumming it into your head that the check is “mixture full rich” before each and every take-off. This is downright dangerous as, if you then find yourself about to get airborne from a short strip further inland where the altitude is 5000’ asl (above sea level) you could be surprised by the lack of power from the engine when you apply full power.

Alternatively, a pilot from higher climes who tries to take off with a mixture leaned for the altitudes he is used to, could be greeted by a whole lot of silence shortly after take-off. I have in fact seen it happen and it wasn’t pretty! The check therefore really must be: “Mixture, set for take off at this altitude”. Ask your instructor to explain it properly and check each time. Do not just say; “Mixture, full rich for take-off”. It may kill you one day.

 

Looking forward to hearing back.

Thanks again for all the good reading.

Captain Nick. 

 

Nick, it has been my experience too that many pilots are actually clueless as to how to set the mixture properly for takeoff. The earth is filled with smoking holes in the ground from pilots that tried to take off with the mixture set incorrectly. The above advice is sage, do get yourself a good instructor to fully explain the intricacies of properly setting the mixture for takeoff in the aircraft that you fly. In the meantime though, the following can be used as a rough guide, and should keep you from peril.

 

If you are below 3000'asl, then set the mixture to full rich for takeoff providing there is plenty of runway. If however you are above 3000'asl and/or the runway length available for takeoff is a bit less than preferable, then line up on the runway and run the engine to full power against the brakes. Then lean the mixture to peak. In other words, lean until the RPM indicates maximum. As soon as the RPM reduces slightly with any further leaning, wind it back in to the highest possible RPM - that will be 'peak'. Then turn the mixture control inwards one full turn (just for safety) and let the brakes go and you're on your way. The engine should then be producing maximum power for the density altitude, but just ever so slightly richer than peak, merely for safety's sake. If during the takeoff there is anything suspicious about the engine note then merely close the power and abort the takeoff. If there is anything odd about the engine note after getting airborne, and with no useable runway ahead, be ready to quickly richen the mixture a bit more, or even fully if need be.

 

The Cessna 152 handbook advises that all flying below 3000'asl should have the mixture set to full rich. What they are doing there though is merely covering their asses so that they don't get sued by someone who got injured or even killed by being foolish with the mixture control. The truth though is that you may well want to take a low-level coastal trip of a few hundred miles and flying full rich under such circumstances would be silly as you would be wasting presious fuel. Merely be sure to set the power to 75% or less and then go right ahead and lean the mixture properly for the cruise. Just remember though that, if you need to climb, you will need to first richen the mixture before increasing power. That is why Cessna advise that you can only lean the mixture above 3000'asl, they know full well that their engines cannot produce more than 75% power above that altitude and therefore they are once again merely covering their bums in case of idiocy.

 

Gary  

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