9 fatalities

Shannon Airport Approach Accident Due to Altimeter Error (NC86505)

Shannon, IrelandLanding (descent or approach)

On December 28, 1946, a Lockheed L-049 Constellation (registration NC86505) operated by Trans World Airlines - TWA was involved in an aviation accident near Shannon, Ireland during landing or approach. 9 people were killed. Investigators recorded the probable cause as: An error in altimeter indication due to reversed static source lines led to an approach at a dangerously low altitude. This summary draws on records from the Bureau of Aircraft Accidents Archives (B3A); 8 related events involving the same aircraft type or operator are linked below.

Sourcesthe Bureau of Aircraft Accidents Archives (B3A)Primary reportUpdated 2026-08-05Data APIEditorial standards

An aircraft crashed near Shannon Airport after a low-altitude approach caused by reversed static source lines and poor visibility conditions.

What happened

At 0135, the flight reported its position over the Irish coast at 7,000 feet to Shannon Radio. The crew was subsequently cleared to cross the Limerick marker at 5,000 feet. At 0153, the aircraft reported over the Shannon radio range station at 5,000 feet and received clearance to descend on the southeast leg. During the procedure turn at 0200, the flight transmitted a position report and received updated weather information indicating rain, drizzle, and visibility of two miles with heavy cloud cover. The Shannon control tower then cleared the aircraft for an approach to Runway 14.

At 0206, the flight reported being over the range station at 1,200 feet. At this time, Shannon Tower advised the crew that current conditions included 10/10 cloud cover at 400 feet and visibility reduced to one mile. The tower requested a ceiling check, which was acknowledged by the pilot. Around 0208, airport personnel observed the aircraft approaching on a heading parallel to Runway 32. The plane continued on this path until reaching the airport area, where it turned right toward a northerly heading before disappearing from view.

Approximately one minute later, witnesses reported seeing a brilliant flash west-northwest of the airport and hearing a loud noise. Emergency crews were immediately dispatched to the scene after confirming the crash.

Findings

The investigation determined that the primary cause was an error in altimeter indication resulting from reversed primary and alternative static source lines. This mechanical fault led the pilot to conduct the approach at a dangerously low altitude. Contributing factors included maintenance negligence in certifying the static system without performing required tests, as well as restricted cockpit vision caused by fogging on unheated windshield panels.

Probable cause

An error in altimeter indication due to reversed static source lines led to an approach at a dangerously low altitude.