http://en.wikipedia.org/wiki/Eastern_Air_Lines_Flight_401

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The flight was routine until 11:32 p.m., when the flight began its approach into Miami International Airport. After lowering the gear, first officer Stockstill noticed that the landing gear indicator, a green light identifying that the nose gear is properly locked in the "down" position, did not illuminate. This was discovered to be due to a burned-out light bulb. The landing gear could have been manually lowered either way. The pilots cycled the landing gear but still failed to get the confirmation light.

Loft, who was working the radio during this leg of the flight, told the tower that they would discontinue their approach to their airport and requested to enter a holding pattern. The approach controller cleared the flight to climb to two thousand feet (610 m), and then hold west over the Everglades.

The cockpit crew removed the light assembly and second officer Repo was dispatched into the avionics bay beneath the flight deck to check visually if the gear was down through a small viewing window. Fifty seconds after reaching their assigned altitude, captain Loft instructed first officer Stockstill to put the L-1011 on autopilot. For the next eighty seconds, the plane maintained level flight. Then, it dropped one hundred feet (30 m), and then again flew level for two more minutes, after which it began a descent so gradual it could not be perceived by the crew. In the next seventy seconds, the plane lost only 250 feet (76 m), but this was enough to trigger the altitude warning C-chord chime located under the engineer's workstation. The engineer (second officer Repo) had gone below, and there was no indication by the pilot's voices recorded on the CVR that they heard the chime. In another fifty seconds, the plane was at half its assigned altitude.

As Stockstill started another turn, onto 180 degrees, he noticed the discrepancy. The following conversation was recovered from the flight voice recorder later:

Stockstill: We did something to the altitude.

Loft: What?

Stockstill: We're still at 2,000 feet, right?

Loft: Hey—what's happening here?

The jetliner crashed at 25°51?53?N 80°35?43?W. The location was west-northwest of Miami, 18.7 miles (30.1 km) from the end of runway Nine Left (9L). The plane was traveling at 227 miles per hour when it flew into the ground. The left wingtip hit first, then the left engine and the left landing gear, making three trails through the sawgrass, each five feet wide and more than 100 feet (30 m) long. When the main part of the fuselage hit the ground, it continued to move through the grass and water, breaking up as it went.
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