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Schatzberg, Eric, 1956- / Wings of wood, wings of metal : culture and technical choice in American airplane materials, 1914-1945

10. World War II and the revival of the wooden airplane,   pp. [192]-222

Page 216

happened to be the only major part made of metal.80 Concerns about the
structure did arise as a result of the relatively high rate of fatal accidents.
The great majority of these accidents resulted from pilot error, typically
pulling out of a dive too quickly, which literally snapped the wings off. The
great agility of the Mosquito made it easy for even an experienced pilot to
stress the structure beyond its design limits. Escape from the tight cockpit
was difficult, contributing to a high fatality rate in such accidents.8'
Critics of wood construction often insisted that the uncertain strength
properties of wood and the unreliability of glued joints made wooden air-
planes unsafe. Experience with the Mosquito proved these fears to be exag-
gerated. Accident investigators carefully probed any hint of manufactur-
ing defects or poor-quality wood. Only one accident was clearly attributed
to such problems, an Australian-built Mosquito with improperly glued
wings.82 A few airplanes were discovered with defective gluing, largely due
to teething problems at new production facilities. Considering that Mos-
quito factories shifted from casein to urea-formaldehyde glues during the
war, the gluing problems were relatively minor. Improved procedures and
strict quality control kept defective gluing to a minimum.83
The Mosquito also suffered weather-related maintenance problems, some
of them serious but none insoluble. The Mosquitos were generally kept
dispersed on airfields and given no special protection from the elements.
The waterproof covering did a pretty good job of keeping moisture out, but
in service some aircraft developed problems with water soakage, especially
in the tropics. De Havilland devised various minor modifications to elimi-
nate the trouble spots.84 More serious problems occurred in India, where
the long dry season caused major changes in the moisture content of the
wooden structure. These changes produced large internal stresses in glued
joints due to the differential shrinkage of solid wood and plywood. In Octo-
ber 1944 a Mosquito in India broke up in flight due to deterioration in the
wing structure. A subsequent investigation found major problems in all
Mosquitos assembled with casein glue, but not in those using the new urea-
formaldehyde adhesives. Resin-glued Mosquitos soon returned to service in
India, where they performed well in operations over the Burmese jungles
despite the harsh climate. Mosquitos continued to operate in southeast Asia
after the war, flying extensive photo-reconnaissance missions over the Ma-
layan jungles from 1949 to 1955 in support of the British counterinsurgency
campaign against communist guerrillas.85
Overall, the wooden structure accounted for a small fraction of the total
maintenance required for the Mosquito. Most maintenance work was re-
lated to mechanical systems not the airframe structure. Furthermore, metal
parts were hardly immune to maintenance difficulties, as illustrated by the
continuing failures of the metal engine cowling and the serious corrosion of
a magnesium casting in the control system.86 When the wood structure did

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