Performance modifications are available for many airplanes that enable them to fly faster or slower, carry more, or be more fuel efficient. Online forums can provide some insight into mods others are making to your type of airplane—along with endless debates about their effectiveness. Perhaps the best source of knowledge about performance modifications is aircraft type clubs.
We called the experts at the Grumman Owners and Pilots Association, and they helped us sort through a bewildering array of modifications available for the 1978 AA–5B Tiger. We’ll bet the winner of this sweepstakes airplane is going to love the engine, propeller, and drag reduction upgrades that will increase speed, and the ignition and exhaust upgrades that will increase efficiency.
Engine. This Tiger’s engine was last overhauled in 1993 and has just over 1,000 hours. We could install new cylinders and it would likely run great for years to come. However, to make sure all 180 horsepower are available on the Tiger, we’re installing a factory-rebuilt Lycoming O-360 engine, contributed by Air Power Inc. A factory-rebuilt engine comes with a new logbook and has zero time when it’s installed on the airplane. We’re also ditching the vacuum-driven flight instruments, so the engine will no longer need a vacuum pump; fewer engine accessories means more power available to spin the propeller. Granted, it’s a small difference—but it all adds up.
Exhaust. We found another way to gain much more power—installing a tuned exhaust system from Power Flow Systems Inc. Less restrictive than stock systems, a tuned exhaust enables the Tiger’s engine to produce an additional 10 to 15 horsepower right out of the box. As a bonus, Power Flow says to expect up to a 1.5 gph reduction in fuel burn at equivalent cruise speeds.
Ignition. To further increase fuel efficiency, we’re swapping out the right magneto for an Electroair electronic ignition system. Electronic ignition systems maintain optimal spark timing automatically by using a MAP sensor; timing is also adjusted with altitude. This level of precision—compared to mags—will improve fuel economy 10 to 15 percent.
Propeller. To maximize the power and efficiency of the engine, we’ll install an electrically controlled constant-speed propeller, provided by MT-Propeller. The MTV-18 propeller features three composite wood core blades wrapped in an epoxy fiberglass housing with stainless steel leading edges. Simply turn a dial on the instrument-panel-mounted control unit to your desired propeller rpm and you get automatic pitch control. The package enables a shorter takeoff roll, higher climb rate, and faster cruise speed—or increased fuel efficiency during cruise—compared to the Tiger’s original fixed-pitch propeller.
Fairings. The Tiger is already an aerodynamically clean airplane. Regardless, we’ll investigate various fairings and cowlings that can further improve its cruise speed. But obviously missing on our Tiger are its wheel fairings (many call them wheel pants). FletchAir Inc. makes its own Grumman-style wheel fairings and will provide a set for the AOPA Sweepstakes. This Tiger will claw back the 5 to 7 knots of cruise speed it lost when its pants were discarded.