These later engines were named after birds: Eider, Courlis (en:curlew), Pétrel and Sterna.

The upper crankcase section also had integrally cast water channels as part of the cooling system.

The pistons were forged from alugir, with three compression and one scraper ring and floating bronze bushes for the gudgeon pins.

The Pétrel's output could be left or right handed; a Lorraine patent planet gearset, with six satellite gears, provided an 11:17 reduction of propeller shaft speed.

[1] Like the Koolhoven F.K.55, many of the aircraft types to use the Pétrel were one-offs, testing the Lorraine against better known engines from Hispano-Suiza and Rolls-Royce but the Potez 542 version of the Potez 540 family were built in numbers, with 74 of these twin-engined, multi-role (bomber, reconnaissance and transport) aircraft supplied to the French and Spanish air forces.