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Naval Aircraft Factory (NAF) PN-12
Douglas PD-1
Martin PM-1 / PM-2
Keystone PK-1


Keystone Pk-1

The two PN-12s represented the definitive design. Like its predecessors in the PN-series, the PN-12 was a biplane designed specifically for the patrol/antisubmarine role. Single .30-caliber machine guns were fitted in the bow and amidships, and four 230-pound bombs could be carried under the lower wing. Equally powered by twin 525-hp engines, one PN-12 had twin Pratt and Whitney Hornet R-1850s, and the other Wright Cyclone R-1750s. They gave the aircraft a top speed of 114 mph and a range at cruising speed of just over 1,300 miles. It was flown by a crew of five (in open cockpits), and a relief crew could be carried for long patrols. On 3-5 May 1928, the Cyclone-powered PN-12 set another world seaplane record, covering a distance of 1,243 statue miles in 17 hours, 55 minutes.
The Naval Aircraft Factory was not capable of large-scale production, and the Navy decided to have the PN-12 manufactured by private aircraft companies. Douglas received a contract from BuAer on 27 December 1927 to build twenty-five Naval Aircraft Factory-designed PN-12, under the designation PD-1. Other than the engine nacelles with flat top and bottom profiles, PD-1s were constructed according to the PN-12 specification without variation. The Douglas Aircraft Company produced 25 PD-1 aircraft and the Martin Company built 30 PM-1 variants based on the NAF design.
The first production PD-1s were accepted and placed into servive with San Diego-based VP-7 in June 1929. As deliveries proceeded, the type also equipped both VP-4 and VP-6 at Pearl Harbor, Hawaii.
Subsequently, Martin built 25 PM-2 variants and the Keystone Aircraft Corporation built 18 similar PK-1 aircraft, the latter being twin-rudder versions. Thus, the PN-12 gave birth to 98 offspring. These aircraft served in the Fleet until all had ben withdrawn from service by the end of 1936.
In 1927 the Hall Aluminum Aircraft Company developed another PN derivative, the XPH-1. This was the first U.S. Navy flying boat to have all-metal stressed skin construction, which provided a considerable savings in weight. In the event, only ten PH-1s were built as the Navy moved to more advanced flying boat designs. But the Coast Guard procured seven improved Hall PH-2s and seven PH-3s for air-sea rescue missions. Some of these aircraft served into World War II.
Thus, the same basic flying boat design-from the F-5-L to the PH-3-spanned two world wars, a most notable achievement.


Engines: 2 x Wright: R-1750D, 525 hp
Prop: 3 blade ground adjustable metal
Max speed: 114 mph
Ceiling: 10,900 ft
Range: 1310 mi
Empty weight: 7699 lb
Loaded weight: 14,122 lb
Span – upper: 72 ft 10 in
Length: 49 ft 2 in
Wing area: 1217 sq.ft
Armament: 2 x .30 mg
Bombload: 4 x 230 lb
Douglas PD-1
5-place naval patrol boat
Engines: 2 x Wright R-1750 Cyclone, 535 hp / later R-1820, 575 hp
Props: 3 blade, ground adjustable metal
Wingspan: 72 ft 10 in
Length: 49 ft 2 in
Wing area: 1162 sq.ft
Max speed: 114 mph
Cruise 94 mph
Ceiling: 10,900 ft
Range: 1309 mi
Empty weight: 8349 lb
Gross weight: 14,988 lb
Armament: 2 x .30 mg
Bombload: 920 lb underwing
Total built: 25





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