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June 2016 Mystery Airplane – The Curtiss Model “N” Military Tractor

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The Curtiss Model “N” military tractor which has found great favor both here and abroad.  A Squadron of eight of these craft have just been ordered by the U. S. Army.

The first correct identification of VAA’s June Mystery Plane was submitted by Ulrich Rist. Wayne Muxlow, Ed Cook and Frank Nichols also submitted correct answers.

An article describing the newly introduced Curtiss Model N Tractor Trainer appeared in the March 29, 1915 issue of AERIAL AGE WEEKLY.   A reprint of this article appears below.

In his reply Ulrich Rist referred to an article about the Model N that appeared in VAA’s May 1980 issue of  THE VINTAGE AIRPLANE magazine.  This article, titled “A Curtiss Album” by George Hardie, Jr., a former editor of the magazine, is reprinted below.

And to further illustrate the evolution of the Curtiss N, with the Model J, is a reprint of Peter M. Bowers’ “Jenny’s Younger Sister’ which sheds  light on the remarkable development of this series of Curtiss aircraft.

(The following is a reprint of an article that appeared in the March 29, 1915 issue of AERIAL AGE WEEKLY)

The Curtiss Model “N” Military Tractor

By Walter H. Phipps

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Raymond V. Morris flying the Model “N” in successful tests at San Diego.

In view of the great work being accomplished by the new Curtiss Model “N” military tractors abroad and the fact that the Curtiss Aeroplane Company has just received an order for a squadron of eight of the latest model “N” types for the U. S. Army, particular interest attaches to this type of machine.

The splendid achievements of the new Curtiss land and water planes in the European war has demonstrated conclusively the worth of American machines as compared with the best European types.  The accompanying photographs and description of the new model “N” will show why this is the case:

Model “N” tractor is arranged for pilot and observer, seated in tandem, and is equipped with double controls so that either man may take charge.  With Curtiss model O-X 90-100 h.p. motor it has an extreme flying range of from less than forty to more than eighty miles per hour.  Carrying two men and four hours’ fuel its speed range is from 45 to 75 miles per hour.

Wings

The wings of the model “N” type are of latest approved section: one-piece type.  Wing frames are built up carefully of ash and spruce, with beams shaped and groved by hand, important joints copper strapped, the whole securely stayed with piano wire.  Covers are of unbleached linen, thoroughly coated with Curtiss Aero varnishes.  The wings have a spread of 32 feet, for both the upper and lower surfaces:  the area of lifting surface is approximately 350 square feet.

Fuselage

The fuselage is of rectangular section, 26 inches wide by 35 inches high at the cockpit, tapering to nothing at the rudder.  The longerons are ash strips 1 ¼ inches in diameter, tapering to 1 inch.  The fuselage is corner braced with 9 sets of struts, which are joined with corner clamps without piercing the longerons.  Each section is cross-wired in three directions.  The third and fourth vertical struts are placed so as to act as wing struts, and they have extensions running to the upper surface.

The streamline effect is preserved throughout by enclosing the front of the fuselage, with motor and mountings, in a cowl of Duralumin, slotted to admit air to the motor.  Streamline cowls protect the cockpits, and deflect the wind from the pilots as well as shield from the weather, the dashboards on which the instruments are mounted.  Behind the cockpits the fuselage is covered with waterproofed linen.

The Curtiss Model “N” Military Trainer

The Curtiss Model “N” Military Trainer

Motor Installation

The Curtiss Model O-X motor mounted on engine beds of laminated ash and spruce 2 inches by 3 inches.  It is fastened in front to a plate of 3-32 inch steel, which joins the longerons and also carries the radiator.  The rear ends of the engine beds are mounted on a hardwood cross member framed into the second pan of vertical struts of extra size.

Landing Gear

The fuselage is supported by an undercarriage consisting of two supporting struts on each side, borne on two streamlined wire wheels. The tires are 26 inches by 5 inches.  Wheels are attached with rubber band shock absorbers.  Protection from an upset in case of an unusually hard landing is afforded by two white oak skids, six feet long, turned up in front:  they also help shield the propeller.  The tail skid is of white oak and sprung on with rubber bands.

Controls

Single acting turn-up ailerons are attached to the trailing edge of the upper and lower surfaces. The vertical rudder has an area of 30 inches by 36 inches, is well secured to the stern-post, and is double wired.  Horizontal rudders, or flippers, have an area of 16 square feet.  Either the Curtiss system of control, consisting of shoulder yoke and steering wheel, or the Deperdussin system, with foot-bar, is to be provided.

Dimensions

Span Top—32 feet

Span bottom—32 feet

Chord—5 feet

Gap—5 1-2 feet

Area—320 square feet

Length Over All—24 feet

Landing Gear—Two Wheel Curtiss with tail skid

Lateral Control—Ailerons between Beams

Fuel Capacity—32 gallons

Propeller—Curtiss 8 feet 4 inches by 5 1-2 feet

Propeller Position—Tractor

Speed Range Loaded—40–80 M.P.H.

Climbing Speed—4000 in 10 minutes

Gliding Angle—1 in 6

Useful Load—Pilot and passenger, 4 hours fuel and extras—500 lbs.

Weight of Machine Loaded—1800 pounds

Load per Square Foot of Surface—5.6 pounds

(The following is a reprint of an article that appeared in the May 1980 issue of THE VINTAGE AIRPLANE)

A Curtiss Album

By George Hardie, Jr., EAA #500, EAA Historian

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Glenn Curtiss on a test flight in the Model J—Hammondsport, N. Y., 1914

Probably the best known of all Curtiss airplanes is the famous (or infamous) Jenny.  Designed as a military aircraft, it became a legend through its use by barnstorming pilots in introducing aviation to the American public in the 1920’s.  Many pilots who later attained fame—Lindbergh, Doolittle, Wittman and many others—learned to fly in Jennies

The type originated in 1914 as the Curtiss Model J designed by B. D. Thomas, an Englishman who had been hired by Glenn Curtiss.  Curtiss decided he had to acquire an engineer with experience on tractor-type airplanes to establish a line of military aircraft to meet government demands.  The Model N appeared in 1915 as a further effort to improve this line.  Both the J and the N were two-place tandem-seat- biplanes.  The J was powered with the 90 hp Curtiss OX engine and the N with the 100 hp OXX.

The first JN model, combining the best features of the J and N, was the JN-2.  What was more natural than to adopt the name “Jenny” to refer to the JN model..  The name stuck, and was applied to the period after World War I as “The Jenny Era”, arising from the widespread use of the type by barnstorming pilots all over the country.

A Model N “military tractor” March 1915.

A Model N “military tractor” March 1915.

Eight JN-2’s were ordered by the U. S. Signal Corps. for the First Aero Squadron.  On delivery in May 1915 at North Island, San Diego, the first JN-2 was flown for government tests.  In spite of many modifications the  type failed to meet all performance requirements.  Curtiss then delivered two Model JN-3’s as an improved version.  Eventually all JN-2’s we modified to JN-3 standards, but still were not satisfactory.

The JN-4 series which followed were the first ordered specifically as trainers.  While U. S. orders lagged, the British engulfed in the European war, required large numbers.  A Canadian branch of the Curtiss Co., was established in Toronto to handle some of the production.  Since the British asked for changes in the design, their model was designated JN-4 Can, which became known as the “”Canuck”.

The Curtiss JN-4 series led to a variety of models and modifications.  The original American JN-4 appeared in July, 1916, followed by the JN-4B, a greatly improved model.  (The JN-4A designation had been assigned to the British model .)

Two JN-4A’s in training formation.  These were delivered in 1917.   

Two JN-4A’s in training formation.  These were delivered in 1917.

The U. S. Signal Corps placed an order for 36 JN-4B’s and delivery began in December , 1916.  An additional 36 JN-4B’s were ordered and all 72 had been delivered when the U. S. entered the World War on April 6, 1917.

With the urgent demand for aircraft for the U. S. training program, agreement was reached on production of a modification of the British version, which retained the JN-4A designation.  By late November, 1917 600 JN-4A’s had been delivered to the U. S. Signal Corps.  In December 1917 deliveries of a new model, the JN-4D began.  This design incorporated modifications resulting from a meeting of engineers to determine specifications for a model for mass production.  By the end of the war on November 11, 1918 a total of 2,812 JN-4D’s had been delivered to the U. S. Army, produced by Curtiss and six other contracting companies.

The JN series did not end with the D model.  When an aircraft for advanced training was required, the 150 hp Hispano-Suiza engine was installed in a D model and became the JN-4H.  Special trainers were given new designations—JN-4HG for gunnery trainers, JN-4HB for bombing trainers and JN-4HO for observation.  More modifications resulted in the JN-6H.  Other variations of the design included a twin-engined version designated the Twin JN.  While actually a development of the N model, the U. S. Navy’s N-9 seaplane was basically a JN-4B with longer wings to carry the weight of the floats.

The lineage of the Curtiss JN series is a complicated subject.  A very complete and detailed account of the origins and use of this famous airplane can be found in the books “Encyclopedia of Military Aircraft” by Robert B. Casari, published by Military Aircraft Publications, Six Applewood Drive, Chillicothe, OH 45601.

Curtiss Jennies after the war, piloted by barnstormers, brought aviation to the American public by offering rides and performing in air shows.  Government regulations outlawed the Jenny in 1927.  A few example still exist in museums and owned by antique fans.

(The following is a reprint of an article that appeared in the February/March 1966 issue of AIR PROGRESS)

 Jenny’s Younger Sister

The JN-1 combined the best features of the J and N models and introduced the unequal wing span used on most subsequent J’s and JN’s.  This seaplane version built for the Navy was designated JN-1S to distinguish it from the landplane model.

The JN-1 combined the best features of the J and N models and introduced the unequal wing span used on most subsequent J’s and JN’s.  This seaplane version built for the Navy was designated JN-1S to distinguish it from the landplane model.

By Peter M. Bowers

The seagoing member of Jenny’s family turned out to be quite a gal, too.  Strange that so many aviation types spent years dreaming of Jenny when they might have been making time with Sis.

The Curtiss “Jenny” particularly the JN-4 in its various versions, is one of America’s most famous airplanes.  However its very close relative, the N-9 seaplane, is virtually unknown today in spite of having served as the Navy’s principal primary trainer for nearly a decade.

The common ancestor of both the N and the JN is the Curtiss Model J of 1914.  By 1912 , it had become apparent that the established open “Pusher” designs were on the way out and that the “Tractor,” with the engine mounted in the nose of an enclosed fuselage, was the coming thing.  With an eye on the contemporary Burgess models as an example of the trend, Curtiss developed the Model G.  This was not a notable success and only two were built.  Glenn Curtiss then decided that the easiest way to catch up with the competition would be to obtain the services of a designer who was already thoroughly experienced in tractor designs.  Following this decision, he hired B. Douglas Thomas, an Englishman, who had worked for Avro and Sopwith, both notable for having turned out highly successful tractor designs.  Thomas started design work on the new Curtiss tractor, designated Model J, while still in England and completed it after moving to the Curtiss plant at Hammondsport, New York.

Prototype N-9 with standard JN-4B tail surfaces.  Note deeper nose than on 90 hp N’s and JN’s with flat bottom radiators.  Additional aileron area provided by moving the trailing edge of the aileron aft of the trailing edge of the upper wing.

Prototype N-9 with standard JN-4B tail surfaces.  Note deeper nose than on 90 hp N’s and JN’s with flat bottom radiators.  Additional aileron area provided by moving the trailing edge of the aileron aft of the trailing edge of the upper wing.

Other Curtiss designs were being developed while the J was under construction, including another landplane tractor, the Model N (the K and M were contemporary flying boats but the L, a tri- plane tractor didn’t appear until 1916).  The J was finished first and proved to be a most significant airplane.  Not only did it re-establish Curtiss as the leading U.S. manufacturer but it pretty well standardized the aerodynamic and structural pattern for all subsequent American tractor biplanes.  The control system was a unique Curtiss feature, however.  The ailerons were operated by a shoulder yoke with the pilot leaning in the direction that he wanted the airplane to bank while operating the rudder with the steering wheel.  This system did not use rudder pedals.

The major change on improved versions was to adopt the more efficient airfoil and some of the minor structural details of the Model N.  This combining of the best features of several airplanes into a single new model was common practice at the time and Curtiss acknowledged the union of the J and N designs by naming the new model JN-1.  Even at that early date airplanes had come to be regarded, like boats, as having feminine characteristics and personalities and were often given unofficial feminine names.  The pilots soon and qujte logically converted the initials JN into the name “Jenny,” which turned out to be one of the most suitable airplane names of all time.

N-9’s were not only rugged enough to stand the extra hard abuse that seaplanes, with no shock absorbers, took when landing on rough water but they could take the jolts of catapult launching as demonstrated on this deck-mounted catapult.

N-9’s were not only rugged enough to stand the extra hard abuse that seaplanes, with no shock absorbers, took when landing on rough water but they could take the jolts of catapult launching as demonstrated on this deck-mounted catapult.

The principal customer for the new models and its descendants was the U.S. Army, which bought 6163 to the end of World War I from Curtiss and various sub-contractors.  Including those built in Britain and Canada,  JN production reached an estimated total of 6759.  The N model continued to develop independently, however, with both the Army and Navy as customers.  Both models underwent essentially the same state-of-the-art refinements to the point where the N-8 and the first JN-4 of 1916 were virtually indistinguishable from each other externally.  The N retained the shoulder yoke aileron control system while the JN-4 used the “Deperdussin” type of control where the wheel operated the ailerons and the rudder was controlled by the pilot’s feet through a rudder bar.  This system had been adopted on the JN-3 which had been built in quantity for the British Royal Flying Corps (R.A.F.) and the Royal Naval Air Service (R.N.A.S.).

The most famous N model was the N-9 that appeared at the end of 1916 and can be regarded as one of the most remarkable aeronautical adaptations of all time.  With increasing indication that the United States would be drawn into World War I, the Navy sought to expand its aviation training program and expressed interest in a seaplane primary trainer.  With all the leading U.S. manufacturers competing for the order, Curtiss decided to save time and adapt existing production models to the job instead of designing a new one from scratch specifically for the purpose.  In most of its structural details, the N-9 can be considered a seaplane version of the standard JN-4B landplane fitted with the extra-span wing of an experimental N-8.  The additional wing area was considered necessary to carry the extra load imposed by the large four-compartment wood veneer main float and the two cylindrical metal wingtip floats that were fitted with planning boards and pointed end cones.   To avoid having to alter the existing factory wing jigs to build longer wing panels, the increased span was obtained for the production N-9’s the same way it had been obtained on the experimental N-8—by building a wider center section for the upper wing that had ten foot more span than the standard type.  The lower wing span was increased an equal amount by adding separate five-foot panels on each side of the fuselage and anchoring their outer ends to the upper center section with extra struts for a total of three bays on each side instead of the original two.  The JN-4H wing used the Eiffel 36 airfoil but the N-9 used the R.A.F.  6.

Each change seemed to generate a requirement for another adaptation.  Since the cutout for the ailerons in the outer wing panels remained the same size as on the short-wing models, the need for additional aileron area was met by increasing the chord of the aileron.  More vertical tail area was found to be necessary, so the JN-4B fin was enlarged by humping the straight line of the leading edge to add area without having to change the base dimensions or relocate the existing fittings.

An N-9H with a special all-white postwar paint job.  The word ” Victory” on the side indicates that this might have been flown in connection with the Victory Bond drive of 1919.  The size and location of the white-center wing circles shown here were not standard for N-9’s.

An N-9H with a special all-white postwar paint job.  The word ” Victory” on the side indicates that this might have been flown in connection with the Victory Bond drive of 1919.  The size and location of the white-center wing circles shown here were not standard for N-9’s.

The original powerplant of the N-9 was the 100-hp Curtiss OXX-6 engine.  This was essentially the well-known OX-5 with dual ignition and the bore increased by a quarter of an inch to provide an additional ten horsepower.  This increased power, combined with the lower airspeed of an equivalent seaplane model, required additional cooling surface.  This was provided by enlarging the standard 90 hp Curtiss radiator through the addition of area at the bottom, which was then rounded to match the top.  Even with the extra 10 hp the performance of the N-9 was less than that of the 90 hp land planes and it was a pretty marginal airplane suited to little other than use as a primary trainer.  Performance improved considerably and more advanced use could be made of  the airplane after the American built version of the 150 hp French Hispano-Suiza engine became available from the Simplex Automobile Division of the Wright-Martin Company late in 1917.   Although known officially as Wright Models A and I for the 150 hp versions, these engines were universally referred to as “Hissos.”  N-9’s fitted with this powerplant were identified as N-9H.

The increased cooling requirement of the Hisso engine was met by what seemed to be a long step backward in aerodynamic refinement.  Instead of a neat nose radiator, the first N-9H used two side mounted radiators.  Production models used a single vertical radiator standing on top of the fuselage ahead of the wing and projecting some distance above it.   A concession to streamlining was made by installing a large diameter shallow spinner on the nose.  The Hisso-powered JN-4H’s and JN-6’s on the other hand were able to use  nose radiators  in the original N-9 shape because their higher landplane speeds made less cooling area necessary.  Fuel capacity was 20 U.S. gallons for the N-9 and 23 gallons for the N-9H.

Delivery of N-9’s to the Navy training school at Pensacola, Florida and to various State Naval Militia units began before U.S. entry into WW I.  There was no established color scheme  at the time—the fabric was clear-doped and sometimes given an additional coat of varnish that imparted an amber shade to the otherwise light buff or off-white finish.  1918-19 coloring was standard light gray over all that was used by every Navy aircraft.  The shades varied considerably between the products of different manufacturers and repair stations.  In 1920, Navy coloring was changed to all silver, and high visibility orange-yellow was soon added to the top surface  of the upper wing.  Navy airplane identification, from late 1917 through 1924 was by the airplane serial number, painted in large figures on each side of the fuselage in white against gray backgrounds and in black against silver.

There was no standardized U.S. National insignia prior to April 1917.  Some Army aircraft used on the Mexican Border carried a red five-pointed star on the rudders and sometimes on the fuselage.  Most naval aircraft, including the N-9’s adopted a blue anchor marking on each side of the rudder and sometimes under the wings.  The well known star-in-a-circle marking was adopted on April 17, eleven days after U.S. entry in the war.  This was used on wings only, and was initially painted full-chord of the wing and inboard of the aileron.  On the N-9 which did not have lower wing ailerons, the lower wing marking was located directly under the upper wing marking.  The rudder marking was the same vertical red, white, and blue striping  used by the British and the French..  The U.S. marking changed in January 1918 to a tricolor circle similar to the pattern of other Allies.  This is actually the former Imperial Russian marking, with the red circle on the outside, then blue, and a white center.  The order of the tail stripes was reversed at the time to put the blue stripe at the trailing edge of the rudder.  This combination was retained until August 1919 at which time the star and rudder stripe arrangement of 1917 was adopted.

There was considerable mixing of markings in 1918, however, for not all planes with 1917 markings were repainted and some were later fitted with spare surfaces carrying 1918 markings.  Similarly, 1918 airplanes sometimes acquired spares that carried 1917 markings.

With the exception of the Curtiss HS-2L flying boat, the N-9 was made in greater numbers than any other U.S. Navy airplane model until the procurement of the Navy-designed N3N trainer during the build-up that preceded World War II.  Five hundred and sixty N-9’s were constructed for the Navy to the end of WW I, but only 100 were built by Curtiss.  The majority were built by Curtiss’ old competitor, the Burgess Company, at Marblehead, Massachusetts.  An additional order for 1200 to be built by Burgess was cancelled after the Armistice.  The Army bought 14 Curtiss powered N-9’s early in 1917 and obtained a few N-9H’s from the Navy on trades for JN-4H landplanes.  It is possible that a few civil models were also sold since the N-9 was advertised in the last pre-war Curtiss commercial catalog.

Fifty additional N-9H’s were created in the early 1920’s by assembling accumulated spare and salvaged parts at Pensacola and assigning new serial numbers to the resulting complete airframes.  The N-9’s, which never did pick up a given name throughout their career, were not declared surplus at the end of the war as were the majoority of the Army Jennies, so they had no chance to earn a reputation in the barnstorming field.  They stayed in service in their original missions as the Navy’s principal primary and gunner trainer until they began to be replaced by the new Boeing NB-1’s and -2’s in 1924.  They were finally retired when the Consolidated NY-1 entered service in quantity in 1927.

Specifications

                                              N-9                                N-9H

Wing Span (upper)            53 ’ 4”                           53’ 4”

Wing span (lower)             43’ 1”                              43’  1”

 Length                               29’ 10”                           30’ 10” (longer pontoon)

Height                                10 ‘ 11”                           10’ 11”

Wing area                          496 sq ft                         496 sq ft

Empty weight                   1900 lbs                         2140 lbs

Gross weight                     2410 lbs                        2750 lbs

High speed                        70 mph                          77 mph

Landing speed                 40 mph                           45 mph

Rate of climb                    2000 ft in 10 min         3240 ft in 10 min

Service Ceiling                  ——-                              8830 ft

 

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