2 BULLETIN 882, IT. S. DEPARTMENT OF AGRICULTURE. 
caused a tremendous drain on material resources, especially upon the 
supplies of flax and linen, for until January, 1917, nothing but 
linen had been successfully used for airplane wing covering. The 
United States was almost entirely dependent upon foreign countries 
for its linen airplane fabric, because our linen factories were making 
much heavier fabrics and labor conditions here precluded the eco- 
nomical raising of flax for fiber. As a result of the partial failure 
of the Canadian flax crop of 1916, the control of the Kussian flax 
and linen stocks by a foreign syndicate, and finally the German 
capture of Riga, which is the export point for Russian flax, the 
shortage of linen became acute, especially for the United States, 
as the allies required all of their available supplies for their own 
airplanes. 
As from 75 to 200 square yards of cloth are necessary to cover a 
set of airplane wings, -the manufacture of several million yards of 
cloth was required to construct the 22,000 machines provided in the 
airplane appropriation act of 1917. Consequently, it was found nec- 
essary to find a substitute for linen, and as the American Egyptian, 
Sea Island, and Sakellaridis Egyptian cottons seemed the most de- 
sirable substitutes available, the United States naturally turned to 
that source to relieve the situation. 
Within 60 days after the actual beginning of the work a satisfac- 
tory cotton substitute had been developed and a million yards had 
been accepted by the War Department. It is understood that before 
the armistice was signed all the principal allies had used the cotton 
fabric and some had used it extensively. 
SIGNAL CORPS SPECIFICATIONS FOR AIRPLANE CLOTH. 
Gen. George O. Squier, Chief of the Signal Corps of the United 
States Army, gives the following qualifications for an airplane 
fabric : 
1. It must not weigh more than 5 ounces to the square yard. 
2. It must resist flame. 
3. It must resist salt water, moist or dry weather, and sudden changes of 
temperature. 
4. It should not stretch in any direction, as the ability to retain its original 
form is very important. 
5. It should have a tensile strength of 75 pounds per inch width in any 
direction. 
6. It should not tear or split because of holes in it. 
7. It should shrink the proper amount when the cellulose solution is applied. 
In September, 1917, the Signal Corps of the War Department 
suggested cooperation between the Textile Department of the Bureau 
of Standards and the Department of Agriculture in developing plans 
for experiments on cotton airplane fabrics. 
