October 2008 Issue

Flying Your Aircraft Above Its Gross Weight

Flying your aircraft above its maximum gross weight can be done, but not in all circumstances.

I regularly fly my airplane some 250 pounds overgross. But, I do it legally, since itís equipped with an STCíd tip tank installation. The STC (supplemental type certificate) allows operation at a maximum gross takeoff weight of 3550 pounds, an increase of around 7.5 percent from the airplaneís original 3300-pound gross weight when it left the factory. But thereís no paperwork accompanying the admittedly older STC providing performance charts at the higher gross weight. Thereís no question performance suffers at the higher weight, but Iím legally allowed to use the older, lighter weight in computing performance. To compensate, I make sure I use runways of adequate length when operating at the higher weight and higher-than-published airspeeds, accepting a lower climb rate. The tradeoff is worth it. Whether by placing too much aboard, or putting it in the wrong place, loading an airplane outside its weight and balance envelope is relatively easy to do with most GA aircraft. Itís one thing to know youíre slightly over the gross weight and have the runway to handle it. Itís quite another to overload the airplane and then fail to consider the impact on performance.

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