The 242 A 1 was perhaps the pinnacle of Chapelon's development of the steam locomotive. The 4-8-4 was a rebuild of Etat 4-8-2 241.101, which retained the 3-cylinder layout, changed it into a 3-cylinder compound system, and introduced more of Chapelon's improvements, including a triple Kylchap exhaust, double high-pressure valves and Willoteaux valves on the low-pressure cylinders. Completed in 1946, and with a continuous power output of 5500 ihp, the locomotive was rather more powerful than contemporary French electric locomotives, resulting in a hasty redesign of subsequent electric locos, increasing their power by another . However, the locomotive was scrapped in 1960.