At the beginning of 1915 there appeared the prototype Curtiss Model R, which was in 1935 given the retrospective designation Model 2, an enlarged version of the Model N with equal-span staggered wings. The prototype with highly-staggered, equal-span wings and with single long cockpit for pilot and observer. Powered by 160 hp (119 kW) Curtiss V-X engine. It was flown both as a land-plane and float seaplane. Pilot and observer of this military reconnaissance biplane were housed in one long open cockpit and the Model R could be distinguished from the Model N by its inter-plane ailerons and lack of a fixed fin.

 

The initial production military utility series version were designated as R-2 introduced unequal-span wings with ailerons attached to the upper wing, a vertical tailplane which incorporated a fixed fin and horn-balanced rudder and there were separate and widely spaced cockpits for the two crew members. The Curtiss V-X engine of the prototype was retained. The R-2 went into production at the end of 1915 and was built in some numbers, 12 going to the US Army (AS64-75), making only limited use of the type. The US Army R-2s were flown in support of the expedition against the Mexican insurgent leader Pancho Villa, but although their serviceability was poor they flew a number of reconnaissance and liaison missions. One hundred were built for the Royal Navy Air Service.

 

The one-off R-2A was an equal-span variant and established an American domestic altitude record of 2740m, carrying pilot and three passengers, in August 1915. Two R-3 seaplanes, resembling the R-2 but with increased wing span, were brought by the US Navy in 1916.

 

The R-3 of 1917 was a USN reconnaissance twin-float development of the Model R with three-bay wings. Two were built as R-3, A66 and A67, and 11 or transfers to the Army, also as landplane, but somehow came off the assembly line as R-9s (AS33748, AS39033-39042).

 

The R-4 (Model 2) of 1917 were an Army ambulance version of the R-2. Fifty-five were converted (AS177-192, AS281-316, AS469, AS2157, and AS37923), plus 12 new-build with a 400hp Liberty 12 as R-4L (AS39362-39367, AS39954-39959). They were refitted with 360hp Liberty 12 engines (de-rated ex-USN motor) as R-4LM.

 

One R-6 Mailplane is recorded as transferred from military surplus for evaluation in air mail service, powered with a Curtiss V-2-3, 200hp.

 

The Model R-4LM were conversion of R-4L into mailplane for the US Army, with the front cockpit converted to a mail compartment with capacity for 400 lb (181 kg) of mail. Many were used after WW1 in air mail service.  

 

The Model 2 / R-6 were two-seat floatplane with long-span wings of R-3 but powered with Curtiss V-2-3 engine. Seventy-six (A162-197) were delivered to the US Navy plus twenty (A302-341, AS504-521, AS68563-68564) floatplanes and landplanes for US Army. They were used for torpedo-bomber trials post war.

 

Forty R-6 (A302-341) were converted to the Model 2 / R-6L with a 360 hp (269 kW) Liberty L-12 engine, plus 122 (A873-994) were built new in 1918.

 

 

Curtiss R-2

Engine: 1 x 160 hp / 119kW Curtiss V-X inline piston

Wingspan: 14.00 m / 45 ft 11 in

Length: 11.70 m / 38 ft 5 in

Wing area: 46.90 sq.m / 504.83 sq ft

Height: 14 ft 4⅜ in (7.43 m)

Take-off weight: 1403 kg / 3093 lb

Empty weight: 826 kg / 1821 lb

Max. speed: 138 km/h / 86 mph

Range: 558 miles (900 km)

Endurance: 6 hours 42 min

Seats: 2

 

R-3 / R-9

Engine: 200hp Curtiss V-2 (also V-X)

Wingspan: 57 ft 1 in

Length: 33'5"

Speed: 83 mph

Seats: 2

Undercarriage: twin-float

 

2 / R-4

Engine: 200hp Curtiss V-2-3, 200 hp (149 kW)

Wingspan: 48'4"

Length: 29'0"

Useful load: 1047 lb

Speed: 90 mph

 

2 / R-4LM

Engine: 360hp Liberty 12

Wingspan: 48'4"

Length: 29'0"

Mail compartment capacity: 400 lb (181 kg)

 

2 / R-6

Engine: Curtiss V-2-3, 200 hp (149 kW)

Wingspan: 57'1"

Length: 33'5"

Useful load: 2149 lb

Max speed: 104 mph

Cruise speed: 82 mph

Stall: 53 mph

Range: 368 mi

Seats: 2

 

R-6 Mailplane

1919

Engine: Curtiss V-2-3, 200hp

Seats: 1

 

R-6L

Undercarriage: Twin-float

Engine: 360hp Liberty 12

Wingspan: 57'0"

Max speed: 104 mph

Cruse speed: 92 mph

Stall: 56 mph

Range: 368 mi

Ceiling: 9,900 ft