O-320-H2AD

The Lycoming O‑320‑H2AD is a four‑cylinder, horizontally opposed, air‑cooled piston engine that has become a mainstay of general‑aviation powerplants since its introduction in the early 1960s. Developed from the successful O‑320 family, the H2AD variant features a 320 cubic‑inch (5.24 L) displacement, a compression ratio of 7.5:1 and delivers 150 horsepower at 2,600 rpm. Its design incorporates a forged steel crankcase, forged aluminum cylinders with integral fin cooling, a dual‑ignition system with two spark plugs per cylinder, and a carburetor‑fueled induction system that meets the stringent standards of the FAA’s Part 33 certification. The engine’s robust construction, low weight (approximately 260 lb dry) and proven reliability made it the power source of choice for popular trainers such as the Cessna 152 and Piper Cherokee series, as well as a myriad of light sport and experimental aircraft. Over six decades, more than 30,000 units have been produced, cementing the O‑320‑H2AD’s reputation as a workhorse that helped democratize private flying, reduce operating costs, and standardize maintenance practices across flight schools worldwide. Its continued availability of overhaul kits and parts through Lycoming’s global service network ensures that operators can maintain the engine for beyond the 2,000‑hour typical time‑between‑overhaul interval, keeping the O‑320‑H2AD relevant in training fleets.