Pilots, aircraft owners, builders and mechanics are increasingly discovering the benefits of vibration analysis as a way to identify and resolve complex vibrations. Spectral analysis, vibration analysis or vibrations surveys are very helpful in pinpointing the source of an elusive vibration or simply doing engine trend monitoring as a preventative maintenance approach. The DynaVibe GX2 is a prop balancer and vibration analyzer. When you use it to perform vibration analysis, it detects and reports the various vibrations that are affecting an airplane. For example, DynaVibe might detect a vibration that is occurring once per prop rotation – what is commonly referred to as a 1-per vibration. There are also half-per, 1.5-per, 2-per and many other vibrations that can occur. What do these vibrations indicate? One way to find out what a vibration means is to contact the DynaVibe team. We’re always happy to help customers understand how to use DynaVibe for spectral analysis and explain the results of a vibration survey. We have also put together the following vibration table using the excellent material originally published by John Schwaner of Sacramento SkyRanch. We hope you find it helpful, with the following disclaimer: this data is for educational purposes only. If your engine is exhibiting symptoms of vibration, properly rated professionals using diagnostic equipment should check it. This table is a good place to start in understanding the cause of vibrations detected through analysis with the DynaVibe GX2. If you would like to know more about vibration orders and causes, we can help. Just reach out to us using the contact information or form below.
The DynaVibe GX2 is he most affordable full-spectrum vibration analyzer on the market. To learn how to use DynaVibe for vibration analysis, enter your email address in the form below to be contacted by a DynaVibe team member. To purchase a DynaVibe, visit our online store, or simply call: 405.896.0026. If you're a DynaVibe Classic owner, RPX Technologies has a limited-time upgrade offer that can put a new DynaVibe GX2 in your hands. The GX2 supports two accelerometers for simultaneous data acquisition, providing substantially more diagnostic capabilities than the Classic. The GX2 is a prop balancer and vibration analyzer, and it is the technology platform into which RPX is building product enhancements. Here’s the short list of what you get when you upgrade from a Classic to a GX2:
Here is how to upgrade your Classic to a GX2: 1. Visit the RPX Technologies online store and purchase the Classic to GX2 upgrade (scroll to the bottom of the store page to see the offer). The cost is $2,995. You’ll receive a $1,000 trade-in credit for your Classic. We’ll reuse your photo tachometer, accelerometer, and case, then provide you with a new GX2 system and a 2nd accelerometer. 2. After you’ve purchased your GX2 upgrade in the online store, you’ll be contacted by DynaVibe and provided with a Return Authorization Number and shipping instructions. 3. Ship your entire DynaVibe Classic kit back to RPX Technologies per instructions. Once we receive it, we can usually turn your upgrade order around the same day. All DynaVibe GX2 systems come with NIST certification, so you’ll have a new NIST certificate as well! If you have any questions about upgrading your DynaVibe Classic to a DynaVibe GX2, just enter your email in the form below, or call us: 405.896.0026. Matthew Mitchell operates Mitchell Flying Service, an agricultural aviation operator based out of Perry Municipal Airport (F22) in Oklahoma. Mitchell has been flying since 1990 and puts about 250 to 300 hours per year on his Grumman Ag-Cat, for which he has two TPE-331 engines that he rotates as needed. The rigors of agricultural aviation have shown Mitchell the value of keeping the prop on his Ag-Cat in good balance, which is done using a DynaVibe GX2. Anytime something changes with the prop, such as maintenance or mounting the prop after an engine change, Mitchell likes to have a dynamic balancing performed. “It is essential to have the prop balanced,” states Mitchell. Doing so eliminates vibration caused by propeller assembly imbalance, which reduces wear on the engine, airframe and instruments. Dynamically balancing a propeller is an excellent preventative maintenance approach that can help eliminate future engine problems that might otherwise ground an operator. Another significant benefit to using the DynaVibe GX2 is the vibration survey capability it provides. “DynaVibe checks other vibration ranges besides the propeller,” says Mitchell. “It’s a good way to keep an eye on the engine, because you may not feel a vibration that DynaVibe can detect.” Anytime Mitchell puts an engine together, he likes to have a baseline vibration analysis done. This allows him to do trend monitoring on the engine with DynaVibe to monitor the health of that engine while it is in use. Regular vibrations surveys can help operators like Mitchell to identify problems before they cause a shutdown or result in a failure.
The DynaVibe GX2 is a dynamic prop balancer and vibration analyzer that can improve performance and maintain engine health. To get your own DynaVibe GX2, visit the RPX Technologies online store, enter your email address below or simply call us at: 405.896.0026. KSFB Aircraft Maintenance Center is located in Seminole County, Florida, and is operated by Chris and Lisa Reilly. Chris is an A&P technician with Inspection Authorization. He is also a private pilot and aircraft owner. Included among the many services he provides to his clients is dynamic propeller balancing, which he uses a DynaVibe GX2 to perform. Chris recently dynamically balanced a client’s Cozy Mk IV with a Lycoming IO-360 (fuel injected) engine and a Sensenich wooden cruise prop. His client was pleased with the outcome and sent Chris some feedback email message to share his thoughts: “After finishing the installation of Belleville washers my prop (ask me why), I suspected those huge, new steel lumps under each prop bolt would play havoc with whatever primitive balance I’d achieved during the build, so today I had my local A&P do a dynamic balance. Can’t believe the results! First run showed it was a long way from acceptable; 0.6 IPS. The second run we homed in on a better solution; 0.19 IPS. 3rd run was spot on; 0.01 IPS. Compare that with the scale on the LHS [DynaVibe balancing report] below which calls 0.05 'Excellent'. The 'feel' of the plane, just sitting on the ground in the driver’s seat was remarkably different, too. I’ll put the cowls back on and fly it at the weekend, but I’m expecting a gross improvement. I’ll report results. Most engineering exercises are a compromise. With this result, I drove home with a big smile on my face! If you haven’t already done this [balance your prop], give yourself a Christmas present!” DynaVibe gives pilots a smoother, safer flying experience, and provides maintenance centers with a new source of revenue. To get your own DynaVibe system, visit the RPX Technologies online store, enter your email address below or simply call us at: 405.896.0026.
There’s nothing about vibration that is good for aircraft, the pilot or the passengers. In 1973, the Army Air Mobility Research and Development Laboratory commissioned a study to examine the difference in reliability and maintainability of two groups of helicopters with distinctly different vibration characteristics. One group was fitted with rotor-mounted absorbers to reduce vibration, and the other group did not have the vibration-reducing absorbers. The study found that the failure rate for the helicopter group fitted with the vibration absorbers was reduced by 48 percent, and corrective maintenance was reduced by 38.5 percent. [1] Because of the damage it can do, locating the source of vibration and eliminating it should be a high priority. Propeller or rotor imbalance is the most common cause of vibration, and thanks to innovations like the DynaVibe prop and rotor balancer, dynamic balancing is quick and easy, and it usually resolves most vibration issues. However, sometimes the source of the vibration is more elusive and when that is the case, a vibration analyzer that does spectral analysis can pinpoint the source. Vibration Symptom, Causes and Effects A vibration issue isn’t always detectable by feel, because often owners and pilots have lived with vibration for a long time and have simply gotten used to it (see our Propeller Vibration Levels Guide for more information). There are always symptoms, however, such as: a panel that shakes, random instrument failure, fatigue cracks that appear or grow, cracked baffling, a compass that won’t “settle”, a rough RPM range and even tingling or numbness in pilot extremities. These symptoms, such as the fatigue crack pictured below, should not be ignored. Beyond propeller assembly imbalance, the causes of vibration are many, and the list of possible sources includes: a weak cylinder, a loose or cracked intake hose, an alternator problem, belt resonance, gearbox issues, an oil-canning spinner, prop wash, and other causes. Because there are many possible sources, troubleshooting vibrations is often problematic, turning into an expensive, trial-and-error process of identifying the source based on someone’s best guess. The DynaVibe team has seen several forum posts from frustrated aircraft owners who have spent years and lots of their money trying to identify the source of a vibration. The effects of aircraft vibration are all negative. When a vibration exists, some of the energy meant for propulsion is directed toward shaking the airplane. Even a seemingly small vibration can steal enough energy to cause a loss of horsepower. More troubling, however, is the damage vibration does by creating fatigue that reduces the life of the airframe, engine and instruments. Dennis Barker, president of Reynolds Aviation, knows well what damage vibrations can do to instruments: “Vibration can destroy those instruments, so balance is huge!” Barker uses a DynaVibe Classic to keep the Reynolds fleet of Cessna 172s in balance. Identifying and resolving vibration is therefore necessary to extend the life of the aircraft and provide a smoother, safer flying experience. Resolving Complex Vibrations With the proper diagnostic equipment and approach, the source of a vibration is easily pinpointed. The approach is spectral analysis, which measures the frequency of vibrations, because vibration frequencies are associated with known causes or sources. When the frequency of a vibration is known it narrows the list of potential causes to few or one, eliminating the need for speculative maintenance actions. Performing spectral analysis is accomplished using a vibration analyzer such as the DynaVibe GX3. By attaching one or two accelerometers and a photo-tachometer to the aircraft, the DynaVibe computer measures vibrations across the full spectrum of frequencies, producing a graph that displays the magnitude of the detected vibrations. For example here is a velocity mode spectral chart produced by the DynaVibe GX3 as the result of completing a vibration survey: Vibration is measured in Inches Per Second (IPS), and this chart reveals a 1.0 IPS vibration at the half-per (H) frequency for this particular aircraft. The half-per vibration is an indicator of engine health, and in the chart above, the presence of this vibration indicates a combustion problem with one of the cylinders. To better understand what vibrations in different frequencies signal, view the recorded webinar, “Top 3 Vibration Causes” or contact a DynaVibe team member.
Brian Smith, owner of Stillwater Aircraft Services, gets value from the vibration survey capability of the DynaVibe GX3: “I can see a half-per vibration using the DynaVibe, and know that it’s caused by a combustion problem. That information eliminates other vibration sources and narrows it down to the specific problem I need to address. That’s a home run. When servicing an airplane, I don’t need to go down as many rabbit trails.” A vibration analyzer like the DynaVibe GX3 does more than make locating vibration sources easy; it is an excellent preventative maintenance tool. Performing regular vibration surveys enables early identification of maintenance issues while they’re still relatively small, before the vibration does much damage, or most importantly, before it results in failure. The DynaVibe GX3 is a dynamic prop balancer and vibration analyzer that is easy and economical to use. To learn about using DynaVibe to troubleshoot aircraft vibrations, visit the contact us page, visit the RPX Technologies online store, or call +1.405.714.2516. Reynolds Aviation provides aerial patrols for pipelines, power lines or any asset that has federal, state, or local reporting requirements. When on patrol, Reynolds’ highly trained pilots provide security, take aerial photos, respond to emergencies and look for encroachments, leaks, pipeline threats, erosions and construction on right of way assets. Reynolds uses DynaVibe to help keep its fleet of Cessna 172s flying smoothly while lowering costs of maintenance and operation.
Dennis Barker, president of Reynolds Aviation, has experience with racing engines and therefore knows what damage vibrations can do to an airplane’s engine, its bearings and instruments: “Vibration can destroy those instruments, so balance is huge!” Barker’s partner had previously used a helicopter balancing solution, giving him some frame of reference on the cost of a prop balancer. When the Aero Performance representative that serves Reynolds Aviation came calling to discuss DynaVibe, Barker expected a pitch for a much more expensive solution costing in the neighborhood of $10,000. Instead, he learned that he could purchase a DynaVibe Classic and own a dynamic propeller balancing system for less than $2,000, and did so. Some of the airplanes in the Reynolds fleet were showing signs of fatigue caused by vibration: cracked baffling, new lights that would burn out or instruments that would fail. Barker knew that eliminating propeller imbalance would stop the damaging vibrations. “Some of the engines vibrated so badly that we couldn’t even read ‘Lycoming’ that was stamped on the engine. Now they’re really smooth.“ The prop imbalance on one airplane measured close to 1 Inches Per Second (IPS). Using DynaVibe, the Reynolds maintenance team was able to balance all the airplanes in the fleet to between .01 and .07 IPS. The Reynolds pilots often fly long days, spending hours in the air, so eliminating vibration from propeller imbalance not only reduces fatigue on the airplane, but on the pilots as well. “The pilots were thrilled with how the yoke feels after we balance an airplane,” Barker said. “They noticed a difference immediately.” Barker is confident that using DynaVibe to keep the fleet in balance will also pay dividends in terms of maintenance and operational costs. “The big enemy of operations like ours is what it costs to keep planes in the air. Long term, we don’t fully know what the maintenance benefits are, but even cutting these costs by just 10 percent would pay for the DynaVibe system three times over.” An unexpected bonus from using DynaVibe is the information provided by the photo tachometer, making it possible to determine how accurate the airplane tachometer is. “An incorrect tach reading can cause us to fly a plane at a cruise RPM that’s actually too high, which can damage the engine,” Barker concludes. “DynaVibe also tells us if the tach is off. It’s a phenomenal product.” To learn about using DynaVibe to dynamically balance propellers and rotors, enter your email address below, visit the RPX Technologies website, or call: 405.896.0026. Perhaps you’ve had enough of the vibration that makes flying uncomfortable, or is damaging your airframe, avionics or engine. Or maybe you want better performance, recapturing horsepower lost to vibration. Perhaps a friend who has dynamically balanced his or her prop recommended that you do the same. Whatever the reason, you’re ready to make an investment in a prop balancer, and a Google search has led you here. Which DynaVibe system is right for you? RPX Technologies currently offers three models of its DynaVibe propeller balancing system. Here’s what you need to know about each one in order to choose the one that best addresses your needs. DynaVibe GX2 The DynaVibe GX2 is the state-of-the-art, flagship solution in the RPX Technologies product line. This unit comes with two accelerometers, allowing users to dynamically balance propellers while also providing full-spectrum vibration analysis capability. When prop balancing, the DynaVibe GX2 automatically calculates a recommended weight solution for achieving balance, unlike the DynaVibe Classic. This feature helps users complete the balancing process faster than is typically possible with the DynaVibe Classic, sometimes in as few as two run-ups. For mechanics, shops, repair stations and service centers where time equals money, this more efficient balancing process is highly desirable. A more advanced feature of the DynaVibe GX2 is its vibration analysis capability. When troubleshooting more complex vibrations, those caused by something other than a propeller assembly imbalance, spectral analysis is essential. It allows users to pinpoint the source, distinguishing between vibrations caused by a combustion issues (e.g. weak cylinder), prop wash induced buffeting, alternator imbalance, and many other sources of vibration. Instead of wasting time and money on trial-and-error maintenance procedures, the GX2 identifies the vibration source. The GX2 has a report generation feature to simplify printing or sharing its vibration analysis data. DynaVibe Classic The DynaVibe Classic is the original prop balancing system offered by RPX Technologies. If balancing a propeller or other rotating machinery is the only thing you need to do, the Classic model does an excellent job at the most affordable price. When it comes to the dynamic balancing process, the main difference between the models is that the Classic does not automatically calculate a weight solution. The implication is that the user may need a few more run-ups to complete the balancing process. The DynaVibe Classic does not offer full-spectrum vibration analysis. DynaVibe Roto DynaVibe Roto is a version of the DynaVibe Classic with some features specifically for rotorcraft. This unit comes with two accelerometers, one for lateral vibration and one for vertical vibration. It also includes an integrated remote control “push-to-talk” switch that can be mounted on the stick for controlling the DynaVibe unit. The DynaVibe Roto will also dynamically balance propellers on fixed-wing aircraft. Summary This table provides a quick reference to help select the right DynaVibe system to meet your needs: If you would like to learn more about selecting the best DynaVibe model for your needs, simply enter your email address using "Contact Us" near the bottom of this page and we’ll contact you or email us with your question at sales@rpxtech.com or call: 405.896.0026.
Our new infographic shows how mechanics, repair stations, shops and service centers can make more money by adding prop balancing to their service mix with DynaVibe:
DynaVibe can balance rotors as well as propellers, and key to accurate rotor balancing is proper placement of the lateral and vertical accelerometers as well as the phototach sensor. Lateral Accelerometer Placement The purpose of the lateral accelerometer is to measure the mass imbalance that occurs once per rotation (1-per) of the rotor. The best way to measure the mass imbalance is to maximize the sensitivity to the mass imbalance while minimizing sensitivity to other vibrations. To do so, mount the lateral accelerometer as high as possible on the rotor mast to maximize sensitivity. It’s also preferable to mount the accelerometer on a rigid structure. If the accelerometer is mounted on a bracket or other secondary structure, that structure may absorb vibration or modify the signal due to structural resonance. Furthermore, to maximize sensitivity, orient the accelerometer so that it is sensitive to the axis of minimum rotational inertia. For rotorcraft, this is usually the roll-axis, hence the reason for laterally mounting this accelerometer. To minimize non-mass vibrations, point or align the accelerometer through the rotor shaft. If the accelerometer is mounted ahead of or behind the main rotor mast, then the accelerometer will receive vibration from the main rotor imbalance plus vibrations from any torsional vibration. This occurs frequently in analyzing engines: the vibration signature will change if the accelerometer is not pointed through the rotating element. When measuring mass imbalance, a key area of focus is measuring the vibration when there is minimal forward airspeed. If the two blades are not identical in lift and drag, then blade asymmetry will cause a 1-per vibration. Measuring the mass imbalance at high forward speeds will cause the sensor to register both the mass imbalance and blade asymmetry. For this reason, it is best to collect mass imbalance data while in a step decent, power off. When the lateral accelerometer and phototach are setup correctly, and the forward speed component of the 1-per vibration is eliminated, then balancing the rotor is just like balancing a prop. Phototach Sensor Placement Position the phototach so that it has a clear view of the rotor system, making sure that it is at least six inches away from the reflective tape target to get a good signal. A piece of reflective tape is applied to rotor system so the DynaVibe computer can determine the relative position of the blades to the vibration signal received by the accelerometer. The phototach position is determined by the polar charts that you will be using, the manufacturer's recommendation, or by talking with a DynaVibe team member. Vertical Accelerometer Placement The purpose of the vertical accelerometer is to measure vertical hop and pitch axis vibration. This requires placing the vertical accelerometer in the forward cabin as pictured. If vertical hop is present at the 1-per, then its cause is blade asymmetry. If it is present twice per rotor rotation (at the 2-per), its cause is the advancing blade lift and drag. It’s usually possible to correct a 1-per vibration through tracking: making tracking better or worse depending on the blades. The 2-per vibration, however, is generally difficult to eliminate. For helicopters, DynaVibe engineers recommend using trim tabs to adjust the forward flight 1-per vibration. For rotorcraft balancing, the full spectrum analysis capability the DynaVibe GX2 provides is excellent for troubleshooting. However, even the basic balancing capabilities of the DynaVibe Classic provide all that is necessary for rotor smoothing. The only frequencies requiring analysis are the prop, 1-per rotor, and 2-per rotor, which are within the scope of the DynaVibe Classic feature set. What also facilitates accurate rotorcraft balancing is expertise and knowledgeable customer service of the DynaVibe team.
Learn more by visiting the DynaVibe Rotorcraft FAQ. DynaVibe is easy and economical to use for prop and rotorcraft balancing. For mechanics, shops and service centers, it adds profit to the bottom line. To learn about using DynaVibe to dynamically balance propellers and rotors, enter your email address below, visit the RPX Technologies website, or call: 405.896.0026. DynaVibe was on hand to support Scotty Wilson's second flight with the Bugatti 100P when he returned to Oklahoma's Spaceport at Burns Flat to continue flight-testing. The Bugatti needed new props after its historic first flight due to a brake failure on touchdown. The DynaVibe team joined Scotty to balance the two, new propellers on the Bugatti and continue the flight-testing program for this innovative and historic airplane. Having previously balanced the Bugatti (click here to learn why dynamically balancing a prop is important) for its inaugural flight, a location for mounting the accelerometer was already determined. It was quick work to install the DynaVibe accelerometer and phototach on the Bugatti. Balancing the contra-rotating propellers started with the rear engine / rear propeller. The initial balancing run revealed that the rear prop required 27 grams of correction weight, which when added, brought the propeller imbalance down to 0.09 Inches Per Second (IPS). The front propeller was then balanced down to 0.10 IPS by adding 18 grams of weight. Shortly afterward, the Bugatti successfully took to the air once again. DynaVibe has balanced the Bugatti 100P, the world-record breaking Anequim, warbirds, Reno Air Racing team aircraft, the AN-2, the world’s largest biplane, and it can balance whatever you fly, delivering better performance and a smoother flying experience. To learn how easy and economical it is to dynamically balance your prop with DynaVibe, enter your email address below, visit the DynaVibe online store, or call: 405.896.0026.
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