Boeing Test Flights Cleared
The ten test flights Boeing is being allowed to schedule will be designed to provide more data for inspectors who are still investigating the failed 787 batteries. The NTSB is planning to release a report around March 7.
First there was a flight to move a 787 from Texas to Washington State, then the Federal Aviation Administration said it would permit the test flights, if flown under stringent rules, in order to to monitor the batteries in while in use.
The NTSB determined after an exhaustive examination of the JAL lithium-ion battery that the majority of evidence from the flight data recorder and both thermal and mechanical damage pointed to an initiating event in a single cell, out of eight. That cell showed multiple signs of short circuiting, leading to the thermal runaway condition, which then cascaded to other cells. The temperature inside the battery case exceeded 500 degrees Fahrenheit, charring the battery components.
Currently the assumption is that the potential causes of the initial short circuit include battery charging, battery construction and design, and manufacturing defects.