J.Wegg General Dynamics Aircraft and Their Predecessors Since 1912 (Putnam)
In 1918, Thomas-Morse was invited to design a new single-seat fighter, superior to the latest SPAD models, around the 300hp Wright H licence-built Hispano-Suiza water-cooled V-8 engine. The all-wooden design was entirely conventional with a one-piece upper wing and two separate lower sections of RAF 15 aerofoil with solid spruce spars and three degrees of dihedral. Ailerons were fitted to the upper wing only which accommodated a radiator and a 3-gallon gravity fuel tank and featured a large cut-away section to enable the pilot access to a very cramped cockpit. Space was so limited that there was no room for a panel for instruments and these were scattered around wherever space could be found. Two other fuel tanks were placed in the fuselage, one of 18US gal capacity forward of the pilot and one 20US gal under the rudder bar. Two 0.30in Marlin machine-guns were mounted beneath a turtle-deck cowling.
Four prototypes (40092/40095) were ordered in September 1918 and the first of these flew at Ithaca on 21 February, 1919, achieving a speed of 168mph and climbing to 10,000ft in 4min 52sec - claimed as an unofficial world record for Service-type aircraft. Shipped to the Air Service's Engineering Division at McCook Field, Dayton, Ohio, for static testing, 40092 did not fly again. The other three prototypes were assigned 'P-numbers' by the Flight Test Section, P-66 (40093, cannibalised for parts after 1921), P-124 (40094, damaged in transit and returned to factory for repairs, crashed 30 March, 1921), and P-121 (40095, survived until October 1926).
Although the McCook pilots found the MB-3 easy to taxi and the flight characteristics generally favourable, they reported that the pilot's view in the air was poor and the cockpit was far too small. Maintenance was a severe problem, especially concerning fuel leaks from the complicated shape of the main tank and oil would become trapped in the bottom of the fuselage causing the supports to rot and allow the tank to break through after only ten hours of flight. The radiator gave trouble, as did the untried and complicated fuel system which necessitated the cutting of holes into the fuselage structure to gain access to the magnetos. Also, the airframe suffered badly from engine vibration. In response to these criticisms, several modifications were made to 40095. The cockpit was lengthened (but not widened), the radiator was moved slightly to the right of the centreline to allow for a larger 12US gal gravity fuel tank, and structural strengthening increased the empty weight by 130 lb.
In this revised form, together with a cut-down vertical fin, the Army ordered 50 production MB-3s (63331/63380) from Thomas Morse on 19 June, 1920, which were delivered from November. Four production aircraft were tested at McCook (P-164/63332, P-197/63336, P-201/63338, and P-208/63337) to develop further improvements including more structural reinforcement and a revised cooling system with radiators each side of the cockpit instead of one on the upper wing.
A contract for two hundred MB-3As (68237/68436) with the above revisions plus an armament of one 0.30in and one 0.50in Browning machine-gun was given to Boeing in April 1921 which had underbid Thomas-Morse (and four other manufacturers) under the competitive bidding system then prevailing. Worth nearly one and a half million dollars, it was the largest contract for pursuit fighters awarded until 1937. One pattern aircraft (63332) was sent to Boeing but crashed on landing at Seattle. The first Boeing-built MB-3A was flown at Camp Lewis on 7 June, 1922, and on landing, ran through a small ditch and overturned. All aircraft were delivered between 29 July and 27 December, 1922. Two and four-bladed propellers, the latter an attempt to reduce vibration, were used interchangeably on the MB-3A and the final fifty aircraft had redesigned tail surfaces with the fin area more than doubled (a feature tested on 68237/P-259 at McCook).
After replacement in front-line service by Boeing MB-3As, some MB-3s became MB-3M advanced trainers at Kelly Field, Texas, with the 43rd School Squadron and were finally withdrawn from use in 1929. The MB-3B was a Boeing-proposed model with a 2ft stretched fuselage and four ailerons but was not accepted.
The MB-3 and MB-3A were both used for air racing, starting in 1920 when Capt Harold E Hartney was placed second in the Pulitzer Trophy Race in a prototype MB-3 (number 41). Another prototype MB-3 (number 43) was entered by Lt Leigh Wade but had to retire after the first lap. Army use of the MB-3 in the races continued until 1923.
For the following year's races, Thomas-Morse received a contract for three MB-6s on 24 May, 1921 (68537/68539). These were clipped wing (19ft span) versions of the MB-3 with a 6in shorter fuselage, gross weight reduced to 2,023 lb, and a 400hp Wright H-2. The three were shipped unflown from Ithaca to McCook Field and after one was used for static testing (68539/P-370), another (68537) was first flown on 21 October by Lt John A Macready. However, this was destroyed in a landing accident four days later when flown by Capt C C Moseley (winner of the 1920 race). Therefore, the surviving MB-6 (redesignated R-2 in the Army Racer series) was shipped directly to Omaha, and with Macready came second with a speed of 160.7mph.
A second Army contract had been placed on 16 May, 1921, for twelve MB-3s for delivery to the Marines. This was later changed at the Navy's request to ten MB-3s (BuA-6060/6069) and two MB-7 monoplane racers (BuA-6070/6071 ex-64373/64374). The MB-7 featured a modified 24ft span strut-braced parasol 'Alula' wing and a 400hp Wright H-2. First flown on 24 October at Ithaca by Hartney, the first MB-7 (64373) crashed after fuel pump failure during the races. Completed in February 1922, the second MB-7 had a Wright H-3 engine and was first flown on 14 April by Marine Lt Francis P Mulcahy. However, it failed to finish in the 1922 Detroit event because of an overheated engine. After the race, the MB-7 was stored at the Naval Aircraft Factory, Philadelphia, until scrapped in May 1925.
An eleventh MB-3 was built to replace the crashed MB-7 and assigned the unused serial A-6070. All the MB-3s were delivered to MCAS Quantico during February 1922 for use by the Third Marine Air Squadron. After limited use they were stored, then delivered to the Army at Langley Field in 1923.
In 1927, several MB-3Ms and MB-3As were used in the filming of Wings to portray SPADs and German aircraft. Filming was mostly done at McCook and several were destroyed in crash scenes.
One 300hp Wright H (Hispano-Suiza) eight-cylinder water-cooled engine.
Armarnent: Two 0.30in Marlin machine-guns.
Span 26ft 0in (upper), 24ft 6in (lower); length 19ft 11 in; height 8ft 6in; wing area 250.5sq ft.
Weight empty 1,506 lb; gross weight 2,094 lb.
Maximum speed 152mph at sea level; cruising speed 144mph; climb 1,930ft/min; 6,500ft/3.9min; service ceiling 23,700ft; range 288 miles (41 US gal fuel capacity).
G.Swanborough, P.Bowers United States Military Aircraft Since 1909 (Putnam)
Thomas-Morse and Boeing MB-3/R-Series
When the problem of producing new aircraft of American design instead of building current European types was handed to the U.S. aircraft industry in the spring of 1918, Thomas-Morse was asked to develop a single-seat fighter superior to the French Spad. Four MB-3 prototypes were ordered. Power plant was the new 300 h.p. Wright “H”, American production version of the French Hispano-Suiza, and the general appearance of the MB-3 showed heavy Spad influence. The first prototype did not fly until the spring of 1919, but even with the War over the Army was sufficiently impressed to order 50 service models.
A further order for 200 improved MB-3As was won by Boeing in 1920, under the competitive bidding system which then prevailed. The MB-3 As, which retained the old manufacturer’s model number in spite of the new designating system then in effect, differed from the MB-3 mainly in a revised cooling system, with radiators on each side of the fuselage by the cockpit instead of in the upper wing. Armament consisted of one 0-30-inch and one 0-50-inch machine gun or two 0-50s firing through the propeller. Two- and four-blade propellers were used interchangeably on MB-3 As, and some Boeing-built four-bladers were installed on the earlier MB-3.
The MB-3As got off to very inauspicious beginnings at the Boeing plant in Seattle. A Thomas-Morse model provided as a sample had flipped onto its back during a landing at the nearest military airfield, so the first of the Boeing-built MB-3As was taken by road to a more suitable field at Camp Lewis, 50 miles south of Seattle. The flight was successful but the Army test pilot did not see a small ditch in a portion of the field. His wheels encountered this during his landing roll and the first MB-3A, too, ended upon its back. Later, Army pilot Tyndall pulled the wings off an MB-3A flown from a short runway near the factory and parachuted to safety after a spectacular low-level bail-out. Boeing made minor structural refinements, and designed and built completely new tail surfaces for the last 50 machines delivered.
The design was constantly plagued by loosening of the structural members as a result of vibration of the heavy engine in its wooden mount, and mechanics complained of poor access to the engine and its accessories. Boeing dissatisfaction with traditional wooden fuselage construction, where the various members were joined through metal fittings, led directly to research that resulted in the arc-welded steel tube fuselage introduced on the Boeing PW-9 and the DH-4M.
One of the first units supplied with the MB-3A was the 94th Pursuit Squadron of World War I fame, then based at Selfridge Field, Michigan. Some MB-3As were also shipped directly from the factory to overseas bases. As MB-3As were replaced in service by newer models, they were relegated to advanced training duties under the designation of MB-3M at Kelly Field, Texas, where they served into 1928.
When the Army became interested in postwar air racing, various manufacturers were asked to produce suitable designs. Thomas-Morse took the simplest course and modified the MB-3 into the MB-6 (68537) by clipping the wings and installing a hotted-up Wright “H” engine of 400 h.p. This plane was re-designated R-2 in the Army Racer series and entered in the 1921 Pulitzer Race. A more extreme racing variant of the MB-3 was the MB-7 (64373) with the same fuselage and power plant but a major change to strut-braced parasol monoplane configuration.
Two R-5 racers were ordered from T-M for the 1922 Pulitzer race. Powered with special 600 h.p. Packard 2A-2025 V-12 engines, these were all metal TM-22 parasol monoplanes developed from a combined primary trainer and pursuit model that B. Douglas Thomas was trying to sell to the Army. The pursuit version, MB-9, was a relatively conventional single-seat all-metal parasol monoplane while the trainer, MB-10, was the same airframe with a new section spliced onto the fuselage to accommodate the second cockpit and a longer nose that placed the 80 h.p. Le Rhone rotary engine farther forward than the fighter’s Curtiss D-12 for balance purposes. The R-5s were notably unsuccessful, as was the trainer-cum-fighter, and the only significant design feature to survive was the wrap-round corrugated metal fuselage construction, which finally won official acceptance on the production O-19 series.
TECHNICAL DATA (MB-3A)
MANUFACTURER: Boeing Airplane Co., Seattle, Washington.
TYPE: Single-seat fighter.
ACCOMMODATION: Pilot in open cockpit.
POWER PLANT: One 300-h.p. Wright H-3 piston Vee in-line.
DIMENSIONS: Span, 26 ft. 0 in. Length, 20 ft. 0 in. Height, 8 ft. 7 in. Wing area, 229 sq. ft.
WEIGHTS: Empty, 1,716 lb. Gross, 2,539 lb.
PERFORMANCE: Max. speed, 141 m.p.h. at sea level. Cruising speed, 125 rn.p.h. Initial climb, 1,235 ft./min. Service ceiling, 19,500 ft. Endurance, 2 1/4 hours.
ARMAMENT: Two fixed forward-firing 0-30-inch guns.
MB-3: 40092/40095; 63331/63370.
G.Swanborough, P.Bowers United States Navy Aircraft Since 1911 (Putnam)
The MB-3, designed in 1918, was to be America's fighter contribution to World War 1. The Army ordered 50 examples from the designing company Thomas-Morse in 1919 and 200 improved MB-3As from Boeing in 1920. Eleven more MB-3s were built on an Army contract (as 64374-64384) for transfer to the Navy in 1921 and use by the USMC as advanced trainers (A6060-A6070). Power plant, 300 hp Wright-Hispano. Span, 26 ft; length, 20 ft; gross weight, 1,818 lb; max speed, 152 mph.
P.Bowers Boeing Aircraft since 1916 (Putnam)
THOMAS-MORSE MB-3A (No Boeing Model Number) - Under the Army Air Service procurement system in effect right after WW-I, Boeing was the low bidder on a production aircraft for 200 MB-3 single-seat fighters designed late in 1918 by Thomas-Morse. The originating firm had received an order for 50 of its own MB-3 model while Boeing got the larger order for improved MB-3As with its low bid of $1,448,000.
The MB-3A was a conventional wood and wire fabric-covered biplane powered with the 300 hp Wright Model H engine, an Americanized French Hispano-Suiza. General structural and aerodynamic configuration was heavily influenced by the French Spad fighter of 1916-18. Construction began early in 1921 and the final delivery was made on December 27, 1922. Some were fitted with two-blade propellers and others with four-blade, but the last 50 aeroplanes were fitted with entirely new tail surfaces of Army design. One model was built with special wings using four ailerons. The Army serial numbers for the MB-3As were the 68000 range while the MB-3 prototypes were 40092 to 40095 and the 50 MB-3s were 63331 to 63380. The Thomas-Morse models had the radiator in the centre section of the upper wing, but side radiators proved more efficient and the Boeing-built MB-3As were fitted with side radiators built by Thomas-Morse.
After a period of service as first-line fighters, many of the MB-3As were rebuilt by Fairfield Air Intermediate Depot (FAID) and sent to Kelly Field, Texas, where they were used as advanced trainers as late as 1927. Several, destined for the junk pile, were used as German fighters for crash scenes in the air-war film 'Wings', most of the flying sequences being taken near Kelly Field with Army co-operation.
TECHNICAL DATA - MB-3A
Accommodation: 1 pilot
Power plant: Wright H-3, 320 hp
Span: 26 ft 0 in
Length: 20 ft
Height: 7 ft 8 in
Wing area: 228 sq ft
Empty weight: 1,716 lb
Gross weight: 2,539 lb
Max speed: 140 mph
Cruising speed: 125 mph
Climb: 1,350 ft/min
Service ceiling: 19,500 ft
Armament: Two .30 cal MG
Army serial numbers: 68237/68436
W.Green, G.Swanborough The Complete Book of Fighters
THOMAS-MORSE MB-3 USA
Ordered by the US Army on the basis of a promised 150 mph (241 km/h) maximum speed and a 1,500 ft/min (7,62 m/sec) initial climb, the MB-3 designed by B Douglas Thomas was a single-seat unstaggered single-bay biplane of wooden construction with fabric covering. It featured intermediate interplane struts through which the flying and landing wires passed. Powered by a 300 hp Hispano-Suiza H eight-cylinder water-cooled Vee-type engine, the MB-3 carried an armament of two 0.3-in (7,62-mm) guns, the first of four prototypes entering flight test on 21 February 1919, and subsequently becoming the structural test article at McCook Field. Handling and manoeuvrability were adjudged excellent, but the small size of the cockpit and the poor view for the pilot that it offered were criticised, as was also the fuel system, the main tank developing leaks and tending to break through the fuselage after a few hours flying owing to inadequate structural support. The engine cooling system was inefficient and modifications - at some cost in performance - were necessary before, in June 1920, Thomas-Morse received a contract for 50 MB-3s powered by the licence-built Wright-Hispano H. An Army requirement for a further 200 aircraft was to be fulfilled (after competitive bidding) by Boeing, these aircraft being of the improved MB-3A model (radiators transferred from upper wing to fuselage sides, additional fuel and a 320 hp Wright-Hispano H-3 engine) and delivered between 29 July and 27 December 1922. These, like the production MB-3s, carried an armament of one 0.5-in (12,7-mm) and one 0.3-in (7,62-mm) gun rather than the twin guns of the smaller calibre mounted by the prototypes. The last 50 MB-3As were fitted with an entirely new tail unit (not retrofitted to earlier aircraft). Eleven MB-3s (not MB-3As) were ordered from Thomas-Morse by the US Navy for use by the Marine Corps, this contract being completed in February 1922. In November of the following year, the 10 surviving Marine MB-3s, having been in storage from July 1922, were “sold" to the Army and several were flown at Langley Field. The following data relate to the late-production MB-3A.
Max speed, 140 mph (225 km/h) at sea level, 138 mph (222 km/h) at 6,500 ft (1980 m).
Initial climb, 1,235 ft/min (6,27 m/sec).
Endurance, 2.25 hrs.
Empty weight, 1,716 lb (778 kg).
Loaded weight, 2,539 lb (1152 kg).
Span, 26 ft 0 in (7,92m).
Length, 20 ft 0 in (6,10 m).
Height, 8 ft 6 in (2,59 m).
Wing area, 228.55 sq ft (21,23 m2).