The Felixstowe F series flying boats were a joint British and American development during the First World War. The British Felixstowe F-5, and the American-built version, the Felixstowe F-5-L, were the final and best of the series produced during the war. The F-5-L was operational in the last months of the war, but made its principal contribution after the war, and continued in U.S. Navy service until 1928.
The Felixstowe F series was an outgrowth of a prewar project to build a flying boat capable of a transatlantic flight. In 1913, British publisher and aviation enthusiast, Lord Northcliffe, established a $50,000 prize offered by his newspaper, the London Daily Mail, to cross the Atlantic Ocean in a hydroaeroplane. An additional $5,000 was added to the prize by the Women's Aerial League of Great Britain. Aviation pioneer Glenn Curtiss, in association with Rodman Wanamaker, a wealthy American department store owner and supporter of aeronautics, designed and built a flying boat intended to try for the prize. Curtiss and Wanamaker planned the ocean-crossing attempt for 1914, to commemorate the centennial of the cessation of hostilities between the United States and Great Britain in 1814. To further the theme of international cooperation, a former Royal Navy officer and acquaintance of Curtiss, John Cyril Porte, was chosen as pilot, and American George Hallett was later selected as the co-pilot. The airplane was given the name America. Construction of a second, back-up, airplane was begun in the event the original was damaged or lost.
The large, 23 m (76ft) span, twin-engined America was first flown by Curtiss and Porte on June 23, 1914. They were both very pleased with its initial performance. A takeoff date for the transatlantic attempt was proposed for July. Early confidence was quickly dampened, however, when preliminary tests with the load required for the record flight were disappointing. A long and frustrating series of design changes began. At one stage a third engine was mounted on the top wing. But its value was canceled out by its added weight and the weight of the extra fuel that had to be carried. After a few tests the America was converted back to the twin-engined configuration. Curtiss and his team were still hard at work on readying the America for the flight when the First World War began in August. Consequently the project was canceled because of the outbreak hostilities.
John Porte returned to England for duty with the Royal Naval Air Service as a squadron commander and took command of the Felixstowe Naval Air Station. He was a strong advocate and innovator of the flying boat before the war, and he would continue to make substantial contributions to future designs and applications of the military flying boat during the war. Upon his return home, Porte used his influence with the British Admiralty to acquire the America, its sister ship, and an initial small order of similar Curtiss flying boats. An order followed for more than 60 additional flying boats from Curtiss.
Porte experimented with one of the new Curtiss boats, replacing the original Curtiss engines with more powerful ones to make it suitable for military operations. This aircraft, and the subsequent aircraft delivered from the large Curtiss order were designated the H-4. Porte continued to experiment with different hull forms to improve durability and handling qualities on the water. The resulting design, incorporating the wings and tail unit of the Curtiss H-4, the new hull, and two 100-horsepower Anzani radial engines, was designated the Felixstowe F.1.
The Curtiss company continued to refine its flying boats, based on the original America design. The H-8 appeared in mid 1916, quickly followed by the H-12. With a wingspan of more than 90 feet, the H-12 was known as the Large America. The earlier H-4s were now referred to as the Small America. Fifty H-12s, powered by 275-horsepower Rolls-Royce Eagle engines were delivered to the British. The design was one of the most successful flying boats of the war. The German Zeppelin L-22 was destroyed by an H-12 on May 14, 1917 (the first enemy aircraft to be downed by an American-built airplane) and six days later another H-12 sank the German submarine UC-36.
Porte again improved upon the H-12 Curtiss hull, and a new production aircraft, powered by 345-horsepower Rolls-Royce Eagle VIII engines, began to be supplied to British naval air units late in 1917. This version was designated the Felixstowe F-2A. The Curtiss-built version of the F-2A was identified as the Curtiss H-16. The F-2B and F-2C with minor improvements followed, as did a larger version of the F-2A, the Felixstowe F-3. The F-3 lacked the handling characteristics of the F-2A, so work began on yet another version, the F-5. It was the last of Porte's biplane flying boat designs.
The Felixstowe F-5, as with the earlier Porte designs, incorporated the wings and tail unit that were essentially of Curtiss origin, but with an improved hull design that enabled the aircraft to take off more quickly under heavy load, and also to stand up to the rough waters of the North Sea. The U.S. Navy was interested in the British F-5, and also in having it built in American factories after making the necessary modifications to facilitate American production techniques. Engineering drawings for the F-5 were received at the Naval Aircraft Factory (N.A.F.) in Philadelphia in March 1918, and modifications to the original design were undertaken immediately.
The N.A.F. substituted 400-horsepower Liberty 12A engines for the Rolls-Royce Eagles, changed the single controls to dual controls, and made numerous other modifications to adapt the aircraft to American production standards. The American-built Liberty-powered version was designated F-5-L. Its distinguishing feature was the use of ailerons with parallel leading and trailing edges instead of the tapered planform found on earlier models. The ailerons were balanced, but the elevators were left unbalanced, and a much larger and strengthened vertical tail was later standard on all F-5-Ls. The N.A.F. flew the prototype F-5-L on July 15, 1918, just four months after the receipt of drawings from Britain. The N.A.F. ultimately delivered 137 F-5-Ls to the U.S. Navy. Curtiss built 60 and Canadian Aeroplanes Limited of Toronto, Canada, constructed 30, for a total of 227 North American-produced F-5-Ls.
Flying boats had proved their value during the First World War, carrying out patrol and reconnaissance missions of four to six hours duration, and participating in successful combat engagements with enemy submarines, Zeppelins, and seaplanes. In peacetime, F-5-Ls performed shore patrol duties and served as spotters for coastal guns. Most were naval aircraft, but a few saw limited service with the U.S. Army as well. The wooden hulled F-5-L, along with the Curtiss H-16, continued as the U.S. Navy's standard patrol flying boats until they were replaced by the N.A.F.'s PN-12 in the late 1920s.
Six to eight F-5-Ls were converted for civilian use by the Aeromarine Plane and Motor Company in 1919. Known as the Aeromarine 75, the converted aircraft were capable of carrying ten passengers, and were operated by Aeromarine Airways and Aeromarine West Indies Airways flying from Key West to Havana (carrying the first-ever U.S. Post Office foreign air mail); New York to Atlantic City; and Cleveland to Detroit.
In March 1919, the N.A.F. shipped a specially-built, exhibition only, F-5-L to the 69th Regiment Armory in New York City for an aeronautical exhibition sponsored by the Manufacturers Aircraft Association. The airplane was a cutaway example to reveal the intricate method of construction. Although never intended for flight, the N.A.F. exhibition F-5-L was given U.S. Navy serial number A-3882. It was transferred to the Smithsonian Institution in 1920 and put on display. In 1930, in the course of reviewing plans to renovate the exhibition building in which the F-5-L was housed, the Smithsonian determined that it was not worth the labor and resources required to re-exhibit the airplane and proposed returning it to the Navy. The Navy assented to the request and made arrangements to retrieve the airplane. In the end, the Smithsonian decided to retain the hull, a wing float, one propeller, and a bomb. The Navy disposed of the wings and most of the rest of the aircraft, but salvaged the Liberty engines and other usable small components. No complete Felixstowe flyng boats exist. In addition to the parts of F-5-L serial number A-3882 retained by the Smithsonian in 1930, a nose section of a Felixstowe is on display at the Norfolk and Suffolk Aviation Musuem in Flixton, Suffolk, UK. No other Felixstowe flying boat compopnents survive.