IrishAl Posted April 30, 2016 Report Share Posted April 30, 2016 Eddie, No. 3 at 69/80? Didn't that merit further investigation at the time? Link to comment Share on other sites More sharing options...
FastEddieB Posted April 30, 2016 Author Report Share Posted April 30, 2016 Eddie, No. 3 at 69/80? Didn't that merit further investigation at the time? It does seem to fall into the acceptable range as published by ROTAX: "The maximum permissible pressure drop is 25 %, e.g. from 6 to 4.5 bar (87 psi to 65 psi) (D). If the pressure loss is less than 25% then the valve seats and piston rings are working properly." That minimum figure at 80 psi would be 60 psi. Not arguing that it doesn't seem lower than most - just that ROTAX still puts it in the acceptable range. Link to comment Share on other sites More sharing options...
Roger Lee Posted April 30, 2016 Report Share Posted April 30, 2016 Hi Eddie, "The maximum permissible pressure drop is 25 %, e.g. from 6 to 4.5 bar (87 psi to 65 psi) (D). If the pressure loss is less than 25% then the valve seats and piston rings are working properly."That minimum figure at 80 psi would be 60 psi." This is bad info and misleading. We all wish Rotax would revise it. Will the engine run here, yes, but not a single class does anyone subscribe to that as being okay. They will all tell you if there is even a 10 psi drop from the other cylinders it's time to find out why. That's because of the very tight tolerances of this engine. The air cooled engines aren't this way so the 25% is acceptable,but not here. Your case is different. You don't have a single drop. Yours are like that across the board so that leads me to suspect bad gauges or a leak in your test equipment. If there is a large drop in differential the good news it usually isn't the rings and is more likely the valves are coated with lead or carbon. Typically a differential compression test is only 1-2 psi difference between cylinders and usually only 2-4 psi below test pressure. This is one point not to try and stand on the Rotax manual. You absolutely don't want to have that differential drop. Link to comment Share on other sites More sharing options...
FastEddieB Posted April 30, 2016 Author Report Share Posted April 30, 2016 This is one point not to try and stand on the Rotax manual. You absolutely don't want to have that differential drop.I'm not doubting your expertise in the least, but... ...this is exactly what others have complained about - that there seems to be a privileged cabal of cognoscenti that hold the true knowledge of all things ROTAX. Kinda like, "Who you going to believe, me or the manual?*" But I'm taking all this to heart, an I'm going to post to my EAA chapter right now about getting another set of gauges to compare. I'll also take a close look at mine to see if there's any possibility of a leak in the gauge/valve/orifice setup - should be pretty straightforward with some soapy water. I'll let you know what I find. *Stipulated that manuals do get it wrong, sometimes - as shown in my recent Marc Ingegno brake thread! Link to comment Share on other sites More sharing options...
Roger Lee Posted April 30, 2016 Report Share Posted April 30, 2016 Rotax in this case isn't absolutely wrong. That is their limit as it is the rest of the aviation community. The huge but is that they believe there is an issue if you have any cylinder 10 psi down from test or that is different from the others. The knowledge is out there. This is why anyone that does their own maint. or wants this info ABSOLUTELY HAS to go to classes. This is the only place to get your info unless you want to take what people say to heart on a forum. Then you have to know if that person has been going to classes and is up on their game. The knowledge isn't hidden or secret, but you have to get involved at another level and it cost money. That's the bad part. There is only one difference between you and me. I go to Rotax classes every year, take classes from Rotax people and ask lots of questions. p.s. I finally got all my approvals and got everyone on the same page from all sources and will start teaching the Service level class in Tucson at a nice facility. The difference is this service level class compared to what is normally taught will be on steroids. We are going to get out of the classroom (some is still required), work on live engines and target going through an entire annual. Students will be turning wrenches and you will get a Rotax certificate for this. I'm in the process of setting up the dates as we speak. I should have them nailed down by Monday. These will be weekend classes instead of weekday classes. Link to comment Share on other sites More sharing options...
Tom Baker Posted April 30, 2016 Report Share Posted April 30, 2016 Eddie, check your gauges. With the cylinder fitting removed set your air pressure to 87 as you would doing the test, and read the pressure on the other gauge. If it is not 87 use the difference to come up with a correction factor. It is not uncommon for gauges to be off. They should probably be tested annually, but most are never tested. Link to comment Share on other sites More sharing options...
FastEddieB Posted April 30, 2016 Author Report Share Posted April 30, 2016 Thanks. I have a friend on the way to the hangar with another set of gauges. Seems like checking mine should be trivially easy - cap the hose going to the cylinders and see if both gauges measure the same, right? Tom - thanks! We both posted at the same time. Link to comment Share on other sites More sharing options...
Roger Lee Posted April 30, 2016 Report Share Posted April 30, 2016 Spray a little soapy solution around the fitting that screws into the spark plug hole and make sure it doesn't leak and possible spray all your fittings. Staying well informed is all about networking. Get in the system and get to know the people in the know. Networking is the cornerstone of the 21st. century. Too much info for any one person to have it all. Link to comment Share on other sites More sharing options...
Anticept Posted April 30, 2016 Report Share Posted April 30, 2016 We all feel like rotax needs to do some serious manual revisions, FastEd. Link to comment Share on other sites More sharing options...
Roger Lee Posted April 30, 2016 Report Share Posted April 30, 2016 The manuals are written for world use, 3 different engines, different setups and upper and lower limits. It's up to the end user to get the education to know the differences. That said there are a few spots for sure that can be redone, but you have to convince Rotax hierarchy in Austria. A different culture. They have to be doing something right. They supply over 80% of the world's light aircraft engines. Link to comment Share on other sites More sharing options...
FastEddieB Posted April 30, 2016 Author Report Share Posted April 30, 2016 Well, the gauges are at least part of the problem, about 2 or 3 psi worth with both gauges measuring the same pressure: Doing the checks again cold with my friend's gauges showed just a slight improvement, between 1 and 3 psi: For now, not going to worry excessively. Rather than replacing the gauges, next time probably just take the left gauge to 89 psi for testing purposes and reading the right gauge as is. Did not remember to look up Roger's readings - I'll try to remember tomorrow. BTW, spent another 4 hours or so with a friend helping and did most of the fuselage/cockpit stuff. Still need to finish that up, do the wings and landing gear and a couple of things to the engine and throw everything back together. Figure about 1/2 way there. Going pretty smoothly so far. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted May 1, 2016 Report Share Posted May 1, 2016 Am I reading right that the second test was on a cold engine? A warm up and re-test might get you the rest of the way to completely normal readings. Link to comment Share on other sites More sharing options...
Roger Lee Posted May 1, 2016 Report Share Posted May 1, 2016 Hi Andy, A cold versus warm engine on a Rotax many times doesn't have any difference and when it does it's 1 psi. I did a research project on it and tested numerous engines. Link to comment Share on other sites More sharing options...
FastEddieB Posted May 1, 2016 Author Report Share Posted May 1, 2016 Worked another 4 or 5 hours today. Tomorrow just need to reassemble the cockpit, replace the ELT batteries, and go through the drudgery and mess of the landing gear stuff. Roger, here are the compressions you got in 2012: #1 87/83, #2 87/83, #3 87/84 and #4 87/83. Link to comment Share on other sites More sharing options...
Roger Lee Posted May 1, 2016 Report Share Posted May 1, 2016 Hi Eddie, Those are all normal. My bet is you have a leak or bad gauges. Link to comment Share on other sites More sharing options...
Anticept Posted May 2, 2016 Report Share Posted May 2, 2016 Eddie: You can adjust those gauges, but you need a reliable source to calibrate against... since it would not be possible to answer if it's the left, or the right, that is inaccurate. Basically, you pull the faces off, then pull the needles off and put them back on in the right orientation, while under test pressure. Bourdon tube gauges also work the best in the mid range. I'm surprised there isn't much in the way of digital gauges yet. I know they exist, but they are extremely expensive for a reliable one. Still, it's extremely rare to have to calibrate a solid state device. Link to comment Share on other sites More sharing options...
FastEddieB Posted May 5, 2016 Author Report Share Posted May 5, 2016 Wrap up... Basically wrapped things up Tuesday and knocked off the paperwork yesterday. Too windy and cold and rainy today to test fly, but I still have to - 3i provides a post-maintenance checklist I like to follow (below, if you're curious). About 5 hours a day for 5 days. No real surprises. Caught a small drip from an inline fuel filter I had installed - it just needed to be snugged up a bit. Cost was probably less than $100 - the cost of the spark plugs, oil and filter, some distilled water to top off the coolant reservoir (along with antifreeze I already had), and about $12 for new D cells for my ELT. Anyway, rewarding to get down and dirty and get 'er done - for another year, anyway! Link to comment Share on other sites More sharing options...
Doug G. Posted May 5, 2016 Report Share Posted May 5, 2016 That's a much shorter list than I deal with on my CTLS. and what about the Rotax list? Link to comment Share on other sites More sharing options...
FastEddieB Posted May 5, 2016 Author Report Share Posted May 5, 2016 That's just for the test flight after the annual. The annual checklist is 5 pages, and includes the engine. I'd be happy to post those if anyone is interested. Link to comment Share on other sites More sharing options...
Doug G. Posted May 7, 2016 Report Share Posted May 7, 2016 That'll teach me to read what I'm looking at. The maintenance checklists (FD and Rotax) are a lot more than 5 pages for the CTLS. 11 pages for FD (not all completely full) and 5+ for the Rotax. Link to comment Share on other sites More sharing options...
FastEddieB Posted May 7, 2016 Author Report Share Posted May 7, 2016 Well, those 5 pages take me about 25 hours to go through, and seem pretty darn thorough. Thorough enough that I'll sign off that the little guy has been found to be in a condition for safe operation! Link to comment Share on other sites More sharing options...
gbigs Posted May 7, 2016 Report Share Posted May 7, 2016 Well, those 5 pages take me about 25 hours to go through, and seem pretty darn thorough. Thorough enough that I'll sign off that the little guy has been found to be in a condition for safe operation! You will discover if that is true in the air. Link to comment Share on other sites More sharing options...
FastEddieB Posted May 7, 2016 Author Report Share Posted May 7, 2016 You will discover if that is true in the air.As will every pilot on their first flight post-maintenance/inspection flight, whether they did the work or trusted someone else with it. Coincidentally, I just got back from my test flight. You'll be pleased to know everything checked out perfectly. Link to comment Share on other sites More sharing options...
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