A look at two of the four powerhouses that propel this legendary aircraft.

In 2006, the B-29's original Wright R-3350-57AM engines were exchanged for new engines built using parts from later model engines over a period of three years due to a series of engine problems, including engine failure at an airshow.

The so-called hybrid engines currently installed are a custom built combination of the Wright R-3350-95W and Wright R-3350-26WD engines.