Last year, the F.A.A. said it was also investigating claims by a Boeing engineer that parts of the fuselage, or body, of the Dreamliner were improperly fastened together, which the whistle-blower said could cause premature damage to the plane over years of use.

Investigators hope the device will provide clues about the cause of the accident that killed 241 passengers and crew, and a number of others on the ground.