1948 Airborne Transport DC-3 disappearance

Investigation

In a report released 15 July 1949, the board convening the investigation filed several factors about the aircraft:

The aircraft was originally built on 12 June 1936, and had a total of 28,257 flying hours prior to the landing in San Juan. It had been inspected several times in the previous two years and certified to be airworthy.

The aircraft was given a partial overhaul, including the replacement of both engines, in November 1948. An in-flight test was conducted to judge the results of the overhaul, including flying to New Jersey and back. Again, the aircraft was certified to be airworthy.

The report noted that although the carrier, aircraft, and crew were certified, at the time of takeoff, the aircraft did not meet the requirements of the operating certificate.

The company's maintenance records were incomplete. In one case, a subcontractor working on an engine in October 1948 completed the task but did not save any records proving it.

As far as human error, the report cited several occurrences:

Captain Linquist told San Juan that his landing gear down indicator lamps did not work. This led to the discovery that his batteries were low on water and electrical charge. While he ordered the refilling of the batteries with water, he ordered the reinstallation of the batteries on board the aircraft without recharging them.

The aircraft left with the batteries charged only enough to satisfy two-way radio communication with the tower, with the understanding that an in-flight flight plan would be filed before they left the vicinity of San Juan. This was not done, and the plane continued on a course for Miami. It was noted in the report that the plane's radio transmitter did not function properly due to the low battery charge.

The aircraft left San Juan with a cargo/passenger weight 118 lb over the allowable limit.

A message was sent to the plane concerning a change in wind direction that could have been strong enough to push the plane off course. It was not known if the plane received the message.

The plane's electrical system was not functioning normally prior to departing San Juan.

The aircraft had fuel for 7½ hours of flight; at the time the last transmission was intercepted, the flight had gone on for 6 hours and 10 minutes after takeoff, and thus "an error in location would be critical."

Because of a lack of wreckage and other information, probable cause for the loss of the aircraft could not be determined.