Naval Aircraft Factory PN

The Naval Aircraft Factory PN was the designation for a series of closely related flying boats that were developed from the Curtiss F-5L, an American version of the British Felixstowe F.5, which was in turn the final member of a series of flying boats developed from the earlier Curtiss H-4. The last members of the PN family didn’t retire from US service until 1944, extending the life of the Curtiss H and Felixstowe F families across both World Wars!

The NAF PN was a direct descendent of the Curtiss H-1 ‘America’ of 1914. This was a twin-engined pusher flying boat built for an attempt to fly across the Atlantic, but the outbreak of war prevented the flight from taking part. However during the development of the H-1 a former Royal Naval officer, John Porte, had moved to America to join the Curtiss team as one of the pilots for the H-1. After the outbreak of war he returned to Britain, rejoined the Navy, and was appointed commander of the Naval Air Station at Felixstowe. In his new role he convinced the Admiralty to purchase the two H-1s, and to place orders for the very similar Curtiss H-4. On arrival in Britain these aircraft proved to be somewhat disappointed. They performed well in the air, but their hulls weren’t designed to cope with the North Sea. They were considered fragile, and struggled to take off with a full military load. Porte began work on an improved hull, which eventually resulted in the Felixstowe F.1 This combined the wings of the H-4 with his new Porte I hull, and was a great improvement on the Curtiss original.

Next came the Curtiss H-8, the British designation given to the prototype of a larger flying boat. This was even more  disappointing, as it struggled to take off with a full military load. More powerful engines got it into the air, but it still handled very poorly on the water. Once again Porte produced a new hull and matched it with the wings of the H-8 to produce the sole Felixstowe F.2 of 1916. This was given more powerful engines and entered production as the Felixstowe F.2A. This entered service early in 1918, and was a great success, with the endurance to carry out anti-submarine patrols and the agility to tangle with German seaplanes and even shoot down a Zeppelin. The F.2A was quickly followed by the F.3, which had a longer wingspan, improved payload and endurance, but reduced agility, making it more suited to the anti-submarine role. The final  member of this family was the Felixstowe F.5, which introduced a new wing layout.

The US Navy was sufficiently impressed by the F.5 decide to put the Felixstowe F.5 into production in the United States. The Naval Aircraft Factory was given the job of modifying it to American production and service standards, and the new aircraft entered service as the F-5L (L for Liberty engines). This and the similar Curtiss H-16 became the standard US Navy patrol flying boats for most of the 1920s. Although the F-5L was officially considered to be a Navy design, and the Naval Aircraft Factory produced the largest batch, it generally became known as the Curtiss F-5L.

In 1922 the Navy adopted a new designation system. Under this new system the F-5L officially became the PN-5, which stood for Patrol, Navy, with the -5 kept to avoid confusion. The new designation wasn’t actually used for the F-5L, but all post-war developments from the PN-7 onwards used the new designation.


In 1922 all surviving F-5Ls were officially redesignated as the PN-5, but the new name was rarely if ever used.


The F-6L was the designation for two F-6Ls that were given a new tail. In 1922 the F-6L became the PN-6, but this designation wasn’t used, and most existing F-5Ls had also been given the new tail, so it was effectively obsolete.


Two examples of the PN-5 were given redesigned wings and two 525hp Wright T-2 engines, becoming the PN-7. The new wings were recognisably more modern than the old F-5L type, with ailerons that were flush with the rest of the wing, a set of struts supporting the Wright engines and a set of struts level further out, with floats below them. The Wright T-2 engines were contained within streamline fairings. The new wings had a metal framework with a fabric covering, and a thicker USA 27 aerofoil, which produced more lift, allowing the wingspan to be reduced by over 8ft to 95ft. The new wings were considered to be a great success, but by this point the wooden hulls were becoming outdated, so work moved onto the PN-8.


The two PN-8s had a new metal hull, although this was the same shape as that of the PN-7, the wings of the PN-7 and 475hp Packard 1A-2500 engines in streamlined nacelles, with large spinners.


One of the PN-8s was later given a new tail and engine nacelles with nose radiators, and became the PN-9. This aircraft became famous after attempting to fly from San Francisco to Hawaii. The aircraft took off on 1 September 1925 under the commander of Commander John Rogers, the Navy’s second aviator, following a route that was lined with warships. It managed almost 1,900 miles, before it was forced down 559 miles short of Hawaii. This triggered a massive rescue effort, but even though the aircraft had been seen from many of the warships on the route, and was fairly close to one when it came down, the Navy was unable to find it. Luckily Rogers and his men were able to rig up a sail using fabric from the wings, and sailed almost all of the way to Hawaii! They were finally discovered only a few miles from shore, and escorted safely into harbour. Although they hadn’t completed their flight, their flight of 1,841 miles was accepted as a new world seaplane distance record.


The PN-10 was similar to the PN-9. Four were ordered, but only two were completed with their water cooled Packard engines. The other two were completed with different air cooled radial engines, as the PN-12.


The PN-11 was designation given to four aircraft that were built with a new wider hull, with the boat surfaces built into the main fuselage, thus eliminating the flat sided fuselage and wide sponsons of the F-5L and earlier Felixstowe hulls. The first of the PN-11s was powered by geared Pratt & Whitney R-1850 Hornet engines and had a new tail with twin vertical tail surfaces. This was later used on two of the production versions of the PN-12. The other three used Wright Cyclone engines and kept the single vertical tail surface.

These three aircraft went through a number of changes of designation. They briefly became the P2N-1, a designation that had been allocated to the Curtiss NC Boats but not used. This was then replaced by XP4N-1 for the second aircraft and the XP4N-2 for the third and fourth aircraft.

A modified version of the PN-11/ XP4N was built by the Hall Aluminium Aircraft Company as the XPH-1. This was then ordered into production as the PH-1 for the Navy and PH-2 and PH-3 for the Coast Guard. Some of the Coast Guard aircraft remained in service until 1944, becoming the last members of the family that had developed from the Curtiss H-1 America in service.


The two PN-12s were originally ordered as two of the four PN-10s, but they were completed with rival air cooled radial engines. One was powered by a Wright R-1750 Cyclone and the second by a Pratt & Whitney R-1850 Hornet, two families of engines that would go on to power many of the most famous American aircraft of the inter-war and Second World War periods. Otherwise they kept the basic layout of the PN-8, with the flat sided fuselage and wide boat surfaces inherited from the Felixstowe F boats.

On 3-5 May 1928 the Cyclone powered PN-12 set a world seaplane duration record of 1,243 miles and a speed record for a flight over 2,000km of 80.28mph, while carrying 1,000kg payload.

This performance convinced the Navy to order the PN-12 into production to replace its aging F-5Ls and H-16s. It was built by three different companies, with four different designations. The standard model was built as the Douglas PD-1 (25 aircraft) and the Martin PM-1 (30 aircraft). A modified version with twin tails was built as the Martin PM-2 (25 aircraft) and Keystone PK-1 (18 aircraft).

Engine: Two Wright T-2s
Power: 525hp each
Crew: 5
Span: 72ft 10in
Length: 49ft 1in
Height: 15ft 4in
Empty weight: 9,637lb
Gross weight: 14,203lb
Maximum take-off weight:
Max speed: 104.5mph at sea level
Climb Rate: 10.2mins to 5,00ft
Service ceiling: 9,200ft
Range: 655 miles
Armament: One 0.30in machine gun in bows, one amidships
Bomb load: Four 230lb bombs

Engine: Two Wright R-1750Ds
Power: 525hp each
Crew: 5
Span: 72ft 10in
Length: 49ft 2in
Height: 16ft 9in
Empty weight: 7,669lb
Gross weight: 14,122lb
Maximum take-off weight:
Max speed: 114mpg at sea level
Climb Rate: 16min to 5,000ft
Service ceiling: 10,900ft
Range: 1,310 miles
Armament: One 0.30in machine gun in bows, one amidships
Bomb load: Four 230lb bombs

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How to cite this article: Rickard, J (9 March 2021), Naval Aircraft Factory PN ,

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