Page 35 - Volume 17 Number 10

burning a lot more fuel per hour than it is in normal, two-engine cruise flight. If you’ve shut down one engine and have a long way to go, it may make sense to transition to crossfeed for the level-flight remainder of the trip.Balancing the fuel load: Another reason for having the crossfeed system is to be able to alternate between wing tanks during extended single-engine flight, to keep the weight distributed roughly equally on either side of the airplane’s longitudinal axis. Some autopilots, for instance, are limited to operate properly only with an approximately symmetric fuel distribution. Hand- flying an airplane is easier with a balanced fuel load also, especially when making an approach and landing on one engine.When to use crossfeed?Now to the crux of the matter: Other than training, when would you actually use the crossfeed system? I tend to think the whole idea of fuel crossfeed was necessitated by early pre-World War II multiengine airline operations, when airfields were few and far between; and in military aircraft of the Second World War, when combat damage was a very real concern and fuel tanks themselves could be damaged and drained dry, necessitating use of the other wing’s tanks in order to make it back to base. Airplane designers created the capability of crossfeedand flight instructors trained pilots on how to use it.The reality today is that most Twin & Turbine readers fly in parts of the world where suitable runways are rarely very far away. If an engine quits, they’ll need to begin descending for the approach almost right away, leaving very little time in level flight for crossfeed operation and no real need to extend range or balance the fuel load. As the Airplane Flying Handbook puts it, “Crossfeed is ordinarily not used for completing single-engine flights when an alternate airport is readily at hand, and it is never used during takeoff or landings.”If, in fact, you have a long way to go after shutting an engine down in flight—you’re crossing the Canadian tundra on your way to Alaska, or ferrying an airplane across the Atlantic, or doing missionary work in remote areas of the world—then knowing how to use the crossfeed system gives you a valuable tool for making it to the nearest (albeit distant) airfield. For most of us, however, the crossfeed system is nice to have, but not something that we’d use in an actual emergency. You’ll only know for certain whether to use the fuel crossfeed system after shutting down an engine if you consider what it is, what limita•tions apply, how to use it, and there- fore when it’s appropriate and necessary to use the crossfeed system. T&TOCTOBER 2013TWIN & TURBINE • 33