The first french rotary engines used castor oil as the engine lubricant. The fumes had a laxative effect on the pilots. One frenchman came up with a trap door affair in his flying uniform and cut a hole in the seat and lower fuselage. Feeling the effects of the fumes, he would dive bomb the nearest german position. A french general learned of this and awarded our hero the Croix de Guerre. What the germans thought of this has never been discovered, but then they had Werner Voss.