Page "Eastern Air Lines Flight 401" Paragraph 6

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.