Chances are that your aircraft’s performance is somewhat less than the “book” numbers in your operations manual. One explanation is that “book” performance numbers were gathered with an absolutely perfect aircraft, on a perfect day, flown by a perfect pilot. Another explanation is that someone simply fudged the numbers to get a leg up on the competition; but I digress. Regardless of whether any of our airplanes actually flew quite as fast as the original advertisements boasted, there is a lot that you can do to get reasonably close.
Start with the simplest item of all: paint. Believe it or not, the speed difference between a dirty aircraft and a newly cleaned and waxed one can be substantial. A 1997 CAFÉ scientific study tested a Mooney M20E with and without wax, documenting a 3-knot speed improvement for an aircraft that was already free of bugs, oil, etc. This was calculated to be the equivalent of adding 8 horsepower to the engine. If your aircraft has an oily belly and bug-splattered wings, you could improve your cruise performance by as much as 5 knots with little more than sweat equity invested!
Once everything is clean and shiny, it’s time to turn your attention to how everything is fitting together on your aircraft. Start with a tour of all the doors on the aircraft. That includes crew/passenger doors, cowl doors, gear doors, and any inspection doors. Are they in alignment? Are there excessive gaps that can be adjusted? Do they close tightly? Every one of these items can cause excess drag. Keep in mind that how they work in flight is what really matters. A loose cowl can look fine on the ground, but expand and move as soon as air pressure fills the baffles. Next, check the aircraft’s exterior fairings, making sure that they fit as tightly as possible without any obvious gaps, cracks, or misalignment. Depending on the situation, parts can be modified to conform more closely to the aircraft or small gaps can be filled with clear silicone. The goal is to ensure that the air flows as smoothly across the airframe as possible. Be sure not to ignore the underside of the fuselage and wings. These often-neglected areas are very important to drag reduction.
Propellers are another opportunity for efficiency improvements. All propellers are designed to exacting standards when they leave the factory, but they change a great deal in the field and become less efficient over time. Erosion is the main reason for this lost efficiency. Erosion occurs from dirt, sand, and rocks being pulled into the propeller while it’s running. This begins by wearing off the paint, but continues to gradually change the profile of the propeller as the leading edge and propeller face wear. Another way that propellers erode is through intentional, and necessary, repairs and overhauls. Ultimately, the propeller loses at least some degree of efficiency. The best solution is to keep it clean, smooth any roughness in the leading edge and face of the blades, and be sure to wax it as well.
These few, simple tasks may burn up a Saturday or two, but the result will be a faster aircraft with little cash outlay involved (and a better looking plane as a bonus).
Next time, we’ll get deeper into the aircraft and see if you’re actually flying as straight as you think.
Jeff Simon is an A&P mechanic, pilot, and aircraft owner. He has spent the last 14 years promoting owner-assisted aircraft maintenance as a columnist for several major aviation publications and through his how-to DVD series: The Educated Owner. Jeff is also the creator of SocialFlight, the free mobile app and website that maps more than 5,000 aviation events. Free apps available for iPhone, iPad, and Android, and on the Web at www.SocialFlight.com.