C-76 Caravan
Encyclopedia
The Curtiss-Wright C-76 Caravan (company designation CW-27) was an 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
. 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.
was contracted by the United States Army Air Force to design and construct an all-wood military transport aircraft, with performance specifications meeting or exceeding that of the C-47 Skytrain
then in service.
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 construction with a tricycle undercarriage. Though the British de Havilland Mosquito
had successfully employed a ply construction using a balsa wood core and birch hardwood exterior, Curtiss-Wright engineers, using research provided by Forest Products Laboratory
, rejected this approach, insisting instead on a ply construction of dense mahogany, which greatly increased the plane's weight. At Curtiss' request, Army Materiel Command laid in large supplies of mahogany, and a number of furniture manufacturers, including the Baldwin Piano Company
, were subcontracted to build components for the plane, which would be assembled at Curtiss-Wright's new defense plant in Louisville, Kentucky
.
A radial engine
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 so out-size loading could be done, including a jeep or small artillery pieces.
The original contract called for 11 YC-76 pre-production aircraft, and the first aircraft would be built and tested at Curtiss-Wright's St. Louis, Missouri
Division plant. Subsequently, orders for five C-76 production aircraft and nine revised YC-76A were placed by the USAAF, with line production to commence at the Curtiss-Wright plant in Louisville as well as a Higgins Aircraft
factory in New Orleans, Louisiana
.. To keep the plywood flexible during construction the factory was kept hot and damp. The prototype
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
.
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. 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
plant, 43-86918, lost its tail unit at 1729 hrs. due to lack of "forgotten" securing bolts during test flight, crashing at Okolona, Kentucky
, killing three Curtiss test crew, pilot Ed Schubinger, co-pilot John L. "Duke" Trowbridge, and engineer Robert G. Scudder. 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
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, and the remaining prototype aircraft were recalled from testing and active service. Only five production and nine pre-production aircraft had been completed by the time of the project's cancellation, with two aircraft lost in crashes, and other airframes cannibalized for parts. The remaining flyable aircraft were all grounded by 12 September 1944. Four C-76s at the St. Louis, Missouri
plant were granted one-time flight clearance and flown directly to Air Training Command
bases for use as instructional airframes. In the interim, the Curtiss-Wright plants at Buffalo, New York
and Louisville, Kentucky went over to full production of the C-46 Commando
. 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.
C-76A
YC-76A
C-76A
Duralumin
Duralumin is the trade name of one of the earliest types of age-hardenable aluminium alloys. The main alloying constituents are copper, manganese, and magnesium. A commonly used modern equivalent of this alloy type is AA2024, which contains 4.4% copper, 1.5% magnesium, 0.6% manganese and 93.5%...
. 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.
Design and development
In 1941, Curtiss-WrightCurtiss-Wright
The Curtiss-Wright Corporation was the largest aircraft manufacturer in the United States at the end of World War II, but has evolved to largely become a component manufacturer, specializing in actuators, aircraft controls, valves, and metalworking....
was contracted by the United States Army Air Force to design and construct an all-wood military transport aircraft, with performance specifications meeting or exceeding that of the C-47 Skytrain
C-47 Skytrain
The Douglas C-47 Skytrain or Dakota is a military transport aircraft that was developed from the Douglas DC-3 airliner. It was used extensively by the Allies during World War II and remained in front line operations through the 1950s with a few remaining in operation to this day.-Design and...
then in service.
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 construction with a tricycle undercarriage. Though the British de Havilland Mosquito
De Havilland Mosquito
The de Havilland DH.98 Mosquito was a British multi-role combat aircraft that served during the Second World War and the postwar era. It was known affectionately as the "Mossie" to its crews and was also nicknamed "The Wooden Wonder"...
had successfully employed a ply construction using a balsa wood core and birch hardwood exterior, Curtiss-Wright engineers, using research provided by Forest Products Laboratory
Forest Products Laboratory
The Forest Products Laboratory 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 uses in partnership with academia, industry, tribal, state,...
, rejected this approach, insisting instead on a ply construction of dense mahogany, which greatly increased the plane's weight. At Curtiss' request, Army Materiel Command laid in large supplies of mahogany, and a number of furniture manufacturers, including the Baldwin Piano Company
Baldwin Piano Company
The Baldwin Piano Company was the largest US-based manufacturer of keyboard instruments, most notably pianos. It remains a subsidiary of the Gibson Guitar Corporation, although it ceased domestic production of pianos in December 2008.-History:...
, were subcontracted to build components for the plane, which would be assembled at Curtiss-Wright's new defense plant in Louisville, Kentucky
Louisville, Kentucky
Louisville is the largest city in the U.S. state of Kentucky, and the county seat of Jefferson County. Since 2003, the city's borders have been coterminous with those of the county because of a city-county merger. The city's population at the 2010 census was 741,096...
.
A radial engine
Radial engine
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders point outward from a central crankshaft like the spokes on a wheel...
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 so out-size loading could be done, including a jeep or small artillery pieces.
The original contract called for 11 YC-76 pre-production aircraft, and the first aircraft would be built and tested at Curtiss-Wright's St. Louis, Missouri
St. Louis, Missouri
St. Louis is an independent city on the eastern border of Missouri, United States. With a population of 319,294, it was the 58th-largest U.S. city at the 2010 U.S. Census. The Greater St...
Division plant. Subsequently, orders for five C-76 production aircraft and nine revised YC-76A were placed by the USAAF, with line production to commence at the Curtiss-Wright plant in Louisville as well as a Higgins Aircraft
Higgins Aircraft
Higgins Aircraft was a subsidiary of Higgins Industries set up to build aircraft during World War II.Higgins Aircraft was contracted to build the all-plywood-construction Curtiss-Wright C-76 Caravan, and later, the C-46 Commando, but both contracts were cancelled at an early stage, and the company...
factory in New Orleans, Louisiana
New Orleans, Louisiana
New Orleans is a major United States port and the largest city and metropolitan area in the state of Louisiana. The New Orleans metropolitan area has a population of 1,235,650 as of 2009, the 46th largest in the USA. The New Orleans – Metairie – Bogalusa combined statistical area has a population...
.. To keep the plywood flexible during construction the factory was kept hot and damp. The prototype
Prototype
A prototype is an early sample or model built to test a concept or process or to act as a thing to be replicated or learned from.The word prototype derives from the Greek πρωτότυπον , "primitive form", neutral of πρωτότυπος , "original, primitive", from πρῶτος , "first" and τύπος ,...
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
C-46 Commando
The Curtiss-Wright C-46 Commando was a transport aircraft originally derived from a commercial high-altitude airliner design. It was instead used as a military transport during World War II by the United States Army Air Forces as well as the U.S. Navy/Marine Corps under the designation R5C...
.
Operational history
The first flight of the YC-76 prototype took place on May 3, 1943. The C-76 proved severely underpowered from the start, with a cruise speed of 160 mph, a service ceiling of 22,600 feet, a range of only 750 miles, and a cargo capacity of under 8,000 lbs. 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. 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, Kentucky
Louisville is the largest city in the U.S. state of Kentucky, and the county seat of Jefferson County. Since 2003, the city's borders have been coterminous with those of the county because of a city-county merger. The city's population at the 2010 census was 741,096...
plant, 43-86918, lost its tail unit at 1729 hrs. due to lack of "forgotten" securing bolts during test flight, crashing at Okolona, Kentucky
Okolona, Kentucky
Okolona is a former census-designated place in southern Jefferson County, Kentucky, United States. It is centered around the intersection of Preston Highway and the Outer Loop. The population was 17,807 at the 2000 census. When the government of Jefferson County merged with the city of Louisville,...
, killing three Curtiss test crew, pilot Ed Schubinger, co-pilot John L. "Duke" Trowbridge, and engineer Robert G. Scudder. 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
Fairchild PT-19
|-See also:-Bibliography:* Mondey, David. American Aircraft of World War II . London: Bounty Books, 2006. ISBN 978-0-7537-1461-4....
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, and the remaining prototype aircraft were recalled from testing and active service. Only five production and nine pre-production aircraft had been completed by the time of the project's cancellation, with two aircraft lost in crashes, and other airframes cannibalized for parts. The remaining flyable aircraft were all grounded by 12 September 1944. Four C-76s at the St. Louis, Missouri
St. Louis, Missouri
St. Louis is an independent city on the eastern border of Missouri, United States. With a population of 319,294, it was the 58th-largest U.S. city at the 2010 U.S. Census. The Greater St...
plant were granted one-time flight clearance and flown directly to Air Training Command
Air Training Command
Air Training Command is a former major command of the United States Army Air Forces and United States Air Force. ATC came into being as a redesignation of the Army Air Forces Training Command on July 1, 1946...
bases for use as instructional airframes. In the interim, the Curtiss-Wright plants at Buffalo, New York
Buffalo, New York
Buffalo is the second most populous city in the state of New York, after New York City. Located in Western New York on the eastern shores of Lake Erie and at the head of the Niagara River across from Fort Erie, Ontario, Buffalo is the seat of Erie County and the principal city of the...
and Louisville, Kentucky went over to full production of the C-46 Commando
C-46 Commando
The Curtiss-Wright C-46 Commando was a transport aircraft originally derived from a commercial high-altitude airliner design. It was instead used as a military transport during World War II by the United States Army Air Forces as well as the U.S. Navy/Marine Corps under the designation R5C...
. 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.
C-76A
- Production aircraft built at St Louis, five built.
YC-76A
- Production variant, nine built.
C-76A
- Production variant, order for 175 cancelled, non-built.