until 1938 when they were replaced by Grumman F3F-2s. A single F4B-3 (BuNo) 8911 was assigned to Headquarters, U.S. Marine Corps and was the personal aircraft of Col. Ross “Rusty” Rowell, Director of Marine Corps Aviation. Production history The production runs are shown below with the P-12 designations for Army aircraft and the F4B designations being for the Navy. The remaining aircraft are civilian or export. Variants P-12 Model 102, U.S. Army Air Corps version of the F4B-1 with a 450 hp R-1340-7 engine, nine built. XP-12A Model 101, 10th built P-12 with NACA cowl a 525 hp R-1340-9 engine and shorter undercarriage, one built. P-12B Model 102B, as P-12 with larger mainwheels and improvements tested on XP-12A, 90 built. P-12C Model 222, as P-12B with ring cowl and spreader-bar undercarriage, 96 built. P-12D Model 234, as P-12C with a 525 hp R-1340-17 engine, 35 built. P-12E Model 234, as P-12D with semi-monocoque metal fuselage, redesigned vertical tail surfaces, some were later fitted with tailwheels instead of skids, 110 built. P-12F Model 251, as P-12E with a 600 hp R-1340-19 engine, 25 built. XP-12G P-12B modified with a R-1340-15 engine with side-type supercharger, one converted. XP-12H P-12D modified with a GISR-1340E experimental engine, one converted. P-12J P-12E modified with a 575 hp R-1340-23 engine, and special bomb sight, one conversion. YP-12K P-12E and P-12J re-engined with a fuel injected SR-1340E engine, seven temporary conversions. XP-12L YP-12K temporary fitted with a F-2 supercharger, one converted. A-5 designation for proposed use of P-12 as a radio-controlled target drone (cancelled) XF4B-1 Designation given to two prototypes for Navy evaluation, the former Model 83 and the former Model 89. F4B-1 Boeing Model 99 for the United States Navy, split-axle landing gear and ventral bomb rack, 27 built. F4B-1A One F4B-1 (BuNo A-8133) converted to unarmed executive transport for the Assistant Secretary of the Navy, fuel tank moved to upper wing centre section. F4B-2 Boeing Model 223, spreader bar landing gear, frise ailerons, tailwheel replacing skid, 46 built. F4B-3 Boeing Model 235, as F4B-2 but with semi-monocoque metal fuselage and equipment changes, 21 built. F4B-4 Boeing Model 235, as F4B-3 but with redesigned vertical tail surfaces, 550 hp R-1340-16 engine, underwing racks for two 116 lb bombs, last 45 built had an enlarged headrest housing a life raft, 92 built and one built from spares. F4B-4A 23 assorted P-12 aircraft transferred from USAAC for use