Originally Posted by
Cows getting bigger
Thoughts? A $2 nut (or thereabouts before being associated with an EASA Form 1), mitigated by a piece of locking wire, presents the potential of a catastrophic single point of failure.
You are aware that helicopters are littered with single point failures aren't you.
Any MR Servo Mount bolt. Any MR Blade Bolt. Any TR Blade Bolt. The "Jesus" nut, to name but a few. There are certification limits for the probability of failure of these critical items, which has been mentioned here already.
This nut is double locked. A dirty fat Split/Cotter Pin and lockwire. No single locking method failure should induce a failure of the control. Both locking systems have to fail. And with the nut being upstream of the servo assist it does not have flight loads on it only the same loading that the pilot feels on his/her feet.
This "nut on the end of the servo" system has flown for years and years on the 139 and 189. Although the 139 nut is slightly different. The 189 also has an SB out for inspection of the nut (out this morning).
I anxiously await the next update from the AAIB.