On August 8, 1996, at 0757 hours Hawaiian standard time, a Douglas DC-9-51, N420EA, was brought to a stop on runway 8R after the nose landing gear collapsed during landing at Honolulu International Airport, Honolulu, Hawaii. The aircraft, which received minor damage, was operated by Hawaiian Airlines, Inc., under 14 CFR Part 121, as flight 113. There were no injuries among the 71 passengers, 3 cabin crew, and 2 cockpit crew aboard. The flight was on an instrument flight plan and departed Honolulu in visual meteorological conditions about 0700 destined for Lihue, Hawaii. It returned to Honolulu without landing at Lihue when the unsafe nose gear indication was observed during the approach there. Personnel from the FAA's Honolulu Flight Standards District Office reported that the flight crew observed alignment marks on the nose gear linkage through an inspection window in the cockpit which confirmed that the nose gear was not locked down. En route back to Honolulu, the captain declared an emergency, ordered emergency equipment, and instructed the cabin crew to prepare the cabin. The cabin crew reported that there was ample time to prepare the cabin and that the landing was uneventful until the aircraft was relatively slow and the nose gear gently collapsed. The aircraft came to a stop on the runway on its nose. There was some smoke and burning odor in the cabin and the cockpit crew ordered an evacuation of the cabin. About 25 passengers exited via the aft slide before crash and rescue personnel arrived and determined that it would be safe to deplane the remaining passengers through the forward doors using stepladders. Four people went to the hospital for observation; two were the front cabin flight attendants and two others were non-revenue flight attendants aboard the flight. Investigation revealed that a flexible hydraulic hose was not secured in the nosewheel well. The flexible hose had been temporarily installed in the nosewheel steering system to replace a previously broken fixed line. The hose become trapped in the nose gear over center, down lock mechanism (Douglas part numbers 3913968-13 and 5920210-3) during the gear extension. The incident occurred on the first flight cycle following the maintenance alteration of the hose installation.