Flying in a new or different airplane is always fun. Such is the case with Jacob who had the joy of flying in his friend’s Mooney. Unfortunately, the technique that his friend used to start the Mooney’s engine left him a little confused about starting techniques so he writes in asking:
I was flying in a friends plane the other day, a Mooney Ovation 2gx. When he started the airplane he had full mixture, with his hand on the throttle and the ignition. I didn’t ask him why the plane starts that way. I fly a 172. Whats the difference? Why do you start the 172 the way you do(prime, mixture lean, then upon starting full rich)? Would a “mixture full rich” start work on a 172? Just curious.
Aren’t Mooneys great? I’ve had the opportunity recently to fly a Ovation 2GX once as well. Man, was it a FAST airplane. Mooney’s really do seem like the “Porsche” of the general aviation fleet. Very slick.
There are obviously a lot of differences between your airplane, a Cessna 172, and your friend’s Mooney (as I am sure you noticed). However, I am a little curious about the starting technique that you use in the Cessna. I’m going to assume for a second that you have a carburetor equipped Cessna and every carb equipped Cessna I’ve ever flown in you DO start with the mixture in full rich. I am sure your instructor or FBO has a good reason why you start your particular airplane leaned out, but without further information about your particular model 172, I can’t really tell you much more. The only exception to a full rich start that I know of is a hot start or when attempting to start at an high altitude airport. In both cases, you want the engine leaned out to prevent flooding due to the decreased density of the ambient air.
If in fact you are not a high altitude airport or conducting hot starts, then I’m a little worried about the condition of your carburetor. It might be worth checking out the condition of your float. The FAA just released a Special Airworthiness Information Bulletin on October 16, 2009 that addresses this exact issue. You can check out the Airworthiness Bulletin for yourself at FAA.gov. The service bulletin is NE-10-05 and the subject is “Control/Reciprocating Engine – Float-type Carburetors”. This bulletin recommends that pilots “examine the engine area for evidence of fuel leakage. During engine start be alert for carburetor flooding or the need for excessive leaning. Hard starting might be an indicator of a deteriorating or damaged carburetor float” The service bulletin also warns that “improper metering of fuel or fuel leaking from the carburetor…can lead to complete loss of power or engine fires.” I’m not saying that there is something wrong with your engine (especially if you are at higher altitudes or practice a lot of hot starts) but it might be worth checking out.
Feel free to respond with any particularities that might help us figure out why your aircraft engine starting technique is a little different.
UPDATE: Shortly after posting this article I have received several comments about the starting procedures on the newer fuel injected Lycomming engines. I haven’t flown one in a while and forgot that yes, you do indeed start with the mixture leaned and slowly increase the mixture during the start sequence. Why Lycomming and Continentals have different starting techniques is inherent to the design of the engine. I’m still looking up specifics and will post this information when I find out more. Still, if you have a carb equipped C172 and are starting full lean, you might need to get something checked out.