Bell 412 hydraulic pressure reading after shutdown

[Abdelrahman]

Any one have explanation for this issue which occurs in bell 412
Hydraulic pressure indicator still reading after helicopter shutdown
Some times hydraulic takes between 5 to 10 min to drop to zero but also some times it was not drop even after one hour ,,,!!!!

[hueyracer]

Is this with Bat cb pulled out?

Faulty gauge?Have you tried swapping gauge 1 and 2?

[Abdelrahman]

Gauge works normal
Hydraulic pressure is real not false indication

[sycamore]

I don`t know the system ,but after the blades have stopped,then gentle `stirring` of the stick should dissipate the pressure,and then revert to `manual`.If it does go to manual,and the gauge still shows pressure,then you have a gauge problem I would suspect.If there is an `accumulator` in the system ,you should also check that for it`s static charge pressure....

[Dexus]

A check valve which fully closes when the system pressure is dropped to 600psi is incorporated in the pressure port of all the servo actuators and a return shut off valve which closes when the system pressure is reduced by 600psi. So, it's normal and the system pressures will be maintained for several hours in case of all the valves are in a good condition. If you move the pedal, the System 1 pressure will drop and move the CYC or CLTV stick, both System 1 & 2 will drop :ok:

[CTR]

Almost all 412's have a small spring energized accumulator in both Systems 1 and 2. They are part of the Lock-n-Load feature preventing the stick from being back driven by rotor loads when hydraulic pressure is unavailable. The accumulators are only a few cubic inches and at 600 psi are only there to keep fluid in the actuator in case of a leak. As Dexus stated, a few control motions normally empties the accumulators. Note 412s as of 2015 eliminated the accumulators. Turns out they were an unnecessary carry over from the original single boost aircraft.