Bristol Aquila

The Aquila was a nine-cylinder single-row radial aircraft engine designed by the Bristol Engine Company starting in 1934. A sleeve valve engine, its basic design was developed from the Bristol Perseus. The Aquila was never used in production, but further developments led to the Bristol Hercules, Bristol Taurus, and Bristol Centaurus.

Design and development
The Aquila was developed two years after the somewhat larger Perseus, both being sleeve valve designs. The primary difference was in size, the Perseus being based on the 5.75 by cylinder used in the Mercury engine, while the Aquila used a new and smaller 5 by sized cylinder. The result was a reduction in displacement from 1520 to 950 cubic inches (24.9 to 15.6 L).

The first Aquila engine delivered a modest 365 hp, which was unspectacular for an engine of this size. It soon developed into more powerful versions as improvements were worked into the line (as well as similar changes to the Perseus), and by 1936 it had improved to 500 hp. This would have made it an excellent replacement for the Bristol Jupiter, which ended production at 590 hp three years earlier, but by this time almost all interest was on ever-larger engines.

Applications
Note:
 * Bristol Bulldog
 * Bristol Bullpup
 * Bristol Type 143
 * Vickers Venom