Navy Patrol Flying Boats, 1920-1932
PN-11, PN-12, XPN-11, PM-1
Page 3
Meanwhile, the Naval Aircraft Factory built two PN-11 boats with a wider metal hull minus the sponsons seen on Navy boats since the H-12, a new airfoil section for the wings, and twin rudders. The first with 525-hp Hornet engines began tests in October 1928, and the second with 575-hp Cyclones began flying in April 1929.
The Navy XP2Ns were redesignated, and the first was delivered December 23, 1930, as the XP4N-l with the PN-11 hull, twin rudders, and 575-hp Wright Cyclones. Two X4PN-2s, similar but for increased fuel capacity, were not delivered until March 1932, the last prototype flying boats from Philadelphia.
The twin rudder tail was chosen for 18 Keystone PK-ls ordered November 30, 1929, and 25 Martin PM-2s bought June 10, 1930, but ring cowls on their 575-hp Cyclones gave them a little more speed. Keystone deliveries from Bristol, Pennsylvania, went to VP-l at Pearl Harbor from April to December 1931, while 28 Martin boats were delivered from June to September 1931, filling out squadrons VP-2, VP-5, and VP-10. Pilot cockpit enclosures were fitted in 1934 to both the PM-l and PM-2, as well as Norden Mk. XI bombsights, and the PM-1s were modified with
R-1820-64 Cyclones in ring cowls.
Charles Ward Hall was a specialist in aluminum aircraft structures who was given a contract on December 29, 1927, to build a refined all-metal version of the PN series. The prototype XPH-l was built in a Buffalo factory shared with Consolidated and appeared in December 1929 with an improved all-metal hull, cowled 537-hp GR-1750D Cyclones, Clark Y airfoil, a tall, balanced single rudder, four open cockpits with twin Lewis guns on the bow and stern cockpit rings, and 2,000-pounds of bombs.
Nine production PH-ls ordered June 10, 1930, were first tested on October 19, 1931, and served with VP-8 at Pearl Harbor from 1932 to 1937. They had enclosed pilot’s cockpits, R-1820-86 Cyclones, and four separate Browning guns at the fore, aft, and side positions.
These were the last twin-engine biplanes built for the Navy, since the big Consolidated monoplanes were coming in. But the biplane was not quite through; since the Coast Guard had need of a patrol and rescue boat smaller than the PBYs, Hall got an order for a new version of the old design in June 1936. Deliveries began in April 1938
on seven Hall PH-2s with 750-hp Wright R-1820-F51 Cyclones, followed in 1940 by seven PH-3s with improved engine cowls and pilots’ enclosure. Built in the old Keystone-Fleetwings factory alongside the Delaware River at Bristol, the Hall boats were armed during the war for anti-submarine work.
By 1932, the Navy had eight patrol squadrons with twin-engine biplanes developed from the PN series. Three squadrons served at Pearl Harbor (VP-1,-4,-6,), three with the aircraft tenders USS Argonne and Wright at San Diego (VP-7,-8 -9), and two at Coco Solo in the Canal Zone
(VP-2,-5), along with the twin-float torpedo planes of VP-3. The end of the biplane was in sight, however, when VP-10 was activated to handle the big new P3M monoplanes. Until monoplanes like the PBY came into large-scale production in 1937, the biplanes continued to serve, often embellished with refinements like cockpit enclosures, and late-model Cyclone engines.
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