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
Partnair Flight 394
Partnair Flight 394
Vickers hardness test