Connie Lover
I remember being told long ago that DC-4s were not pressurized. Is that true? If not, how could they have had what Wikipedia claims is a service ceiling of 22,300 feet without everyone on board needing oxygen? And -- if DC-4s were, indeed, pressurized, how did their aft toilet flush without depressurizing the airplane?
The original DC-4E (one off) of the 1930'2 had pressurization. Production C-54/DC-4 built in the US were not pressurized. Canadair bought license rights and produced the DC-4M North Star (Argonaut) fitted with Merlin engines and did pressurize them
CINTA, a Chilean airline, briefly operated DC-4 to New York where I serviced them.
For trans-Andean flying they had fitted a passenger oxygen system; the flight crew of course had one. The pax system consisted of industrial Aviator's Breathing Oxygen tanks on the front bulkhead and metal tubing running down left and right the sidewalls above the windows. A each seat row there were taps with valves and a length of flexible plastic tubing. When needed you uncoiled the flex tubing and put the end in you mouth and turned on your valve and sucked oxygen. CINTA, unlike most R-2000 engine users naturally maintained the two speed supercharger. Most utfits had locked them in low due to sludging problems with the clutch.
Another customer of ours, flying freight on DC-4 trans-Atlantic rewarded crews for low fuel use. This led to some adventurous crews going on oxygen, going high and then manually leaning mixtures past Auto-Lean. Unfortunately it put them into the high combustion temperatures and there were a lot of valve problems. They ended locking the superchargers in low and accepted a little more fuel usage.
So yes, the DC-4 was unpressurized but could get up there to where you needed oxygen. Pardon thread drift off ARAMCO.