What do the aeroplanes learn from the flares used by the infantry?
Information re flares for contact aeroplanes
These could be used to mean different things for particular operations. However, the same technology was available to all sides so confusion could happen, in an 'allied' attack the Germans would send up SOS signals, if they happened to be the same as 'allied' ones there could be some confusion especially if the German SOS signal was the same as the 'allied' Success signal.
At the Battle of Messines the 'British' troops used Green Flares (these are ground burning) to show their location to Contact Aeroplanes. Green was chosen because it was known the Germans were using Red (which was the preferred colour as it showed up better) to avoid confusion. However, when the sun rose high the Green flares were very hard to see.
The RFC observers were told in 1916 to fire their White Very lights (signal used to call for infantry flares) upwards so they were less likely to be confused with White Very lights fired by the infantry. The RFC were always looking for more distinctive pyrotechnic signals to avoid confusion. In 1918 a Smoke Signal that burst into 14 trails of yellow smoke (also 7 yellow and 7 purple was being developed as the yellow could not be seen in bright sunlight) to replace the white Very light for Contact Patrols. A Red Parachute flare was also developed for the Counter Attack Patrol aeroplane in 1918, this meant:
"That the enemy has been seen to leave his front line trenches in the direction of our lines."
Images for contact aeroplanes ww1 Link:
Also contact patrol work attempted to follow the course of a battle by communicating with advancing infantry while flying over the battlefield. Link:
by cyngast moderator
Erik, the basic answer is that the contact aeroplane patrols, as described in these orders, were supposed to locate the position of troops on the ground during a battle or advance. Certain types of flares identified the troops and then the pilots relayed the troops' position back to headquarters.
At least, that was the theory. As the information posted by Marie shows, it could get complicated. Certain colors of flares were hard to see in sunlight or might duplicate enemy flares and so could be misinterpreted by the pilots.