Dynamic Propeller Balancing
Posted: Wed Feb 28, 2018 3:59 pm
As a noob aircraft owner myself, this is written primarily for all the other noobs that will follow me in coming weeks/months/years.
Summary: I had 62C's propeller dynamically balanced two weeks ago, and it was a positive experience/outcome.
Detail: I've owned 62C for approximately six months now and any maintenance activities I've invested in have primarily been to increase the longevity of the aircraft, not to fix broken stuff. 62C has been a tight flyer with no complaints. I did notice a very slight "buzz" in the control yoke (and you could see it, faintly, looking at the shoulder straps of the passenger seat) extending up into the yoke-mounted iPad holder which seemed to change based on RPM. Not a "vibration" per se, just a "buzz" - and nothing I was overly concerned about
After researching dynamic propeller balancing, I was pleased to discover that Sensenich Propeller Services has one of its two maintenance facilities just off the field at the Gainesville, GA airport, a short one-hour flight north of my home field. On a beautiful Thursday morning I flew 62C north and met one of the techs at the airport, taxied over to the end of the hangars where they typically do run-ups, and spend the next two hours running the tests.
Equipment consisted of a single accelerometer mounted under the cowl near the front of the engine, an optical sensor taped on the top of the cowl using 500-mph tape, and a piece of reflective tape affixed to the back of the prop. Cables from both sensors were taped to the side of the aircraft and run out to the computer unit. It took approximately one hour to have all the equipment secured and ready for the test.
We ran three tests, which involved me running the engine to full static power (on ground, chocked, w/brakes) for approximately 15-20 seconds while the computer analyzed the RPMs and the vibration, after which I slowly brought the engine back to idle and shutdown. The first test showed a reading of .2 IPS (inches per second). According to the tech, the average reading for aircraft which haven't received balancing before is .4-.5. He also mentioned that there was general agreement by both engine and propeller manufacturers that anything below about .3 is undetectable by a human, though it can still be a source of concern over the life of the engine. The computer analyzed the results and recommended a weight and location to affix a "test weight" to the spinner. The weights were in the form of washers, and affixed using the standard screws holding the spinner in place. The two remaining tests were performed equally, with the computer making minor adjustments to weight and location.
Once the final weight and location recommendations were received, the spinner was removed and a bolt and washer permanently affixed to the spinner back plate. The tech had to drill a hole to accommodate the weight. A fourth, and final test, was performed once the spinner was reassembled showing a final reading of .02 IPS, which was below the typical final reading of .05 IPS according to the tech.
I received a 337 in the mail a few days later for the logs and have a logbook entry indicating the work that was done.
In the several flights since that time I have noticed that slight "buzz" completely gone. I also am left with peace of mind that this was another step in keeping overall engine vibration to a minimum, and life of the engine to a maximum.
For folks with more experience than me, please feel free to suggest edits to clear up any misinformation in the above - I'd like to make this as useful as possible.
Photos below show the process that I have outlined above.
Summary: I had 62C's propeller dynamically balanced two weeks ago, and it was a positive experience/outcome.
Detail: I've owned 62C for approximately six months now and any maintenance activities I've invested in have primarily been to increase the longevity of the aircraft, not to fix broken stuff. 62C has been a tight flyer with no complaints. I did notice a very slight "buzz" in the control yoke (and you could see it, faintly, looking at the shoulder straps of the passenger seat) extending up into the yoke-mounted iPad holder which seemed to change based on RPM. Not a "vibration" per se, just a "buzz" - and nothing I was overly concerned about
After researching dynamic propeller balancing, I was pleased to discover that Sensenich Propeller Services has one of its two maintenance facilities just off the field at the Gainesville, GA airport, a short one-hour flight north of my home field. On a beautiful Thursday morning I flew 62C north and met one of the techs at the airport, taxied over to the end of the hangars where they typically do run-ups, and spend the next two hours running the tests.
Equipment consisted of a single accelerometer mounted under the cowl near the front of the engine, an optical sensor taped on the top of the cowl using 500-mph tape, and a piece of reflective tape affixed to the back of the prop. Cables from both sensors were taped to the side of the aircraft and run out to the computer unit. It took approximately one hour to have all the equipment secured and ready for the test.
We ran three tests, which involved me running the engine to full static power (on ground, chocked, w/brakes) for approximately 15-20 seconds while the computer analyzed the RPMs and the vibration, after which I slowly brought the engine back to idle and shutdown. The first test showed a reading of .2 IPS (inches per second). According to the tech, the average reading for aircraft which haven't received balancing before is .4-.5. He also mentioned that there was general agreement by both engine and propeller manufacturers that anything below about .3 is undetectable by a human, though it can still be a source of concern over the life of the engine. The computer analyzed the results and recommended a weight and location to affix a "test weight" to the spinner. The weights were in the form of washers, and affixed using the standard screws holding the spinner in place. The two remaining tests were performed equally, with the computer making minor adjustments to weight and location.
Once the final weight and location recommendations were received, the spinner was removed and a bolt and washer permanently affixed to the spinner back plate. The tech had to drill a hole to accommodate the weight. A fourth, and final test, was performed once the spinner was reassembled showing a final reading of .02 IPS, which was below the typical final reading of .05 IPS according to the tech.
I received a 337 in the mail a few days later for the logs and have a logbook entry indicating the work that was done.
In the several flights since that time I have noticed that slight "buzz" completely gone. I also am left with peace of mind that this was another step in keeping overall engine vibration to a minimum, and life of the engine to a maximum.
For folks with more experience than me, please feel free to suggest edits to clear up any misinformation in the above - I'd like to make this as useful as possible.
Photos below show the process that I have outlined above.