We can’t all be Arctic aces like Santa Claus, but each year many pilots contemplate flying gift-delivery missions under tight time constraints. If you could sit Santa down and get his advice on how to fly your own merry mission as a private pilot, he’d offer a package of insights about doing it right.
Santa might first mention that pilots who trained in aircraft larger than two-seaters like his sleigh (when in freight-hauling configuration) rarely experience the performance and behavior of their aircraft at maximum loadings. Flying a familiar aircraft with an unusual loading can be like flying a completely different aircraft—and it’s a jolly good idea to learn its characteristics before the holiday outing.
Getting the loading right is more than a paper-and-pencil exercise—even if you check it twice. It also means policing your passengers so no one slips just one more piece of baggage way in back; you may feel like the grinch doing this, but passengers sometimes decide at the last minute to bring along one more (heavy) item.
Someone who commits this elfin infraction wouldn’t know, as the Pilot’s Handbook of Aeronautical Knowledge explains, that “generally, an aircraft becomes less controllable, especially at slow flight speeds, as the CG is moved further aft.”
Even if an improperly loaded aircraft seems to be flying well after takeoff, add a little turbulence, or let that box containing Uncle Ralph’s new bowling ball shift position, and now you are flying a sled made of lead. In extreme cases, “an aircraft that cleanly recovers from a prolonged spin with the CG at one position may fail completely to respond to normal recovery attempts when the CG is moved aft by one or two inches.”
That’s not much of a CG displacement, but to get some perspective, note that for a 1978 Cessna 172—spin-approved in the utility category but not the normal category—the difference in aft CG limit between the categories is just about seven inches.
Extra pounds hauled by an overloaded aircraft punch above their weight if the aircraft experiences high Gs. The Pilot’s Handbook of Aeronautical Knowledge discussion reminds pilots that “the structure of an aircraft about to undergo a load factor of 3 Gs, as in recovery from a steep dive, must be prepared to withstand an added load of 300 pounds for each 100-pound increase in weight.”