
On the old single engine radial "Otter" I flew for the Royal Canadian Air Force "Air Transport Command" we had a relief tube in the cockkpit.
The urine was sent directly out into the airstream just behind the double dutch doors on the port side on the belly of the aircraft.
What we used to do to the new mechanics coming on Squadron strength was the "Hydraulic Test" on the ground. We had the new mechanic hold his hands under the tube while someone relieved themselves in the cockpit. Hydraulic fluid then was red in colour and the first reaction from the new mechanic was it was the wrong colour

I was flying an Amphibious Otter one fine morning over some remote lakes when my crewman said he had to have a crap and really bad. The Otter only has a relief tube so being early I put the aircraft down on a remote lake with just a light mist coming off it.
Sure enough he was hanging his bare ass over the pontoons when four boats came rushing out figuring we were in trouble. I tried to maneuver the aircraft with water rudders only and no power so as to give him some time to get his pants up but all that happened was he fell off the pontoon into the cold lake.

The cottagers took him to shore and dried him off and we were both given a good breakfast. He ended up getting some dry clothes free.
I wrote another chapter in RCAF History I guess

Cheers...Happy Landings...Doug