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In my last article, I discussed the failure and replacement of the starter adapter on the aircraft. The adapter connects the starter motor to the internal gears of the engine, providing a “clutch” of sorts to engage the starter motor during starting and disengage it once the engine is running on its own power. Anytime that a component is removed from the aircraft, such as the starter motor in this case, good mechanics use the opportunity for inspection, repair, or upgrade. After all, aircraft maintenance is a labor-intensive endeavor. If you already have components sitting on the bench, it pays to get ahead of the curve and give them the TLC they require before putting them back on the aircraft.
In the case of starter adapter work, it’s critically important to ensure that the starter is working properly because a faulty starter could quickly destroy the investment made in a new adapter. The starter/adapter relationship is critical in Continental engines, and there are many starters to choose from. I met with the experts at Quality Aircraft Accessories (QAA) and Hartzell Engine Technologies to understand how they determine the best starter for different applications. Brett Benton, president of QAA, has been at the helm of the business since 2008. During that time, the company has seen some unintended consequences of starter design changes in the industry.
In nearly every facet of aviation, creating lighter components is considered a major design goal because it directly affects the useful load of the aircraft. When lightweight starters came onto the market, they were considered perfect for this role. In versions where they were not directly connected to the engine, such as in Lycoming engines, they were extremely successful and had few major issues. However, when installed directly on engines through starter adapters, some of the designs caused problems. The Iskra starter is one example.
The Iskra lightweight starter (and some other early lightweight starters) used a system of planetary gears to generate the necessary torque to start the engine. This gearing introduced a significant “drag” on the starter shaft when the starter was not in use. In other words, if you held the starter in your hand and tried to spin the drive shaft, it would be fairly difficult to turn. An unintended side effect of this drag was eventually discovered in the fleet of in-service aircraft as some starter adapters began to fail
This post was originally published by AOPA on . Please visit the original post to read the complete article.