Planes of that era did not have efficient carburation to prevent "gas line freeze" at altitude, nor fuel injectors to keep the petrol flowing during evasive maneuvers, or loops.
To assist the free flow of fuel, castor oil was used as an additive, successfully, but with one major problem.
Castor oil fumes were an efficient laxative by anyone breathing it from an open cockpit, and the need to evacuate bowels was fairly common, (and little reported in those times).
Some pilots carried chamber pots for such emergencies, but others, (with a sense of practicality, if not humor), had square openings cut into the bottoms of their planes, and tried to control their urges till over the enemy trenches.
The infantry learned early on these planes were indeed a very personal enemy.
http://www.century-of-flight.net/new%20 ... _frame.htm
