Boeing FB.5 (model 15) (1923)

US Navy Carrier Fighter (1933), built

The Boeing FB.5 was a biplane fighter used by the United States Navy in the early 1920s, part of Boeing's FB series evolving from the PW-9 Army fighter. It was essentially navalized version of the PW-9 adapted to meet Navy’s requirements for a carrier-based aircraft. It featured a strong, lightweight biplane design with modifications for carrier operations, powered by a Packard 1A-1500 water-cooled V-12 engine for a top speed of 150 mph (241 km/h) and armed with two forward-firing .30-caliber machine guns. The FB.5 was one of the first U.S. Navy aircraft equipped with arrestor hooks and reinforced landing gear, to be tested on USS Langley. It saw in the end limited operational service due to rapid advancements. It was still an important stepping stone in the development of US naval aviation, paving the way for more advanced carrier fighters.

Development

Boeing and the Navy

In the long lineage of carrier aircraft, Boeing was certainly a prime pioneer, despite its models seemingly out of the loop for many years. Crucially in the late interwar and in WW2, Boeing models were absent from carrier service, and only returned recently via major players such as McDonell Douglas. Other Boeing models linked to the Navy were the later BFB (Model 236 1933 fighter proto) and the BFC/BF2C Goshawk in association with Curtiss. The Boeing OB-O2B were prototype convertible seaplane recce models. There were the whole FB series ending with the F6B, F7B, and XF8B (see later), the 1962 helicopter HRB Sea Knight in assoc. with Vertol. There were also a navalized maritime patrol variant of its legendary bombers, the PB Flying Fortress and P2B Superfortress. The XPBB Sea Ranger remained a prototype, the company also produced in the war the PB2B-2 Canso, it's own take on the Catalina. There were also the 1927 Boeing TB (3 made), and the 1923 Boeing NB navy trainer (72 made), declined into the N2B and NC floatplane. It's major opus in terms of flying boats was the Boeing 314, a civilian model (12 built) which was used by the Navy (5).

The roots for Boeing's naval fighter

The US were always keen to look at foreign design, and the reputation of German aircraft in 1918 was considerable. The entente members were quick to obtain as many of the latest kit as war prize that was possible. In that guise, no less than a hundred and forty two Fokker D.VII were brought back to the U.S. for evaluation as part of the Armistice Agreement. The D.VII was certainly the best German fighter in 1918, at least of those in large numbers, some being kept in service as long as 1930 in several countries. Boeing obtained many of these and they were comprehensively dismantled for study. In the end, features were incorporated in a first prototype destined to the Army, in 1921. This model was named the Boeing Model 15 as per the company's register, later declined under the acronym PW-9 for the Army and FB for the Navy.

The Boeing 15 was completed with a 300 hp Wright-Hispano engine at first. It was tested and showed qome qualities, but pilots estimated it was still a bit underpowered. Thus when the 435 hp (324 kW) liquid-cooled Curtiss D-12 became available, the Model 15 was entirely redesigned. The radiator was moved from the nose intom a "tunnel" under the engine, making a prominent "chin" in the nose. There were other minor design changes notably to reinforced attachments in the fuselage and the wings, and the design was finalized on January 10, 1922. It was tested again and found performances were almost day and night compared to the previous version, despite the added weight and greater drag by the new radiator.

Since the army had priority, it expressed interest in the new design, agreing to provide its armament and pay for extra engines, for more tests. Boeing coukld thus cointinue improving on the model, all expenses paid by the taxpayer, while keeping all rights to the design. The contract was signed on April 4, 1923 for a first amry prototype designated XPW-9. The acronym stands for "Experimental Pursuit, Water-cooled engine". It first flew on June 2, 1923, assimilated for the FB series. The XPW-9 competed with the Curtiss Model 33 in order to replace the Thomas-Morse MB-3A in what was called then the "United States Army Air Service" or USAAS.

The commission in charge of the evaluation however could not decide between the two. They were heavenly matched. Thus, both models were accepted, with the Curtiss PW-8 and Boeing PW-9 greenlighted for production. Still when tested by officers of the Air Service, the latter expressed the superiority of the Beoing PW-9, which for them outperformed the PW-8 in all but speed. It was considered also more rugged and easier to maintain. The congress allowed the funding of an order for 113 aircraft but in the end, only 25 Curtiss PW-8s were procured, the rest being the Boeing PW-9 which became the new interceptor of the continental US. The Navy at last tested the model with its own pilots and asked Beoing for revisions, before the naval version was developed as the "FB", with 44 aircraft produced in several iterations.

Design of the Boeing 15

General layout

The Model 15 was a modified D.VII by Claire Egivelt with some unique solutuions. It had a fuselage of welded steel tubes, all braced with piano wire. There were tapered single bay wings made of fabric on a wooden frame using spruce and mahogany wing spars. These were combined by three-ply wood ribs. The wing struts became streamlined steel tubes instead of wooden struts. The landing gear was given a straight axle, which was streamlined into a small 16 in (410 mm) chord wing.

Engine and performances

Of the 158 built, 147 were standard production models, the rest prototypes or small series for tests. Engines changed only the the last models. The first 30 army PW-9 built in 1925-1926 had the early Curtiss D-12 engine. The next twenty-four PW-9A (1926-1927) obtained the better Curtiss D-12C, then forty 40 PW-9C (1927-1928) fitted with the Curtiss D-12D just as sixteen imprved 16 PW-9D (1928-1934) fitted wit the Curtiss D-12D engine. At last, there were ten FB-1 preseries for the Navy (1924) powered by the early Curtiss D-12 before the army decided to swap on the Packard 2A-1500 in 1926 for its 27 FB-5 produced in 1927.

Variants

F6C-3 in flight (pinterest)

Army PW-9 (all):

Three prototypes XPW-9 built for Air Service evaluation. First aircraft scrapped at McCook Field on February 21, 1925, second static tested in October 1928 and the third was still flying in December 1928. The proper serial PW-9 had 30 produced 1925-26, first production variant, D-12 engine. Later 24 PW-9A made 1926-27 arrived with D-12C engine, one prototype PW-9B delivered in 1927 and 40 PW-9C built 1927-28 with the D-12D engine and 16 PW-9D in 1928-34 as final production variant. The later XP-4 was a prototype re-engined with a 510 hp (380 kW) Packard 1A-1500 engine, also Boeing Model 58. The AT-3 wzs a trainer with a Wright-Hispano engine.

FB-1:

Ten built as FB-1s from initial order of 16, remaining six modified to other sub-types (FB-2, FB-3, FB-4). Powered by a 435 hp (324 kW) Curtiss D-12. Initial Navy delivery, shore-based only.

FB-2 (Model 53)

Two FB-1s modified for carrier operation, 510 hp (380 kW) Packard 1A-1500 engine. Later converted to FB-1 standard. A Boeing FB-5 preserved at the Steven F. Udvar-Hazy Center.

FB-3 (Model 55)

Three built to evaluate the 510 hp (380 kW) Packard 1A-1500 engine. Like the FB-4, the FB-3 was fitted with floatplanes. Following a crash in December 1925, the remaining two were converted to conventional landing gear.

FB-4 (Model 54)

One built, experimental model with a 450 hp (340 kW) Wright P-1 radial engine and fitted with floatplanes. Later converted to FB-6 standard.

FB-5 (Model 67)

27 built, production version. Powered by a 520 hp (390 kW) Packard 2A-1500 engine.

FB-6

FB-4 re-engined with a 450 hp (340 kW) Pratt & Whitney R-1340-B Wasp engine.

FB-7 (Model 67A)

Development of FB-5, powered by a Pratt & Whitney R-1340-A Wasp engine, not built.

XFB-5 (Model 97)

Designation for one FB-5 (A-7101) used for development tests in 1927.

⚙ Boeing FB.5 specifications
Base Weight	1,117 kg (2,458 lb)
Gross weight	1,477 kg (3,249 lb)
Length	7.3 m (23 ft 10 in)
Wingspan	9.8 m (32 ft)
Height	2.9 m (9 ft 5 in)
Wing Area	260 sq ft (24 m2)
Engine	Packard 2A-1500 V-12, 520 hp
Top Speed, sea level	159 mph (256 km/h, 138 kn)
Cruise Speed	142 mph (229 km/h, 123 kn)
Range	390 mi (630 km, 340 nmi)
Climb Rate	1,630 ft/min (8.3 m/s)
Ceiling	18,925 ft (5,768 m)
Armament	2x .30 cal. M1919 Browning LMGs
Crew	1 pilot

Operational History

Deliveries of the first batch of PW-9s started on October 30, 1925 on a total of 114 PW-9s of all variants plus prototypes for the US Army Air Corps until February 1931. They all served with overseas units, Hawaii at the 5th Composite Group, Luke Field or 18th Pursuit Group, Wheeler Field) or the Philippines (4th Composite Group at Clark Field, Luzon) but also the 3rd, 6th, and 19th Pursuit Squadrons until 1931.

On the naval side, the small numbers obtained were in relation to emergencies at national level and the low number of carriers available. In 1925 there was just one, USS Langley, followed later in 1927 by USS Lexington and Saratoga. The Navy obtained forst the FB-1, 16 ordered but 10 received on December 1 and 22, 1924. In addition they were modified for naval operations, lacking among others an arresting hook. So instead of the Navy they were assigned to Marine Corps squadrons VF-1M, VF-2M, and VF-3M, all deployed to China in support of the Marine Expeditionary Force.

Two FB-2s were altered for USS Langley at last with one arresting gear plus a straight-across axle for the landing gear in order to perform rough landings. They entered service with VF-1 in December 1925. Results of tests led to order 27 FB-5s. In 1926 they entered service also with the VF-1B "top hatters". They were modified in depth, following stringent navy specs, and thus became the very first US Navy dedicated carrier fighters, specifically tailored and intended for carrier operation.

To come with the extra weight they were given a beefier, 525 hp (391 kW) Packard 2A-1500 engine. There were new hooks at the bottom of the axle to guide the plane via cables on deck as well. The first FB-5 flew October 7, 1926, delivered to the Navy in January. They were ferried on barges in Puget Sound from Boeing's factory. The barged eventually reached USS Langley, anchored in Seattle's harbor. They were hoisted aboard to make their first official flights from the deck. As part of the training, then the model fill VF-2 and VF-3 squadron on board, respectively, USS Lexington (CV-2) and USS Saratoga (CV-3) from Nov-Dec. 1927. But this was for a short while. In 1931 they were superseded by the F4B, from the same manufacturer. Needless to say they never saw "combat", apart perhaps those of the USMC in China.

The Marine Corps VB-1s were sent to support Brigadier General Smedley D. Butler and his 3d Brigade in China, as part of Fighting Squadron 3 (VF–3M). They sailed from San Diego fo Shanghai on 17 April 1927 with 9 officers, 48 enlisted men, and 8 FB–ls . It was reinforced by a new observation squadron (VO–5M) which was organized in China with aircraft (six 02B–l.) sent from San Diego and four officers and 94 men from the unit on Guam . These deployments made the Marine brigade, when it moved up to Tientsin, the center of trouble, the only foreign contingent in the area with its own aviation. Commanded initially by Major Francis T.("Cocky") Evans and then by Lieutenant Colonel Turner, the Marine squadrons stayed in China for a year and a half.

They operated from a pasture levelled into a flying field by coolie labor about 35 miles from Tientsin. Isolated from the rest of the Marine brigade and with columns of troops from the rival Chinese armies frequently marching past them, the Marines formed their own base guard detachment and mounted machine guns on their hangars and barracks. No combat occurred for these Marines, however, either in the air or on the ground. The squadron flew 3,818 sorties in support of the Marine brigade's peace-keeping mission. They spent most of their time in observation and photographic reconnaissance, tracking for General Butler the movements of the Chinese forces.