"The Latécoère 570 was a twin-engined medium bomber designed to a 1934 specification. It did not fly until 1939, by which time competitor aircraft had gone into service."
"The Latécoère 570 was the French company's response to the specification of a four-seat bomber (B4) in the programme A-21 of November 1934. This called for an aircraft that could deliver, for example, a 1000 kg (2,200 lb) bomb load over a range of 1,500 km (940 mi), have a maximum speed of 400 km/h (250 mph) at about 4,000 m (1,200 ft) and to be able to reach this altitude in 15 minutes. The latest devices were specified, such as variable-pitch propellers, retractable undercarriage and retractable dorsal and ventral gun turrets. Nine manufacturers responded but only Latécoère and three others produced prototypes. These were the Amiot 341, the Lioré et Olivier LeO 45 and the Romano 120."
What is interesting in the case of the Latécoère 570 is the engine Hispano-Suiza 14AA.
In 1928, Hispano-Suiza (HS), specialist in in-line engines, bought from Curtiss-Wright the licenses of 5 and 9 cylinders radial engines. All the HS dérivatives of these engines (5Q, 9Q, 9V, 14Hb/AB and 14Ha/AA) were failures. The most powerful was the 14Ha (45.6 L), renamed later 14AA. This engine was seen as an alternative to the Gnome & Rhône (GR) french radial engines for the future french combat Aircrafts. So, the HS 14AA was foreseen for a lot of prototypes. But because of its lack of reliability on a lot of flying prototypes, it was finally replaced for all the foreseen prototypes by the GR 14 N. It's a reason (among a lot of others) in the retards of these planes to be tested and/or built before and during the first months of the WW2.
But Hispano-Suiza continued the work on this engine. Because of the lack of GR 14 N (because of the need to build a lot of ordered warplanes), there were finally two planes to equip : the not French Koolhowen FK 58 and the delayed Latécoère 570. No problem of the HS 14AA is known on these two planes...
But it was too late. The HS 14AA was abandoned and the GR 14N and the HS 12Y continued to be built... But the engines beyond the versions GR 14N-49 and HS 12Y-49 were not reliable (including the most powerful dérivatives GR 14R and HS 12Z), when the finally reliable HS 14AA (as powerful as the 14 N and more powerful than the 12Y) was no more there...