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Rotax 135 HP Engine

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  • #31
    Originally posted by deandob View Post
    Thank you Brian for the advice.
    No problems dean, only too happy to help, I have been fortunate to see a fair bit & have learnt from watching & listening plus having a few thousand hours of flying around in ever diminishing circles. My first gyro was an open frame single seat powered by a EA 81 suby. It was a bit heavy, cruised at 4200 revs & wide open at 4400 revs so I learnt a lot about rotor management plus managing speed


    • #32
      Wow, that is a lot of experience. You must be dizzy with all those circles

      I drove a Subaru Leone in the 80's for a number of years and worked on the EA81 (usual things teenagers did to hot up their cars....) - I'd never imagine it strapped to a gyroplane back then. I guess this engine is popular due to the Boxer configuration (lower center of gravity, reliable, good power to weight ratio).

      Regarding open frame single gyros, I can't get over the raw experience of hanging out there in the breeze at 500 feet up and 60 knots.... Even the open cockpit models like TAG I have some hesitation but could get used to it. Closed cockpit & especially side by side gyros are a little easier for newbies like me (and will attract more new people to the sport) - but I can see that a gyro like the TAG would end up being more fun in the long run. I definitely want a 2 seater (likely tandem) that I can be trained in / get used to, and eventually take a passenger when I'm competent enough.


      • #33
        Fourth time lucky, I have been trying to post this for awhile but it wouldn't let me.😠

        Automotive turbo failures are normally a result of high engine loads (especially at low rpms), high boost pressures, poor maintenance and poor operating proceedures. Aircraft engines operate at maximum load at maximum rpm as determined by the pitch of the prop, hence maximum continuous rpm in the aviation world. Additionally the boost pressures are very conservative.

        Turbo bearing failures are generally from poor maintenance, poor oil quality, over fuelling, very high oil temps, putting too much load on the engine/turbo before it is at operating temp and shutting down the engine when turbo is still hot turning the oil into carbon on the bearings.

        Sure high egt's can damage a turbo but there is generally low boost pressures associated with aviation engines. Theoretically there is a "safety" margin in there so overspeed should not issue for turbo failure. The extra boost from the extra speed could cause an issue. As aviation engines don't need instant boost reponse running a bigger than normal turbo will supply larger volumes of cooler air (from not working as hard to compress the air - heat) in the upper rpm region where the power is most needed for aircraft applications.

        Setup properly the Bing carbs lend themselves well to turbo application but they do have their limits. Turbo engines add alot of extra complexity, especially on the fuelling and ignition timing side of things. I am still unsure as what is done with the timing on these engines. The compression ratio has been lowered. At 5psi and 8.0:1 static compression ratio, the effective compression ratio will be roughly 10.7:1. That is not much more than the standard 10.5:1 but anymore boost could be bad without timing modifications.

        My concern is how thin the piston crowns are. A lean mixture will cause pre ignition or detonation and possible melting. The 9 series Rotax have liquid cooled cylinder heads and air cooled barrels unlike automotive engines that are fully liquid cooled which can dissipate the heat more efficiently. One of the earlier guys pioneering this 100 hp Rotax turbo was welding the underside of the piston to allow for extra crown thickness. Mind you he was pushing out more than 135 hp.😁

        There are also weak spots in the crank case if you look in the right spot.

        Extra power can get a inexperienced pilot into trouble as well so my humble advice is get yourself a second hand single seat gyro powered by a suby EA 81 & go fly that around for a couple hundred hours & then you will have excellent base to work off. - That is the best advice you will ever receive.

        Flying marginally powered machines has saved my bacon on a few occassions. You actually have to fly the machine and not rely on the power. The extra power is good when you know how to use it effectively


        • #34
          West Oz Flyer - excellent post that explains some of the details of the rotax & turbo implementation, and has helped my understanding. Consensus seems to be for a newbie like me to go for a cheaper/lower power/smaller gyro and practice on that before graduating to a more sporty / larger / power machine.

          I just have to get over my trepidation of the feeling that the smaller gyros are basically a seat on the front of a motor, a prop, rotor and tail - nothing between you and the elements, and as a beginner this is a significant confidence challenge to overcome. Also to eventually graduate to my 'dream gyro' at a later stage (when more experienced) means having to sell the old one & purchase another machine, which is a hassle.

          I'm sharing this as these are the thoughts going around my head as a new person interested in learning & being part of the gyro community but trying to work out the best pathway to entry (safety and getting the right instruction are the other dimensions). What I like about the larger more powerful new generation gyros is that they feel like a small fixed wing, factory built / tested (so takes away some of the mechanical / structural concerns) and (in my opinion) make it easier for new people to come into the sport. But I can also see that the smaller more agile gyros will be more fun to fly, but not until I have the confidence / experience.


          • #35

            Regarding open frame single gyros, I can't get over the raw experience of hanging out there in the breeze at 500 feet up and 60 knots.... [/QUOTE]

            I have been lucky enough to fly around the country in both a side x side and tandem machines, but the one flight that sticks in my mind more than any other is flying around Kununurra in an open frame Rosco at 40 knots.


            • #36
              Yes it's incredible to think that after 10 or so hours flying time in a day that you never got further than 30ks from point of departure & possibly clocked up around 7 to 800 ks distance flown!
              I was a fw pilot before gyros & it did take a hour or two to get over the open frame thing but after that it didn't bother me .Great thing about learning in an open frame hand prop /hand start rotors is that you learnt all about rotor management & the wind on your face whilst doing practice forced landings was good experience when you did have an engine out.
              Got to say though that the sleds are very safe to fly even if they feel like a mack truck to fly .


              • #37
                Great advice on a couple of fronts & it's great to see the forum being used constructively. There's so much knowledge around but possibly not enough being shared.


                • #38
                  Had a visit from Vince Mack from WA today and he says that he has almost 500 hours on his 135 HP Rotax and had not had any problems at all. He said fuel burn was about 22 l/hr cruising at 4900 RPM. No boost or MAP gauge. Also said that these engines have the 80 HP core (black heads). The other Xenon I know a bit about is the one for sale in the ;last GN. Again, no problems that I know of.


                  In aviation, the only stupid question is the one you don't ask!


                  • #39
                    Good to know, thanks Allan, I think it is safe to say that the Xenon engine is OK, lots of units been flying for a while with no significant problems reported.

                    Lots of good advice in this thread, and I have been soaking it all up as well as reading up about flight and gyro theory (found a very interesting thread on rotarywingforum about the pros and cons of high versus centre thrust line which delves into gyro theory & safety considerations). I'm compiling a document with the aim to summarise gyro flight principles and I'll post it in another thread to check if I'm on the right path, and it may also help others starting to learn.


                    • #40
                      Originally posted by deandob View Post
                      I'm compiling a document with the aim to summarise gyro flight principles and I'll post it in another thread to check if I'm on the right path, and it may also help others starting to learn.
                      by all means
                      That is what the forum is for.
                      Nothing stopping you just at the forum, ASRA (board) is made up of volunteers, that are willing promote safe gyro operations, and tackle all the handbrakes on the behalf of its members.

                      Remember: no matter where you go, there you are


                      • RossM
                        RossM commented
                        Editing a comment
                        Shyte, I should not have said that, scaring Dean off already.

                    • #41
                      All good Ross. I have found this community very helpful, Allan in particular has gone out of his way to answer a barrage of questions from me. It is appreciated, I'm looking forward to starting my lessons and buying a gyro and hopefully contributing back once I'm more experienced.


                      • #42
                        Your right deandob Allan has a wealth of knowledge in gyrocopters and aviation in general, We are very lucky to have him.


                        • #43
                          One more rotax question...

                          With the new rotax fuel injected motors (912 IS & 915), wouldn't they be the choice for a new gyro? Aside from better fuel efficiency (which doesn't really help due to the extra costs of the fuel injected versions), the maintenance & most importantly the reliability of the motor should be improved? Although there is more complexity in a fuel injected system (mostly due to extra electronics), in the auto world fuel injection has been one of the reasons for improved motor reliability, so this should be the same for aircraft engines unless rotax stuff up the implementation.

                          An engine that is going to be more reliable (with less maintenance) is worth paying extra for if it saves even just one engine problem in flight over its lifetime. Or doesn't it work this way for aviation engines? I notice that rotax seems to have a lot of service bulletins for what is a rather old engine design, which isn't a good sign, but should mean over time the engines get more reliable / robust if you implement their service bulletins, or buy a new engine.


                          • #44
                            Having had a suby 2.2 fuel injected engine that did about 4.000 hours & now a 912 Rotax for about 600 hours i feel i can comment on the subject. Fuel injection on the suby had been trouble free except for high pressure fuel pumps that can fail after 300 hours. They aren't cheap but they are readily available. The bing carbies on the 912 are nearly trouble free from the info i have so to me it comes down to 2 things, difference in price between carbs & FI 915 and the complexity between carbs & FI if anything goes wrong .
                            If I was building a new single seat gyro i would go carbs every day of the week however a 2 seater i would go the 915. In my new helicopter i would go the 915


                            • #45
                              We have without any doubt a very impressive wealth of talent in the asra board &appointees. Allan, dr Paul , Mark R, can mix it with anyone at the highest level & then you have a incredible pool of talent backing them up who are all very talented &have a vast wealth of knowledge combined with experience.