Hi all.. In the ole ATPL(H) material Hydraulic Lock is described as different to Jack Stall- which if I remember correctly is a hydraulic force overload.
Hydraulic Lock as I understood it from the ATPL(H) studies is a failure (design or mechanical) in which the hydraulic pressure gets around the back of the relevant actuator(s) and the controls become hydraulically 'locked'. Turning off your HYD may make no difference..? Does anybody know of this?
While training in NewZealand I was flown over the site of an AS350 accident where the pilot had pulled a hard right turn (fully loaded with 4 Pax) to show a view of something. He had (I was told) got 'Hydraulic Lock' and continued into the ground at high speed. I was told it was well known with As350s, in NZ at least, that high positive G and especially right turns in the As350 was to be avoided.. (If I recall correctly). I asked which type of hydraulic failure he meant and was not given a definite response either way..'Is there a difference?'
For interest in this Dauphin
clip... he seems to be straight and level, but this looks more likely to be just Jack Stall from an aggressive pull back on the stick.
see here
Can anybody shed light on this issue of Hyd Lock...? (not a big discussion about Jack Stall that has been talked about in depth in other threads).
(Note: My previous refs to specific recent accidents have been removed out of respect and sensitivity to those affected. I ask to keep the thread on the technical issue proposed, Hydraulic Lock
)