An A-Star AS350B air ambulance helicopter crashed November 14 at Doyle, California, killing the three crew members on board. According to an article in the Reno Gazette Journal, the pilot made a distress call before the crash. That indicates that the pilot was likely experiencing a mechanical emergency. The photographs accompanying the article show that the wreckage was spread over a fairly large area. That indicates that the pilot lost control of the helicopter well before he was able to attempt an emergency landing.
Under the circumstances, the NTSB will be looking at the helicopter’s
hydraulic actuator system carefully. The actuators move the helicopter’s rotor blades, allowing the pilot to control the flight of the aircraft. The AS350B’s hydraulics — similar to a power steering system in a car — help move the helicopter’s actuators.
The A-Star helicopter’s hydraulics have a troubled history. The hydraulic system seems to fail frequently. Without hydraulic assistence, the pilot may find it hard to move the actuators and thus the helicopter can be difficult to control. In fact, one of the country’s largest operators of A-Star helicopters is on record as saying that the design of the helicopter’s hydraulic system is so prone to failure that it is defective and dangerous and needs to be redesigned.
While a problem with the hydraulic system can make the helicopter difficult to control, a disconnected actuator control rod will make the helicopter impossible to control. That’s what happened in 2007, when an AS350B just like the one in involved in this accident crashed in Hawaii, killing four tourists.
Days after the accident in Hawaii, the A-Star helicopter’s manufacturer, Eurocopter, issued a Special Airworthiness Bulletin (see below) prompted by two previous fatal accidents, warning of the consequences of loose servo control rod end fittings.
This condition could lead to flight control disconnect and subsequent loss of aircraft control. Two fatal accidents have occurred after the servo-control rod end-fitting became detached from the servo-actuator.
Of course, it’s far too early to say what caused the Mountain Lifeflight accident. But the helicopter’s hydraulic actuator system is certainly something that needs to be looked at very carefully.
December 6 Update: More on this accident here.
January 14 Update: On Compensating the Mountain Lifeflight Families here.