Paul Armstrong is the founder and owner of Skywest Aviation, an aircraft sales and maintenance company that operates out of Midland, Texas, at KMAF Airport. Skywest began operations in February 2014 and has already grown to 14 employees. “We’re aircraft mechanics – if it comes in the door, we work on it,” states Armstrong, who is also a commercial pilot, and an integral part of the flying community. Skywest works on aircraft ranging from Cessna 150s up to King Airs, Citations and Commanders. In addition, it also services Embraers through its contract with Mesa Airlines.
Dynamic Balancing: SOP
Armstrong is an advocate of dynamic prop balancing, a practice he learned early in his aviation career when the company he worked for sent him out to small fields that didn’t have maintenance shops. He would arrive to find owners lined up, waiting to have their props balanced. Today, Armstrong uses a DynaVibe GX2 to dynamically balance props that come through Skywest Aviation. “We always require a dynamic balance when we install a propeller,” says Armstrong. “When I do a prop overhaul, or remove and reinstall a prop, we do a dynamic balance on the prop or both props, depending on what we’re working on. It seems to be a pretty good calling card for us.”
Balancing & Vibration Analysis
The DynaVibe GX2 is more than just a dynamic propeller balancing solution – it also does full spectrum vibration analysis, a capability that Skywest takes full advantage of. “It’s a really good piece of equipment,” Armstrong continues. “I have used these things and found alternator problems, broken brackets. That’s one reason I sell the tool. Just because there’s a vibration doesn’t mean it’s the prop. We can find a weak cylinder – it will show up at the ½ per.”
Armstrong had previously used another vendor’s prop balancer, so when he decided to purchase a balancing system for Skywest, he was of the mind to purchase the one he was familiar with from past usage. “The cost was so prohibitive, and I couldn’t get these people to call me back,” notes Armstrong. “I was in a real rush because I had two prop overhauls I had just done, and I was trying to contract a local prop shop to do the balance. What I was charged for that was through the roof, $400 a side. That’s when I went ahead with the purchase of the DynaVibe system.”
Balancing = Profits
Since purchasing his DynaVibe GX2 in October 2014, Armstrong estimates that Skywest has done between 15 and 20 balancing jobs. While Skywest does dynamic balancing as a service, most balancing jobs are part of his overhaul package. Including balancing in this package creates value for Skywest customers and profit for Armstrong. “There is definitely hidden profit from balancing work that can’t directly be accounted for,” states Armstrong. “That machine has absolutely paid for itself. It also gives us a little bit of status, because there is only one other shop in the area – a prop shop – that has this capability. Now that we have this capability, it makes us more competitive.”
The DynaVibe GX2 is helping Skywest deliver the highest quality maintenance services to its clients. “It’s a very good preventative maintenance tool, and it’s a good troubleshooting tool,” Armstrong concludes. You can pick up other problems. It’s good for more than just prop balancing. If a shop uses it, it can bring them other work.”
DynaVibe Benefits for Skywest Aviation
Contact RPX Technologies to learn how your service center can benefit from DynaVibe: firstname.lastname@example.org or 405.896.0026.
The Airventure 2015 show in Oshkosh ended a week ago. The show was a great experience for us, and now that we’ve had a week to think about it, we wanted to share a few observations about our time in Oshkosh, what we learned and what made it so great.
Prop Balancing Awareness
Topping the list of what we learned was how many pilots and owners still don’t know what dynamic propeller balancing is, and why it’s important. Our booth in the Aircraft Spruce pavilion was in a great location, with lots of traffic. There was a steady stream of Airventure attendees that wandered by our booth, scanned our information, and popped the question: “what is prop balancing?” It was a great opportunity for us to educate attendees about dynamic prop balancing, its benefits and of course, promoting the DynaVibe as an easy-to-use, low cost prop balancer. If you are among those who want to know why balancing is important, check out and share our infographic.
Prop Balancing is Still King
In 2015, we have been working to educate the aviation community about how full-spectrum vibration analysis can help troubleshoot complex vibrations. The interest in this application of DynaVibe is growing. We are getting testimonials of owners and mechanics who have wrestled with thorny vibration problems for years that were able to quickly isolate the source of the vibration by using the DynaVibe GX2 for full-spectrum vibration analysis. That said, prop balancing is still the primary reason why people buy and use DynaVibe. We think the day will come when vibration analysis will eclipse prop balancing as the primary application for the DynaVibe GX2, but for now, prop balancing is king.
Vibration Tolerance is High
We had a few discussions at our booth that mirror our experience in the field. When discussing full spectrum vibration analysis as a means to troubleshoot complex vibrations, often the response we’d get was “I don’t need that” or “I don’t have that problem.” As we continued to describe the common scenarios and symptoms of aircraft vibration, many times the response was “I do have that problem!” It seems there are more than a few pilots and owners that have vibration problems to which they’ve become immune. They’ve simply lived with it for so long that they’ve developed a tolerance for it. Meanwhile, the vibration persists and the damage to engine, instruments or airframes continues to accumulate.
DynaVibe Price and Value
Price is what you pay; value is what you get. We continued to get validation at Airventure 2015 that DynaVibe delivers great value at a very competitive price. More than once, we did a demo in our booth for a prospect, who said “I’ll think about it” and wandered off. Later, they returned, confessing that they had been shopping our competitors who also had a presence at the show. Most of the time, they acknowledged that DynaVibe’s price performance characteristics brought them back to make a purchase.
Seeing Old Friends
Perhaps the most gratifying part of being at Airventure 2015 was the opportunity to meet with DynaVibe customers and users. In the 8+ years since DynaVibe was launched, we’ve managed to sell many DynaVibe units. It is wonderful to have our customers come by our booth to tell us about their experience using DynaVibe to get a smoother, safer flying experience.
It was a great week in Oshkosh. Thanks to everyone who took the time to visit with us. We look forward to going to Airventure next year!
Ascutney Air is a shop that provides a variety of general aviation repair services. In 2014, Ascutney purchased a DynaVibe so that it could offer dynamic propeller balancing as a service to its clients. Ascutney owner Steve Keen is an EAA tech counselor, and also flies a Cessna 172. Some time ago, he noticed that his 172 had a fairly severe vibration on landing and rollout that was getting progressively worse.
The left wheel was the vibration source, so Steve tore it down but found no problems other than an out of balance tire. He balanced the tire with a cone-type static balancer, but he could not achieve good balance when the tire was mounted on the wheel assembly. Understanding that his new DynaVibe can balance anything that spins, he set the system up on the problem wheel and balanced it, sharing that, “It worked really well!”
Steve’s experience with his 172 caused him to realize there was a business opportunity to dynamically balance airplane tires: “Out of balance tires can beat an airplane up. Tires aren’t always perfect, and static balancing may or may not work.”
Just like prop balancing, Steve understood that the best way to balance a tire is when it is mounted to the wheel assembly on the airplane, and it is spinning at takeoff or landing speed. So he built a tire-spinning device to get the wheel turning at the proper speed and he now uses the spinner and DynaVibe to balance airplane tires.
The experience Ascutney Air has had balancing airplane wheels with DynaVibe has been good for the airplane owners and the pilots the shop serves.
Balanced tires add a new level of safety. Out-of-balance tires can cause torque links to wear, or affect braking action: “Many pilots think vibration or rumbling noises are due to bad runways. They don't know that tire balance is the cause.” For example, one pilot came to Ascutney Air reporting a vibration on landing. Using the DynaVibe, Steve was able to get the tires on this pilot’s airplane perfectly balanced, and the vibration went away.
Steve credits the dynamic balancing process with generating these positive outcomes, because the process balances the entire wheel assembly, mounted on the airplane, while turning at takeoff or landing speed: “Dynamic balancing equals certainty.”
For Ascutney Air, dynamic wheel balancing with DynaVibe has created a new revenue stream for the shop. Testing to see if wheels are out of balance is easy using the wheel spinner Steve fabricated to do the balance test when the wheel is on a jack. If the wheel is out-of-balance, he hooks up DynaVibe to balance it.
Ascutney Air continues to balance propellers, and as far as balancing tires, “It’s just like doing a propeller,” concludes Steve. “DynaVibe has paid for itself more through tire balancing than prop balancing. Balanced tires make flying a little easier. There’s a huge benefit to taking off and landing with smooth tires, such as better braking.”
Shops interested in building a spinner for balancing airplane tires can purchase the plans and parts list by contacting Steve: email@example.com.
To learn more about DynaVibe or purchase one for dynamic prop or tire balancing, contact the RPX Technologies team: 405.896.0026 or firstname.lastname@example.org.
Aircorps Aviation, specializing in the restoration, maintenance, and rebuilding of vintage WWII aircraft, recently purchased a DynaVibe GX2 to perform dynamic prop balancing and vibration analysis on the warbirds that come through its shop. RPX Technologies co-founder Matthew Dock visited Aircorps Aviation to demonstrate how the DynaVibe GX2 works.
During the visit, Bruce Olson’s T-6 was analyzed and balanced with the DynaVibe system. The initial reading revealed a propeller vibration of 0.45 Inches Per Second (IPS), indicating a prop imbalance. Making some adjustments over the course of a few runs, the vibration was reduced to 0.06 IPS, reducing stress on the airplane and providing a smoother ride.
The T-6 owner, Bruce Olson, found the DynaVibe GX2 demonstration interesting beyond just the dynamic prop balancing that was done. “It made it clear to me that there are certain, other areas of that airplane that showed no vibration whatsoever. It gives me an awful lot of confidence that the engine is in good shape. Now we have a baseline for the engine, so if we come back next year and put it on the test stand, and something changes, we’ll know that there’s something going on in the engine.”
The preventative maintenance value of the DynaVibe GX2 analysis was not lost on Olson: “After having a baseline and basically finding out if there is anything wrong with my airplane, it’s like having a full physical of your own body. You now feel comfortable that everything’s okay, and there’s nothing I have to worry about… it lets us see if there’s anything going on inside that airplane that you could catch well in advance of a failure.”
Olson summarized the experience of having his T-6 dynamically balanced and getting a full-spectrum vibration analysis: “I’m very happy with what the guys did, it’s better than it was before.”
To learn more about DynaVibe and how to dynamically balance your prop, use the form below and enter your email address, visit the RPX Technologies online store or contact us directly: 405.896.0026 or email@example.com.
We were chatting not long ago with an aircraft owner whose propeller we had balanced during a DynaVibe demo session. He related a conversation he had with a prop shop tech about dynamic prop balancing. The tech’s position was this: “when we come out with a prop, it's balanced, it's perfect. By putting weight on it [during the dynamic balancing process], you're just fixing a problem somewhere else in the engine."
This statement merits some scrutiny and analysis to uncover the truth. There’s a myth that needs busting here, so let’s dissect this statement and examine it more closely:
“When we come out with a prop, it's balanced, it's perfect.”
This may sound like pride of craftsmanship, but that’s okay! Airplane owners want professionals who stand by their work to take care of their airplanes. Regarding the truth of the statement, it’s highly likely that it is true. Shops as a matter of course statically balance props before they’re mounted. The ability for a shop to ensure that a prop is perfectly, statically balanced requires no stretch of the imagination.
What’s wrong with the statement is the assumption that nothing changes once that propeller is mounted. In fact, many things can change, because now the entire prop assembly enters the picture, not just the perfectly balanced, ready-to-hang prop. Even the slightest change in mass anywhere in this assembly can throw the balance off, introducing vibration. Here are some numbers to illustrate: a perfectly balanced prop, if offset by even .0005 inches during installation, can cause a .6 Inches per Second (IPS) vibration! How common is this scenario? It happens more often than most pilots or owners realize, because most blades don’t have an indexing mechanism to ensure that a prop is perfectly centered with the crankshaft when it is mounted.
For these reasons, dynamically balancing a statically balanced prop is still recommended, because the dynamic balancing process corrects “coupling” errors that result from mounting the prop.
“By putting weight on it, you're just fixing a problem somewhere else in the engine."
The second part of the statement we’re dissecting simply reveals a misunderstanding about the need for, and benefits of, full-spectrum vibration analysis. One of the frustrations with troubleshooting vibrations is the many potential sources of those vibrations. The prop is often the culprit, but not always, and we listed many of these sources in a recent blog post. Fortunately, the science of vibration analysis comes to the aid of frustrated pilots, owners and mechanics that have spent time and money trying to chase down the source of a complex vibration. Different frequencies of vibration point to different sources, and when the source is not the prop, putting weight on the prop isn’t the solution to stopping the vibration. The best approach is to address the root cause of the vibration. The DynaVibe GX2 is a prop balance and vibration analyzer that tells you what the source or sources are, so you can fix them.
As a case in point, the RPX Technologies team worked with the owner of a Grumman Widgeon (pictured) where each engine exhibited a vibration. The DynaVibe analysis was able to pinpoint different vibration sources in each engine, and the propeller was not the cause of either one. Full-spectrum vibration analysis creates certainty about vibration causes and sources, preventing speculative service work.
If you’re experiencing a vibration problem, there’s no need to guess where it’s coming from. The DynaVibe GX2 can perform a full-spectrum vibration analysis and tell you exactly where to focus your efforts to fix complex vibration problems.
How often should your prop be dynamically balanced? There are differing opinions on this subject, and we wanted to weigh-in with ours.
Almost everyone in the flying community agrees that where balancing is concerned, once is not enough. You should not assume that once a prop is in balance, it stays in balance. There are simply too many ways a propeller can achieve an imbalance. Here are some conditions under which you should dynamically balance your prop:
Anytime any of the conditions listed above occur, the balance of your prop can change and dynamically checking the balance is advised.
Wood propellers require special attention because of variations in humidity. Typically, wood props should be retorqued and rebalanced every 25 hours, or anytime the aircraft experiences a shift in ambient humidity.
For more information on why to balance your prop, or on how to do it, enter your email address below to be contacted by a member of the DynaVibe team. The DynaVibe GX2 is a second-generation prop balancer with full-spectrum vibration analysis capability available for purchase online. The GX2 “learns” as you balance, making balancing quick and easy by telling you precisely how much weight to add and where to add it. It will balance your propeller with a minimum number of runups!
Aircraft fatigue is the result of stress, and it can seriously erode the longevity of your airframe. There are no good outcomes to leaving fatigue unaddressed. “Fatigue damage and its consequences are the most serious structural design and maintenance issues that have to be addressed.”* From an engineering perspective, fatigue is caused by vibration and the number of vibration cycles. The greater the magnitude of the vibration, the more stress it produces. When a propeller that isn’t in balance is producing the vibration, you can’t eliminate the cycles, or prop rotations, but you can reduce – even eliminate – the vibration associated with each one.
An out-of-balance propeller produces a vibration with each rotation. This stress often manifests itself as airframe fatigue cracks, as pictured in the photo above. There is good news: stress that is the result of propeller imbalance is easy to address. Dynamically balancing your propeller can eliminate almost all of this vibration, and it’s important that you do so, as there’s a direct relationship between stress and the number of prop rotations. Unresolved, each prop rotation produces stress that steadily produces fatigue cracks and then propagates their growth. Pilots and owners don’t have to live with prop vibration that stresses the airframe.
If you have fatigue cracks you’ll still need to stop-drill them, but dynamically balancing your prop will reduce or eliminate the source of the stress, arresting fatigue crack propagation and preventing new ones from forming. Using the DynaVibe Classic, a dynamic prop balancer, it’s easy to reduce or eliminate this damaging vibration (the DynaVibe GX2 allows you to identify all sources of vibration, not just prop imbalance-induced). It’s a great investment in extending the life of your aircraft, and a balanced prop produces a smoother safer ride!
If you have fatigue cracks on your airplane and you’d like to know about propeller balancing and vibration resolution, contact us for a consultation at firstname.lastname@example.org or by calling: 405.896.0026.
If you do a Google search on the term “aircraft engine vibration problem” or use the make of your aircraft or engine in the search, the search results page will invariably include a forum posting like this one or this one. If you take the time to read the posts, what you’ll find are essentially pleas for help with a complex vibration problem. The initial posts in the thread describe the conditions under which the vibration occurs, and list the things the owner has already done to troubleshoot it. These initial posts conclude with statements like “Any ideas would be interesting” or “Any help would be appreciated.”
What follows in these posts are suggestions and statements of sympathy: “Welcome to my world! I have been fighting a vibration problem for over half a year now.” What’s clear from reading these forum posts is the elusive nature of solutions to vibration problems. Many offer suggestions by posting ideas, things to try or what’s worked for them. In one post, the following suggestions were made to the owner with a vibration problem:
One poster was convinced that the vibration was a design feature of the engine. Another poster who was experiencing similar vibration problems shared plans to pull a new prop off and put the old prop back in hopes that might eliminate the vibration. Still another poster theorized that the source of the vibration could be “rubber engine isolators, engine mount bolt torque, bad carb setup or poor gearbox shimming.”
What’s troubling is that these vibration problem forum threads don’t always have a happy ending. What’s also clear is that most of the advice provided is speculative and well meaning, but those who post in response don’t have certainty about how to address complex vibration problems
These forums that chronicle the frustrations of trying to diagnose complex vibration problems reinforce the value of full-spectrum vibration analysis. The DynaVibe GX2 is a vibration analyzer, identifying the frequency of vibrations and thereby directing the user to the source of that vibration. It eliminates the guesswork in troubleshooting complex vibrations. This video case study illustrates how quickly and precisely the DynaVibe GX2 can identify the source of a complex vibration.
Sometimes, there are multiple sources of vibration, as depicted in this case study, making full-spectrum vibration analysis even more critical as a diagnostic tool.
It's wise to be persistent in tracking down and eliminating vibrations, because left unresolved, vibration damages engine components, instruments, the airframe and it make passengers uncomfortable. Most of the time, dynamically balancing the propeller eliminates vibration. When balancing doesn't help, then a full-spectrum analysis with the DynaVibe GX2 vibration analyzer will get to the source of the problem.
The RPX Technologies team recently helped a Kitfox owner with a Rotax 912 engine troubleshoot a complex vibration problem.
This episode illustrates how to isolate the source of complex aircraft vibrations.
This Kitfox owner has struggled over the past two years trying to locate the source of a troubling vibration. The symptom was an engine that ran rough in the mid-RPM range, producing a lot of vibration. Trial-and-error service procedures failed to correctly guess the vibration source. In this case, the owner had the gearbox rebuilt because it was a suspected vibration source, but this remedy was ineffective. The owner was unwilling to continue having speculative service work done to fix the vibration, because these procedures were cost prohibitive.
A friend of the owner recommended analysis using the DynaVibe GX2, a full-spectrum vibration analyzer and prop balancer. DynaVibe was able to pinpoint the vibration source, and the graphs that follow are the actual reports generated by the DynaVibe during this analysis.
To perform this analysis, two DynaVibe accelerometers were placed on the engine, and readings were taken at various RPM levels, as illustrated in the following DynaVibe GX2 charts showing readings from the accelerometer mounted on the gearbox:
Step 1. The initial reading, shown above, was taken at an engine RPM of 2270 and a prop RPM of 1000. Here, a 2 inches per second (IPS) vibration peak, the highest on this chart, is seen at the 1.2-per interval. This is indicative of a carb imbalance.
A peak at the 1-per interval is also present, but is difficult to see because as it is eclipsed by the 1.2-per vibration peak. A second reading was then taken at a slightly higher RPM to see what might change:
Step 2. This second reading, shown above, was taken with the engine running at 3000 and the prop turning at 1350.
The prop vibration, shown at the 1-per interval on the chart, seems to be increasing, which is indicative of a propeller mass imbalance, while the carb imbalance is decreasing.
These readings show the complexity of vibration analysis: changing RPM levels can simultaneously cause one vibration to increase and another type to decrease. A third reading was taken, at still a higher RPM setting:
Step 3. This third reading, shown above, was taken with the engine running at 3632 RPM and the prop turning at 1600 RPM.
The chart from this reading shows that the prop vibration at the 1-per interval continues to increase, while the carb vibration at the 1.2-per interval continues to decrease. A fourth and final reading was taken to confirm these vibration trends:
Step 4. A final reading was taken at near-cruise RPM, and it confirms that there are indeed two vibration issues: a propeller vibration of almost 1 IPS which appears at higher RPMs, and a carb vibration, which is present only at lower RPMs. Note that the carb vibration has almost disappeared at this RPM level.
A key benefit of the DynaVibe GX2 is the ability to monitor the vibration spectrum in real-time, allowing the RPM to change while watching the change in vibration. This real-time vibration review is critical for diagnosing complex problems.
With this data, this Kitfox owner can confidently address the vibration issues because the sources are known. The right approach is first to balance the prop, and then address other vibration sources, in this case, the carburetor balance.
If you have similar, hard to pinpoint vibration issues, contact the RPX Technologies team to discuss how DynaVibe can provide an accurate, full-spectrum analysis to locate the source.
Here at RPX Technologies, we believe that planes shouldn't shake themselves apart, and therefore propeller balancing should be easy. Read the "Why Balance Your Prop?" webpage for a complete discussion of reasons to balance your prop. This infographic summarizes why it is so important, and how simple it is to dynamically balance your prop with Dynavibe:
The DynaVibe Classic is the most affordable dynamic balancing solution on the market. For dynamic prop balancing and vibration survey capability, use the DynaVibe GX2. Buy the right DynaVibe for your needs by visiting our online store. If you have any questions, please call us at 405.896.0026 or simply enter your email address in the form below.