I enjoy Aviation Safety and usually end up reading it from cover to cover. The August 2015 article, “Some Weight In The Back?” is pretty good for those wishing to eke out a little more speed by carefully loading the airplane toward its aft CG.
As you point out, when the CG moves forward, a greater downward force must be applied by the horizontal stabilizer, thus inducing more drag. However, this aerodynamic load is as real as if weight were added, so the wing must carry this added “load” as well as the gross weight.
Consequently, as the CG moves forward, the wing must produce more lift by increasing its AoA and thus also inducing more drag. This added “load” also increases stall speed three to eight knots in a typical Cessna 172 at gross weight, depending on bank angle and flap setting. So there is an operational advantage on both ends of the speed range with a CG toward the aft limit.
Frank L. Miller
Thanks for the kind words. It’s important for pilots to understand too much of anything can be a bad thing. There’s nothing intrinsically wrong with intentionally loading an airplane to have an aft CG, as long as its limitations are respected, and the pilot determines what effects the anticipated fuel burn will have. And some airplanes like the Cessna 182 will have limited pitch authority with a forward CG, making the landing flare more problematic than it has to be.
The Limits Of Expertise
Many thanks to Rick Durden for his insightful discussion of our book, The Limits of Expertise, in his article, “Why Smart Pilots Crash” (September). I wish to call attention to my co-authors, Ben Berman and Loukia Loukopoulos, whose contributions to the study and to the book were absolutely essential.
I am an avid reader of Aviation Safety for its analysis of safety issues and its practical advice.
Thanks for correcting our oversight. As it happens, we were two or three chapters into The Limits of Expertise when your note came in. We strongly recommend the book to anyone for its deeply detailed discussions of how well-trained and experienced pilots still can become involved in accidents.
Benefit of the doubt
Your response to a letter from a student pilot appearing in November’s Unicom surprised me. Although he admits being a student with the grand total of 32.3 hours, he states he knows how to land. Furthermore, he has been through three instructors in that short amount of time.
He complained that all the instructors had their hands and/or feet on the controls during landing. He then blames them for his bad landings. I don’t suppose it has ever occurred to him that the instructors were on the controls because of his poor technique and that he was the one actually responsible for his problem landings.
Three instructors in 32 hours, total confidence in his piloting skills and criticism of three instructors should be a major red flag for an anti-authority personality. Over-confidence in his skills and criticism of instructor intervention all mark this individual as headed for trouble. I would really question his fitness for piloting.
T. James Gallagher
Thanks for highlighting the other side of this coin. We wrestled with our response to the reader, eventually opting to give him the benefit of the doubt for several reasons.
For example, we went through at least five instructors before earning our private certificate. When we soloed with less than 10 hours, we knew how to land. And we’ve definitely seen some inexperienced instructors along the way, including one who thought we were responsible for an unsettled ride, not the turbulence, until he took the controls.
There’s clearly a point in a pilot’s training where he or she thinks they know it all, and instructors frequently must choose between the twin evils of giving a student enough leeway to get into trouble and rescuing the situation before it becomes obvious. From here, it’s hard to know which is which.