March Fly-Bys
Engine Management on the Fly

By Austin Meyer
Laminar Research

When I started flying back in the late 80’s, I spent most of my time in old rented 152s, 172s, and Warriors. Back then, thanks to the old-school systems and instruments in most planes, engine management methods were pretty rough - just lean until the engine starts to run rough and then richen one-and-a-half turns. To this day I don't even know if that was rich of peak or lean of peak! Gasp! And what WAS my actual fuel-flow, anyway? I would just look up an rpm and altitude in the POH and use that number to predict how much fuel was going out of the tanks (which of course could be different than my actual burn that day), so I never really knew what the thermal loads on the engine were, how much fuel I was burning, how much I had left, or how much I would have when I arrived! Throw in the fact that I was constantly trying to manually steer from one VOR to another (which takes about 50% of my concentration right there, leaving me little time to check on weather down the road) and no wonder I took every cross-country with some trepidation! Of course the flying was still fun, in much the same way driving a classic Model-T down your neighborhood street to the amusement of the neighbors is fun: it is cool to recall the old days, enjoying the antique machinery and lifestyles of the past.

Anyway, I flew that way for about 15 years and built about 600 hours in those old rentals. Two years ago, I grabbed a Centennial Edition Cirrus SR-22. Since then, I’ve flown over 300 hours in the bird and have learned what engine management REALLY is . . . AND I WANT YOU TO KNOW TOO!!!

With the systems in the Cirrus, I MANAGE the flight to maximum safety and efficiency rather than constantly needing to obsess over heading and altitude to make it from one VOR to the next. This means realizing minimum fuel-burn and maximum situational awareness. With the Cirrus, I just dial in my destination with a bit of twisty-twisty on the Garmin-430 and while, the Cirrus whisks me to my next destination, I get to spend my time on other things, like asking: "What is the weather here?" "What is it where I am going?" "What is the EGT, CHT and fuel flow now?" "How hard am I running the engine?" "How close to max power am I?" "How close to max EFFICIENCY am I?" "How much fuel, in minutes, will I have in the tanks when I land?" With the tools in the Cirrus, all of these questions are easily answered. When you MANAGE the whole of the flight rather than just focusing on the next VOR, your flying gets a lot safer.

So, how do you fly a Cirrus efficiently? Well, in my case I fly as high as possible! You’ll usually find me at 17,000 feet, sniffing oxygen and running lean of peak. At that altitude, there is less traffic, less parasite drag on the plane, and less fuel being drunk by my engine. With a wide-open throttle, I am only producing 49% power, but I can easily run lean-of-peak at Best Economy while making 165 KTAS, burning 10.5 gallons per hour, and seeing nearly 18 miles per gallon. Compare that to the 175 KTAS, 18 gallons per hour, and 11 miles per gallon I would get at a lower altitude and Best Power mixture setting: The choice is a no-brainer. I mean, imagine! Only 10 knots less speed, but fuel savings of about 40%! WOW! Of course, up high we also get a smoother ride, greater gliding distance and better radio reception.

Some people think that running lean of peak might damage the engine and cringe when I say I run at Best Economy. NO WAY! While you’d better NOT lean the engine to peak EGT at 100% power and leave it there (because of course that WOULD cause problems!), having an EGT on each cylinder means that we can ALWAYS go back to 50 degrees LEAN of peak with 100% confidence that we are NOT running right at that dangerous peak. Instead, we’re 100% sure that we ARE being safe with the engine while realizing huge fuel-savings as well. The old days of being afraid to lean the mixture to LOP for fear of damaging the engine are OVER! We can now lean safely, every time, and burn less fuel to get where we are going.

Now, using these techniques, I can easily make a non-stop flight from South Carolina to Texas, Kansas, or Massachusetts without touching my IFR fuel reserves, even with a moderate headwind! If I had flown lower, my fuel consumption would have increased by nearly 75%, while my speed would have gone up by only 6%! Again, the choice is obvious.
Now, let's say I did NOT have the engine-monitoring. Let's say I did NOT have the fuel-remaining-on-arrival prediction from the EMax. Let's say I did NOT have the autopilot. Let's say I did NOT have the dual GPS. What would it be like flying then? I would be burning more fuel, afraid to run LOP for fear of being too close to peak EGT, focusing on the next VOR instead of the BIG PICTURE, and watching my altimeter and HSI rather than my fuel and weather situation. That's less safe, less convenient, less capable. With my Cirrus, I know and can reach my steed's capabilities and limits. That's the difference between traveling and antiquing.

Austin Meyer is the founder and owner of Laminar Research, the development group responsible for the X-Plane flight simulator. To download a free demo of X-plane, go to www.x-plane.com.

Austin is also offering Pilot’s World readers a free altitude and fuel optimizer, downloadable at www.x-plane.com.

Back to top