An Israeli Air Force team determined that a fire in one of its heavy transport helicopters last month appeared to have been caused by a technical failure in a gear connected to its left motor, the military said Thursday.
IAF chief Amikam Norkin grounded the military’s fleet of Sikorsky CH-53 Sea Stallion helicopters, known in Israel as the Yasur, in light of the incident on November 26. The aircraft remain grounded, the army said.
According to the air force’s initial investigation, the fire, which destroyed the helicopter, originated in a gear that was part of a relay from the aircraft’s left motor, and not within the engine itself as originally suspected.
“Due to the high heat caused [by the gear], the relay caught fire, which led to the helicopter catching fire,” the military said.
The air force said it did not yet know the cause of the gear’s technical failure and was working with local and foreign experts in order to identify the source of the problem.
“At this time, a bit more than a week after the event, we understand what happened, but not what caused the technical failure. The team will continue with the investigation until it is completed, and the Yasur fleet at this time is still grounded,” Norkin said in a statement.
The investigatory team confirmed that the pilots’ quick actions — landing the helicopter in under a minute — allowed all 14 soldiers on board to escape the aircraft unscathed.
The helicopter had been en route to a base in southern Israel for a training exercise. Eleven of the soldiers on board were members of the elite Shaldag commando unit, along with two pilots and a mechanic.
Three teams of firefighters were called to the scene to combat the blaze.
Israel’s fleet of Yasur heavy transport helicopters was purchased from the United States in the late 1960s. Though the aircraft have been upgraded and restored in the interim five decades, they are widely seen in the military as ready for retirement, in favor of newer models.
In 2010, an Israel Defense Forces Yasur helicopter crashed during a joint exercise of the IAF and Romanian Air Force, killing the five people on board.
That crash was found to have apparently been caused by human error.
In 1997, two Yasur helicopters collided in the air while en route to locations in the country’s then-security zone in southern Lebanon. Seventy-three soldiers were killed in what was Israel’s most devastating air disaster.