Classic American Fighters – The Boeing F4B

by Chris Chant on 10/10/2011

A Boeing F4B fighter plane in flightIn June and August 1928 Boeing flew its Model 83 and Model 89 private-venture fighter prototypes. With the first forays into the air by these machines it can truly be said that the last chapter in the history of US biplane fighters had begun, for features of these basic types started an extraordinarily successful series of fighters for the US Army and US Navy, together with a moderately large number of export variants, that effectively saw out the day of the biplane fighter.

The development of the type reflected Boeing’s concern that its position as the primary supplier of land-based and carrierborne fighters was being eroded by new generations of Curtiss fighters, and it was this threat that persuaded the company that it represented a worthwhile financial risk to design and built a prototype that could succeed Boeing’s current fighters, namely the PW-9 and F2B/F3B serving with the US Army and US Navy respectively. Given the aeronautical state of the art in the late 1920s and the innate technical conservatism of the US forces, Boeing sensibly decided to avoid anything radical in the prototype of its new fighter, and in its design and structure this was really the consolidation of all the developments that the company had steadily built into its earlier fighters and other aircraft, combined in this instance with a high-powered radial piston engine and a number of detail design refinements that helped to boost performance by an appreciable margin over those attainable with current fighters.

The core of the design was the fuselage, which was based on a rectangular-section structure of light alloy tubes: the section between the nose and a point in line with the rear of the cockpit was of round-section Duralumin tubes welded together, and the section aft of this point was of square-section aluminium alloy tubes bolted together through Duralumin gussets. This core was then faired out to the required aerodynamic shape for minimisation of drag, and covered in light alloy panels forward and along the upper surface, and fabric aft. From front to rear, this fuselage carried the powerplant, fuel and oil tanks, pilot’s open cockpit, and tail unit. This last was of light alloy semi-monocoque construction with corrugated Duralumin skinning and comprised single horizontal and vertical surfaces, the former including an adjustable tailplane that was braced to the lower longeron on each side by a single strut and carried plain elevators, and the latter including a small wire-braced fin carrying a large horn-balanced rudder that was hinged at its lower end to the vertical knife-edge in which the fuselage terminated.

The staggered and unequal-span biplane wing cellule was of fabric-covered wooden construction with the exception of the ailerons, which were of light alloy semi-monocoque construction with corrugated Duralumin skinning and installed on the outboard ends of only the upper wing’s trailing edge for operation by a system of bell cranks and pushrods in the lower wing. The wings were a further step in Boeing’s shift away from tapered surfaces, as first introduced in the Model 77 (F3B) series although in this instance of the straight type on the upper surface as well as the lower surface. The lower wing was built in halves which were bolted together before attachment to the lower fuselage as a unit whose flat panels extended from the lower longerons, while the upper wing was built as a single flat unit whose centre section was supported over the fuselage by two sets of outward-canted N-type cabane struts. The upper and lower wings were separated on each side by a single set of N-type interplane struts that angled out from bottom to top, and the whole wing cellule was braced with the normal arrangement of flying and landing wires. The airframe was completed by the landing gear, which in each case was of the fixed tailskid landing gear, but the arrangements differed from each other mainly in the disposition of their main units: the Model 83 had two V-type units with a spreader bar braced to the lower longerons by diagonal struts extending from its midpoint and was also fitted with arrester gear, while the Model 89 had divided main units based on two tripod legs, and had provision under the fuselage centreline for a 500 lb (227 kg) free-fall bomb.

The Model 83 and Model 89 were each powered by one Pratt & Whitney R-1340-B Wasp air-cooled nine-cylinder radial engine rated at 500 hp (373 kW) for take-off and 450 hp (335.5 kW) for cruising flight, and these were installed in the nose without any cowling but with fairings behind each cylinder. The engine drove a two-blade metal Hamilton Standard propeller whose pitch was ground-adjustable between two angles.

Both aircraft were evaluated by the US Navy during the summer of 1928 with the unofficial designation XF4B-1, and the Model 89 was also tested by the US Army. Each of the services was highly enthusiastic about the performance and handling of the new fighter, and the US Navy then ordered an initial batch of 27 F4B-1 fighters of the Model 99 type that combined the arrester hook of the Model 83 with the main landing gear arrangement and 500 lb (227 kg) bomb capability of the Model 89; the US Navy also bought the Model 83 and Model 89 prototypes and had them brought up to F4B-1 standard for a total of 29 such aircraft. The first F4B-1 flew in May 1929, and delivery of all 27 aircraft was effected between June and August of the same year so that two squadrons could be partially equipped with the type: the VB-1B squadron attached to the carrier Lexington operated some aircraft in the bomber role with provision for one 500-lb (227-kg) bomb under the fuselage and up to 10 25-lb (11.3-kg) bombs under the lower wing, while the VF-2B squadron attached to the carrier Langley operated the rest of the aircraft in the conventional fighter role. The aircraft were each powered by one R-1340-8 engine rated at 450 hp (335.5 kW) for take-off and 500 hp (373 kW) at 6,000 ft (1830 m), and supplied with fuel from an internal capacity of 57 US gal (47.5 Imp gal; 216.75 litres) that could be supplemented by up to 50 US gal (41.6 Imp gal; 189.25 litres) of auxiliary fuel in a jettisonable ventral tank, and the engine installation featured no ring cowling round the cylinder heads but rather streamlined fairings behind the protruding part of each cylinder. After a short time these fairings were removed as trials revealed that their existence not only had an adverse effect on cooling but also reduced speed by some 2.6 kt (3 mph; 4.8 km/h).

The other details of the F4B-1 included a span of 30 ft 0 in (9.14 m) with area of 227.50 sq ft (21.13 m²), length of 20 ft 1.375 in (6.13 m), height of 9 ft 4.5 in (2.86 m), empty weight of 1,916 lb (869 kg), normal take-off weight of 2,716 lb (1232 kg), maximum take-off weight of 3,135 lb (1422 kg), maximum speed of 153 kt (176 mph; 283 km/h) at 6,000 ft (1830 m) declining to 144 kt (166 mph; 267 km/h) at sea level, cruising speed of 130 kt (150 mph; 241 km/h) at optimum altitude, initial climb rate of 2,110 ft (643 m) per minute, climb to 5,000 ft (1525 m) in 2 minutes 54 seconds, service ceiling of 26,400 ft (8045 m), maximum range of 580 nm (668 miles; 1075 km), and typical range of 434 nm (500 miles; 805 km).

Later in their lives, the aircraft were retrofitted with a ring cowling and the larger vertical tail surface pioneered on the F4B-4 variant (see below).

The fourth of the aircraft was completed to the special F4B-1A standard as the unarmed personal transport of David S. Ingalls, the Assistant Secretary of the Navy and, with five victories, the only US Navy ace of World War I.

As it was producing the F4B-1 for the US Navy and the early variants of the P-12 series for the US Army Air Corps, Boeing felt that there was considerable scope for the technical evolution of the basic aeroplane and therefore built the Model 218 as a privately funded prototype that made its first flight in September 1930 as a development of the P-12B with a semi-monocoque metal fuselage structure based on type pioneered in the Model 96 (XP-9), Model 202 (XP-15) and Model 205 (XF5B-1), a main landing gear unit of the spreader-bar type and, soon after the start of the trials programme, a vertical tail surface of revised shape as pioneered in the XP-15 and XF5B-1. This prototype was evaluated by the US Navy and USAAC, the latter according it the prototype designation XP-925 with the R-1340-D engine, rated at 500 hp (373 kW) at 6,000 ft (1830 m), but this was later replaced by an R-1340-E engine to produce the revised designation XP-925A. With the R-1340-D engine, the XP-925 had an empty weight of 1,954 lb (886 kg) and a maximum take-off weight of 2,694 lb (1222 kg), and recorded a maximum speed of 169 kt (195 mph; 314 km/h) at 8,000 ft (2440 m). At the end of its trials programme the Model 218 was sold to China, where it was flown by Robert Short, an American volunteer with the Chinese forces, for a 1932 engagement in which the Model 218 shot down one Japanese fighter before succumbing to two others.

The Model 218 led to the USAAC’s P-12C that was a generally improved P-12B, and the US Navy ordered a derivative of the P-12C as the F4B-2 that Boeing designated as its Model 223. This differed from the F4B-1 mainly in its spreader-bar main landing gear unit, ring-cowled engine, a tailwheel in place of the previous tailskid, Frise-type ailerons with their hinge lines parallel to the wing spar, and a restressed lower wing with hardpoints for the carriage of four 116-lb (53-kg) bombs when operating in their alternative fighter-bomber role. The 47 aircraft were delivered between January and May 1941, and were used initially by the VF-5B and VF-6B squadrons attached to the carriers Lexington and Saratoga respectively.

The details of the F4B-2 included a powerplant of one R-1340-8 engine rated at 450 hp (335.5 kW) for take-off and 500 hp (373 kW) at 6,000 ft (1830 m), and supplied with fuel from an internal capacity of 55 US gal (45.8 Imp gal; 208.2 litres) that could be supplemented by 55 US gal (45.8 Imp gal; 208.2 litres) of auxiliary fuel carried in the ventral tank, span of 30 ft 0 in (9.14 m) with area of 227.50 sq ft (21.13 m²), length of 20 ft 0.7 in (6.11 m), height of 9 ft 1.25 in (2.77 m), empty weight of 2,067 lb (938 kg), normal take-off weight of 2,799 lb (1270 kg), maximum take-off weight of 3,260 lb (1479 kg), maximum speed of 161.5 kt (186 mph; 299 km/h) at 6,000 ft (1830 m), cruising speed of 137 kt (158 mph; 254 km/h) at optimum altitude, climb to 5,000 ft (1525 m) in 2 minutes 30 seconds, service ceiling of 26,900 ft (8200 m), maximum range of 641 nm (780 miles; 1255 km), and typical range of 504 nm (580 miles; 933 km). By an order issued late in 1932 and also applicable to the F4B-1, all these early aircraft were then retrofitted with the larger vertical tail surface of the F4B-4.

While the Model 223 (F4B-2) adopted a number of Model 218 and P-12C features, the next variant for the US Navy was the F4B-3 that was in effect the Model 235 production derivative of the Model 218 with its semi-monocoque metal fuselage construction. As such the F4B-3 may be regarded as the naval counterpart of the USAAC’s P-12E with slight differences in equipment and in the fuselage structure around the cockpit. The US Navy ordered 21 examples of the F4B-3 in April 1931, and these aircraft were delivered between December 1931 and January 1932 for the use initially of the VF-1B squadron attached to the carrier Saratoga. Evidence of the type’s metal fuselage was provided by the colouring of this section, which was now painted light grey rather than the silver of the earlier variants.

The details of the F4B-3 included the powerplant of one R-1340-16 engine rated at 450 hp (335.5 kW) for take-off and 500 hp (373 kW) at 6,000 ft (1830 m), and supplied with fuel from an internal capacity of 55 US gal (45.8 Imp gal; 208.2 litres) that could be supplemented by 55 US gal (45.8 Imp gal; 208.2 litres) of auxiliary fuel carried in the ventral tank, span of 30 ft 0 in (9.14 m) with area of 227.50 sq ft (21.13 m²), length of 20 ft 4.7 in (6.215 m), height of 9 ft 9 in (2.97 m), empty weight of 2,202 lb (999 kg), normal take-off weight of 2,918 lb (1324 kg), maximum take-off weight of 3,379 lb (1533 kg), maximum speed of 162 kt (187 mph; 301 km/h) at 6,000 ft (1830 m), cruising speed of 139 kt (160 mph; 257.5 km/h) at optimum altitude, climb to 5,000 ft (1525 m) in 2 minutes 54 seconds, service ceiling of 27,500 ft (8380 m), maximum range of 658 nm (758 miles; 1220 km), and typical range of 508 nm (585 miles; 941 km).

The F4B-4 was the US Navy’s equivalent of the USAAC’s P-12E with a larger vertical tail surface and the flotation system in the upper wing replaced by an inflatable rubber life raft in the enlarged pilot’s head rest. The type was ordered at the same time as the F4B-3, but deliveries were delayed by the US Navy’s permission for the first 14 aircraft to be diverted to the Brazilian air force (see Model 256 below). Delivery of the 92 aircraft was therefore completed between July 1932 and February 1933, and a 93rd aeroplane was later created from spare parts. Of this total, 71 were delivered to the US Navy for initial use by the VF-3B and VF-6B attached to the carriers Langley and Saratoga respectively, and the others to the US Marine Corps for initial use by the VF-10M squadron as land-based warplanes without an arrester hook, although this was refitted when USMC pilots undertook their mandatory carrier qualification trials. The F4B-4 entered service in the middle months of 1932, and remained in first-line service to 1937 and 1938, when the aircraft were gradually replaced by the Grumman F2F and F3F fighters.

This marked the passing of an era in the US Navy, for although the F4B was not the service’s last biplane fighter, it was the last biplane fighter with fixed landing gear. After their withdrawal from first-line service, the aircraft were allocated second-line roles such as training until they were pressed into emergency service as home defence fighters in early 1942. Thereafter they passed quickly from the scene.

The F4B-4A designation was applied to 23 P-12 aircraft of various models (four P-12C, two P-12D, 16 P-12E and one P-12F machines) that the USAAC transferred to the US Navy in 1940 for use as radio-controlled targets. At the end of 1941 the US Navy still had 34 F4B-4 aircraft in flyable condition, and after final service as emergency home defence fighters these too were generally converted into target drones.

As noted above, the first 14 aircraft were diverted from the US Navy’s order to Brazil, which received the aircraft with the company designation Model 256 between September and October 1932. The aircraft had no provision for carrierborne use, and therefore lacked an arrester hook. The Model 267 designation was applied to a second version of the fighter for Brazil, who ordered nine of the type as a derivative of the F4B-3 with the wing cellule of the P-12E. All of the aircraft were delivered in February 1933.

Specification

Boeing F4B-4

Type: carrierborne fighter and fighter-bomber

Accommodation: pilot in the open cockpit

Powerplant: One Pratt & Whitney R-1340-16 Wasp air-cooled nine-cylinder radial piston engine rated at 550 hp (410 kW) for take-off and 500 hp (373 kW) at 6,000 ft (1830 m)

Performance: maximum level speed ‘clean’ 160 kt (184 mph; 296 km/h) at 6,000 ft (1830 m) declining to 145 kt (167 mph; 269 km/h) at sea level; cruising speed 139 kt (160 mph; 257.5 km/h) at optimum altitude; maximum rate of climb at sea level 1,980 ft (604 m) per minute; climb to 5,000 ft (1525 m) in 2 minutes 42 seconds; service ceiling 24,800 ft (7560 m); maximum range 611 nm (703 miles; 1131 km); typical range 508 nm (585 miles; 941 km)

Weights: empty 2,312 lb (1049 kg); normal take-off 3,087 lb (1400 kg); maximum take-off 3,519 lb (1596 kg)

Dimensions: span 30 ft 0 in (9.14 m); area 227.50 sq ft (21.13 m²); length 20 ft 4.7 in (6.215 m); height 9 ft 9 in (2.97 m)

Armament: one 0.5-in (12.7-mm) Browning M2 fixed forward-firing machine gun with 200 rounds and one 0.3-in (7.62-mm) Browning fixed forward-firing machine gun with 600 rounds, or two 0.3-in (7.62-mm) Browning fixed forward-firing machine guns with 600 rounds per gun in the upper side of the forward fuselage with synchronisation equipment to fire through the propeller disc, and up to 732 lb (332 kg) of disposable stores carried on three hardpoints (one under the fuselage rated at 500 lb/227 kg and two under the lower wing with each unit rated at 116 lb/53 kg), and generally comprising one 500-lb (227-kg) and two 116-lb (53-kg) free-fall bombs, although the 500-lb (227-kg) weapon could not be carried if the hardpoint was used for the ventral fuel tank as was virtually standard

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