Originally Posted by
AnFI
what's the 'yaw stiffness' on a 139 like? is it really as bad as ShyTorque suggests?
I can only describe, how it is modelled in the Sim... but within 5-6 sec the nose will turn approximately 90 degrees to the right... if the pilots are not doing anything e.g. during cruise flight and the TR shaft failure occurs... and the turning tendency will continue...
Btw. e.g. S76 behaviour was modelled a similar way and AS332L1 (of course the nose was then turning to the left) as well.
Btw. I can understand your description: ”
There are accident reports, an H369 in Australia is one, non-event. and a gazelle in UK where the drive shaft failures were bearly noticeable (in the Gazelle for HALF AN HOUR !!)”
Especially concerning ”the Gazelle case”... IMHO. the helicopters with a Fenestron Tail are different... when I got my EC135 TRI training in Germany, the EC TRI Didi B. told me his experience with a TR shaft failure... He could fly level flight with that failure and autorotate later on, when he was close by a suitable landing area. I don’t have any other referencies from pilots, who have experienced a real TR shaft failure.🤔
Cheers! 😉