The coal fire in Bunker #5 was not put out before Titanic left Belfast, seriously weakening the plates on the starboard side where the iceberg hit.  Of the 160 men hired to stoke the boilers with coal, only 8 stayed on after seeing the fire on board.  The high court judge, Lord Mersey, investigating the sinking, dismissed these claims as irrelevant.
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A few days before Titanic set sail, Second Officer David Blair was replaced by Charles Lightoller, and in Blair’s haste to leave the Titanic, he forgot to hand the key to the binoculars locker to Lightoller for lookouts to use in the crow’s nest.
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Failure of Captain Smith to reduce speed from 21.5 knots (almost full speed) despite repeated warnings of icebergs (Smith was clearly eager to please his boss, Bruce Ismay, who wanted to set a record time for crossing the Atlantic)
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Failure of Captain Smith to order crew to use tools and break into locker containing binoculars requested by ship’s lookouts, to enhance safer navigation of the ship at night
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Insufficient moonlight to disclose iceberg dead ahead, struck at 11:40 PM, April 14
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Calm seas reduced wave action around the base of the iceberg, making it much more difficult to see until it was too late
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Titanic radioman Jack Phillips failed to forward last and most critical iceberg warning to ship’s bridge, as Californian had stopped dead in the water to avoid colliding with icebergs
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Titanic radioman ordered Californian’s communications room to “Shut up, shut up” as they attempted to warn of dangerous icebergs nearby, just ten minutes before Titanic hit the iceberg
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The Californian’s radio operator, Cyril Evans, shut his radio off at 11:30 PM after being told to “Shut up!” Therefore, he could not receive the subsequent SOS calls nearby.
(Captain Stanley Lord, commanding the SS Californian, ordered the ship to a full stop for the night to avoid collision with an iceberg.)
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Spotting of iceberg by lookouts in the crow’s nest was too late to avoid a collision, but early enough (37 seconds) to commence evasive maneuver which compounded damage beyond survivability - a 230-foot-long tear in the Titanic’s hull, flooding six separate compartments (Four flooded would not have sunk her.) Had the lookouts been posted on the bow, forty feet lower, they might have seen the outline of the iceberg against the faint horizon sooner. The ship’s searchlight should have been lit to illuminate the path ahead, even though it was not standard procedure. It was, after all, a moonless night with no waves washing against ice floes.
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Watch officer throwing all engines in reverse while ordering the helm hard a-port, robbing the rudder of the authority it had while running. (If instead he had reversed only the port engine, leaving the center and starboard engines in forward, or if he had reversed all engines while maintaining the original track, the Titanic might not have sustained fatal damage. A direct hit surely would not have flooded all six compartments.)
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Inexcusable failure of Captain Edwards or any officers to oversee filling all 20 lifeboats, 4 of which were collapsible, to rated capacity of 1,178, much less to some arbitrary but reasonable number over theoretical capacity (say 18 more children plus small women - sit on laps) in view of the exceptionally calm seas.  Only 705 survivors in lifeboats were rescued, 473 less than rated capacity.
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