ABU DHABI // Engine malfunction does not appear to be the cause of a plane crash that killed four Americans in Al Ain last year.
An interim report released late last month has failed to shed light on what caused the seaplane, which was built in 1944, to crash at Al Ain International Airport shortly after taking off.
Both engines were shipped to the manufacturer for examination and results indicated they had been operating normally at the time of the crash.
Steven Kushnick, a US mechanical-engineering consultant and turbomachinery expert, said the report did not provide any clues.
"It sounds like it had nothing to do with the engines and it doesn't sound like a fuel problem," Mr Kushnick said. "It sort of suggests a controls problem but we really can't know."
The General Civil Aviation Authority released the report and is consulting with US authorities as part of the investigation. Examination of the plane's propellers is continuing.
A final report is expected within four months.
The McKinnon G21G turboprop was flying to Riyadh, Saudi Arabia on the first leg of a week-long trip that would have taken the four men to Morocco and South America before landing in Texas.
The private plane was owned by Triple S Aviation, a Texas company with a consultancy in Dubai. The aircraft was being flown by the owner of Triple S, Landon Studer.
The plane had been stored in a hangar in the UAE for six months.
It had undergone routine upkeep on the day of the crash, work described in the preliminary report as preventive maintenance that included installing an extra fuel tank, the history of which is being investigated.
The aircraft had only two minor modifications in the year before the crash, when a flight display and panel lighting were installed. Both were approved by US flight authorities.
The interim report said the crew indicated to air-traffic controllers that they intended to perform a test flight because "they haven't flown the aircraft for a while".
The take-off time was pushed back an hour while the crew waited for fuel.
The investigation has been hampered because the plane was not required to have a flight data recorder, or black box recorder, due to its size.
