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In the world of general aviation, few components have quietly supported countless flying dreams like reliable aircraft engines. The Lycoming Engine Company in Williamsport, Pennsylvania, may not attract Hollywood-level attention, but with nearly a century of history, it has become an indispensable cornerstone of general aviation. Among its most famous products is the O-320 series engine—a workhorse that has powered generations of aircraft.

Lycoming's roots trace back to 1845 as Demorest Manufacturing Company, but its aviation journey truly began after Charles Lindbergh's transatlantic flight. In 1929, Lycoming commenced aircraft engine production, with the O-320 emerging as its most iconic model. Certified by the FAA on July 28, 1953 (Type Certificate No. E-274), this four-cylinder, horizontally opposed, air-cooled, direct-drive engine originally featured an automotive-style generator and starter, capable of driving single-acting adjustable-pitch propellers. The initial O-320 was later redesignated as the O-320-A1A.

"The O-320 engine is extremely robust and durable, like all our engine series," said Jeff Shanks, Lycoming's Customer Development Manager. "Many of our OEM airframes utilize 320 powerplant solutions, both certified and experimental." While specific production numbers for the O-320 aren't available, Lycoming has manufactured over 300,000 engines across all models, with approximately 200,000 currently in service.

Lycoming has continually refined the O-320 to keep pace with industry advancements. In 2005, the company introduced roller tappet valve train technology—considered the most significant improvement in aircraft reciprocating engines in over a decade. According to Textron's press release, "Roller tappets eliminate sliding motion between cams and tappets, improving wear characteristics and enabling more advanced materials."

The most recent innovation is Lycoming's certified electronic ignition system, marketed as the Integrated Electronic Engine (iE2), now available for O-320 series engines.

The O-320's versatility shines through its numerous variants and applications. In 1968, Cessna selected the O-320-E2D (Lycoming P/N 9794) to power its new 172 models, beginning a long relationship with this legendary aircraft. The 1977 172N featured the controversial O-320-H2AD (P/N 10282)—the first 172 engine designed for 100LL avgas, replacing the previous 80/87 octane fuel. This 160-horsepower model introduced barrel-type hydraulic lifters and stamped rocker arms but proved less reliable than its predecessors.

Cessna corrected course with the 172P, reverting to the more conventional O-320-D2J. The current 172S Skyhawk now uses the 180-horsepower IO-360-L2A, demonstrating how Lycoming engines have evolved alongside aircraft designs.

Piper aircraft also extensively use O-320 variants. The PA-28-140 Cherokee typically employs either the O-320-E2A or O-320-E3D. Flight schools particularly value these engines for their reliability in high-utilization environments.

The experimental aircraft community equally embraces the O-320. Van's Aircraft, a leading kit-plane manufacturer, utilizes 150/160-horsepower O-320 engines across multiple models including the RV-4, RV-6/6A, and optionally in RV-7/7A and RV-8/8A configurations. As Van's Aircraft notes: "These engines are the most readily available, economical, and reliable of all possible choices. While other engines with similar configurations, weights and power may be used, only Lycoming engines will fit the mounts and cowlings provided with our kits."

Proper maintenance remains crucial for O-320 longevity. J.D. Kuti, President of Pinnacle Aircraft Engines, LLC, explains: "The O-320 is one of Pinnacle's most popular engines. Most flight school fleets in the U.S. use Lycoming O-320 series engines. For many pilots, the O-320 represents their first engine experience."

Kuti notes that while generally reliable, O-320 engines have specific maintenance considerations: "Camshafts and tappet bodies are susceptible to corrosion and spalling. During rebuilds, we carefully review service documents—some updates appear in service bulletins rather than overhaul manuals."

Current supply chain challenges also affect parts availability. "Post-pandemic, obtaining new cylinders remains difficult," Kuti observes. "Fortunately, quality used cylinders can often be refurbished effectively."

For those seeking deeper technical knowledge, Lycoming offers comprehensive training through its Piston Engine Service School—a five-day program covering O-320 and other models. This program serves aircraft owners, mechanics, and enthusiasts alike, providing hands-on experience with these aviation workhorses.

From flight schools to experimental builders, the O-320's legacy continues as a testament to Lycoming's engineering excellence—powering everything from vintage Cessnas to modern kit planes with equal reliability. As aviation technology advances, this seven-decade-old engine design remains remarkably relevant through continuous improvement and adaptation.