The Curtiss JN-4 "Jenny" was one of a series of "JN" biplanes built by the Curtiss Aeroplane Company of Hammondsport, New York, later the Curtiss Aeroplane and Motor Company. Although the Curtiss JN series was originally produced as a training aircraft for the US Army, the "Jenny" (the common nickname derived from "JN-4", with an open-topped four appearing as a Y) continued after World War I as a civil aircraft, as it became the "backbone of American postwar [civil] aviation."
Thousands of surplus Jennys were sold at bargain prices to private owners in the years after the war and became central to the barnstorming era that helped awaken the US to civil aviation through much of the 1920s.
The JN-2 was an equal-span biplane with ailerons controlled by a shoulder yoke in the aft cockpit. It was deficient in performance, particularly climbing, because of excessive weight. The improved JN-3 incorporated unequal spans with ailerons only on the upper wings, controlled by a wheel. In addition, a foot bar was added to control the rudder.
Curtiss JN-3, the progenitor of the JN-4, deployed to Mexico, around 1916
The 1st Aero Squadron of the Aviation Section, US Signal Corps received eight JN-2s at San Diego in July 1915. The squadron was transferred to Fort Sill, Oklahoma, in August to work with the Field Artillery School, during which one JN-2 crashed, resulting in a fatality. The pilots of the squadron met with its commander, Capt. Benjamin Foulois, to advise that the JN-2 was unsafe because of low power, shoddy construction, lack of stability, and overly sensitive rudder. Foulois and his executive officer Capt. Thomas D. Milling disagreed, and flights continued until a second JN-2 crashed in early September, resulting in the grounding of the six remaining JN-2s until mid-October. When two new JN-3s were delivered, the grounded aircraft were then upgraded in accordance with the new design. In March 1916, these eight JN-3s were deployed to Mexico for aerial observation during the Pancho Villa Expedition of 1916-1917.
After the successful deployment of the JN-3, Curtiss produced a development, known as the JN-4, with orders from both the US Army and an order in December 1916 from the Royal Flying Corps for a training aircraft to be based in Canada.[N 1] The Canadian version, the JN-4 (Canadian), also known as the "Canuck", had some differences from the American version, including a lighter airframe, ailerons on both wings, a bigger and more rounded rudder, and differently shaped wings, stabilizer, and elevators.
As many as 12 JN-4 aircraft were fitted with an aftermarket Sikorsky wing by the then fledgling company in the late 1920s.
Curtiss JN-4Ds at Camp Taliaferro, Texas, circa 1918
The Curtiss JN-4 is possibly North America's most famous World War I aircraft. It was widely used during World War I to train beginning pilots, with an estimated 95% of all trainees having flown a JN-4. The US version was called "Jenny", a derivation from its official designation. It was a twin-seat (student in front of instructor) dual-control biplane. Its tractor propeller and maneuverability made it ideal for initial pilot training with a 90 hp (67 kW) Curtiss OX-5V8 engine giving a top speed of 75 mph (121 km/h) and a service ceiling of 6,500 ft (2,000 m). The British used the JN-4 (Canadian), along with the Avro 504, for their primary World War I trainer using the Canadian Aeroplanes Ltd. indigenous variant. Many Royal Flying Corps pilots earned their wings on the JN-4, both in Ontario and later in winter facilities at Camp Taliaferro, Texas.
Converted JN-4 ambulance, operated by the Camp Taliaferro medical teams, around 1918
Although ostensibly a training aircraft, the Jenny was extensively modified while in service to undertake additional roles. Due to its robust but easily adapted structure able to be modified with ski undercarriage, the Canadian Jenny was flown year-round, even in inclement weather. The removable turtle-deck behind the cockpits allowed for conversion to stretcher or additional supplies and equipment storage, with the modified JN-4s becoming the first aerial ambulances, carrying out this role both during wartime and in later years. Most of the 6,813 Jennys built were unarmed, although some had machine guns and bomb racks for advanced training. With deployment limited to North American bases, none saw combat service in World War I.
The Curtiss factory in Buffalo, New York, was the largest such facility in the world, but due to production demands, from November 1917 to January 1919, six different manufacturers were involved in production of the definitive JN-4D. Production from spare or reconditioned parts continued sporadically until 1927, although most of the final orders were destined for the civil market in Canada and the United States.
Like the re-engined JN-4H version of the most-produced JN-4 subtype, the final production version of the aircraft was the JN-6, powered by a Wright Aeronautical license-built, 150-hp (112-kW) Hispano-Suiza 8 V-8, first ordered in 1918 for the US Navy. A floatplane version was built for the navy which was so modified, it was essentially a different airframe. This was designated the N-9. In US Army Air Service usage, the JN-4s and JN-6s were configured to the JNS ("S" for "standardized") model. The Jenny remained in service with the US Army until 1927.
One of the many daredevil stunts performed by JN-4 pilots was to work with a "wingwalker".
After World War I, thousands were sold on the civilian market, including one to Charles Lindbergh in May 1923, in which he then soloed. Surplus US Army aircraft were sold (some still in their unopened packing crates) for as little as $50, flooding the market.[N 2] With private and commercial flying in North America unhampered by regulations concerning their use, pilots found the Jenny's stability and slow speed made it ideal for stunt flying and aerobatic displays in the barnstorming era between the world wars, with the nearly identical Standard J-1 aircraft often used alongside it. [N 3] Some were still flying into the 1930s.[N 4]
Between 1917 and 1919, the JN-4 type accounted for several significant aviation firsts while in service with the US Army Signal Corps Aviation Section and the United States Marine Corps (USMC) including flying the first US Air Mail in May 1918.
In a series of tests conducted at the US Army's Langley Field in Hampton, Virginia, in July and August 1917, the world's first "plane-to-plane" and "ground-to-plane, and vice versa" communications by radiotelephony (as opposed to radiotelegraphy which had been developed earlier) were made to and from modified US Army JN-4s[N 5] by Western Electric Company (Bell Labs) design engineers Lewis M. Clement and Raymond Heising, the developers of the experimental wind generator-powered airborne wireless voice transmitter and receiver equipment.
In early 1919, a United States Marine Corps (USMC) JN-4 was also credited with what is believed to be the first successful dive bombing attack during the United States occupation of Haiti. USMC pilot Lt Lawson H. Sanderson mounted a carbine barrel in front of the windshield of his JN-4 (previously, an unarmed trainer that had a machine gun mounted in the rear cockpit) as an improvised bomb sight that was lined up with the long axis of his aircraft, loaded a bomb in a canvas mail bag that was attached to the JN-4's belly, and launched a single-handed raid at treetop level, in support of a USMC unit that had been trapped by Haitian Cacos rebels. Although the JN-4 almost disintegrated in the pullout, the attack was effective and led to Sanderson in 1920 developing further dive-bombing techniques to provide Marine pilots with close aerial support to infantry comrades.
A JN-4 C227 "Canuck" (USAAS #39158) operated by the US Air Army Air Service in 1918, is now restored and on display at the Canada Aviation and Space Museum.
Although the first series of JN-4s were virtually identical to the JN-3, the JN-4 series was based on production orders from 1915-1919.
JN-4A -- production version of the JN-4, 781 built
JN-4B -- This version was powered by an OX-2 piston engine; 76 were built for the US Army, and nine for the US Navy.
JN-4C -- experimental version, only two were built
JN-4 (Canadian) Canuck -- Canadian-built version, 1,260 built by Canadian Aeroplanes Ltd. for the RFC in Canada/RAF in Canada and USAAC: Independently derived from the JN-3, it had a lighter airframe, ailerons on both wings, a bigger and more rounded rudder, and differently shaped wings, stabilizer, and elevators. Its use by the USAAC was curtailed as the lighter structure was claimed to cause more accidents than the US-built aircraft, although no air fatalities were attributed to the structural integrity of the type.
JN-4D -- improved version, adopting the control stick from the JN-4 (Canadian) 2,812 built
JN-4D-2 -- One prototype only, the engine mount was revised to eliminate the down thrust position.
JN-4H -- two-seat advanced trainer biplane with ailerons on both wings, 929 built for the US Army, notable for introducing the use of the Wright Aeronautical license-built Hispano-Suiza 8 V-8 engine for greater power and reliability
JN-4HT -- two-seat, dual-control trainer version
JN-4HB -- bombing trainer version
JN-4HG -- gunnery trainer version
JN-4HM -- communications conversion of JN-4HT, powered by Wright-Hisso E 150-hp (112-kW), six converted, used to fly the first US Air Mail (May-August, 1918)
JN-5H -- advanced trainer biplane, only one built
JN-6 -- improved version of JN-5 trainer biplane series, notably used four ailerons, 1,035 built for the US Army and five for the US Navy
JN-6H -- improved version of the JN-6
JN-6BH -- bomber trainer version
JN-6HG-1 -- two-seat, dual-control trainer version, 560 built from JN-6 production, 34 for US Navy
Ericson Special Three -- Some reconditioned aircraft built by Canadian Aeroplanes Ltd. were fitted with a third cockpit.
Hennessey Monoplane --  a 1926 monoplane conversion by James R. Hennessey, three-place transport, 90-hp Curtiss OX-5, span: 36 ft (11 m) length: 25 ft (7.6 m)
Severski 1926 biplane -- a JN-4 modified with a roller/ski undercarriage, one experimental aircraft converted by the Seversky company[N 7]
Sperry Monoplane -- conversion offered by the Sperry Company that mounted a parasol wing in place of the biplane configuration
Twin JN -- An enlarged twin-engined version of the JN-4, they were powered by two OXX-2 V-8 engines, built in 1916 as the JN-5 for an observation role; among the many other modifications was an enlarged wingspan and new rudder adapted from the Curtiss Model R-4. Two of the series saw action with the US Army on the Mexican border in 1916-1917. A total of eight Twin JNs were built, with two in US Navy service.
5368 - JN-4D on static display at the Museum of Science and Industry in Chicago, Illinois. It is displayed upside down next to a wraparound balcony, and details of the cockpit can readily be seen. This airframe was built in 1917. It was cleaned and reskinned by Century Aviation in 2006.
6200 - JN-4D being restored for flight by Ranger Airfield Foundation in Ranger, Texas.
Unknown ID - JN-4 on static display at the Cradle of Aviation Museum in Garden City, New York. This airframe is the aircraft owned by Charles Lindbergh in which he barnstormed long before his transatlantic flight. Lindbergh purchased this aircraft in Americus, Georgia, for $500 in May 1923, and sold it to his flying student in Iowa the following October. It was restored by the late George Dade in the 1970s and is on loan from the Long Island Early Fliers Club.
Unknown ID - JN-4 on static display in unskinned condition at the Cradle of Aviation Museum in Garden City, New York.
Time to altitude: 2,000 ft (610 m) in 7 minutes 30 seconds
In popular culture
The "Inverted Jenny" stamp
"Inverted Jenny" (C-3a P57)
The "Inverted Jenny" (C-3a) is a 24-cent 1918 US Air Mail postage stamp printing error in which the blue central vignette of US Army Curtiss JN-4HM #38262, the nation's first mailplane, appeared as "inverted" on a single sheet of 100 stamps owing to an inadvertent error made by the operator of a hand-rolled spider press by printing the blue vignette impressions upside down after the red frames had previously been printed on the sheet. As the Jenny vignette was only inverted on one sheet, this stamp represents the rarest and most valuable known USPOD printing error of all time. A single example (sheet position 57) sold at auction in 2007 for $977,500.00.
Notable appearances in media
In 1921, Lee De Forest made a short filmFlying Jenny Airplane in his Phonofilmsound-on-film process. The film depicted a JN-4 flying, and recorded the sound of the Jenny, as well. The short documentary was the first production of the De Forest Phonofilm company.
This 1917 Curtiss Jenny still flies on occasion. Its home base is the Call Memorial Museum in Wichita Falls, Texas.
^Both the US Army version and the Canadian derivative for the Royal Flying Corps were known as JN-4s. To differentiate between the types, unofficially, the RFC designation was the JN-4 (Canadian).
^Surplus JN-4s typically fetched between $200 and $500, depending on condition.
^The front cockpit that was normally for the student in military training was usually used for passengers in postwar joy rides, so the pilot could keep an eye on his paying customer/s.
^The JN-4 Canuck was often chosen for barnstorming as the lighter, more responsive, and more economical variant was also in large supply.
^Quote: "A JN-4-d plane was used; speed was successful, transmitting about 3 miles from plane to plane and was also received from ground to plane, and vice versa." 
^Stinson's aircraft built to her specifications was used for fundraising tours for the American Red Cross. During exhibition flights in Canada, she set a Canadian distance and endurance record, and made the second air mail flight in Canada between Calgary and Edmonton, Alberta. A replica is at the Alberta Aviation Museum.
^"Report of the Chief Signal Officer to the Secretary of War, October 15, 1919". Annual Report, War Department, 1919, pp. 262-263.
^"Handwritten letter, dated August 18, 1917, from Western Electric Co (Bell Labs) design engineer Lewis M. Clement to Vesta L. Clement, his wife, with a detailed first-person account of the first successful test of 'plane-to-plane' and 'plane-to-ground' radiotelephony from JN-4-d airplanes in flight conducted that day at Langley Field, VA." The Cooper Collection of U.S. Aviation History (Private collection: original letter location), Ardmore, Pennsylvania.