Article #1: A New Spin | Article #2: More Blades Make Sense


A New Spin

An Article about New England Propeller Division and their New Blade

Article by Nicholas E Silitch of Private Pilot Magazine

 art1.gif - 19735 BytesIN THE BOOM DAYS of aviation, McCauley Propeller was bought by Cessna Aircraft Company and became part of the Cessna aviation empire. Like other aviation manufacturers, McCauley expanded at the height of the boom, and in the 1970s moved its production from downtown Dayton to a shiny new facility at the James M. Cox Dayton International Airport. The new factory was designed with the most modern production technology and the capacity to carry McCauley well into the 21st century. But just about the time that McCauley finished moving in and everybody got used to all the space and new-fangled high-production machinery and computerized facilities, the boom days were over. Then Cessna, McCauley's parent and best customer, decided to get out of the piston-engine airplane business, and McCauley was stuck with an expensive, brand-new and very big factory. And a very small market. Worse yet, that market consisted of a few small OEMs and the relatively insignificant replacement market. In the boom days, McCauley had spent most of its time and earned most of its money filling Cessna's orders, but now there were a variety of customers, all of whom had to be sold.

 But all wasn't lost, for while McCauley was trying to get used to its new, almost nonexistent market, US Propeller Services, a large propeller shop headquartered in the unlikely location of East Haddam, Connecticut, had been inventing a new market. Like most prop shops, US Propeller's primary business was repairing, rebuilding and overhauling propellers. Though it also sold new propellers and parts, sales were mostly parts. Whole propeller sales were limited to those few unfortunates whose propeller, for one reason or another, had to be scrapped. Then, in 1989, a customer asked Artie D'Onofrio, US Propeller's president, if he could put a McCauley three-blade propeller on his Piper Arrow 200. "I don't think you can do that," was D'Onofrio's response, "but I'll look into it." D'Onofrio looked into it, and a year later had an STC for a three-blade propeller on a Piper Arrow. Unfortunately, like most things in aviation, it wasn't that simple. Certification of the propeller for the Lycoming 360 required McCauley to do a $10,000 vibration test, a cost that it wasn't willing to eat for an order of less than 50 propellers. D'Onofrio mulled it over and, loath to part with 510,000, made his decision. "I'll take 50," he told McCauley. Shortly thereafter, the specially designed, manufactured and expensively vibration-tested propellers arrived in East Haddam, and D'Onofrio's check for $300,000 arrived in Dayton. The only problem was that the STC didn't go quite as smoothly as planned (nothing new here), and eight months later, D'Onofrio still had a stack of propellers in his warehouse, was still out $300,000 and was still working on obtaining the STC.

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All the parts-except the bearings-in these propellers were unique. "I was sweating a little," admitted D'Onofrio, those propellers and parts were useless for any other application. If I couldn't get the STC, I was in trouble." But D'Onofrio got the STC, and the rest is propeller history. Really history, for US Propeller is in the process of completely changing the economics of the propeller business. The effect is most noticeablc in the sales of new propellers. US Propeller's STC'd conversion kits cost (on the average) $5995, including the propeller and polished spinner. less trade-in for the old propeller, which can he as high as $2000. Because three new blades for a McCauley threaded propeller can easily run more than $6000, buying a new propeller is usually cheaper than rebuilding an old one. Today, more than half of McCauley's production is sold through US Propeller. Less obvious is the reaction that sales of new propellers havc had on the rebuilding market, for the traded-in propellers have been turned into a surplus of once-rare used rebuilding parts. Good used blades and hubs-parts usually damaged in accidents and therefore unobtainable except new from the manufacturer-are now available in the used market. This has reduced the need for new and very expensive replacenient parts aud has made rebuilding propellers much cheaper than it was a few years ago. Presumably. McCauley is happy with the arrangement. which results in selling fewer parts and more new propellers. US Propeller didn't work up its present volume of new propeller sales selling conversions just to Arrow owners. As soon as it got that STC, it started working on a three-blade conversion for the Mooney. It now has STCs for more than 65 models of airplanes and is still working on more. Presently. its conversions favor under-200-hp engines. but a recent STC for a new three-blade for the Continental IO520 in the Cessna 206 should be considered a harbinger for US Propeller's future course. US Propeller has branches in Tampa, Florida'. Greensboro. North Carolina'. Dayton, Ohio; and San Carlos. California. It rebuilds more than 200 propellers a month-McCauley, Hartzell, Sensenich. Hamilton-Standard and Dowty-Rotol-and sells about half that many. The most popular reason for converting from a two-blade to a three-blade propeller is that it looks better. but in addition to the esthetics, there are some other differences that can make a switch attractive. Three-blade propellers generally have a slightly better climb and slightly slower cruise than their two-blade equivalents. hut these differences are seldom large enough to be really noticeable. The most noticeable difference is the three-blade's distinct advantage in smoothness and noise reduction. This is coupled with improved ground clearance in installations, which means less propeller damage from stones and less chance of a ground strike.

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Another practical advantage of the three- blade is reduced maintenance. This comes from the reduced rotational stresses from the shorter blades, which can make a real difference, particularly if the conversion is replacing one of those troublesome 'dreaded threaded" two-blade propellers with blades more than 82 inches long. These blades have had a history of problems and a three-blade replacement (either in a threaded or new style) can result in real long-term savings. Particular installations can have even more advantages. The reduced diameter of the three-blade conversion on a Cessna 185 floatplane eliminates water damage due to the reduction in diameter and eliminates the noise problems associated with water-borne 185s by reducing the tip speeds. This keeps the blade tips from going supersonic at takeoff horsepower. which is what causes the infamous 185 whine. In addition, the increased climb performance, however marginal, is always appreciated in a water airplane. The idea of STC'ing propeller swaps wasn't originated by US Propeller-the idea has been around for some time-it is just the first to go into it in such a big way. Previously, STCs were done on a piecemeal basis to solve real or imagined specific problems and usually were connected with some other modifications. Examples are the 185 three-blade conversion, which is a P.K. STC designed specifically to improve the airplane's performance with the installation of P.K. floats, or RAM Aircraft's three-blade Hartzell conversion for the big Cessna twins, which is usually performed in conjunction with other modifications. US Propeller's efforts aren't the only recent change in the propeller business. Historically, McCauley has been the propeller supplier for Continental engines, with Hartzell putting its propellers on Lycomings. Now that Textron owns both McCauley (through their recent purchase of Cessna) and Lycoming, that's probably going to change. Hartzell, which just celebrated its 75th anniversary, is reacting to the threat from US Propeller and McCauley by buying outside Hartzell swap STCs, like the RAM one for the large Cessna twins, but at present it is not developing any of its own.


More Blades Makes Sense


A BlackMac from New England Propeller Division
cuts maintenance expense while it improves performance.

Article from Dec 91 Flying Magazine Written BY J. MAC MCCLELLAN

art4.gif - 13923 BytesMost PILOTS KNOW THE ADVANTAGES OF a three or four-blade prop over a two- blader. The extra blades add static thrust, which improves takeoff acceleration and climb. A three-bladed prop lessens-or at least greatly changes the vibration and noise levels in the airplane in a way most people find more comfortable. And a three-blade prop looks better on the ramp. Any airplane looks more powerful, fast and capable with an extra blade. But these are not the reasons U.S. Propeller Service began offering three-blade prop conversions. The real reason is maintainability. The other three-blade prop benefits are a bonus. U.S. Propeller's primary business is prop overhaul at its shops in Connecticut, North Carolina and Florida. Prop overhaul is a business best suited for technical zealots. Props-even on light airplanes are so highly stressed that any corrosion, nick or slight imperfection can lead to failure of the blades or hub. And a prop failure is usually fatal because the severe imbalance of the engine turning with only part of a prop jerks the engine out of its mounts. Once the engine departs, an airplane is usually beyond the bounds of its flyable CG range and cannot continue with a controlled glide. As the general aviation fleet ages. the technicians at U.S. Propeller are finding an increasing number of unairworthy props. Even the smallest amount of corrosion in critical areas of the prop hub or blades demands immediate component retirement. In other words, the prop you thought was working fine when it went in for overhaul may actually be dangerous unairworthy junk. Many of the unrepairable props are of older design dating back 30 or more years. An airplane owner could buy a newly manufactured prop of the old design to replace his unairworthy prop, or buy enough new parts to make the old prop airworthy, but either way he'd still end up with an old prop design that was not as efficient or long-lived as more recently designed props. U.S. Propeller's solution is to obtain an STC for a modern prop and offer it at the same price as a newly manufactured prop of old design. Most of the prop conversions are to three-blade because U.S. Propeller can offer the increased performance and comfort for no extra cost. From the naturally aspirated Piper Arrow that was U.S. Propeller's first three-blade conversion, the airplanes that have been certified since make an ever-growing list.

All conversions use McCauley's Black-Mac series propellers. To obtain a prop conversion STC, U.S. Propeller purchases an analysis of the engine-airframe vibration characteristics from McCauley. This analysis determines that no harmful vibrations or resonant frequencies will result from the new three- blade prop. The test-flying requirements for the prop conversion focus on engine cooling and balked-landing climb performance~ The FAA asked for much more testing on the first few STCs, including V-dive tests VD speed is at least 10 percent faster than redline. But as both U.S. Propeller and the FAA gained experience, the required tests were somewhat simplified. It is conceivable that a prop change can alter cooling flow into the cowling, so the FAA requires a full-power climb test under 100 day conditions. Because 100 days are mercifully rare in Connecticut, the test can be flown under available ambient conditions and a correction factor is applied to simulate century-mark air temperature. During the climb test, no engine temperature limit may be exceeded. This is the same cooling test required for new aircraft certification. The balked-landing climb-rate requirement stipulates that the airplane must climb at a minimum rate in the landing configuration. The required rate is a ratio of the aircraft's stalling speed. Because a three- blade prop provides more static thrust than a two-blader, this test is never a problem for the Black-Mac. I flew in a Mooney 201 with a Black-Mac three- blade conversion and was extremely impressed by the takeoff acceleration and initial climb improvement. And the noise and vibration levels seemed much, much better to me after 2,000 hours of flying in Mooneys with two-blade props. An unexpected benefit was the added drag of the extra blade when trying to slow the Mooney down. Steeper approaches and quicker deceleration to landing- gear extension speed are very noticeable with the three-blader.

The tough, rigid airframe of the Mooney has always transmitted engine vibration into the cabin, but the Black-Mac will change the way you feel about the airplane. If you love two-blade Mooneys, you'll go nuts with a three-blader installed. If you thought the sound level and vibration too high, take another flight with an extra blade installed. It may change your mind. U.S. Propeller people are pleased with the results of all conversions so far, but think the performance change is most dramatic with the Cessna 182s. Climb rates increase by several hundred feet per minute and cabin vibration is dramatically reduced, they say. The one negative of three-blade prop versus two is a slight loss of cruise thrust with the extra blade. This phenomenon increases with altitude, so the pilot of a turbo-charged airplane may notice the loss of several knots of cruise speed while flying in the high teens or low 20s, the pilot of a naturally aspirated airplane won't be able to measure more than a knot or two loss of cruise speed. The more advanced design of the Black-Mac props can sometimes even overcome this inherent cruise efficiency advantage of a two blader. U.S. Propeller pilots found that the new three-blader was actually a couple of knots faster at maximum-power level flight than the two-blade on the 260 Comanche. And takeoff distance, climb, sound level and vibration were also improved as you would expect.

 Installation of the Black-Mac conversion involves nothing more than having your mechanic bolt on the new prop and spinner, and, of course, add the required paperwork to the aircraft records. The three-blader will probably he slightly heavier than your old one, but more recently designed props typically weigh less overall, helping to cancel the weight penalty of the extra blade. Bonanza owners will actually welcome the added weight on the nose to help their airplane's chronic AFF-CG problem. The Black-Mac conversions from U.S Propeller range in price from #1.995 fro the two blade fixed pitch prop on a Piper Cherokee 180 and Arch to $5,995 on a Bonanza. The company allows a $300 trade-in on the Cherokee prop and a $500 to 1,000.00 trade on the Bonanza. Other High performance singles have similar prices. The Cherokee Black-Mac Conversion is especially valuable because up to two inches can be trimmed from the new prop to repair damage, while the original had to be junked if the blade tips were even slightly dinged. The company also sells Black-Mac conversions for most light turboprops, offering improved performance, lower maintenance and a quieter ride. The turboprops are converted from three to four blades and prices are understandably higher than for piston powered airplanes, but U.S. Propeller believes the new props can pay for themselves in fuel and prop maintenance savings. The typical pilot opts for the Black-Mac conversion after finding out that his present prop has serious problems. But many others-particularly Bonanza and Mooney owners-simply want the improved performance and comfort. U.S. Propeller will be happy to take your current prop in on trade and may even offer some credit for the airworthy parts of a prop that is otherwise uneconomical to repair.