The Curtiss flying boat the HS-2L was used extensively in the war for anti-submarine patrols. Bases were built in Nova Scotia, France and Portugal for the purpose.
Standard Aircraft Corp contract-built 350 Curtiss HS-2L USN flying boats.
Designed by the US Army Engineering Division as a specialised single-seat night fighter, two prototypes of the PN-1 were built by Curtiss, powered by the 220hp Liberty L-825 six-cylinder water-cooled engine. Optimised for docile handling characteristics at the lower end of the speed range in order to ease operation from small blacked-out fields, the PN-1 was completed without interplane struts, but steel-tube N-struts were introduced to improve torsional stiffness before any attempt to fly the first prototype. Only one PN-1 was completed, and the results of any flight testing are not on record. It is known, however, that the sole prototype was used for static tests at McCook Field during 1921.
Take-off weight: 1048 kg / 2310 lb
Empty weight: 740 kg / 1631 lb
Wingspan: 9.40 m / 30 ft 10 in
Length: 7.16 m / 23 ft 6 in
Height: 3.12 m / 10 ft 3 in
Wing area: 27.87 sq.m / 299.99 sq ft
Max. speed: 174 km/h / 108 mph
Range: 410 km / 255 miles
The first single-seat fighter of indigenous US design to achieve production status, the Model D was conceived around the 300hp Hispano-Suiza H eight-cylinder water-cooled engine. The first of four prototypes built by the Ordnance Engineering Corporation (Orenco) was completed in January 1919. Curtiss was assigned a production contract for 50 aircraft and undertook some redesign. This included the introduction of dihedral and overhanging, balanced ailerons, and revision of the engine installation. Of wooden construction with plycovered fuselage and fabric-covered wings, the Curtiss-built Model D utilised a 330hp Wright-built derivative of the Hispano-Suiza and carried an armament of two 7.62mm machine guns. Deliveries commencing in August 1921.
One Model D was experimentally fitted with French Lamblin radiators attached to the fuselage sides, and another was fitted with a turbo-supercharger for high altitude trials.
Take-off weight: 1279 kg / 2820 lb
Empty weight: 865 kg / 1907 lb
Wingspan: 10.05 m / 32 ft 12 in
Length: 6.54 m / 21 ft 5 in
Height: 2.54 m / 8 ft 4 in
Wing area: 25.36 sq.m / 272.97 sq ft
Max. speed: 224 km/h / 139 mph
US Army interest in the 18-T prompted Curtiss to offer the same basic design in two-bay biplane configuration, and an order was placed by the US Army for two examples in August 1918. Known unofficially as the “Hornet”, the 18-B two-seat fighter employed an identical fuselage to that of the 18-T and a similar Curtiss- Kirkham K-12 engine. The proposed armament comprised two forward-firing Marlin guns and two Lewis guns on a flexible mount. The two prototypes were delivered to the US Army during the summer of 1919, AS40058 and AS40064, one being confined to static testing and the other crashing shortly after the commencement of flight trials. Further development was then abandoned.
Photo above clearly shows a tail number of “40054,” but all recorded registrations have that number as the 18T triplane.
Engine: Kirkham K-12, 400hp
Wingspan: 11.41 m / 37 ft 5 in
Length: 7.11 m / 23 ft 4 in
Wing area: 28.43 sq.m / 306.02 sq ft
Take-off weight: 1300 kg / 2866 lb
Empty weight: 767 kg / 1691 lb
Useful load: 1177 lb
Max. speed: 257 km/h / 160 mph
Seats: 2
Designed by Charles B Kirkham, the Curtiss 18-T two-seat fighter triplane was ordered by the US Navy on 30 March 1918 when a contract was placed for two prototypes. The first (AS40065) was flown on 7 May 1918. Designed around the Curtiss-Kirkham K-12 water-cooled 12-cylinder engine of 350 hp and four-blade prop, the 18-T was a clean aerodynamic design by contemporary standards and featured a monocoque three-ply fuselage and side radiators positioned between the lower wings. The proposed armament was two forward-firing synchronized 7.62mm Marlin machine guns and two 7.62mm Lewis guns on a Scarff mounting in the rear cockpit.
The 18-T initially suffered some tail heaviness which was corrected by applying five degrees of sweepback to the wings for further trials. A max speed of 262km/h was achieved with full military load in August 1918, the 18-T being acclaimed as the world’s fastest aeroplane as a result.
The US Navy promptly ordered two examples, the first (A3325) of which was delivered in February 1919 with a single float undercarriage.
In the summer of 1919, the first Army prototype (AS40054) was fitted with longer-span two-bay wings, these having a span and area of 12.38m and 37.16sq.m respectively and 5° of sweepback were added, and in this form the aircraft became the 18T-2 (A3326), the short-span version becoming the 18T-1 (AS40059). The 18T-2 established a world altitude record of 34,610 ft / 10640m on 18 September 1919 (pilot Roland Rohlfs), and a second 18T-2 was built by Curtiss for export to Bolivia, where it arrived in 1920.
Both Navy ships, used as land racers, crashed at the 1923 NARs.
18T-1
Engine: Curtiss-Kirkham K-12, 350 hp
Wingspan: 9.70 m / 31 ft 10 in
Length: 7.11 m / 23 ft 4 in
Height: 3.02 m / 9 ft 11 in
Wing area: 26.76 sq.m / 288.04 sq ft
Take-off weight: 1383 kg / 3049 lb
Empty weight: 898 kg / 1980 lb
Max. speed: 265 km/h / 165 mph
Cruise speed: 145 mph
Stall: 58 mph
Ceiling: 22,000 ft
Seats: 2
18T-2
Engine: Curtiss D-12, 400hp
Wingspan: 40 ft 7 in
Length: 28 ft 3 in
Speed: 139 mph
Ceiling: 21,000 ft
Designed by Capt B L Smith of the US Marine Corps as a two-seat patrol fighter floatplane for use in the Dunkirk-Calais area, the HA – known unofficially as the “Dunkirk Fighter” – was intended to combat the Brandenburg float fighters. The HA was built at the experimental plant of the Curtiss Engineering Corporation. Of conventional wooden construction with fabric skinning, the HA was powered by a 425hp Liberty 12 engine and proposed armament was two synchronized 7.62mm Marlin machine guns and two Lewis guns of the same calibre on a Scarff mounting in the rear cockpit.
The HA was flown for the first time on 21 March 1918, but was found to be unstable longitudinally and seriously tail heavy. The initial test terminated in a crash. Curtiss was then awarded a contract for two further prototypes, the first of which, the HA-1, utilized salvaged components from the original HA and featured revised vertical tail surfaces, an annular-type radiator and relocated wings. The HA-1 demonstrated appreciably improved handling qualities, but was written off after a fire in the air. The third HA prototype, the HA-2, differed appreciably from the HA-1.
The third HA float fighter prototype embodied considerable redesign as the HA-2. Powered by a 12- cylinder Liberty 12 water-cooled engine, like the preceding prototypes, the HA-2 had longer-span wings of marginally increased chord and gap, the upper wing being raised clear of the fuselage, the decking of which was lowered. The radiator was redesigned, but cooling problems were encountered and although the HA-2 proved more docile than the lighter HA-1, it possessed insufficient promise to warrant further development.
HA-1
Take-off weight: 1634 kg / 3602 lb
Empty weight: 1111 kg / 2449 lb
Wingspan: 10.97 m / 35 ft 12 in
Length: 9.37 m / 30 ft 9 in
Height: 3.23 m / 10 ft 7 in
Wing area: 35.95 sq.m / 386.96 sq ft
Max. speed: 203 km/h / 126 mph
HA-2
Take-off weight: 1772 kg / 3907 lb
Empty weight: 1336 kg / 2 lb
Wingspan: 12.80 m / 41 ft 12 in
Length: 9.37 m / 30 ft 9 in
Height: 3.48 m / 11 ft 5 in
Wing area: 45.52 sq.m / 489.97 sq ft
Max. speed: 190 km/h / 118 mph
The CB (Curtiss Battleplane), unofficially known as the “Liberty Battler”, was an experimental two-seat fighter developed and flown early in 1918 as a result of difficulties being experienced with the Liberty-engined version of the Bristol F2B. Powered by a 425hp 12-cylinder Liberty 12 water-cooled engine, the CB two-bay biplane was of “Curtiss ply” construction – two layers of 5cm wide wood veneer being cross-laminated over a form to build up a monocoque fuselage shell. In an effort to maintain fuselage streamlining, the radiators were slung under the upper wing centre section, where they were found to have a seriously detrimental effect on the airflow. The fairing of the upper wing into the top fuselage contour resulted in a very narrow wing gap, with consequent aerodynamic penalties. While it provided the rear gunner with an excellent field of fire, it impaired the forward and downward view of the pilot, necessitating the provision of small windows in the fuselage sides. Flown in May 1918, the sole prototype CB proved to have extremely poor handling characteristics and crashed early in its test programme.
Empty weight: 1622 kg / 3576 lb
Wingspan: 11.98 m / 39 ft 4 in
Length: 8.25 m / 27 ft 1 in
During 1917, the US Navy issued the Curtiss company with a contract for five single-seat fighting scout float seaplanes powered by a US-built version of the 100hp Gnome nine-cylinder rotary, the GS designation indicating “Gnome Scout”. These were completed under the designation GS-2 when a supplementary contract was issued for a sixth aeroplane which was assigned the designation GS-1. The GS-1 was a single-seat triplane with a single central float and outrigger stabilizing floats which drew heavily on Curtiss S-3 experience. The GS introduced shock absorbers in the struts between the fuselage and the central float. These resulted in the float angle changing at high speed on the water and producing an undesirable porpoising. Delivered to the US Navy early in 1918, the GS-1 was flown several times by US Navy acceptance pilots, but was eventually damaged beyond repair as a result of a heavy landing. The five similarly-powered GS-2s differed from the GS-1 primarily in being of biplane configuration, but little is recorded of these aircraft apart from the fact that they suffered from tail heaviness.
A refined version of the S-3 with revised strutting carrying the centre section of the upper wing and the root attachments of the centre wing, a modified undercarriage and other changes. The S-6 triplane of 1917 was the first US “scout” to be fitted with twin forward-firing machine guns, these being gas-operated Lewis guns (which were mounted side-by-side on inverted and inclined “V” struts immediately beneath the centre section of the upper wing and firing outside the propeller disc.
Only a single example of the S-6 was built and tested.
Take-off weight: 625 kg / 1378 lb
Wingspan: 7.62 m / 25 ft 0 in
Length: 5.94 m / 19 ft 6 in
Height: 2.62 m / 8 ft 7 in
Wing area: 13.25 sq.m / 142.62 sq ft
Max. speed: 177 km/h / 110 mph
The only ‘production’ models of the S-series were four S-3 (Model 10) triplanes sold to the US Army early in 1917 (serial numbers 322 to 325). These used the basic fuselage, engine, and tail of the S and S-2 fitted with single-bay triplane wings using the RAF 6 aerofoil. These were the Army’s first single-seat Scouts, but they were still more than two years behind equivalent European types.
Essentially a triplane derivative of the S-2 “Wireless” (signifying lack of wing bracing wires) unarmed biplane “scout”, the S-3, or “Triplane Speed Scout”, possessed a similar fuselage and 100hp Curtiss OXX-3 engine, and initially retained the ducted propeller spinner featured by the biplane. Interplane bracing employed “K”-type struts and, on its second flight during the summer of 1917, the S-3 attained an altitude of 5030m, which was a record at the time. For initial trials, the centre wing was attached to the fuselage at low shoulder position, but the gap between all three wings was subsequently increased and the centre wing was raised above the fuselage.
Several modifications included smaller span, and all three planes equal. The body is of better streamline form, and the chassis struts are arched.
After redesign of the rudder and the discarding of the ducted spinner, the S-3 successfully completed evaluation trials and four were ordered during the course of 1917 for the US Army Signal Corps. It was proposed to arm the S-3 with two unsynchronised Lewis guns which were to fire over the propeller arc, but the S-3s were delivered to the Signal Corps without armament.
The four US Army Curtiss S-3s of early 1917 carried the new US national aeroplane markings but did not carry guns although they were classified as Scouts, which was synonymous with Pursuit at the time.
In 1918 and 1919, Curtiss experimented with seaplane versions of the S-3, designated S-4 and S-5.
The S-4 (Model 10A) was a triplane similar to the S-3 intended as a seaplane Scout for the US Navy (serial A149). Although tested as a land plane, the S-4 was intended to be a seaplane and had longer wings than the similar S-3 to carry the weight or the floats. This was Curtiss’s first experience with the twin-float configuration.
As with other Curtiss seaplanes, it became necessary to increase the span of the S-4 to carry the extra weight. The front float struts collapsed during a heavy alighting in January 1918 and the aircraft was struck off charge.
The S-5 Model 10B seaplane version was similar to the S-4 except for being fined with a single main float and small wingtip floats. Navy serial number A150, struck off on 6 August, 1919.
The S-6 (Model 10C) was an improved version of the S-3 and was the first American Scout fitted with twin forward-firing machine-guns. This may have been only an inoperative test installation intended to check weight, balance, and location, for the guns were gas-operated Lewis models which were not used for synchronized fire through the propeller. The sole Curtiss S-6 was flown in 1917 and was slightly larger than the S-3. The Army ordered twelve early in 1917 but only one, serial number 492, was delivered.
The S-6 triplane had revised strutting carrying the centre section of the upper wing and the root attachments of the centre wing, a modified undercarriage and other changes.
S-3
Engine: Curtiss OXX-3, 100 hp
Wingspan: 7.62 m / 25 ft 0 in
Wing area: 13.25 sq.m / 142.62 sq ft
Chord: 24 ins
Wing gap: 28 ins Length: 5.94 m / 19 ft 6 in
Length: 19 ft 6 in (5.94 m)
Height: 2.62 m / 8 ft 7 in
Take-off weight: 599 kg / 1321 lb
Empty weight: 440 kg / 970 lb
Max. speed: 185 km/h / 115 mph / 100 kn
Service ceiling: 16,500 ft (5,029 m)
Climb, 10,000 ft. in 10 mins
Crew: 1
S-6
Take-off weight: 625 kg / 1378 lb
Wingspan: 7.62 m / 25 ft 0 in
Length: 5.94 m / 19 ft 6 in
Height: 2.62 m / 8 ft 7 in
Wing area: 13.25 sq.m / 142.62 sq ft
Max. speed: 177 km/h / 110 mph
