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Roger Lee

Carb bowl obstruction - Don't be stranded

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I hope you are not taking me wrong either Roger. I am greatly in your debt for all the help you have given me, and I truly appreciate it.

I have read through the manuals, but I will never see 15-30 planes a year - I know of one other LSA anywhere near me - and I have no plans to make this another career.

I am not trying to "shoot the messenger." I am fully aware that it is not your fault. I just believe Rotax and FD could make this easier by making their manuals clearer and more inclusive, and by making information more available.

I don't own a motorcycle, so I can't speak to that situation. I do know about electronics, never went to school for it. I was able to learn it by reading, and what I know applies to all electronics. The big difference is that 1) the government does not require me to take my, or anyone else's TV apart once a year to inspect it, and 2) my (or someone else's) life does not depend on my TV knowledge.

I have a repairman certificate. That should mean that with reasonable care and careful reading of available information, I should be able to carry out the responsibilities of a repairman. If this is not possible, then the whole repairman concept is called into question. If a repairman needs to have x hours of extra training, and x hours of experience to set an appropriate RPM then the system does not work.

Please do not take this as a personal thing Roger. I know of very few people who are as willing to help others as much as you, or who have the knowledge and experience you do. I just find it frustrating that Rotax and FD are, in some cases, so far behind in their ability to provide clear, concise manuals and instruction for common and necessary tasks for repairman.

I am not trying to shoot the messenger...I wasn't even trying to aim in his direction... sometimes I am just a lousy shot. :) Sorry if you took it that way.

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Doug, you comments are right on. Roger is wrong in saying that we should have to go to school to learn about RPM settings. You are right that Rotax should have put it in a manual and if there is doubt should have clarified it. The LSA community shoots itself in the foot when it operates this way. As an example, do any of us think for a second that FD can get away with this when it releases the C4 to the GA community? Absolutely not. The GA press would eat them alive. We can bet that FD will know this and provide top quality manuals.

Look at Rotax warranty work. Can you talk to Rotax? No. Rotax has no people or assets in the U.S. You talk to repair centers and the repair centers talk to Rotax and months later you get a response as to whether Rotax will cover a condition that is questionable on the warranty side, such as a design flaw that didn't show up during the warranty but was not a fault of engine operation.

There is no need for Roger to apologize for Rotax or to defend their policies. At the same time, he should not feel he has to put himself in a position to interpret for them, because that is a losing spot to be in. He can pass on what he learned in class and it may be right to the best of his knowledge but if there is a problem caused by operating according to that info (such as an rpm setting) and it is not in the manual, Rotax can simply disavow that unprinted information and Roger along with it.

Doug, when I took the Line Maintenance course at LEAF last year, I did not hear one single word from the instructor that was not strictly according to the Rotax manual. The Rotax instructional team seems to me to be a very small, very intimate community. You very much get the feeling that Roger has implied that there is an informal pecking order of who calls the shots on maintenance information. I'm not sure that is all good. I think it should be more open and communal. I hope you will ask all kinds of questions and report to us what your conclusions are.

 

 

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I'm not taking any of it personal. It isn't my style, but standing on the side lines and just complaining isn't my style either.

The problem is for all types of service work we have become too space age speciallized. It isn't just the wheel any longer, it's high tech systems. We always want bigger and better and with that comes more specialized knowledge that isn't just always handed to us. You have to go out, take the bull by the horns and get what you believe you need. It's the system we as people have created in one way or the other.

It's the system that's out there and we can just sit and get beat back, complain and walk away or learn to suck it up and navigate through it and not let obstacles stand in our way. For 30 years the fire department forced me to learn and go to continuing education weekly and now I'm retired nothing has changed. I don't complain I get things done, that's what the fire service taught me. Complaining waist time and it's un-productive.

 

My personality is more of an analytical, detail oriented bull in the china shop. Sometimes that's good and sometimes not. Not knowing something bugs the hell out of me so I am forced by my personality to go out and get information. It cost lots of time and sometimes a lot of money. I want to know about the fuel injected engines so I'll have to pay $3K to go get that knowledge.

 

 

I'm a victim of our system and society like all of us. I just choose not to let it hold me back.

 

The knowledge is out there and it may not be in the format you want, but it is there for the taking.

 

It boils down to how committed do you really want to be?

 

For me it's a personality trait I have never been able to shake.

 

 

Getting out of my first Rotax school and getting my repairman certificate just put me in a grade school level for Rotax and LSA aircraft knowledge. It was up to me to go out and learn everything through the middle school and high school levels. Then you have to decide if want to commit to the college level studies for the knowledge you seek.

It's all about commitment.

 

 

Jim, you don't have to go to school, but don't say the info isn't out there. How do you think everyone else got the knowledge, it wasn't from just 1-2 classes. School is just the easiest more direct and cleanest way to obtain the info and it puts you in grade school level of education and it's up to you to continue to add to that education. Search the web, call Rotax in Austria for a direct answer, call Lockwood, Leading Edge, CPS or Rotech in B.C. Canada or listen to the techs that have been doing this for 10 years. All this information is out there and it won't be voluntarily sent in the mail. You'll have to go out and spend the time to get it. You always want documentation. Do you ever listen to other people in any of your normal life endeavors or do you always want documentation from all. Sometimes it just isn't readily available. That's why you pay doctors, lawyers, fire personnel, police personnel, mechanics, teachers and airline pilots, ect... to do these things for you and or give you advise and they all went to school. They did all the leg work for you.

You just don't trust them.

Does it make them any more right if it is printed on a piece of paper verses verbal?

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Jim,

 

Now that I thought about it a few minutes you have the perfect profession to prove my point. Farming and it's one of the most important professions of today and it is a far cry from what it was 100 years ago with its machinery and knowledge base.

 

I'll be the first in line to state I know absolutely nothing about farming. You are a 1000% ahead of me in knowledge base. Did you go to school to learn all you know? Did you learn it all in the first 1-2 years? Did you get documentation for every thing you know? Did you learn any more through the many years you have put in? Did you have to go out and learn how to do certain other things over those years? Did you learn some tips and tricks that aren't in any readily available documentation to make life a little easier? Do you agree with all the government documentation that was given to you? Do you have personal ways that you like to do your farming compared to the next guy? Have you ever talked to the agriculture guys and listened and taken their advise without documentation?

If I ever need to learn more about farming I could go to years of school or I could pick up the phone and just ask you a question since your the resident expert to me and I'll be happy to believe every thing you tell me because I believe you would try your best to steer me in the right direction and wouldn't purposefully steer me wrong.

 

No different than our other conversation, just a different profession.

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I'm not a mechanic just an owner and pilot. When I got my CTSW in 2006 I read the ROAN document that asserted that the 912ULS was designed to run its entire life at 5,500 RPM.

 

I have flown for the last 3+ decades from Mammoth Lakes where normally aspirated engines need WOT to even approach 75% power so WOT has always been the norm for me. If this was not true and I had been flying 5,500 all the time to comply with a document that has no author and is not in agreement with Rotax docs I would now feel mislead.

 

Beyond that we cannot even find the basis for the ROAN assertion so it is hard to make a decision about its value.

 

Lastly I don't think this assertion has resurfaced in print in recent years.

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So, if I am reading this correctly, the Repairman certificate is not what it appears. It does not allow you, at the point of receiving the certificate, to competently do annual inspections and approved work on LSA. That is only possible with more Rotax and LS training. If that is the case, they need to up the hours on the certificate, or go back to A&Ps who generally know less than a Repairman about these planes - and often have a distain for Rotax (in my experience). I don't think this is what the committee had in mind when they fought for the 120 hr. certificate. I took the class to work on my own plane, not start a business. I believe that is, in part, what what the committee had in mind. If I had a CTLSi that certificate would mean nothing when it came to the Rotax engine since I don't believe I would have been invited to Nassau.

 

Roger, I agree completely about your philosophy that there is a constant need to learn, to understand, and to refer to experts. (Not only when it comes to airplanes.) I guess it is working and despite some of my frustrations with the system, I feel that with input from you and others I am able to competently, and safely maintain my aircraft, and that is the bottom line for me.

 

I hope you understand. I am at times frustrated with the system, and with Rotax's continued attempts to require only their training. (Even though the FAA has said that it does not have to be Rotax training.) The new 912i is starting out in the same place as the ULS (Rotax training required) if Repairmen are taught only by invitation and in Nassau. One can only hope that eventually that will change.

 

I'll leave it there, and get off my soapbox.

--- Wait a minute, how do I get down...Alright, who took my ladder! Dang, and that's one I use for wing removal! Help! (Hmm...don't think anyone is listening, guess I'm stuck here for a while.) :)

 

Have a great day Roger!

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I don't see this as any different than the norm. Would I take my Audi for service to a fresh grad of Audi training or to someone more experienced? Why -- because the experienced mechanic may have learned a thing or two along the way.

 

Rotax specifies idle rpm to be '1400 rpm approximately'. What does approximately mean? I'd hope that training clarifies what different settings may do. The manufacturer may also add their expertise by way of guidance or defer to Rotax. In the case of the Sting, they specify 1800 rpm. I go with 1800 because the engine feels smoother than 1400. Neither is wrong but there is opinion that one may reduce maintenance in the long run.

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Everything I have come across suggests 1800 for the 912. That is what I set mine to when I last balanced the carbs. Yes it would be nice if you could go lower so the taxi didn't have to use brakes, but you can tell the difference in the gearbox chatter. I would much prefer changing brakes a bit earlier to replacing or refurbishing the gear reduction drive.

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'gotta agree... 1400 is WAY too low (if it will even run there)... I could feel the hurt on my engine/gearbox when mine ran at 1600.

tim

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Hi Doug,

 

If you take the Repairman course and get the airplane rating and have some type of engine training the FAA says you can work on SLSA with a Rotax. Rainbow's course includes the Rotax Service module, but it's fairly anemic, but you are good to go as far as working on your own plane. The FAA came out a number of years ago and stated that Rotax could not demand or make it policy that you have to have their specific schooling to work on an engine. This came about because 14 A&P's were violated by the FAA for working on a Rotax with no Rotax schooling. An A&P from this forum challenged that ruling and the FAA legal came down and said that to work on an engine you must have some training on that engine which can come from anyone, you must have all the manuals and you must have the proper tools to work on that engine. There is no mention that it must come from the factory.

 

If you do go to a Rotax school the first thing they cover is the manuals and how and where to find things. One of the first things to know is the manual is written for the 912UL, 912ULS and the 914. It is up to you to look at which numbers go to which engine. Sometime things like the 1400 rpm idle was meant for the 912UL (still too low for the 9.0:1 compression and excessively too low for the 912ULS at 10.8:1), but it isn't clear which engine it goes to. I agree many things should be better separated and or explained, but many things get lost between here and Austria with translation.

 

This journey for me has taken many years and many thousands of training and research hours including many classes and schools and all I wanted was to work on my own plane.

 

Now I feel like I'm ready. :)

 

 

p.s.

Got to help a few others in my journey. Makes me feel good to give back as other have helped me during my journey. Life's good when you look at the glass as half full and work to fill it more.

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Quick note...

 

I think it was mentioned before that it's hard to find where ROTAX specifically says the 912 can run continuously at 5,500 rpm and still exoect to make it to 2,000 hours.

 

I think it's clearly stated when they rate the engine at 5,500 max continuous power. If running at that rpm shortened engine life, it would not be specified as "continuous", would it?

 

It was the same in the Cirrus world, except 2,700 rpm was the number for the IO550N. It will run all day, every day, at that rpm and still should run to overhaul. If it couldn't, again, it would not be specified as an acceptable "continuous" rating.

 

It may be an open question whether an engine run at lower rpm will last longer or wear less than one run at a higher continuous rpm. But I don't think there's anything in the Cirrus or TCM manuals that would indicate such, and sometimes "common sense" can lead us astray.

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Thanks Roger for the response. Eddie, just going by automotive understandings, less RPM ( as long as there is no foulingand the plane is safe to fly) should make the engine last longer, shouldn't it? If I drive my car near red line all the time I would not expect it to last as long as if I let it drop down to the speeds it would normally run at.

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Doug,

 

Long ago Roger and I used to argue about this, at the time he said more RPM = more wear.

 

I say more work = more wear, 5,000RPM at a flat setting could be realizing less wear than 4,000RPM at a coarse setting.

 

The throttle position might be a better indicator of wear than RPM.

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That's, I think, where the "common sense" gets us on this issue... just letting the Rotax "lope along" isn't the same as letting your car engine "lope along". Maybe this article will help... it explains why the very best car engine in the World, would make a very poor aircraft engine.

http://www.flyingmag...irplane-engines and http://www.sdsefi.com/air51.htm

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Tim, informative, but the second article refutes a lot of what the first one says. Also, it is difficult to compare auto engines, Continental/Lycoming and Rotax. I suppose that was your point. I don't know however if a Rotax can be compared to an auto engine or not, but there is a vast difference between a Rotax and an O-200 Continental. it is similar to the difference between a car engine and an old two cylinder tractor engine, isn't it?

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Better to compare the Rotax to a motorcycle engine, but the article from Tim would still be relevant. Once you look at the Rotax like a motorcycle engine then things become more clear and not pertinent to other air cooled aircraft engines.

Anyone that compares or tries to relate the Rotax to a Cont. or Lycoming isn't going to work on my plane. There is nothing similar to make it relevant to make it applicable and the person then just demonstrates he already doesn't understand or hasn't done his homework.

 

Most things about running the Rotax has ranges, i.e. temps, pressures and of course the rpm's. Then you have to be able to interpolate or interpret the difference between an in flight adjustable prop and a ground adjustable prop and apply those ranges.

Remember the manuals are written for three engines and it's up to you to use the correct numbers.

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Doug,

 

Long ago Roger and I used to argue about this, at the time he said more RPM = more wear.

 

I say more work = more wear, 5,000RPM at a flat setting could be realizing less wear than 4,000RPM at a coarse setting.

 

The throttle position might be a better indicator of wear than RPM.

 

In Rotax 912 engines, high RPM is higher wear on the engine, low RPM is more wear on the gearbox due to vibration. This information comes from Lockwood.

 

Also, high RPM greatly accelerates wear on bearings. Loading at low RPM increase wear on rings. Best is to run low and easy.

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Another excellent video. I would be a little cautious if the engine was hot. Maybe it would be unlikely to start a fire but I don't want to be a test case.

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Hi John,

 

Heat won't affect this operation. By the time you pull the carb off the exhaust is too cool. Most of the time the carb bowl doesn't pop off like the one in the video. it usually just drops down.

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Hi Anticept,

 

The 912 was designed to not only run over 5000 rpm, but actually actually designed to run at 5500 rpm for the life of the engine. (2000 hrs.) Running in the mid 4K rpm usually will cause more EGT heat and internal vibration that the pilot will not feel. I do in part agree with more rpm and more wear, but only up to a point.

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