Vref Posted March 13, 2012 Report Posted March 13, 2012 I was rather hesitant to publish this but I think we can all learn from this.... Received some bad news today....my aircraft was in for a dynamic prop balancing...the final stage of my major overhaul process after solving all of the avionics issues, I was on top for a week or two ......;-). The balancing was not successful....So adding weights didn't bring the value down to below a significant number <0.1 IPS......the consequence of this, the crankshaft needs to be rebalanced....pffffffffft. The value is not to unsafe but not good neither.... The aces pro balancer computer analysis shows no harmonics (indicating no accessories contribute to the vibration) but a steady amplitude which can not be compensated with a prop balancing......The company claims they are almost sure it's the crankshaft fly weight assy that needs balancing.... I need to check if this is a dynamic or static balancing .....? I am not even sure how many companies can do this dynamically... Prop is newly overhauled, crankshaft was re manufactured (overhauled) but the flyweights where re-used... It's a pain but too continue flying like that would become more painful I think if i don't address the problem seriously....Only in the yellow when short final) band I sensed some vibration but not to the level I would have found it abnormal... . In cruise I even found my engine running very good.... I don't think cranckshaft re-balancing (including the flyweights) is part of a shock loading inspection is it...? Anybody went through the same exercise? I am learning another lesson the hard way I am afraid...;-(((... I am wondering how many aircraft are actually flying around not knowing the vibration level...? If I would buy a ready to go aircraft (knowing what I now now...) I would certainly ask for a recent prop balancing report....it's like a doctor check-up listening to your ECG.... Luc Quote
jetdriven Posted March 13, 2012 Report Posted March 13, 2012 Is a dynamic balance even required? Can you re-index the prop 180 degrees and try again? Can you check the static balance of the prop? How about the engine builder? Someone signed off on that. FWIW, our plane had a .395 IPS starting balance and a final of .052. Point is it had flown that way for 1400 hours with no issues. We didnt like the compass buzzing at 2700 RPM. It still buzzes. If they could only get it down to .1 IPS, what is the big deal? Quote
John Pleisse Posted March 13, 2012 Report Posted March 13, 2012 Luc... I had the same issue a number of years ago. My engine was modified under an STC and had higher compression pistons. Over time, this did it's damage. We identified the crank issues with prop balancing. Byron.... .052 is a good as you'll get it. If it doesn't fly smooth, you developed a harmonic and I'd put it back. But there is no way of knowing for sure if you were at .352 all those years. It could have been progressive. Quote
Vref Posted March 13, 2012 Author Report Posted March 13, 2012 Well it was a consequence of things, the old crank was out of tolerance (pilot flange)after a shock load inspection. An overhauled (re manufactured) was found in the US and installed (with the old fly weights)...the prop is newly overhauled and should have been statically balanced anyway...Byron my value is double your initial value something around 0.8...unacceptable for longer run. I will limit it to a ferry flight....What I only find strange I don't notice the vibration round 2400 RPM.....or even higher values..only on the lower RPM you could say there is some roughness...Apparently from the analysis they can identify some known sources......crank, magneto, etc...I only hope that after this painful exercise things will improve...Only some companies in Europe have sophisticated prop balancers for verifying this...... Quote
Vref Posted March 13, 2012 Author Report Posted March 13, 2012 Quote: N4352H Luc... I had the same issue a number of years ago. My engine was modified under an STC and had higher compression pistons. Over time, this did it's damage. We identified the crank issues with prop balancing. Byron.... .052 is a good as you'll get it. If it doesn't fly smooth, you developed a harmonic and I'd put it back. But there is no way of knowing for sure if you were at .352 all those years. It could have been progressive. Quote
John Pleisse Posted March 13, 2012 Report Posted March 13, 2012 Quote: Vref John, how did you solve the issue? Quote
Vref Posted March 13, 2012 Author Report Posted March 13, 2012 I know the one in it now was 7000$..the engine only has 700 Hrs since overhaul....if this one does not pass the inspection after 50 Hrs run-time ...I have a serious problem......... Quote
bnicolette Posted March 13, 2012 Report Posted March 13, 2012 I had mine done in May of last year. The starting IPS was .33 @2600 and they installed some weights. The ending IPS was .01 @2600 I had new engine mounts installed after that. I wonder if I should have the balance done again? What do you guys think? The previous owner of the airplane had it balanced in May 2003 and it doesn't state the beginning IPS but the ending was .080 Quote
John Pleisse Posted March 13, 2012 Report Posted March 13, 2012 Quote: Bnicolette I had mine done in May of last year. The starting IPS was .33 @2600 and they installed some weights. The ending IPS was .01 @2600 I had new engine mounts installed after that. I wonder if I should have the balance done again? What do you guys think? The previous owner of the airplane had it balanced in May 2003 and it doesn't state the beginning IPS but the ending was .080 Quote
pjsny78 Posted March 13, 2012 Report Posted March 13, 2012 does anyone know how long a prop balance lasts? i want to get myne done. Quote
Vref Posted April 2, 2012 Author Report Posted April 2, 2012 Progress Report: I decided to go for a second opnion and I flew over my Aircraft to the biggest/best GA MRO company in Europe (Germany) capable of doing prop's, piston engines, fuel servo's, turbine engines etc..and Guess what...? They called me this morning and told me.... my engine doesn't have a problem it was at 0.3 IPS and they brought it back below 0.1 IPS...with a balancing report.......YEAHHHHH This will save me MEGA Euro's...lessons learned only trust the best professionals you can find and sometimes having a second opinion pays off...What a relief.... Lessons learned I will only do my prop balancing with a company capable of statically & dynamically balance a prop and having the capability of checking the prop pitch angle blades, crankshaft within a minute of precision...You really need specialists for this analysis .. Thank you Roder Presizion in Frankfurt Egelsbach http://www.rp-eg.de/ rgds Luc Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.