RMS Arlanza was a ocean liner of the Royal Mail Steam Packet Company. She was built in Belfast in 1912 for RMSP's scheduled route between England and South America. She was a Royal Navy armed merchant cruiser from 1915 until 1920. She returned to civilian liner service in 1920 and was scrapped in 1938. Development Owen Philipps had become Chairman of RMSP in 1903, and over the next five years had introduced five new, larger ships on the company's premier route between Southampton and the east coast of South America. The new ships came to be called the "A-series", as each had a name beginning with that letter. Philipps was interested in using steam turbines in the "A-series", and discussed this with Charles Parsons who invented the turbine. But when the RMSP ordered the first member of the series, RMS Aragon, turbines were new to merchant shipping and almost untried. She and the next four "A-series" ships were therefore ordered with a pair of conventional quadruple-expansion engines powering a pair of screws. After the fifth ship, RMS Asturias, was completed in 1908, it was clear that fuel consumption by steam turbines tended to be high, propellers driven directly by turbines were too fast for merchant service, and turbines running slowly enough to give a slow propeller speed for merchant service were inefficient. Reduction gearing was therefore being applied to allow turbines to run efficiently at high speed but drive propellers at low speed. After Asturias another four "A-series" liners were built to a revised and enlarged design, with three screws instead of two. Each of the two outer screws was driven by a four-cylinder triple-expansion engine. The middle screw was driven by a low-pressure steam turbine, driven by exhaust steam from the low-pressure cylinders of the two reciprocating engines. Building Arlanza was the first of the "A-series" ships to have three screws and a low-pressure turbine. Harland and Wolff in Belfast built her and her engines. She was launched on 23 November 1911 and completed on 8 June 1912. The ship had berths for 400 first class, 230 second class and 760 third class passengers: a total of 1,390. She had five holds and refrigerated cargo space for frozen meat. Early civilian career Arlanza began her maiden voyage from Southampton on 21 June 1912. Two years later, on 27 June 1914, she gave a short publicity cruise for UK dignitaries,