FM-2 version of the F4FWildcat
fits handily inside the 40-foot circle. Many examples of World
War II fighter designs are on
display at AirVenture 2008. Photo
by Frederick A. Johnsen
working on a display once observed the value of the 40-foot circle when
dealing with World War II fighters. Sure, exceptions exist, but the
dimensions of length and wingspan for many of the great single-engine
fighters of the war are handily contained in a 40-foot circle.
reasons are many–powerplants of the combatant nations tended to rival
each other in horsepower. Structures, metals, and state-of-the-art were
similar tools for all nations. The optimal airframe to put behind an
air-cooled or liquid-cooled engine had to minimize drag and weight,
while employing aerodynamics appropriate to fighter maneuvering tactics
of the era. The math tended to favor the same general layout over and
Army Air Forces had several 40-foot (or smaller) fighters on its roster:
P-39: Span, 34 ft.; length, 30 ft., 2 in.
P-40N: Span, 37 ft., 4 in.; length, 33 ft., 4 in.
American P-51D: Span, 37 ft.; length, 32 ft., 3 in.
P-47D: Span, 40 ft., 9 in.; length, 36 ft., 1 in.
the Navy, dimensions ran large for fighters that had legendary
maneuverability–and lower wing loading–to match maneuverable
F4F: Span, 38 ft.; length, 28 ft., 9 in.
F6F: Span, 42 ft., 10 in.; length, 33 ft., 10 in.
F4U: Span, 41 ft.; length, 33 ft., 8 in.
and foe generally lived in the 40-foot circle as well:
Hurricane: Span, 40 ft.; length, 32 ft., 3 in.
Spitfire: Span, 36 ft., 10 in.; length, 29 ft., 11 in.
Zero: Span, 39 ft., 4 in.; length, 29 ft., 8 in.
FW-190A: Span, 34 ft., 5 in.; length, 29 ft., 6 in.
In the caldron of combat,
pilots quickly sized up their adversaries and learned who had the
maneuvering advantage, and who was favored by speed in a dive.
Regardless, the dots in the sky that materialized into onrushing
fighters tended to be of a common size–within the 40-foot circle.