The Accident Investigation Bureau (AIB) said on Monday that it was yet to determine the cause of the crash of the Bristow Helicopters S-76 chopper, which went down into the Lagos Lagoon on Aug.12.

AIB's Commissioner, Mr. Felix Abali made this known on Monday while presenting the bureau's preliminary report on the incident to newsmen in Lagos.

The News Agency of Nigeria (NAN) reports that six persons, including the pilot and the co-pilot, were killed after the helicopter, which was enroute Lagos from Akure, crashed into the Oworonshoki area of the lagoon.

Abali said preliminary findings by the bureau's investigators revealed that the “pushrod assembly of the chopper became disjointed and could not hold together.”

According to him, the failure of the pushrod assembly can result in a loss of main rotor or tail rotor flight control and consequent loss of control of the helicopter.

He, however, said that it was too early to speculate on the cause of the crash as further investigation was still ongoing.

Abali said the AIB investigators were still putting together the findings of download carried out in the United Kingdom on the flight data and cockpit voice recorders recovered from the crashed chopper.

He disclosed that the Abuja laboratory of the AIB could not carry out downloads of the flight data and cockpit voice recorders because the models were outdated.

According to him, the bureau has been working with Sikorsky Aircraft Corporation, the aircraft manufacturers, and the U.S. Federal Aviation Administration officials to establish probable cause of the accident.

He said following the preliminary investigation the manufacturer and the Federal Aviation Administration took some measures to guard against future occurrence

“On Sept.10, Sikorsky Aircraft Corporation issued Alert Service Bulletin (ASB) 76-67-57 on all S-76 model helicopters equipped with Control Pushrod Assembly P/N 76400-0034-059 and 76400-00014-071.

“On Sept.14, the Federal Aviation Administration issued Emergency Airworthiness Directives (EAD) 2015-19-51 to owners and operators of Sikorsky Aircraft Corporation model S-76A, S-76B, S-76C and S-76D helicopters.”

NAN reports that in its preliminary safety recommendations, the AIB urged Sikorsky to consider a redesign of the affected control pushrod assembly by introducing additional wire locking safety features between the Jamnut and the Pushrod to enhance better security.

The bureau also urged the Nigerian Civil Aviation Authority (NCAA) to immediately carryout appropriate oversight action on all the Sikorsky S-76 series helicopters flying in Nigeria.

It said this was to ensure the implementation of the Emergency Airworthiness Directives (EAD) and Alert Service Bulletin (ASB) issued by FAA and Sikorsky Aircraft Corporation. (NAN)

•Photo shows Crash site of Bristow Helicopter