Plane & Pilot
Tuesday, September 21, 2010

Artificial Speed

Believe it or not, there are some easy, inexpensive ways to fly faster

Another good idea is to store what weight you must carry as far aft as possible, consistent with CG limitations, of course. Any airplane will always fly faster with an aft CG because of the decrease in the download on the tail. The late Lyle Shelton, former owner of the Grumman F8F Bearcat Rare Bear, used to tell me that his airplane carried a lead weight in the tail cone to realize that last little bit of speed advantage around the pylons.

Rig is something most pilots who aren’t A&Ps can’t easily change, but it’s something you should have checked at every annual inspection. If an aileron, flap, elevator or a wing is out of rig, you can be losing several knots at cruise.

Similarly, prop balance is critical to optimum performance, and it’s not that expensive to correct. A prop that’s out of balance not only causes what seems like rough running, but inevitably hurts cruise performance. A balance job takes only a few minutes and rarely costs more than a few hundred dollars.

Still another factor that can cost you speed is open air vents. If you fly a four- to six-seat airplane with air vents in back but rarely carry more than two people, you may not know that the aft vents are open and causing minor drag. Closing the vents may not be an option on a hot day in summer, but some pilots fly oblivious to the added drag from air vents ejecting plumes of turbulent air into the relative airstream.

Metal airplanes, unlike most fabric-covered and fiberglass models, often are partially held together with screws, nuts and bolts. Many metal designs utilize wing, fuselage, landing gear and tail fairings that are held in place with standard, metal screws and/or nuts.

Again, anything that interferes with the smooth flow of air across the aircraft surface causes drag, especially at critical intersections where fairings are intended to smooth the flow. A fairing that’s loose may tend to suck outboard at speed, causing more drag than you might imagine. Accordingly, grab a creeper and roll under and around the airplane with a pair of screwdrivers and a set of open-end wrenches, tightening anything that appears loose. Landing-gear doors and the underside of the wing or belly are especially susceptible, because they’re probably inspected no more than once a year.

Finally, there’s wax. Some pilots are convinced that a good wax job can have a dramatic effect on an airplane’s cruise speed, often bragging of as much as a five-knot increase with a good wax and polish. The perception is that keeping the wetted area as slick as possible decreases drag and improves lift.


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