Engine, Lycoming AEIO-540-D4A5, Horizontally-opposed 6

Type: Reciprocating, Horizontally-opposed, 6 Cylinders, Air-cooled

Power rating: 238 kW (320 hp) as modified [194 kW (260 hp) basic] at 2,700 rpm, :

Displacement: 8.86 L (541.5 cu in)

Bore and Stroke: 130 mm (5.125 in) x 111 mm (4.626 in)

Weight: 174 kg (386 lb)

This basic Textron Lycoming O-540 is a high-performance, six-cylinder engine used in many general aviation aircraft. In modified form, it also powers many U.S. and European aerobatic aircraft. High-powered aircraft engines make possible complex maneuvers, such as multiple vertical snap rolls and knife-edge flight, required to win aerobatic competitions. Inverted fuel and oil accessories allow aircraft to be flown in unusual attitudes.

The engine in Patty Wagstaff's Extra 260 was highly modified by Barrett Performance Aircraft, Inc. Major changes were made to increase its power, but also to provide strength for increased stress and strain in aerobatic flight. Modifications included increasing the compression ratio, modifying the cylinders to increase intake airflow and to match airflow in all of the cylinders, utilizing a cold air induction system, ensuring superior uniformity among parts, dynamically balancing the rotating assembly, and strengthening critical components. Wagstaff ran the engine continuously at and above the "red line" (maximum rpm).