Curtiss-Wright C-76 Caravan

Le curieux avion de transport Curtiss Wright Caravan de 1943 vu par Wikipedia de langue anglaise

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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 [Vous devez être inscrit et connecté pour voir ce lien].

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.

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Design and development

In 1941, [Vous devez être inscrit et connecté pour voir ce lien] was contracted by the [Vous devez être inscrit et connecté pour voir ce lien] to design and construct an all-wood military transport aircraft, with performance specifications meeting or exceeding that of the [Vous devez être inscrit et connecté pour voir ce lien] 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 [Vous devez être inscrit et connecté pour voir ce lien] had successfully employed a ply construction using a balsa wood core and birch hardwood exterior, Curtiss-Wright engineers, using research provided by [Vous devez être inscrit et connecté pour voir ce lien], 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 [Vous devez être inscrit et connecté pour voir ce lien], were subcontracted to build components for the plane, which would be assembled at Curtiss-Wright's new defense plant in [Vous devez être inscrit et connecté pour voir ce lien].

A [Vous devez être inscrit et connecté pour voir ce lien] 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. ^{[Vous devez être inscrit et connecté pour voir ce lien]
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The original contract called for 11 YC-76 pre-production aircraft, and the first aircraft would be built and tested at Curtiss-Wright's [Vous devez être inscrit et connecté pour voir ce lien] 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 [Vous devez être inscrit et connecté pour voir ce lien] factory in [Vous devez être inscrit et connecté pour voir ce lien].

To keep the plywood flexible during construction the factory was kept hot and damp.

The [Vous devez être inscrit et connecté pour voir ce lien] YC-76 first flew on January 1, 1943.

Only five production aircraft were completed in 1943: three from Curtiss-Wright's St. Louis Division, and two from the Louisville, Kentucky plant (the Higgins Aircraft complex in New Orleans had not been completed at the time of the contract's cancellation).

Operational history

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:

'The first flight [of the C-76] was made and the airplane was very heavy. It developed some serious vibrations. In fact, the pilot was awful glad to make a quick circuit to get back on the ground ... two of the Curtiss test pilots took it out on a flight and the Army requested that our project officer on the airplane be allowed to fly along on this trip. The Curtiss Company refused. We were very glad that they refused because on this second flight, it [the C-76] flew apart and the pilots were lost and so was the plane.

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 capacityThe 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^{[Vous devez être inscrit et connecté pour voir ce lien]} On 10 May 1943, the first YC-76 constructed at the [Vous devez être inscrit et connecté pour voir ce lien] plant, 43-86918, lost its tail unit at 1729 hrs. due to lack of "forgotten" securing bolts during test flight, crashing at [Vous devez être inscrit et connecté pour voir ce lien], killing three [Vous devez être inscrit et connecté pour voir ce lien] 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 [Vous devez être inscrit et connecté pour voir ce lien] 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 [Vous devez être inscrit et connecté pour voir ce lien] plant were granted one-time flight clearance and flown directly to [Vous devez être inscrit et connecté pour voir ce lien] bases for use as instructional airframes. In the interim, the Curtiss-Wright plants at [Vous devez être inscrit et connecté pour voir ce lien] and Louisville, Kentucky went over to full production of the [Vous devez être inscrit et connecté pour voir ce lien].

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.