History of Cubana de Aviación of its fleet, opting to replace its long-range piston-prop Super Constellations with turboprop aircraft, and to expand its existing Vickers Viscount turboprop fleet in the immediate future. Cubana placed orders for four long-range Bristol Britannia (Model 318) and four Vickers Super Viscount (VV-818) aircraft, all turboprops, for its international services (which included Madrid, New York, Mexico City, Miami, Montego Bay, Nassau, Port-au-Prince), and for some of its domestic routes (Camagüey, Santiago de Cuba, Varadero). The first Bristol Britannia (CU-T668) was delivered in late 1958, and was placed in service in the airline's New York route. The new Britannias and Super
Vickers hardness test the material. The fin attachment pins and sleeves in the Convair 580 airliner were specified by the aircraft manufacturer to be hardened to a Vickers Hardness specification of 390HV5, the '5' meaning five kiloponds. However, on the aircraft flying Partnair Flight 394 the pins were later found to have been replaced with sub-standard parts, leading to rapid wear and finally loss of the aircraft. On examination, accident investigators found that the sub-standard pins had a hardness value of only some 200-230HV5. Vickers hardness test The Vickers hardness test was developed in 1921 by Robert L. Smith and George E. Sandland