Nigerian and U.S. accident investigators are at NTSB Washington headquarters to review flight recorder data from a Bristow S-76C+ that crashed Aug. 12 on approach to Lagos. Nigeria's Accident Investigation Bureau asked the NTSB to assist it in reviewing data from the cockpit voice and flight data recorders, which were recovered Aug. 14 from Lagos Lagoon. Investigators from the FAA, Bristow and Sikorsky are expected to assist in reviewing the recorder data. The Sikorsky twin crashed into the lagoon on approach to Murtala Muhammed International Airport after transporting 10 passengers from an offshore rig about 100 mi southeast of Lagos. The crash killed four passengers, the pilot and first officer. In addition to listening to the pilots' conversations before the crash, investigators typically review the voice recording for sounds indicating the state of rotor, engine and flight control performance, as well as the performance of other aircraft systems. They also typically compare flight data parameters from the accident flight with past flights captured on the recorder, as well as any data retained through Bristow's flight operations quality assurance program.