Flight JW1457 was on approach to Santiago de Chile and just lowered the gear, when one of the nose wheels (about 70 kg – 150 lbs) dropped off the airplane and fell into a cornfield approximately 70 meters from a house. The crew did not notice the loss of the wheel, which was discovered only after the safe landing.The wheel was later recovered from the farm owner, whose workers had seen the wheel come down. MOST LIKELY CAUSE The safety bolt, being damaged at its threadless end (nipple), did not fulfill its function, which allowed the turning of the nut, detaching the left wheel of the nose gear during the approach to runway 17L of AMB Airport. CONTRIBUTING FACTOR Use the locking pin to complete the alignment of the nut to the spacer shaft, which was evident in the mechanical damage to the locking pin and spacer, contrary to the Maintenance Manual.