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#21
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Revolution Mini 500 - is it buildable?
Richard Riley wrote: An aviation writer friend of mine went to a Robinson training session a few years ago. He said you had 1.3 seconds to dump the collective in the R22. He was thinking of writing an article and calling it "Small Helicopter Safety: Myth or Fable?" More recently, Frank Robinson has been reporting it as only 1.1 seconds. But having said that and having experienced several "throttle chops" in r-22 helicopters, I can attest that at least my reaction time falls at least a couple of tenths below that ! There's nothing like dumping that collective and feeling the aircraft pull away from your rear end (no matter how tight those cheeks try to hold on to that seat) ! Wayne |
#22
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Revolution Mini 500 - is it buildable?
Richard Riley wrote: An aviation writer friend of mine went to a Robinson training session a few years ago. He said you had 1.3 seconds to dump the collective in the R22. He was thinking of writing an article and calling it "Small Helicopter Safety: Myth or Fable?" More recently, Frank Robinson has been reporting it as only 1.1 seconds. But having said that and having experienced several "throttle chops" in r-22 helicopters, I can attest that at least my reaction time falls at least a couple of tenths below that ! There's nothing like dumping that collective and feeling the aircraft pull away from your rear end (no matter how tight those cheeks try to hold on to that seat) ! Wayne |
#23
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Revolution Mini 500 - is it buildable?
Dennis,
I see you are back with your same old talking points. As has been explained, a finding of pilot error does not in any way provide an endorsement of your design. When your design failed, many pilots found themselves unable to recover in a manner expected from certified aircraft. That is the standard. It does not address the design failures that preceded the pilot errors. It does not address the design's ability to recover from those failures. You like to blame the dead, especially low-time dead pilots. You might have forgotten that you marketed your kit to low-time pilots. Let's look at the chronology again. 1) Everybody gets excited when they see the Cicare CH-6 prototype fly. 2) You and Cicare dissolve your partnership and you are left without a helicopter to sell. 3) Without access to Cicare's design or the CH-6 demonstration aircraft, you attempt to copy the design. 4) While you are still designing your new helicopter, you continue to market and take orders for an unproven design 5) You delivered kits without adequate testing, claiming TBO's of up to 2000 hours, when your prototype only had a a couple of hundred hours, at most. 6) You marketed your kits to low-time pilots A classic bait and switch. |
#24
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Revolution Mini 500 - is it buildable?
Assuming that you make the RIGHT decisioin and don't hesitate or thing
about it. Richard Riley wrote: On 7 Jan 2007 14:49:34 -0800, wrote: More recently, Frank Robinson has been reporting it as only 1.1 seconds. But having said that and having experienced several "throttle chops" in r-22 helicopters, I can attest that at least my reaction time falls at least a couple of tenths below that ! I've seen medical data that says normal reaction time for an expected, life critical event (like, someone draws a gun on you, a car pulls out in front of you) is about 3/4 of a second. So you got that big, .35 second margin to keep you safe. Nothing to worry about. |
#25
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Revolution Mini 500 - is it buildable?
My answer to this post, and below is the last article printed by
KitPlanes Magazine in November 1999 of the flight report wrote by Kin Armstrong. So if you have already made a negative opinion on the Mini-500 saga and don't what your opinion to be confused by the facts, then don't read!!! anon wrote: Dennis, I see you are back with your same old talking points. There's nothing like the facts to counter unfounded and false statements. My talking points stay the same, because they are the true facts. I, unlike people like you, don't have the luxury of changing or making up stories, or making up or passing on unfounded or untrue statements. So yes, you will read what I have to say over and over again, because those are the facts, much to your apparent dissatisfaction. As has been explained, a finding of pilot error does not in any way provide an endorsement of your design. You know, there are people out there that even dispute the fact that America landed a man on the moon. It just does not matter how much evidence you put before them, or who provides the evidence, they choose not to believe it because that is what they want to disbelieve. I give you Federal accident reports followed up with further company reports, and still you choose to disbelieve, because that is contrary to what you want to believe. Even a horse is smart enough to drink water when you lead him to it enough times, but you will never believe because that is not what you want to believe, despite the proof or who prints it. When your design failed, many pilots found themselves unable to recover in a manner expected from certified aircraft. That is the standard. It does not address the design failures that preceded the pilot errors. It does not address the design's ability to recover from those failures. Wrong. Many Mini-500 owners say absolutely the opposite. In fact, attached is a report by the professional test pilot Ken Armstrong, giving the Mini-500 a brilliant review. The Mini-500 he flew the same bird that flew from Kansas City to Oshkosh, the same bird that flew at all the air shows. That Mini-500 was 100% stock all the way, built to factory specs with all factory mods. You like to blame the dead, especially low-time dead pilots. You might have forgotten that you marketed your kit to low-time pilots. I only tell the facts. I don't even want to talk about it, let alone blame live or dead people. But you really haven't given be any alternatives. You put me on the spot, you blame be for killing people with a bad design, you continually place me in a position demanding answers, and I can only answer with the facts. If I said it was not their fault, then I would be lying. Let's look at the chronology again. 1) Everybody gets excited when they see the Cicare CH-6 prototype fly. 2) You and Cicare dissolve your partnership and you are left without a helicopter to sell. 3) Without access to Cicare's design or the CH-6 demonstration aircraft, you attempt to copy the design. 4) While you are still designing your new helicopter, you continue to market and take orders for an unproven design 5) You delivered kits without adequate testing, claiming TBO's of up to 2000 hours, when your prototype only had a a couple of hundred hours, at most. 6) You marketed your kits to low-time pilots A classic bait and switch. You must write fictional books for living!! You have taken history and twisted it around to your satisfaction. I'll tell you what, I'll let Ken Armstrong's article in KitPlanes Magazine do the speaking for awhile. Ken has over 9000 hours flying 40 different types of helicopters. He was a Military helicopter test pilot, and currently instructs in helicopters. BUT EVEN WITH A MAN WITH SUCH IMPECCABLE QUALIFICATIONS AND UNTARNISHED REPUTATION, someone here will find something to discredit him and his report on the Mini-500. The truth is written below, and yet some of you will refuse to believe, simply because it is contrary to what you want to believe. After all, you read all the bad stuff about the Mini-500 right here on this newsgroup by credible people, that you have never met or can even see and some that don't have names... so it must have been true, right???? ********Mini Revolution******** Where is Revolution Helicopter’s Mini-500 series heading? By Ken Armstrong KitPlanes Magazine November 1999 Issue The Revolution Mini 500 possesses an enviable sales record because of the strong demand for low-cost, kit-built helicopters. However, marketing success has created problems for the company and its owners. Revolution has difficulty keeping up with customer expectations, and some builders unrealistically expect the helicopter to be snag-¬free during ownership. In reality, the Mini 500 is no different from any homebuilt helicopter - or from any commercial helicopter ever produced. They have all experienced technical/design problems that required modification, and as a professional helicopter pilot since 1972, I was often the guinea pig who found out what those problems were. No helicopter design is perfect, and there is no fling-wing flying that does not have ongoing problems. What can you do if you own a Mini 500 or plan to buy one? Approach ownership with an open mind and anticipate some down time while you install modifications that Revolution considers mandatory for the safe operation of the helicopter. If you plan to buy a used Mini 500, ensure all of the mandatory modifications have been completed. Is the Mini 500 Safe?..... Any helicopter is only as safe as the pilot in command. There have been a number of Mini 500 crashes, a number of them resulting in fatalities, and there is a common thread among them. Accident data from Revolution and the NTSB, combined with witness reports, indicate there have been few if any mechanical failures that were not caused by improper maintenance. In fact, 100% of the crashes had a pilot error component, with 43% sharing maintenance/pilot error causal factors. Nearly 75% of the pilots involved in accidents had less than 100 hours rotary wing experience, and some didn't even have a helicopter rating (more on this subject in the flight evaluation). Failure to maintain adequate rotor rpm was a contributing factor in almost half of the accidents. Another factor was pilots flying with the wrong carburetor jets for the ambient conditions - an important consideration when operating these hard-working engines. Operating with a two-stroke engine entails a higher risk of engine failure than a four-stroke powerplant would, and pilots must always be prepared to carry out an autorotation. Another primary factor in the high accident rate for the Mini 500 (44 accidents out of only a few hundred flying) is that there are many being flown by pilots with relatively little rotary experience, and in a few of the accidents the pilots weren't even licensed. In the case of an engine out, proper training and experience is critical. But other than the higher incidence of engine failures associated with two-stroke operation and pilot deficiencies, I don't see any particular safety risk associated with this helicopter, and I wouldn't hesitate to fly Mini 500s because the autorotative characteristics are quite reasonable in the event the Rotax takes a time out. Who Needs Politics?.... I believe the greatest non-technical problem plaguing the Mini 500 is the polarization between Revolution and a small number of vocal, dissatisfied owners. Revolution President Dennis Fetters is blessed and cursed with a strong personality that has bolstered him with the drive to create the successful Air Command gyro series and now the affordable Mini helicopter series. But success often breeds problems, and keeping up with the calls for technical revisions while attempting to provide really good customer support has been a challenge at Revolution. As a result, some of the owners have formed the support group known as the International Helicopter Builders Association Inc. (IHBAI). Mentioning this group to Fetters is like waving a red flag at a bull. He feels the organization is trying to undermine his efforts and has been dishonest about its aims. The group says it simply wants to find fixes for Mini 500 problems typically agreed to as excessive vibration creating frame cracks and transmission gears manufactured by a third party that were not of sufficient hardness. For more details on these topics, see the May 1999 KITPLANES©. Having mentioned this builders group, I should add that I met many Mini 500 owners at Sun'n Fun who have experienced no problems with their helicopters and are having a blast with them. Responses to company questionnaires indicate that more than 90% of the attendees at company training programs are completely satisfied with Revolution's efforts. In the Internet era, it's all too easy for a few unhappy owners to promote their discontent. Builders Support Group.... At the 1999 Sun'n Fun meeting, IHBAI members, under President Bill Phillips, decided they would not hire an engineering team to modify or fix the Mini 500's problems because they felt Revolution was adequately tackling the situation. The 14 attendees almost unanimously expressed a desire to work with the company on problems and fixes. However, Fetters wanted no association with this group. For the most part, I found these owners to be levelheaded and simply wanting a solution to their problems at a reasonable price so they could continue flying. Stan Robinson, president of U.S. AirPower, talked about the possibility of installing the three-cylinder, liquid cooled two-stroke engine currently undergoing flight test in the Revolution two-place Voyager, but this is unlikely in the near term, especially without Fetters' blessing. Solutions Are at Hand.... Fetters has always maintained that the company manufactures modifications quickly and prices them realistically to support his clients. After many hours of discussion with him, I can appreciate his point of view and feel the company is striving assiduously to correct deficiencies and expand the performance and safety envelope. Solving vibration problems has been a long slow process not because Revolution wasn't devoting a lot of time to the solution, but because rotor system dynamics are complex. The late model Talon (the model name for the improved Mini 500) I flew for this report had the latest refinements including mast support with rubber isolation, friction damper on the cyclic system and trimtabs on the rotor system. These refinements have apparently reduced the overall vibration level from 10 IPS to 0.01 in hover and 0.1 at 95 mph. Revolution asserts that all of these modifications are recommended because they work together to significantly reduce vibration. Minimizing the shaking reduces wear and tear, extends component life and provides greater system reliability. All new kits include all of the mast support refinements. An Engine Information System (EIS) is a new option that constantly monitors cooling, fuel mixture, lubrication and power output for enhanced reliability. Although I have not evaluated this $675 package, it comes complete with all probes, wiring and displays to provide a visual warning in the form in a red light when an engine parameter has been exceeded. It’s like buying insurance. Power Enhancement Package.... The factory demonstrator I flew at Sun 'n Fun, 500FD, had the optional power enhancement package (PEP) installed. The company recommends that every Mini 500 owner install this system to improve recovery from low rotor rpm. Faustino Padilla, a 240-pound Guatemalan pilot/owner who flies his Mini 500 from a base 5000 feet above sea level at very high temperatures, claims the PEP makes a world of difference to performance. The PEP system comprises a tuned exhaust system and special carburetion settings that provide an additional 18% hp and torque equating to an additional 138 pounds of lift, according to the company. Essentially, the engine is optimized for the narrow power band necessary for the helicopter application. Fetters believes that for $950, this is an inexpensive option that overcomes the need for a more powerful engine, which would be much more expensive. Flight Evaluation.... I don't take flights in single-place helicopters lightly, and I've waited patiently for years for the fleet hours to accumulate demonstrating the inherent safety of the series (about 28,000 hours to date, according to Fetters). It was only after a detailed flight briefing and an impressive demonstration flight by Ricardo Aita, a company pilot, that I was prepared to place air under the skids. It turned out I was overly cautious-if that's possible. Fetters showed me the preferred method for entering the cockpit, and I found the seat firm but comfortable (firm is best for a number of safety reasons). The controls came readily to hand for this paunchy pilot of 200 pounds and average height. The control checks with friction off showed there was no binding or significant friction in the system, and the friction was then cranked on to meet the company wishes. I confirmed that the fuel valve was on, skipped the prime with the warm engine, closed the throttle, neutralized the controls and turned the master switch on. With the-seatbelt secured, I couldn't reach the ignition switch, so I had selected both in advance and used the cyclic mounted starter button to bring the Mini to life. It started easily, and I idled a short time until the Rotax 582's coolant reached the bottom of the green. Raising the collective at idle produced a low rotor rpm warning, the magneto check proved both ignition systems were operating correctly, and the throttle chop at operating rpm provided a needle split between the rotor and engine confirming the one-way driven clutch was operative. At this point, I wanted to eliminate all friction in the control but was advised by the company pilot that it was preferable to leave considerable resistance in the controls. Later I learned that this was to reduce some of the vibration and stick shake. Although many pilots prefer to have considerable resistance in the system to minimize pilot overcontrolling, I prefer no stick trim or friction. I found that the collective requires some friction in the system or it will rise on its own during flight-not unusual in some helicopters. Moreover, if a pilot leaves the cockpit with the engine running, the helicopter could lift off if the collective is not locked down with a mechanical device or adequate friction. Getting Acquainted.... Initially, I had some difficulty mentally adapting to the pedals, which are shaped like foot rests and move in a slightly different axis compared to standard pedals. However, after 15 minutes or so of hovering, I found my body and brain had made the conversion quite readily. I also found the throttle system friction quite high, and this resulted in my chasing the engine/rotor rpm somewhat at first-especially since the correlation system doesn't do it all automatically for the pilot. However, owners can remove the engine access cover and readily adjust the throttle friction from no resistance to absolutely locked. The skill of keeping the rotor rpm at the top of the green can be quite a challenge for pilots like me who normally fly automatically governed turbine equipment. My natural fumbling at rotor speed control coupled with my intentional effort to establish the outside parameters allowed me to get a really good feeling for the Mini's rotor inertia. It also allowed me a glimpse into the scenarios that low-time pilots might encounter and that could lead to the low-rotor-rpm accidents that occur all too often. Once I got a handle on the power lever, it was obvious the Mini was a delight to hover and play with in the ground cushion. It was virtually free of any noticeable vibration at the recommended rotor speed of 104%-positive proof that the Revolution fixes really work in the hover. As the rotor speed falls below 96%, some minor vibration creeps in. However, this is below the normal range and of no real significance during typical operations. With the doors off, visibility was excellent in most directions with minor visual barriers straight down due to the floor and to the sides due to the doorframes. Nothing unusual there. The Mini had 9 gallons of fuel on board during the initial takeoff, and the nearly sea level OAT was 75°F. Fetters says that most problems on this engine are related to poor fuel or jetting problems, and after taking a Rotax maintenance course, I know this to be true in general on two-strokes. As I personally added high-quality, filtered gas for our operations, I was comfortable with the anticipated engine reliability and experimented with a broad spectrum of operating rpms and altitudes. Although the rotor speed's normal operating range is 96-104%, I conducted operations beyond these limits and found no unacceptable characteristics. The combination of relatively high rotor inertia and a sensitive throttle system results in pilots new to the type chasing the rotor rpm, but prolonged hovering operations can teach them effective rotor speed control. While operation in the low yellow rotor rpm band is not recommended, I found the helicopter had adequate power to recover from 90% or slightly less rotor rpm by milking the collective downward slightly while fully opening the throttle. Under the ambient conditions, full throttle produced the following maximum hover height/rpm combinations: 6 foot hover attainable at 100%, 10 feet at 102% and 15+ feet at 104%. The recommended takeoff power is 104%, so the PEP would obviously produce more than sufficient power for hovering with the skids approximately 2 feet off the ground at considerably higher altitudes and/or with much heavier pilots. Unless you are operating well above 5000-foot density altitude, it would appear that this engine with the optional PEP is adequate in terms of power output (assuming that the engine is kept well tuned, with the correct jets for the ambient con¬ditions, and approved, fresh fuel). Control Authority.... During a lengthy period of hovering that resulted in improved rotor speed control as the Mini and I became acquainted, I was able to conduct numerous hovering autorotations, and I found the Mini had plenty of rotor inertia to permit gentle touchdowns - even with a slightly drooped rotor rpm. Over two days, with varying winds, I confirmed that the 20 mph sideways and rearward maximum recommended flight speeds were conservative and safely flown with no tendency to exceed or even challenge the tail rotor's capability. There was plenty of control authority during all maneuvers, and the tail rotor seemed to have as much power as would ever be necessary at this density altitude. (No high-altitude testing was conducted during these profiles.) This Hughes 500 lookalike also transitions through translational lift quite smoothly, and I noted a distinct absence of measurable vibration under all flight conditions up to 30 mph indicated. Circuit restrictions, gusty winds and smoke from a forest fire shut down operations on my second day of flying, so I was unable to conduct a lot of straight and level flying at normal cruising speeds. Fetters wasn't keen on my flying in those conditions at all, but my schedule wouldn't permit a later flight, so I was committed to flying when many of the other gyroplanes and helicopters chose to sit it out. Nonetheless, the helicopter flew smoothly up to the maximum speed of 75 mph - an air-traffic induced limit. I wasn't overly comfortable flying this lightweight under such conditions, but the company pilot who had 60 hours on type subsequently flew the demo in an aggressive and accurate demonstration program with absolutely no difficulty. The Mini is not only responsive but also surprisingly stable in hovering operations, handling like a much larger helicopter. After only 20 minutes in type it was fairly easy to knock over the orange cone markers with a skid and then stand them up again. This can be challenging with any helicopter, and it was surprising to be able to accomplish this intricate task with so little time in type. Cautious Considerations.... The pilot's operating handbook cautions pilots to apply aft cyclic while the collective is being lowered after high-speed engine failures to minimize the helicopter's tendency to nose over. It also advises avoiding low G maneuvers to avoid chopping off the tail boom. These are standard cautions with any helicopter. Also, there is a large area of the height-velocity envelope to be avoided during low-speed and high hovering operations. I conducted autorotations while within the edges of the avoid area, and the chart is conservative. However, this is another way a company can build in additional safety margins for pilots. The major limitation of the helicopter is that it is hoisted aloft by a two-stroke engine. Two-strokes can be reasonably reliable if owners perform the suggested maintenance schedule recommended by Rotax, but these powerplants do require a lot of fiddling with jetting anytime a significant temperature or operating altitude is encountered to meet the carb/mixture/EGT requirements and limitations. Pilot/owners should follow the recommended procedures to keep their engines in optimum health. They should also ensure that their autorotational skills are honed. Now that I have logged a few flights on the updated version of the Mini-500 series, it's difficult to understand the tempest that has ensued between the company and a few owners - unless one considers the personalities involved. The 500 not only looks great, it flies well and appears to be free of significant vices. Helicopters are not toys, and they are not easy for low-time pilots to fly well. But they offer an excellent challenge for pilots who wish to rise above common pilot skills - vertically. The Mini, especially with PEP, boasts heaps of power for hot-and-heavy conditions and a blistering cruising speed for a low-cost helicopter. All this and measly operating expense, too. Revolution's current offerings have solved the initial problems common with the introduction of a new type, and the company is well positioned to increase customer service and success in the market. |
#26
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Revolution Mini 500 - is it buildable?
I've never read a negative artical by Ken Armstrong in COPA or
kitplanes. I've never read a negative aircraft review in Kitplanes by any author. Why would the mini 500 be any different? My answer to this post, and below is the last article printed by KitPlanes Magazine in November 1999 of the flight report wrote by Kin Armstrong. So if you have already made a negative opinion on the Mini-500 saga and don't what your opinion to be confused by the facts, then don't read!!! anon wrote: Dennis, I see you are back with your same old talking points. There's nothing like the facts to counter unfounded and false statements. My talking points stay the same, because they are the true facts. I, unlike people like you, don't have the luxury of changing or making up stories, or making up or passing on unfounded or untrue statements. So yes, you will read what I have to say over and over again, because those are the facts, much to your apparent dissatisfaction. As has been explained, a finding of pilot error does not in any way provide an endorsement of your design. You know, there are people out there that even dispute the fact that America landed a man on the moon. It just does not matter how much evidence you put before them, or who provides the evidence, they choose not to believe it because that is what they want to disbelieve. I give you Federal accident reports followed up with further company reports, and still you choose to disbelieve, because that is contrary to what you want to believe. Even a horse is smart enough to drink water when you lead him to it enough times, but you will never believe because that is not what you want to believe, despite the proof or who prints it. When your design failed, many pilots found themselves unable to recover in a manner expected from certified aircraft. That is the standard. It does not address the design failures that preceded the pilot errors. It does not address the design's ability to recover from those failures. Wrong. Many Mini-500 owners say absolutely the opposite. In fact, attached is a report by the professional test pilot Ken Armstrong, giving the Mini-500 a brilliant review. The Mini-500 he flew the same bird that flew from Kansas City to Oshkosh, the same bird that flew at all the air shows. That Mini-500 was 100% stock all the way, built to factory specs with all factory mods. You like to blame the dead, especially low-time dead pilots. You might have forgotten that you marketed your kit to low-time pilots. I only tell the facts. I don't even want to talk about it, let alone blame live or dead people. But you really haven't given be any alternatives. You put me on the spot, you blame be for killing people with a bad design, you continually place me in a position demanding answers, and I can only answer with the facts. If I said it was not their fault, then I would be lying. Let's look at the chronology again. 1) Everybody gets excited when they see the Cicare CH-6 prototype fly. 2) You and Cicare dissolve your partnership and you are left without a helicopter to sell. 3) Without access to Cicare's design or the CH-6 demonstration aircraft, you attempt to copy the design. 4) While you are still designing your new helicopter, you continue to market and take orders for an unproven design 5) You delivered kits without adequate testing, claiming TBO's of up to 2000 hours, when your prototype only had a a couple of hundred hours, at most. 6) You marketed your kits to low-time pilots A classic bait and switch. You must write fictional books for living!! You have taken history and twisted it around to your satisfaction. I'll tell you what, I'll let Ken Armstrong's article in KitPlanes Magazine do the speaking for awhile. Ken has over 9000 hours flying 40 different types of helicopters. He was a Military helicopter test pilot, and currently instructs in helicopters. BUT EVEN WITH A MAN WITH SUCH IMPECCABLE QUALIFICATIONS AND UNTARNISHED REPUTATION, someone here will find something to discredit him and his report on the Mini-500. The truth is written below, and yet some of you will refuse to believe, simply because it is contrary to what you want to believe. After all, you read all the bad stuff about the Mini-500 right here on this newsgroup by credible people, that you have never met or can even see and some that don't have names... so it must have been true, right???? ********Mini Revolution******** Where is Revolution Helicopter’s Mini-500 series heading? By Ken Armstrong KitPlanes Magazine November 1999 Issue The Revolution Mini 500 possesses an enviable sales record because of the strong demand for low-cost, kit-built helicopters. However, marketing success has created problems for the company and its owners. Revolution has difficulty keeping up with customer expectations, and some builders unrealistically expect the helicopter to be snag-¬free during ownership. In reality, the Mini 500 is no different from any homebuilt helicopter - or from any commercial helicopter ever produced. They have all experienced technical/design problems that required modification, and as a professional helicopter pilot since 1972, I was often the guinea pig who found out what those problems were. No helicopter design is perfect, and there is no fling-wing flying that does not have ongoing problems. What can you do if you own a Mini 500 or plan to buy one? Approach ownership with an open mind and anticipate some down time while you install modifications that Revolution considers mandatory for the safe operation of the helicopter. If you plan to buy a used Mini 500, ensure all of the mandatory modifications have been completed. Is the Mini 500 Safe?..... Any helicopter is only as safe as the pilot in command. There have been a number of Mini 500 crashes, a number of them resulting in fatalities, and there is a common thread among them. Accident data from Revolution and the NTSB, combined with witness reports, indicate there have been few if any mechanical failures that were not caused by improper maintenance. In fact, 100% of the crashes had a pilot error component, with 43% sharing maintenance/pilot error causal factors. Nearly 75% of the pilots involved in accidents had less than 100 hours rotary wing experience, and some didn't even have a helicopter rating (more on this subject in the flight evaluation). Failure to maintain adequate rotor rpm was a contributing factor in almost half of the accidents. Another factor was pilots flying with the wrong carburetor jets for the ambient conditions - an important consideration when operating these hard-working engines. Operating with a two-stroke engine entails a higher risk of engine failure than a four-stroke powerplant would, and pilots must always be prepared to carry out an autorotation. Another primary factor in the high accident rate for the Mini 500 (44 accidents out of only a few hundred flying) is that there are many being flown by pilots with relatively little rotary experience, and in a few of the accidents the pilots weren't even licensed. In the case of an engine out, proper training and experience is critical. But other than the higher incidence of engine failures associated with two-stroke operation and pilot deficiencies, I don't see any particular safety risk associated with this helicopter, and I wouldn't hesitate to fly Mini 500s because the autorotative characteristics are quite reasonable in the event the Rotax takes a time out. Who Needs Politics?.... I believe the greatest non-technical problem plaguing the Mini 500 is the polarization between Revolution and a small number of vocal, dissatisfied owners. Revolution President Dennis Fetters is blessed and cursed with a strong personality that has bolstered him with the drive to create the successful Air Command gyro series and now the affordable Mini helicopter series. But success often breeds problems, and keeping up with the calls for technical revisions while attempting to provide really good customer support has been a challenge at Revolution. As a result, some of the owners have formed the support group known as the International Helicopter Builders Association Inc. (IHBAI). Mentioning this group to Fetters is like waving a red flag at a bull. He feels the organization is trying to undermine his efforts and has been dishonest about its aims. The group says it simply wants to find fixes for Mini 500 problems typically agreed to as excessive vibration creating frame cracks and transmission gears manufactured by a third party that were not of sufficient hardness. For more details on these topics, see the May 1999 KITPLANES©. Having mentioned this builders group, I should add that I met many Mini 500 owners at Sun'n Fun who have experienced no problems with their helicopters and are having a blast with them. Responses to company questionnaires indicate that more than 90% of the attendees at company training programs are completely satisfied with Revolution's efforts. In the Internet era, it's all too easy for a few unhappy owners to promote their discontent. Builders Support Group.... At the 1999 Sun'n Fun meeting, IHBAI members, under President Bill Phillips, decided they would not hire an engineering team to modify or fix the Mini 500's problems because they felt Revolution was adequately tackling the situation. The 14 attendees almost unanimously expressed a desire to work with the company on problems and fixes. However, Fetters wanted no association with this group. For the most part, I found these owners to be levelheaded and simply wanting a solution to their problems at a reasonable price so they could continue flying. Stan Robinson, president of U.S. AirPower, talked about the possibility of installing the three-cylinder, liquid cooled two-stroke engine currently undergoing flight test in the Revolution two-place Voyager, but this is unlikely in the near term, especially without Fetters' blessing. Solutions Are at Hand.... Fetters has always maintained that the company manufactures modifications quickly and prices them realistically to support his clients. After many hours of discussion with him, I can appreciate his point of view and feel the company is striving assiduously to correct deficiencies and expand the performance and safety envelope. Solving vibration problems has been a long slow process not because Revolution wasn't devoting a lot of time to the solution, but because rotor system dynamics are complex. The late model Talon (the model name for the improved Mini 500) I flew for this report had the latest refinements including mast support with rubber isolation, friction damper on the cyclic system and trimtabs on the rotor system. These refinements have apparently reduced the overall vibration level from 10 IPS to 0.01 in hover and 0.1 at 95 mph. Revolution asserts that all of these modifications are recommended because they work together to significantly reduce vibration. Minimizing the shaking reduces wear and tear, extends component life and provides greater system reliability. All new kits include all of the mast support refinements. An Engine Information System (EIS) is a new option that constantly monitors cooling, fuel mixture, lubrication and power output for enhanced reliability. Although I have not evaluated this $675 package, it comes complete with all probes, wiring and displays to provide a visual warning in the form in a red light when an engine parameter has been exceeded. It’s like buying insurance. Power Enhancement Package.... The factory demonstrator I flew at Sun 'n Fun, 500FD, had the optional power enhancement package (PEP) installed. The company recommends that every Mini 500 owner install this system to improve recovery from low rotor rpm. Faustino Padilla, a 240-pound Guatemalan pilot/owner who flies his Mini 500 from a base 5000 feet above sea level at very high temperatures, claims the PEP makes a world of difference to performance. The PEP system comprises a tuned exhaust system and special carburetion settings that provide an additional 18% hp and torque equating to an additional 138 pounds of lift, according to the company. Essentially, the engine is optimized for the narrow power band necessary for the helicopter application. Fetters believes that for $950, this is an inexpensive option that overcomes the need for a more powerful engine, which would be much more expensive. Flight Evaluation.... I don't take flights in single-place helicopters lightly, and I've waited patiently for years for the fleet hours to accumulate demonstrating the inherent safety of the series (about 28,000 hours to date, according to Fetters). It was only after a detailed flight briefing and an impressive demonstration flight by Ricardo Aita, a company pilot, that I was prepared to place air under the skids. It turned out I was overly cautious-if that's possible. Fetters showed me the preferred method for entering the cockpit, and I found the seat firm but comfortable (firm is best for a number of safety reasons). The controls came readily to hand for this paunchy pilot of 200 pounds and average height. The control checks with friction off showed there was no binding or significant friction in the system, and the friction was then cranked on to meet the company wishes. I confirmed that the fuel valve was on, skipped the prime with the warm engine, closed the throttle, neutralized the controls and turned the master switch on. With the-seatbelt secured, I couldn't reach the ignition switch, so I had selected both in advance and used the cyclic mounted starter button to bring the Mini to life. It started easily, and I idled a short time until the Rotax 582's coolant reached the bottom of the green. Raising the collective at idle produced a low rotor rpm warning, the magneto check proved both ignition systems were operating correctly, and the throttle chop at operating rpm provided a needle split between the rotor and engine confirming the one-way driven clutch was operative. At this point, I wanted to eliminate all friction in the control but was advised by the company pilot that it was preferable to leave considerable resistance in the controls. Later I learned that this was to reduce some of the vibration and stick shake. Although many pilots prefer to have considerable resistance in the system to minimize pilot overcontrolling, I prefer no stick trim or friction. I found that the collective requires some friction in the system or it will rise on its own during flight-not unusual in some helicopters. Moreover, if a pilot leaves the cockpit with the engine running, the helicopter could lift off if the collective is not locked down with a mechanical device or adequate friction. Getting Acquainted.... Initially, I had some difficulty mentally adapting to the pedals, which are shaped like foot rests and move in a slightly different axis compared to standard pedals. However, after 15 minutes or so of hovering, I found my body and brain had made the conversion quite readily. I also found the throttle system friction quite high, and this resulted in my chasing the engine/rotor rpm somewhat at first-especially since the correlation system doesn't do it all automatically for the pilot. However, owners can remove the engine access cover and readily adjust the throttle friction from no resistance to absolutely locked. The skill of keeping the rotor rpm at the top of the green can be quite a challenge for pilots like me who normally fly automatically governed turbine equipment. My natural fumbling at rotor speed control coupled with my intentional effort to establish the outside parameters allowed me to get a really good feeling for the Mini's rotor inertia. It also allowed me a glimpse into the scenarios that low-time pilots might encounter and that could lead to the low-rotor-rpm accidents that occur all too often. Once I got a handle on the power lever, it was obvious the Mini was a delight to hover and play with in the ground cushion. It was virtually free of any noticeable vibration at the recommended rotor speed of 104%-positive proof that the Revolution fixes really work in the hover. As the rotor speed falls below 96%, some minor vibration creeps in. However, this is below the normal range and of no real significance during typical operations. With the doors off, visibility was excellent in most directions with minor visual barriers straight down due to the floor and to the sides due to the doorframes. Nothing unusual there. The Mini had 9 gallons of fuel on board during the initial takeoff, and the nearly sea level OAT was 75°F. Fetters says that most problems on this engine are related to poor fuel or jetting problems, and after taking a Rotax maintenance course, I know this to be true in general on two-strokes. As I personally added high-quality, filtered gas for our operations, I was comfortable with the anticipated engine reliability and experimented with a broad spectrum of operating rpms and altitudes. Although the rotor speed's normal operating range is 96-104%, I conducted operations beyond these limits and found no unacceptable characteristics. The combination of relatively high rotor inertia and a sensitive throttle system results in pilots new to the type chasing the rotor rpm, but prolonged hovering operations can teach them effective rotor speed control. While operation in the low yellow rotor rpm band is not recommended, I found the helicopter had adequate power to recover from 90% or slightly less rotor rpm by milking the collective downward slightly while fully opening the throttle. Under the ambient conditions, full throttle produced the following maximum hover height/rpm combinations: 6 foot hover attainable at 100%, 10 feet at 102% and 15+ feet at 104%. The recommended takeoff power is 104%, so the PEP would obviously produce more than sufficient power for hovering with the skids approximately 2 feet off the ground at considerably higher altitudes and/or with much heavier pilots. Unless you are operating well above 5000-foot density altitude, it would appear that this engine with the optional PEP is adequate in terms of power output (assuming that the engine is kept well tuned, with the correct jets for the ambient con¬ditions, and approved, fresh fuel). Control Authority.... During a lengthy period of hovering that resulted in improved rotor speed control as the Mini and I became acquainted, I was able to conduct numerous hovering autorotations, and I found the Mini had plenty of rotor inertia to permit gentle touchdowns - even with a slightly drooped rotor rpm. Over two days, with varying winds, I confirmed that the 20 mph sideways and rearward maximum recommended flight speeds were conservative and safely flown with no tendency to exceed or even challenge the tail rotor's capability. There was plenty of control authority during all maneuvers, and the tail rotor seemed to have as much power as would ever be necessary at this density altitude. (No high-altitude testing was conducted during these profiles.) This Hughes 500 lookalike also transitions through translational lift quite smoothly, and I noted a distinct absence of measurable vibration under all flight conditions up to 30 mph indicated. Circuit restrictions, gusty winds and smoke from a forest fire shut down operations on my second day of flying, so I was unable to conduct a lot of straight and level flying at normal cruising speeds. Fetters wasn't keen on my flying in those conditions at all, but my schedule wouldn't permit a later flight, so I was committed to flying when many of the other gyroplanes and helicopters chose to sit it out. Nonetheless, the helicopter flew smoothly up to the maximum speed of 75 mph - an air-traffic induced limit. I wasn't overly comfortable flying this lightweight under such conditions, but the company pilot who had 60 hours on type subsequently flew the demo in an aggressive and accurate demonstration program with absolutely no difficulty. The Mini is not only responsive but also surprisingly stable in hovering operations, handling like a much larger helicopter. After only 20 minutes in type it was fairly easy to knock over the orange cone markers with a skid and then stand them up again. This can be challenging with any helicopter, and it was surprising to be able to accomplish this intricate task with so little time in type. Cautious Considerations.... The pilot's operating handbook cautions pilots to apply aft cyclic while the collective is being lowered after high-speed engine failures to minimize the helicopter's tendency to nose over. It also advises avoiding low G maneuvers to avoid chopping off the tail boom. These are standard cautions with any helicopter. Also, there is a large area of the height-velocity envelope to be avoided during low-speed and high hovering operations. I conducted autorotations while within the edges of the avoid area, and the chart is conservative. However, this is another way a company can build in additional safety margins for pilots. The major limitation of the helicopter is that it is hoisted aloft by a two-stroke engine. Two-strokes can be reasonably reliable if owners perform the suggested maintenance schedule recommended by Rotax, but these powerplants do require a lot of fiddling with jetting anytime a significant temperature or operating altitude is encountered to meet the carb/mixture/EGT requirements and limitations. Pilot/owners should follow the recommended procedures to keep their engines in optimum health. They should also ensure that their autorotational skills are honed. Now that I have logged a few flights on the updated version of the Mini-500 series, it's difficult to understand the tempest that has ensued between the company and a few owners - unless one considers the personalities involved. The 500 not only looks great, it flies well and appears to be free of significant vices. Helicopters are not toys, and they are not easy for low-time pilots to fly well. But they offer an excellent challenge for pilots who wish to rise above common pilot skills - vertically. The Mini, especially with PEP, boasts heaps of power for hot-and-heavy conditions and a blistering cruising speed for a low-cost helicopter. All this and measly operating expense, too. Revolution's current offerings have solved the initial problems common with the introduction of a new type, and the company is well positioned to increase customer service and success in the market. |
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Revolution Mini 500 - is it buildable?
BUT...are we talking about the highly trained frequent flying helo
pilot or the weekend hobby pilot who tends to be out of practice and less tuned into his aircraft? Is the market for these aircraft really the highly trained pilots or the wannabe's? Richard Riley wrote: On 7 Jan 2007 19:26:04 -0800, "BobR" wrote: Assuming that you make the RIGHT decisioin and don't hesitate or thing about it. Well, of course! I mean, a highly trained helo pilot wouldn't ever do anything but! A third of a second is PLENTY to understand what's going on and begin corrective action! |
#28
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Revolution Mini 500 - is it buildable?
BobR wrote:
BUT...are we talking about the highly trained frequent flying helo pilot or the weekend hobby pilot who tends to be out of practice and less tuned into his aircraft? Is the market for these aircraft really the highly trained pilots or the wannabe's? Richard Riley wrote: On 7 Jan 2007 19:26:04 -0800, "BobR" wrote: Assuming that you make the RIGHT decisioin and don't hesitate or thing about it. Well, of course! I mean, a highly trained helo pilot wouldn't ever do anything but! A third of a second is PLENTY to understand what's going on and begin corrective action! When I was getting my PP-R H rating I had an engine failure in an R-22 while solo. I was in the pattern so locating a landing spot wasn't an issue. Also, I had been practicing Autos to hover that morning with and instructor. That said, there was plenty of time to slam the collective down when the engine failed. That is the real reason helicopters are so loud. They make them that way so it really gets your attention when they stop being loud. What it comes down to is a second is really a pretty long time. Two seconds is twice as long. back in the 90's I shot pistols in competition. IPSC to be exact. One of the standard exercises was called El Presidente. 3 targets at 30 feet. The drill was to draw, fire two rounds on each target, reload and fire two on each target. The going time was around 6 seconds for the drill. The really fast guys were getting close to 5 and may well have beat 5 by now. |
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Revolution Mini 500 - is it buildable?
Drew Dalgleish wrote:
I've never read a negative artical by Ken Armstrong in COPA or kitplanes. I've never read a negative aircraft review in Kitplanes by any author. Why would the mini 500 be any different? BUT EVEN WITH A MAN WITH SUCH IMPECCABLE QUALIFICATIONS AND UNTARNISHED REPUTATION, someone here will find something to discredit him and his report on the Mini-500. The truth is written below, and yet some of you will refuse to believe, simply because it is contrary to what you want to believe. There ya go........ I knew there would be someone insult the man!! As Mr. Armstrong told me, he don't test fly the ones that don't look safe. Besides, how many kitbuilts were out there at the time?...... five or so?? I guess he could only write so many flight reviews per kit, with the very limited numbers to write about. But again, it don't matter if Chuck Yeager wrote a good report about the Mini-500, some of you have your minds made up and don't want to confuse the issues with the facts. |
#30
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Revolution Mini 500 - is it buildable?
Dennis,
I used to read Kitplanes but quit when it became obvious it wasn't much more than a mouthpiece for its advertisers. Much like Zoom's garbage. What Drew wrote was simply the FACTS... not opinion, facts. Two sentences of fact and one sentence with a question. You don't like reading them... that I can understand given your own interest in the Mini-500. John Dennis Fetters wrote: Drew Dalgleish wrote: I've never read a negative artical by Ken Armstrong in COPA or kitplanes. I've never read a negative aircraft review in Kitplanes by any author. Why would the mini 500 be any different? BUT EVEN WITH A MAN WITH SUCH IMPECCABLE QUALIFICATIONS AND UNTARNISHED REPUTATION, someone here will find something to discredit him and his report on the Mini-500. The truth is written below, and yet some of you will refuse to believe, simply because it is contrary to what you want to believe. There ya go........ I knew there would be someone insult the man!! As Mr. Armstrong told me, he don't test fly the ones that don't look safe. Besides, how many kitbuilts were out there at the time?...... five or so?? I guess he could only write so many flight reviews per kit, with the very limited numbers to write about. But again, it don't matter if Chuck Yeager wrote a good report about the Mini-500, some of you have your minds made up and don't want to confuse the issues with the facts. |
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