Massive Prop Vibrations Woodcomp SR3000/ 2 blade from defective adjustment mechanism

[Urs Heim]

I had a scary problem with massive vibrations from the prop, out of the blue, inflight. It turns out, one of the prop blades was loose inside the adjustment mechanism, which permitted it to rotate almost freely within the adjustment range. And this with an airplane, that has 68 total hours on it and after the prop had been returned to Woodcomp after the intial test flight at CZAW had shown the adjustment mechanism to be faulty at certain RPMs.
I am shipping the propeller back to Woodcomp now.
Anyone with similar experiences with Woodcomp props?

[Urs Heim]

Follow up:
After not being able to ship the prop by Postal Service or other shipper (For the Post, the box was too heavy at over 30kg, some shippers refused to accept a shipment from a private person, the other end of the spectrum was covered by Fedex, who charges 2200 SFR for a one way shipment!), I drove straight to the Woodcomp factory near Prague and delivered the prop for repair at 7am sharp Monday morning. Turns out the teeth on the cogwheel of one blade were destroyed over 30 degrees of circumference. I have no idea what caused this. From what I could decipher from the mechanic who only spoke Czech, he installed a new adjusting mechanism, which should prevent this in the future. I am waiting for a work report from the Woodcomp manager, as he was not at the factory at the time. The prop goes back on my SC this Friday and I can't wait to see if it works now.

[Urs Heim]

The prop is back on my plane and it is behaving like it should, ie. absolutely no axial play on the blades and very little vibration inflight throughout the RPM range. I have flown it for two hours in the mean time.

Woodcomp thinks the cause of the damaged cogs on one blade stems from transportation damage when it was sent to CZAW originally.
Urs

[Robert Brazil]

Does make one wonder about the entire quality control process, however.

[Urs Heim]

Below is Woodcomp's report on the repair on my SR3000/2 inflight adjustable prop. It has been working flawlessly for the past 40 hours since the repair.
Urs

please watch the two attached photos.
The photo prop old.jpg shows the older version of expanding system of propeller blades. This system eliminates the backlash of propeller blades. The backlash is caused by centrifugal force which affect the axial bearings. Your propeller was equiped by this version - the long M6 screw push the small wedge between the both propeller blades and push the blades to the axial bearings.
This system must by inspected after the first 25 -50 hours. It means that the M6 srew must be little bit tight during those hours ( the new axial bearings sag little bit)
In your case the small wedge wasn´t adjust correctly and it move between the gears. It caused the propeller failure.
The photo 003 shows the new version of self expanding system of propeller blades. The blades are pushed automatically by special spring washers which are pressed between the propeller blades by special tool. It means that the failure cannot repeat and not adjusting after the first 25-50 hours is needed.
I apologize for delay - I waited when the both systems will be open on our work shop until now.
I apologize for my English - it is not easy to explain you those technical issues :-)
Best regards
Jiri Holoubek - WOODCOMP