The Curtiss-Wright C-76 Caravan (company designation CW-27) was an American all-wood military transport aircraft. The C-76 was intended as a substitute standard aircraft in the event of expected wartime shortages of
light alloys.
[Dreher, Carl, ''Wood Is A War Weapon'', Popular Science, Vol. 141 No.3 (September 1942), pp. 48–74] However, both prototype and production aircraft failed several critical flight and static tests, and after U.S. aluminum production proved sufficient for wartime defense requirements, orders for the C-76 were cancelled and production terminated.
[Kleber, John E., ''The Encyclopedia of Louisville'', University Press of Kentucky (2001) , , pp. xxvii, 235–236]
Design and development
![Curtiss C-76 and AT-9 1943](https://upload.wikimedia.org/wikipedia/commons/3/3e/Curtiss_C-76_and_AT-9_1943.jpg)
In 1941,
Curtiss-Wright
The Curtiss-Wright Corporation is a manufacturer and services provider headquartered in Davidson, North Carolina, with factories and operations in and outside the United States. Created in 1929 from the consolidation of Curtiss, Wright, and v ...
was contracted by the
United States Army Air Forces
The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War II ...
to design and construct an all-wood military transport aircraft, with performance specifications meeting or exceeding that of the
Douglas C-47 Skytrain
The Douglas C-47 Skytrain or Dakota (RAF, RAAF, RCAF, RNZAF, and SAAF designation) is a military transport aircraft developed from the civilian Douglas DC-3 airliner. It was used extensively by the Allies during World War II and remained in ...
then in service.
[Dorrell, David (ed.), ''Curtiss Caravan, Air Pictorial: Journal of the Air League'', Air League of the British Empire, Volume 35, No. 7 (July 1973), p. 69]
The Curtiss-Wright CW-27 was designed by Curtiss-Wright's chief designer George A. Page, Jr. as a high-wing, twin-engine, cargo transport aircraft, utilizing
plywood
Plywood is a material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another. It is an engineered wood from the family of manufactured ...
construction with a tricycle undercarriage. Though the British
de Havilland Mosquito
The de Havilland DH.98 Mosquito is a British twin-engined, shoulder-winged, multirole combat aircraft, introduced during the Second World War. Unusual in that its frame was constructed mostly of wood, it was nicknamed the "Wooden Wonder", or ...
had successfully employed a ply construction using a
balsa
''Ochroma pyramidale'', commonly known as the balsa tree, is a large, fast-growing tree native to the Americas. It is the sole member of the genus ''Ochroma''. The tree is famous for its wide usage in woodworking, with the name ''balsa'' being ...
wood core and
birch
A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus ''Betula'' contains 30 ...
hardwood exterior, Curtiss-Wright engineers, using research provided by
Forest Products Laboratory
The Forest Products Laboratory (FPL) is the national research laboratory of the United States Forest Service, which is part of USDA. Since its opening in 1910, the FPL has provided scientific research on wood, wood products and their commercial us ...
, rejected this approach, insisting instead on a ply construction of dense
mahogany
Mahogany is a straight-grained, reddish-brown timber of three tropical hardwood species of the genus ''Swietenia'', indigenous to the AmericasBridgewater, Samuel (2012). ''A Natural History of Belize: Inside the Maya Forest''. Austin: Unive ...
, which greatly increased the plane's weight.
[Sessums, Col. J.W., ''Design and Engineering Problems of Aircraft Production'' , May 14, 1946, pp. 6–]
National Defense University Archives
At Curtiss' request, Army Materiel Command laid in large supplies of mahogany, and a number of furniture manufacturers, including the
Baldwin Piano Company
The Baldwin Piano Company is an American piano brand. It was once the largest US-based manufacturer of keyboard instruments and known by the slogan, "America's Favorite Piano". Since 2001, it has been a subsidiary of Gibson Brands, Inc. It ceased ...
, were subcontracted to build components for the aircraft, which would be assembled at Curtiss-Wright's new defense plant in
Louisville, Kentucky
Louisville ( , , ) is the largest city in the Commonwealth of Kentucky and the 28th most-populous city in the United States. Louisville is the historical seat and, since 2003, the nominal seat of Jefferson County, on the Indiana border ...
.
A
radial engine
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ca ...
was mounted on each wing, and the aircraft was capable of carrying 23 personnel or a cargo payload. The Caravan had a nose section that swung out to the right to enable outsize loading, including a jeep or small artillery pieces.
The original contract called for 11 YC-76 preproduction aircraft, and the first aircraft would be built and tested at Curtiss-Wright's
St. Louis, Missouri
St. Louis () is the second-largest city in Missouri, United States. It sits near the confluence of the Mississippi River, Mississippi and the Missouri Rivers. In 2020, the city proper had a population of 301,578, while the Greater St. Louis, ...
Division plant.
Subsequently, orders for five C-76 production aircraft and nine revised YC-76As were placed by the USAAF, with line production to commence at the Curtiss-Wright plant in Louisville as well as a
Higgins Aircraft Michoud Factory Field in
Michoud near
.
[Burck, Gilbert, ''Mr. Higgins and His Wonderful Boats'', Life Magazine, 16 August 1943, p. 112] To keep the plywood flexible during construction the factory was kept hot and damp.
The
prototype
A prototype is an early sample, model, or release of a product built to test a concept or process. It is a term used in a variety of contexts, including semantics, design, electronics, and Software prototyping, software programming. A prototyp ...
YC-76 first flew on May 1, 1943.
Only five production aircraft were completed in 1943: three from Curtiss-Wright's St. Louis Division, and two from a new plant at Louisville, Kentucky, which was finished in May 1942.
The Higgins Aircraft Co. contract was cancelled by the Army on August 3, 1943 before the Higgins factory in New Orleans had been completed, and Higgins was awarded another contract to produce the
C-46 Commando
The Curtiss C-46 Commando is a twin-engine transport aircraft derived from the Curtiss CW-20 pressurised high-altitude airliner design. Early press reports used the name "Condor III" but the Commando name was in use by early 1942 in company pub ...
.
Operational history
![Curtiss C-76 on ground](https://upload.wikimedia.org/wikipedia/commons/a/a8/Curtiss_C-76_on_ground.jpg)
The first flight of the YC-76 prototype took place on 3 May 1943.
The C-76 proved severely underpowered from the start, with a cruising speed of , a service ceiling of , a range of only , and a cargo capacity of under . Colonel J.W. Sessums, a USAAF officer at the Air Materiel Command at Wright Field, later related:
Compared to other cargo aircraft then coming into service, the C-76 was already obsolescent, even allowing for its war-priority method of construction. In addition, the C-76 failed a number of critical flight tests.
[Mansfield, Howard, ''Skylark: The Life, Lies, and Inventions of Harry Atwood'', UPNE (1999) , , pp. 204–205] It was discovered in testing that the C-76 was unstable when not carrying a cargo load; in order to obtain a stable center of gravity, the plane had to be ballasted beyond its maximum permissible gross takeoff weight.
At any speed, or in any gusting wind, the C-76's elevators would flap back and forth violently.
The wing structure failed in eight separate static tests, sometimes with a load as low as 40% of the wing's rated capacity. The wing failures were attributed by some sources to the failure of the fasteners used to secure the wood components of the aircraft.
Numerous additional fasteners, metal stirrups, and wood ply reinforcements were added to the structure in an effort to strengthen it, thereby increasing the plane's overall weight.
At the Louisville plant, Curtiss line workers would later recall two C-76 production planes that were kept for some time in the assembly building, with one plane cannibalized to keep the other in flyable condition.
On 10 May 1943, the first YC-76 constructed at the
Louisville, Kentucky
Louisville ( , , ) is the largest city in the Commonwealth of Kentucky and the 28th most-populous city in the United States. Louisville is the historical seat and, since 2003, the nominal seat of Jefferson County, on the Indiana border ...
plant, ''42-86918'', lost its tail unit, due to a lack of securing bolts, during a test flight, crashing at
Okolona, Kentucky Okolona is a former census-designated place (CDP) in southern Louisville/ Jefferson County, Kentucky, United States. It is centered on the intersection of Preston Highway and the Outer Loop. The population was 17,807 at the 2000 census. When the go ...
, killing three
Curtiss-Wright
The Curtiss-Wright Corporation is a manufacturer and services provider headquartered in Davidson, North Carolina, with factories and operations in and outside the United States. Created in 1929 from the consolidation of Curtiss, Wright, and v ...
test crew.
[Boyne, Walt, "''C-46 ic 'The Basketcase Bummer' ''" Airpower, Granada Hills, California, May 1974, Volume 4, Number 3, page 64.]
As war priority measures designed to increase aluminum production proved successful, the feared shortage of light alloys never materialized.
Moreover, USAAF Training Command had begun to forward widespread complaints of insufficient service life on their wooden-winged
Fairchild PT-19
The Fairchild PT-19 (company designation Fairchild M62) is an American monoplane primary trainer aircraft that served with the United States Army Air Forces, RAF and RCAF during World War II. Designed by Fairchild Aircraft, it was a contempora ...
primary trainers when exposed to high heat in training bases located in Texas and Florida.
The War Department cancelled its orders for the C-76 on 3 August 1943.
The Sara Clark Collection, National Archives, Record Group 342, Box 2719, document the disposition of the 25 YC-76 aircraft as Articles #1, #3, # 4, and #5 were placed in the "Z" category, ZC-76, due to the poor gluing conditions and assembly procedures by subcontractors found through a Material Division inspection of the subcontractors work. These aircraft were assigned to the Technical Training Command and used for ground purposes only. Article #2 was destroyed in static testing at Wright Field. Article #6 was lost in a crash. Article #9 was under repair, but repairs were stopped and the airplane placed in Class 26, non-operational status. Air Service Command operated 12 YC-76s on a service test basis for nine months and found that they required excessive man hours to maintain. It was suggested that these be placed into Class 26 or Survey.
The final disposition of the aircraft as of 1 October 1945, by letter of the Air Technical Service Command; 1-Washout upon delivery from factory, 5-Class 26, 10-Survey, 1-Condemned, 8-Reconstruction Finance Corp. to be sold as surplus. In the interim, the Curtiss-Wright plants at
Buffalo, New York
Buffalo is the second-largest city in the U.S. state of New York (behind only New York City) and the seat of Erie County. It is at the eastern end of Lake Erie, at the head of the Niagara River, and is across the Canadian border from South ...
and Louisville, Kentucky went over to full production of the
Curtiss C-46 Commando
The Curtiss C-46 Commando is a twin-engine transport aircraft derived from the Curtiss CW-20 pressurised high-altitude airliner design. Early press reports used the name "Condor III" but the Commando name was in use by early 1942 in company pub ...
.
[News Article, ''New York Times'', August 11, 1944] USAAF Materiel Command later estimated the entire C-76 project cost the U.S. government $400 million dollars and several months in lost production time.
Variants
;YC-76
:Prototypes, 11 built.
[Andrade 1979, p. 80]
;C-76
:Production aircraft built at St Louis, five built.
;YC-76A
:Production variant, nine built.
;C-76A
:Production variant, order for 175 cancelled, none built.
Specification
See also
References
Bibliography
*
*
External links
{{USAF transports
C-076
Curtiss-Wright C-076 Caravan
High-wing aircraft
Curtiss-Wright C-76 Caravan
The Curtiss-Wright C-76 Caravan (company designation CW-27) was an American all-wood military transport aircraft. The C-76 was intended as a substitute standard aircraft in the event of expected wartime shortages of light alloys.Dreher, Carl, ...
Aircraft first flown in 1943
Twin piston-engined tractor aircraft