Aircraft             Start-IPS           Finish-IPS

Cirrus SR22 G2            .344                   .008 231 Hrs since new

Cessna A185F              .279                   .019

Cessna 180                .937                   .038

Cessna 180J               .106                   .009

Piper Warrier 151         .204                   .021

VulcanAir Left            .172                   .023

VulcanAir Right           .105                   .017

Cessna 185                .697                   .020

Piper 18-160              .457                   .008

Cessna 150                .159                   .046

Piper Cherokee 180        .426                   .055

Piper Aztec Left          .566                   .043

Piper Aztec Right        1.046                   .037 Static weights 180 out

Cessna 185                .229                   .015

Cessna 185                .272                   .013

Piper Twin Comanche Left  .315                   .003 AOPA Win A Twin

Piper Twin Comanche Right .539                   .040 AOPA Win A Twin

Cessna 185                .097                   .002

Cessna 180                .304                   .014

Cessna 150                .275                   .033

Beech A36 IO-550          .385                   .013

Piper Comanche            .278                   .071

Piper Comanche            .358                   .016

DSS has computed their industry average at .039 IPS, the average at Aviation Resources
using the same equipment is .02452 IPS.

Accurate measurements, attention to detail, evaluation of the
whole vibration spectrum leads to very low propeller balance IPS.

Accurate measurements, attention to detail, evaluation of the
whole vibration spectrum leads to very low propeller balance IPS.

Our service documentation overview:

-Identifying tags placed strategically on prop/engine advising dynamic balance weights installed

-All forms printed on a laser or archival ink printer for archival permanence

-Two logbook entries printed on 'Sticky' paper; one for each airframe and propeller logbook (twins received sets for each engine)

-Multiple copies of the Pre Balance & Post Balance Spectrum and Waveform plots with annotations of items of particular interest

-An explanation and comparison of the Spectrum peaks as labeled for each particular engine machine file

-FAA Form 337 no longer required by FAA AC 20-37E 300. PROPELLER BALANCING. (c)(2)(c) For aircraft or propeller manufacturers that provide procedures for dynamic balancing of the propeller in their maintenance manuals or instructions for continued airworthiness, propeller balancing is not considered a major airframe alteration.

-All documents presented in archival quality document protectors

-Copies stored in multiple location for future retrieval; 1) Master record file in hangar, 2) Reference Logbook binder in hangar, 3) Billing records stored offsite, and 4) Hard drive back up at my house.

CLICK THE LINKS BELOW FOR FORM SAMPLES


MicroBase NXXL sample Balance History

Form-MicroBase NXXL Pre Balance Waveform Plot

Form-MicroBase NXXL Pre Balance Spectrum Plot

MicroBase NXXL Post Balance Spectrum Plot

MicroBase NXXL Post Balance Waveform Plot

TECH TIPS
Magneto to Engine timing procedure

Magneto Timing Process


The AOPA Comanche "Win a Twin" flew in after attending Oshkosh 2004 so it could have both engines professionally balanced by Aviation Resources.





(AOPA's Tom Horne (left) Jim Barker (right))

Choose Slide Show: Prop Balance on AOPA Twin

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From the AOPA website:
http://www.aopa.org/pilot/twin/0408.html?PF

Prop balancing, and more...
After AirVenture, I flew N204WT to Aviation Resources at its location on the Cumberland, Wisconsin, airport (UBE). There, Jim Barker and his team set to work balancing our/your propellers. Using dynamic prop balancing procedures, it was learned that the left propeller was out of balance by a factor of .315 inches per second (IPS). In other words, the prop disc was wobbling about its axis at a rate of about a third of an inch. That's not much, but it's enough to make the engine and prop vibrate and set up unhealthy stress paths in the propeller blades and engine crankshaft. Abnormally high vibrations can also cause horsepower-robbing friction and abnormal component wear especially of the alternator mounting brackets and exhaust stacks.

By bolting 29.6 grams of nuts, bolts, and washers to a strategic spot on the crankshaft's flywheel, the vibration level was reduced to .003 IPS. That's a 10-times reduction in vibration levels. Barker took about three hours to do the work, using a special tachometer and vibration sensor, plus proprietary computing equipment.

Then it was on to the right engine, and that's where the value of prop balancing kicked in to the max. Barker saw a .539 IPS out-of-balance condition indicating unusually rough vibrations. And in fact, you could see the out-of-balance prop by looking at the spinner as the engine ran. The spinner tip wobbled as it spun around at 2,100 rpm during the ground runs used for balancing trials.

Barker's computer said to place a whopping (a relative term in prop balancing) 96.78 grams of weight to correct for the imbalance. From experience, Barker knew that such a large weight recommendation meant that the odds were that the prop would never balance properly. Something was wrong with the right engine's prop setup. Barker found out, and you won't believe what it was.

The prop was installed incorrectly. It was mounted 90 degrees from its proper location. Turns out, you don't just bolt a prop any old place on the crankshaft flange. You use a reference, or index, bushing to align the blades. In this case, the index bushing was aligned with the top dead center mark on the flange.

The prop was removed, reinstalled in the correct position, then dynamically balanced after three ground runs. All went well, and the right prop's final vibration reading was .040 IPS not bad at all.

Aviation Resources also addressed some other maintenance issues tightening the right engine's alternator belt and number-two cylinder's upper spark plug and replacing exhaust gaskets on the right engine. The oil was changed on both engines as well.

In all, it turned out to be a great maintenance stop. It was the first time in 45 hours that the cowlings had been removed and the new powerplants and props had been inspected. Guess 50-hour inspections really are good ideas.

And I could tell the vibration levels were way down on the four-hour, 30-minute nonstop flight back home to Frederick, Maryland. For the trivia-minded, I averaged true airspeeds in the 174-knot range at my 9,000-foot cruising altitude, saw sustained groundspeeds at 190 knots, burned 81.9 gallons, and logged 45 minutes of actual in some of the bumpiest clouds I've ever encountered cumulus leavings of an aggressive cold front that pushed through the Midwest the day before.


101 Airport Avenue, Hangar 7
Cumberland, WI 54829
Hangar: (715) 822-5787 Office (715) 822-3413 Cell (715) 491-1303
Hours: M-F 8-5
Let's Fix It!!!

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