On November 13, 1986, the rear main spar of the right wing failed as Delta Flight 194 touched down on runway 29 at Newark Airport. The pilots stated that there was moderate turbulence on final approach and initial touchdown was on the right main gear first. The touchdown was firm but not hard, which was confirmed from the 1.4G recorded on the DFDR. The 1.4G force is well within the landing gear certification limits. The spar web failure was caused by a fatigue crack that originated at a 'hi-loc' fastener hole located at the lower inboard corner of a doubler that surrounds the fuel filler valve, which is mounted vertically on the spar web. The fatigue zone in the spar web had progressed about 6 3/4 inches before the web failed as the airplane touched down. The fracture in the spar web extended diagonally downward and outboard at 45 degrees from inboard wing station 241.0 to inboard station 293.5. The flight crew did not report any airplane malfunction during the flight.