EAA Sport Aviation - August 2009

better pilot

time for each thousand feet above pattern altitude. For a typical light aircraft cruising at 120 knots (two miles per minute), that translates to 4 miles of distance for every thousand feet of descent. So if our cruise altitude is 5,000 feet above pattern altitude, we should start our descent at least 20 miles from the airport.

Manage Power for Efficiency

Power management is another key to efficient flying. The first step is to lean the engine according to the manufacturer’s recommendations. Improper leaning can easily cost a gallon per hour in extra fuel burn for a light aircraft. Remember that every time we change altitude or power setting, it’s time to recheck the mixture.

One mistake pilots make is to not plan
an efficient descent profile.

Choosing the proper power setting is also critical to efficiency, and we can often improve performance by selecting an appropriate power setting. In general, we do well to keep our power settings high when struggling against a head wind. However, when the wind is light or comes around to the tail, it’s time to reduce power. On a 250 nautical mile trip in a C-172, we can save 3 gallons of fuel by reducing the power setting from 75 percent to 55 percent, and it costs us just an extra 18 minutes of flight time. Unless we’re renting the aircraft by the hour, the time added to the flight plan might easily be worth the fuel savings.

Aerodynamic Advantages

Another strategy to improve efficiency is to gain all possible aerodynamic advantages. The first step is to make certain the aircraft is properly rigged. To check the rigging, trim the aircraft for cruise flight, and then hold the ailerons level and take your feet off the rudder pedals. If the craft is rigged correctly, the turn coordinator ball should center, indicating coordinated flight. If not, we may be wasting energy in the form of drag as we slip or skid through the air.

If the aircraft has a rudder trim control, we can adjust it ourselves to maintain coordinated flight. If not, consider having a mechanic look at it. Oftentimes, correcting an out-of-rig situation is a simple matter of adjusting a bendable trim tab on the rudder.

Aircraft owners may want to consider some aftermarket modifications to improve efficiency. One angle that pilots of aircraft with fixed-pitch props take is to replace a “climb prop” with a “cruise prop” that has a greater pitch. While this provides the advantage of a higher cruise speed, keep in mind that it increases

takeoff distance and reduces climb performance. Any such change must be accompanied by the requisite changes to the performance section of the pilot’s operating handbook.

Perhaps a more economical strategy is to look at aftermarket accessories such as gap seals to improve the aerodynamic efficiency. Gap seals prevent airflow between the front of the ailerons or flaps and the wing. They are relatively inexpensive and can improve cruise speed for some light aircraft by 3 percent or more. Other technologies such as vortex generators can also improve performance significantly. When considering airframe modifications, be sure to examine the cost-benefit picture before making a decision.

The Sharp Corners of Safety

One place we don’t want to cut corners is in the maintenance department. Too many pilots who have attempted to cut costs by skimping on maintenance have paid dearly for that decision. Even an unplanned diversion to deal with a maintenance issue can be significantly more expensive than dealing with the issue in advance.

Whatever our strategy for improving performance, we need to make certain it makes sense from a weather standpoint. Shaving a few miles or minutes off a flight might not make sense in the grand scheme of things if it means upping the risk by flying in marginal weather conditions. Likewise, we should think long and hard before committing to a long over-water flight to reduce the length of a trip.

Finally, never cut corners on safety procedures in the name of improved efficiency. While it might be tempting to fly a straight-in approach to the runway to save a minute or two, following proper pattern procedures greatly reduces the risk of a midair collision. In addition, intersection departures may seem like a good way to save a few minutes of operating time, but the disadvantage of reduced runway length in an emergency can more than overshadow any potential savings.

In these challenging economic times, keeping costs in line is an important consideration for most pilots. By applying a few simple strategies, we can minimize the costs without compromising safety.

Robert N. Rossier has been flying for more than 30 years. A former aerospace engineer and flight school manager in Colorado, he spent 12 years flying for a small airline/ charter service in the Northeast, serving as chief pilot and check airman. He has been writing for the aviation industry for nearly 20 years and was the recipient of a 2001 Aerospace Journalist of the Year Award.