sikorsky S-61

[planedr56]

Hello, I am an S-61 helicopter Mechanic. I have a problem that I cannot solve. with the rotor head spinning and Nr at 100% when I isolate the primary hydraulic system and the Aux system is still running the aircraft goes into a one for one vertical bounce. what might be a cause for this?

[sycamore]

Control rigging as a starter....

[Variable Load]

Now this is really stretching my memory, but check the bootstrap spring on each servo.

[Phil Kemp]

Have you performed any maintenance to this machine prior to this happening?
What kind of blades?
Does this only happen on the ground or in flight/hover?
When you turn the primary system off, does the blade track change at all?
With the Primary system off, can you see or feel any of the controls moving between the rotor head and the aux pack?
Checked the pitch horn eye bolts, swashplate, uniball and both scissors?

[ken knight]

As Phil said what you done anything recently.
What type of blades are they?
Going back more years than I care to remember when we had the old style blades with the long tip caps fitted rather than the newer extended spar blades with short tip caps when this happened we traced it to a tip cap change and this was causing the blade to be out of Chordwise balance. Most noticeable on the ground with the Primaries off as a bounce and the track was visibly out. We put the old tip cap back on and the problem went away. I would have thought by now all the old blades would be out of circulation but have you changed a blade recently?