Update 2025-11-19

Today I wanted to talk about the Liberator’s heating system.

The Boeing B-17 used glycol to heat air which came in near engine #2, circulating it from the nose back to the ball turret. The Consolidated B-24 was a bit more complex…

The Liberator was equipped with six spot heaters made by Stewart-Warner, an automotive heater company from Chicago. These Model 789 heaters were spread throughout the forward two compartments, with two in the nose for the bombardier, two for the pilots, and two for the navigator and radio operator behind. This arrangement changed somewhat after the US entry to the war but remember, Maid of Athens was an RAF-bird predating the mass-produced B-24D.

The heaters were fed using a fuel-air mixture delivered from blowers on the two inboard engines. Combustion of the mixture was achieved at each heater via an electrical switch which shut off after ignition. The exhaust gases from the heaters returned to the carburetor, cycling the system. Circulation of the air was provided by an electrical fan, pulling air from the surrounding area.

Toward the end of the B-17G and B-24J series, both systems were eventually replaced with heat exchangers with carbon monoxide detectors for the cabins. The heat exchanger system is correct for all surviving B-17Gs but Shoo Shoo Baby and all surviving B-24Js.

These three examples of Stewart Warner 789 heaters give us an excellent start on the heating system for Maid of Athens. It is our intention to restore her interior to precisely as it was in RAF service. The combination of her early-war origins and RAF equipment makes this task quite daunting! So, little details like this are a real thrill.

If anyone can help us round out the Liberator’s needs in acquiring the last three heaters, completing the full set, please let us know!

The newly arrived Stewart Warner 789 heaters for the Liberator II.

Photo taken 19 November 2025.

Manual image of the spot heater by the bombardier's position.

The black tube is the fuel/air line and the silver tube the exhaust line.

Manual image of the radio operator's position aboard a US Army B-24.

The Stewart Warner 789 heater is visible to the right of the BC-375 transmitter. To the right of the heater is the dynamotor for the aircraft's intercom system.

Since Maid of Athens was made for export, her radio equipment was a mix of Bendix off-the-shelf units and RAF pieces installed after delivery.