They’re flying with the engines facing at least partially upwards during takeoff and landing, even when taking off like an aircraft, meaning they’re in trouble if they lose power, not just in a hover. The Japanese crash happened on final approach as they were slowing down, but still a few hundred feet in the air.
This is the combination of airspeed and height you cannot perform an autorotation from, the graph shown is worse than many other helicopters. Robinson aircraft can auto from zero airspeed at around 400 feet. It’s all about having enough forward speed to flare off your rate of descent and land with only forward airspeed, you could successfully flare at head height and enough airspeed over good ground.
They’re flying with the engines facing at least partially upwards during takeoff and landing, even when taking off like an aircraft, meaning they’re in trouble if they lose power, not just in a hover. The Japanese crash happened on final approach as they were slowing down, but still a few hundred feet in the air.
https://en.m.wikipedia.org/wiki/Helicopter_height–velocity_diagram
This is the combination of airspeed and height you cannot perform an autorotation from, the graph shown is worse than many other helicopters. Robinson aircraft can auto from zero airspeed at around 400 feet. It’s all about having enough forward speed to flare off your rate of descent and land with only forward airspeed, you could successfully flare at head height and enough airspeed over good ground.
Other tiltrotors are capable of autorotation.
I like that the chart there has a little red sliver to indicate that it is, in fact, a bad idea to fly very fast at ground level.