My old Dad, who flew RE8s in WW1, remembered that the Camel squadron, with whom they shared an airfield at one stage, were mostly pi$$ed when they took off on long patrols. Their party line was that the castor oil used in their rotary engines left the exhaust in a fine mist which they inhaled. To combat the laxative effect (and the cold - lets not forget they often patrolled at 20,000 ft) they had a good swig at the Cognac before take-off. And who can blame them?