Captain W.F.J. Harvey, 22 Squadron, claimed that Biffs manufactured during the winter of 1917/18 suffered a number of wing failures, attributable to the use of inferior timber necessitated by disruption of the supply of silver spruce from America after the latter entered the war. Bristols developed a modification to strengthen wings, this was applied by squadron riggers, and the problem had been eradicated by early February, 1918.

This is the first I have heard about ‘spruce replacement wood’ being used on front line aircraft, Biff wing failures, and a field mod to rectify it.

Can anyone shed any light on this ?