feet per minute; while gliding angles (ratio of descent to
forward travel over the ground with engine stopped) little
exceeded 1 in 8.

The year 1912 and 1913 saw the subsequently all-conquering
tractor biplane begin to come into its own. This type, which
probably originated in England, and at any rate attained to its
greatest excellence prior to the War from the drawing offices of
the Avro Bristol and Sopwith firms, dealt a blow at the monoplane
from which the latter never recovered.

The two-seater tractor biplane produced by Sopwith and piloted
by H. G. Hawker, showed that it was possible to produce a
biplane with at least equal speed to the best monoplanes, whilst
having the advantage of greater strength and lower landing
speeds. The Sopwith machine had a top speed of over 80 miles an
hour while landing as slowly as little more than 30 miles an
hour; and also proved that it was possible to carry 3 passengers
with fuel for 4 hours' flight with a motive power of only 80
horse-power. This increase in efficiency was due to careful
attention to detail in every part, improved wing sections, clean
fuselage-lines, and simplified undercarriages. At the same
time, in the early part of 1913 a tendency manifested itself
towards the four-wheeled undercarriage, a pair of smaller wheels
being added in front of the main wheels to prevent overturning
while running on the ground; and several designs of
oleo-pneumatic and steel-spring undercarriages were produced in
place of the rubber shock-absorber type which had up till then
been almost universal.