The simplest (but still complex) explanation goes
something like this: The wings function quite
like a helicopter that has two blades; these
rotate in opposite directions less than 180
degrees; then they stop, reverse their pitch, and
begin moving counter to the original rotation;
the process is reversed again, and so on. The
effect is to create only lift and no rotational
movement. If it were possible for a helicopter to
function this way, it wouldn't need the tail
propeller. Sikorski was said to be inspired in
part by the hummingbird when he invented the
The wing muscles of a hummingbird represent a
disproportionately large part of the body
mass--perhaps up to one-third or so--when
compared to members of other bird families. They
can provide nearly equal power on both the
forward and backward strokes, making the
helicopter analogy pretty close.
The wings of a hummingbird are different in
another way: elbow and wrist joints are fused,
and only motion about the shoulder is possible:
in effect, the wings are large "hands."
The wing motion is powerful and controllable.
Picture a hummingbird with beak straight up and
tail straight down. In this position, commonly
seen when a hummer feeds at a fuchsia blossom, to
remain motionless the axis about which the wings
rotate must align with the roll (central) axis of
the bird, resulting in pure downward thrust. The
hummingbird has control of the angle between the
axis of wing rotation (direction of thrust) and
the body axis, permitting the thrust to be
directed and cause motion in any direction; up,
down, forwards, BACKWARDS (the only bird that can
do this!), or to either side.
In level flight, ruby-throated hummingbirds can
attain maximum speeds of 25 miles per hour or
possibly more. During power dives, some species
have been recorded at more than double that.
Going back to the helicopter analogy, the wings
do not stay exactly in a plane when moving
forward or backward. Instead they move downward
slightly during the stroke, slow down, then
during the reversal lift up somewhat, and begin
the reverse stroke. Viewed from the side, the
wingtip traces out a modest figure 8, looking a
bit like the symbol for infinity.