This is from Treadwell and Wood's "German Knights of the Air 1914-1918; The Holders fo the Orden Pour Le Metite":
Kapitanleutnant zur See Friedrich CHRISTIANSEN
The son of a sea captain, Friedrich Christiansen was born at Wyk on Foehr on 12 December 1879. The naval tradition in the family made it obvious where Friedrich Christiansen's future lay. On leaving school, in 1894, he joined the merchant marines where he served for seven years before volunteering for military service in 1901 serving on MTBs.
After one year Christiansen returned to the merchant marine where he served for several more years, becoming second officer of the five-masted sailing ship PREUSSEN, the largest sailing ship in the world. Then in 1913 he decided to deviate from his career and learned to fly. After graduating and gaining his licence, No.707, he became an instructor at a civilian flying school. At the outbreak of the First World War, in August 1914, Christiansen was called up and was posted to Zeebrugge as a naval aviator. For the first year he was flying Brandenburg W12 seaplanes on missions over the North Sea and Britain. He even carried out a bombing mission on Dover and Ramsgate for which he was awarded the Iron cross 2nd Class. For the next year he went on numerous reconnaissance and bombing missions, making the C-Staffel at Zeebrugge one of the most successful units in the German Naval Air Service. On 27 April 1916, as Leutnant der Matrosen Artillerie (Lieutenant of Naval Artillery), Friedrich Christiansen was awarded the Iron Cross 1st Class and the Knight's Cross with Swords of the Hohenzollern House Order.
Christiansen claimed his first victory on 1st May 1917, when he shot down a Sopqith Pup whilst on partol off Dover. On 1 September 1917 he took command of the Naval Air Station Zeebrugge and was promoted to Oberleutnant. He celebrated this appointment by shooting down a Porte FB2 Baby, off Felixstowe. Fortunately for the crew of this flying boat, they were able to land on the water and taxi back into Felixstowe harbour. Christiansen continued to carry out reconnaissance, rescue and bombing missions and by December 1917 had completed 440 missions, including the shooting down of Airship C27. At the end of December he was awarded Germany's highest award, the Pour le Merite.
Christiansen increased his tally on 14 February 1918 when he shot down a Curtiss H12B flying boat from Felixstowe. This was followed by two more Curtiss H12Bs on 24 and 25 April. In June and July he claimed three more flying boats, all Felixstowe F2As. Then on 6 July, while Christiansen was on patrol in the Thames Estuary, he surprised the British submarine C-25 cruising on the surface. He attacked the submarine, killing the captain and five crewmen. He thought he had sunk the submarine, but in fact she managed to limp back, with great difficulty, to harbour.
By the end of the war, Christiansen had raised his personal tally to 13, but this is speculative because there were possibly shared victories. Christiansen returned to the merchant marine for a while before taking a post as a pilot for the Dornier Company. It was whilst with Dorniers, that he flew the largest seaplane in the world at that time, the Dornier Do.X, on its maiden Atlantic flight to New York in 1930.
In 1933 Christiansen joined the Geman Aviation ministry as it struggled to rebuild its air force. He was appointed Korpsfuehrer of the National Socialist Flying Korps (NSFK) at its conception in 1937. Two years later when war was again declared and the German Army occupied Holland, Christiansen was appointed officer commanding occupied Holland, a post he held until the end of the war when he was imprisoned by the Allies. On his release from prison he retired to West Germany and died at Innien in December 1972 at the age of 93, an incredible age for someone who had lived and fought through two world wars.
(The book actually has a picture of his aircraft attacking the submarine!)