The Curtiss JN-4 was the main production version of the Curtiss Jenny, and was the most important American primary trainer during the First World War, and one of the main aircraft used by the barnstormers of the early 1920s. The first version was almost identical to the earlier JN-3, but during its production run it went through several major changes, which gave it more modern controls and a more powerful engine. The JN-4 was the only existing American design that was ordered into mass production after the US entry into the war in 1917.
In 1914 Curtiss had hired a British engineer, B. Douglas Thomas, who had designed the very similar Model J and Model N. When the Army ordered a batch of modified Model Js, the new design introduced enough features from the N for Curtiss to decide to call it the Model JN-2. This first production version had equal span wings, a shoulder yoke aileron control system and ailerons on both wings. Only eight were produced, all for the US Army.
The performance of the JN-2 was disappointed, so when the British RNAS ordered a batch of Jennies in March 1915 Curtiss produced the improved JN-3. This had unequal span wings (originally developed on the second Model J), with ailerons on the upper wing only, and the Deperdussin control system, which had a wheel for the ailerons and a foot bar for the rudder. The British eventually ordered over ninety JN-3s. The US Army also purchased two, and had its six surviving JN-2s brought up to a similar standard. These US JN-3s were amongst the few Jennies to see active service, taking part in Pershing’s Punitive Expedition to Mexico in 1916. However they didn’t perform well, and only one of the eight survived the experience.
In July 1916 Curtiss moved on to the JN-4. This was almost identical to the JN-3, with the same unequal span wings, ailerons on the upper wings only and Deperdussin control system. The British purchased about 105 JN-4s. The US Army purchased twenty one in six batches before the American entry into the war in April 1917. The JN-4 was also used by the Curtiss flying schools and some were sold to private owners.
The British figures are someone confused by the transfer of around 160 JN-3s, JN-4s and JN-4As from the RNAS to the RFC. These were given new RFC serial numbers, some of which were in the same combined system as the original RNAS numbers.
The JN-4A saw a series of modifications made to the design, in response to requests from Britain. This included a new tail, with larger horizontal and vertical surfaces (the vertical surface appears to have been slightly taller and more pointed), and new fuselage lines, both features which were also introduced on the JN-4B. The -4A also had ailerons on the upper and lower wings, which gave the lower wings pointed tips. The dihedral on the wings was increased from one degree to four degrees. A small section was cut out of the trailing edge of the upper wing just above the fuselage. The Curtiss OX-5 engine was given six degrees of downthrust.
The JN-4A later became the Model 1 in Curtiss’s 1935 designation system
A total of 781 JN-4As were built, starting in November 1916, making it the first really mass produced version of the aircraft. This included 601 for the US Army, 100 for the RNAS, 5 for the RFC and five for the US Navy. Some of these aircraft were built by Canadian Aeroplanes in Toronto – at least 87 although 97 serial numbers were assigned.
The JN-4B was produced at about the same time as the 4A, and may have slightly predated it. It had the same modified fuselage and tail as the JN-4A, but had the same engine installation and wings as the standard JN-4, including having ailerons on the upper wing only and a level mount for the engines. The JN-4B was sold to both military and civilian customers after it entered production late in 1916. The US Army purchased 76, and the US Navy nine – three from the Curtiss factory and six from the Curtiss Exhibition Company. The JN-4B also sold well on the civilian market. None appear to have gone to Britain.
The Curtiss built JN-4C must not be confused with the Canadian built JN-4Can ‘Canuck’. Curtiss built two JN-4Cs by modifying two JN-4Bs to use new wings with the RAF 6 aerofoil used on the Model N, and Curtiss OXX-3 dual-ignition engines. Both were purchased by the US Army in June 1917.
The JN-4D was the definitive version of the Jenny. It had the same fuselage and tail as the -4A and -4B and the downthrust engine position of the -4A. Although it isn’t mentioned in any texts, photographs of the -4D show that the prototype had tall exhaust pipes on either side of the fuselage, venting above the upper wing, while production aircraft had standard exhausts running along the side of the fuselage. The prototype had ailerons on both wings, but production aircraft only had them on the upper wing. There were small cut-outs on the trailing edge of both wings – above the fuselage on the upper wing, and on either side of it on the lower wing, to improve the view. Perhaps most importantly, the Deperdussin control system used on the JN-3 and earlier JN-4s was replaced with a control stick system that had been introduced on the Canadian built JN-4Can ‘Canuck’. The JN-4D first appeared in June 1917, and deliveries to the US Army began in November 1917 and continued until January 1919.
A total of 2,812 JN-4Ds were delivered to the US Army, and the type was produced by seven companies. Curtiss produced 1,401. Fowler Airplane Corp of San Francisco produced 50. The Liberty Iron Works of Sacramento received orders for 300, of which 200 were delivered. The Springfield Aircraft Co received orders for 975 in three batches, and delivered 585. The St. Louis Aircraft Company received orders for 650 and delivered 585. The US Aircraft Corp of Redwood City produced 50. Howell & Lesser of San Francisco received orders for 175 and built 75. Some of the Canadian built JN-4Cans were produced on JN-4D contracts.
Most of the cancelled orders would have been built as the modified JN-4D-2.
The JN-4D was the US Army’s main primary trainer in 1917-18. It was also the main type sold off after the war, and as a result the most common type during the ‘Jenny Era’.
The US Navy received three (serial numbers A995, A996 and A997).
This was to have been an improved version of the -4D, produced for the US Army. The main visible change was the return to a level engine position, eliminating the downthrust of the -4D. Other changes were largely internal and were generally minor improvements to the control system and the structure of the aircraft. One prototype was built, with the Army serial number 47816 and was delivered to the Army in September 1918. By that point orders for 1,100 aircraft had been placed with five firms (Curtiss, Liberty, Springfield, St Louis and US Aircraft). Some sources suggest that Liberty’s second batch (serial numbers 47415-47514) were built to the new standard, but this doesn’t really fit with the higher serial number for the prototype.
A small number of JN-4D-2s were sold on the civilian market after the war, but production ended early in 1919 when the type was replaced by the new Curtiss Oriole.
During 1917 the Army realised that it needed an advanced trainer. Instead of producing an entirely new design, it was decided to install a more powerful engine on the Curtiss JN-4. The original plan had been to produce one aircraft that could fill all of the advancing training needs, but it soon became clear that the JN-4H didn’t have enough power to cope with all of that equipment, so a number of specialist sub-variants were produced.
The JN-4H was powered by a 150hp Hispano-Suiza engine built under licence in the States by Wright. This was similar in size to the Curtiss OX-5, but did need a larger nose radiator, and some strengthening of the aircraft’s structure. Fuel capacity was increased from 21 gallons to 31 gallons, and on some aircraft an extra auxiliary fuel tank replaced the centre section of the upper wing. A total of 929 JN-4Hs were built, all by Curtiss, and were delivered between January 1918 and the Armistice.
The JN-4HT was the official designation given to 402 aircraft that were completed as dual control trainers. The Army was the original customer, but the Navy later acquired 203 of them from the War Department between 1918 and 1923, making them slightly the bigger user of the type post-war.
The JN-4HB was a bomber trainer, with the flight controls in the front seat and bomb racks that could carry five 25lb bombs under the fuselage. 100 were built, starting in June 1918.
The JN-4HG was a single-control gunner trainer, armed with a single Marlin machine gun or camera guns. The machine gun was synchronised to fire through the propeller (as on most standard fighters of the period). The camera gun would normally be mounted on top of the wing. The JN-4HG could also carry four one or two Lewis guns on a Scarff ring in the rear cockpit, giving it the standard layout of the main observation aircraft of the period. 427 were delivered, also starting in June 1918. The Navy got ninety of them in 1918 and built another aircraft from spares in 1923.
Curtiss JN-4Can ‘Canuck’
The JN-4 was also built in Canada, at a Toronto factory that had originally been owned by a Curtiss subsidiary (Curtiss Aeroplane and Motors Ltd), before being taken over by the Canadian Government. The new Canadian Aeroplanes Lt then built the JN-4, in a version that was named as the ‘Canuck’. This was produced in response to British requests for changes to the JN-3, and had ailerons on both wings, a revised metal frame tail, and British style stick controls in place of the Deperdussin system. The Canuck first flew in January 1917. Although it appeared half a year after the American JN-4, it kept the same designation and only became the JN-4Can after some went to the US.
Engine: Curtiss OX-5 inline
Crew: 2 pilots
Span: 43ft 7 3/8in
Length: 27ft 4in
Height: 9ft 10 5/8in
Empty weight: 1,390lb
Gross weight: 1,920lb
Maximum take-off weight:
Max speed: 75mph
Cruising speed: 60mph
Climb Rate: 2,000ft in 7.5 min
Service ceiling: 6,500ft
Engine: Wright-Hispano A
Crew: 2 (pilot and gunner)
Span: 43ft 7 3/8in
Length: 27ft 4in
Height: 9ft 10 5/8in
Empty weight: 1,625lb
Gross weight: 2,269lb
Maximum take-off weight:
Max speed: 91mph
Cruising speed: 75mph
Climb Rate: 2,000ft in 3.3 minutes
Service ceiling: 7,500ft
Armament: One fixed forward firing Marlin gun, one or two flexibly mounted Lewis guns