Most English recon aircraft including the Brisfit, Harry Tate, Quirk, Sopwith 1 1/2 Strutter, FE2, and DH4 used wireless transmitters. Vocal communication was never used. The RFC observers began to improve morse code skills in early 1917 so they could tap out 12 to 16 words a minute. They communicated with artillery batteries and provided coordinates and commencing orders to the guns. Ground stations near the front lines would monitor the airwave traffic to weed out any transmission issues. The communcation at first was one way. The ground units would have to use large ground signals to confirm messages.
No. 40 and No. 16 Squadrons were equipped with wireless comm in 1917 I believe.
