Roger Lee Posted September 30, 2014 Report Share Posted September 30, 2014 The vapor lock issue is why we should have good under the cowl air flow, fuel lines in fire sleeve (not its main purpose, but some insulation) and the proper sized fuel re-circulation line orifice. Many people have never had fuel pressure gauges so they never know what the fuel pressure is and have been doing just fine for almost 24 years. Now we have lots of numbers in front of us and we worry about what all the numbers really mean. Sometimes when I go for breakfast on a warm day and come back out to the plane after 45 minutes or so I see a little lower fuel pressure which may not be what the carbs sees. After a few minutes of running at 2100-2300 rpm out to the runway the cooler fuel should be restored and the pressure with it. I have never had a lowered pressure just stay there and it has never been low enough to cause a true issue. There is just too much fuel flowing. Fuel to each carb and fuel through the re-circulation line should take care of warmer fuel that may cause some vapor. The sooner you can taxi and not just sit there will also help under the cowl temps. p.s. Mogas is usually more an issue for people who fail to set the system up properly. (poor air flow, no re-circulation line, no fire sleeve. poor fuel line routing, ect..) Link to comment Share on other sites More sharing options...
fevlok@mmhs.co.za Posted October 1, 2014 Author Report Share Posted October 1, 2014 Roger My centement also Al that you mention sound very familiar because we are building the sportsman 2+2 180 lycoming to run on Mogas and i did some reading Link to comment Share on other sites More sharing options...
fevlok@mmhs.co.za Posted October 1, 2014 Author Report Share Posted October 1, 2014 ""My centement also"" I must come clean about part of my sources : Pieter Geldenhuis that is building the Sportsman is a personal friend ,he is a qualified aironotical engeneer ,and his knowledge is astounding , I love to read up and as yet have to find a thing he does't know on the Mogas isue , but in a very humble way ( He grow up infront of me and I operated his foot after his first microlight accident as a kid ,(He was a pasenger) He has his own own busness ,building and repairing aircrafts ,incredable also how he grow from knowlide to practical know how . Link to comment Share on other sites More sharing options...
mooneyman Posted October 3, 2014 Report Share Posted October 3, 2014 Just had a similar experience Repair Center Changed Mags Went through Carbs performed fuel flow test. Problem was found to be a cracked case. Get the heads as hot as you can shut the engine off pull the prop through the compression stroke. If you feel excessive resistance pulling the prop you may have a craved case. Mine cracked in between the two cylinders on the right side. There isa Rotax SB for this issue. My engine had 510 HRS Rotax no help out of warranty. This is a manufacturer defect. Link to comment Share on other sites More sharing options...
Roger Lee Posted October 3, 2014 Report Share Posted October 3, 2014 You still need to submit a CSIR to Rotax. They do help many out of warranty. I have seen people 3-4 years and or with 800-1000 hrs. out of warranty get help. Rotax many times will pro-rate your hours. They will want a copy of your entire logbook and this is where good documentation makes a huge difference. In Rotax's eyes the logbook is everything and is the only thing they can base a solid judgment on as to how you have maintained your engine. I have seen this and talked to Rotax about this and it is why I preach to everyone to stop with those 2-3 line annuals and maint. log entries. Is this engine a mid 2006 or earlier engine? What was the WOT rpm at cruise altitude? Over pitched props (5300 rpm or less WOT in level flight) is what causes cracked cases on top of the engine. Case fretting which is another issue in earlier engines makes the prop very hard to almost impossible to turn over by hand after shut down. There is an SB spec on this. This issue will eventually cause so much wear that the engine to stop operating. You need to file the CSIR through your regional distributor and they are supposed to push it through channels. If you just walk away or listen to someone tell you they won't help then your right no help is coming. Don't even let the distributor deter you as they don't make the final decision. The worst that can happen is they will say no. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted October 3, 2014 Report Share Posted October 3, 2014 I now have excessive resistance when pulling the prop through after it is hot. I don't experience any power loss though. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 3, 2014 Report Share Posted October 3, 2014 I now have excessive resistance when pulling the prop through after it is hot. I don't experience any power loss though. What is considered "excessive"? Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted October 3, 2014 Report Share Posted October 3, 2014 What is considered "excessive"? I don't know, many owners say they burp after a flight because it is easier. Prior to a flight mine has resistance from compression, after a flight there is additional friction and resistance. Link to comment Share on other sites More sharing options...
fevlok@mmhs.co.za Posted October 3, 2014 Author Report Share Posted October 3, 2014 Some feed back Peter came armed with 2 spair carbs fuel pump and plugs , Taking of the Lt carb the seal between the manufold and carb was damage (leaking air in) He exchance the seal put the carb back and THE PROBLEM WAS SOLVE we test her and fly for about an hour (35degrees celsuis in the shade +- about 9000' presure alt ? ) no problem at all Thanks you all Kiewiet Link to comment Share on other sites More sharing options...
Roger Lee Posted October 3, 2014 Report Share Posted October 3, 2014 The engine is usually slightly harder to turn over after flight verses cold prop rotation. Another issue: You may be talking about crankcase fretting. While running the case swells. After shut down it is hard to rotate the prop by hand. After it is cooled completely down it usually becomes easier to turn. There is an SB out for this and is supposed to be checked at inspection time. There is an allowable poundage value set for this. You run the engine and get it hot. Then shut down and put a scale on the prop and pull it through. I believe the acceptable test value is 110 ft/lbs. This condition usually doesn't cause any power loss, but someday may cause so much wear it will take an overhaul to repair it. Link to comment Share on other sites More sharing options...
FastEddieB Posted October 3, 2014 Report Share Posted October 3, 2014 I don't know, many owners say they burp after a flight because it is easier. Prior to a flight mine has resistance from compression, after a flight there is additional friction and resistance. That sounds worrisome, especially if it has not always been like that. I burp post-flight and have no detectable increase in resistance. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted October 3, 2014 Report Share Posted October 3, 2014 Since you live close to Jeremy give him a call and he can help you. I showed it to Jeremy last year, he said hmmmmm, that's not good. He was on his way home by then and we haven't pursued it. Its annual time again so we will now. Link to comment Share on other sites More sharing options...
Roger Lee Posted October 3, 2014 Report Share Posted October 3, 2014 Hi Kiewiet, Are you referring to the rubber flange between the carb and metal intake manifold? If this was the leak it would cause that side to run lean and create a power loss and a rough engine due to out of sync carbs. These should be changed at the Rotax 5 year rubber change and checked at each inspection. Sometimes looking for a crack here is hard on the ground so an easy way to check is to run the engine, push hard on the carb and rubber flange to make it slightly flex and listen for an rpm change or spray a little starting fluid on the rubber flange while it is flexed and I guarantee if there is a crack you will get an rpm change. Link to comment Share on other sites More sharing options...
Anticept Posted October 3, 2014 Report Share Posted October 3, 2014 I showed it to Jeremy last year, he said hmmmmm, that's not good. He was on his way home by then and we haven't pursued it. Its annual time again so we will now. Have you done a cold compression check? You might have a freaky engine like ours, which doesn't like to show good compression until warmed up. Which is still so odd compared to lyc and conts Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted October 3, 2014 Report Share Posted October 3, 2014 Cold vs warm compression is interesting, we will have to test. Annual in 2 weeks. Link to comment Share on other sites More sharing options...
Roger Lee Posted October 3, 2014 Report Share Posted October 3, 2014 Hi Guys, Static pressure may feel more after a run and you may have a a tiny bit of case or parts swelling after it gets hot. This will make it seem like it is a different compression, but the differential shouldn't change with us. I like everyone else was always told to check compression on a warm engine although that comes from the old loose tolerance Cont. & Lycoming teachings. I tested 10 Rotax engines at annual by checking a cold compression verses a warm compression test. Remember this is a very tight tolerance water cooled engine. It doesn't have as much expansion and contraction as an air cooled engine. The difference was nothing for all ten engines. Compression's were all the same. Most Rotax 912's differential compression test results are 83-85 with a test pressure of 87 psi and 77-78 with a test pressure of 80 psi. Even though the book says to worry with a 25% loss you should really worry if it is 8 psi or more. Sometimes you can get a very odd low reading. Usually just rotating the prop a few times and re-checking it will rectify the low reading. 100LL users are more likely to see a low reading if lead particles get trapped under a valve seat. Link to comment Share on other sites More sharing options...
Anticept Posted October 3, 2014 Report Share Posted October 3, 2014 The difference was nothing for all ten engines. Compression's were all the same. Most Rotax 912's differential compression test results are 83-85 with a test pressure of 87 psi and 77-78 with a test pressure of 80 psi. Even though the book says to worry with a 25% loss you should really worry if it is 8 psi or more. Sometimes you can get a very odd low reading. Usually just rotating the prop a few times and re-checking it will rectify the low reading. 100LL users are more likely to see a low reading if lead particles get trapped under a valve seat. We know roger, but both Tom Baker and I mentioned in another thread that we had an engine that didn't like to hold compression until warmed up. Mine was below 35 psi until I took her out and warmed up, and compression spiked all the way to 80/80 psi. That's why I was asking CharlieTango to give it a try. Maybe he doesn't hold as much compression while cold, and that's where the little extra stiffness comes from. I know my engine feels kinda limpy, but after a flight there's definitely a difference. Since we don't keep pushing air until pressure tops out (we stop at 80 or 86, but it might go way beyond that), it might just be that CharlieTango has an engine that holds good pressure even while cold, but holds phenomenal pressure while warm. I was just suggesting having a look to see if it even registers with normal testing. Link to comment Share on other sites More sharing options...
Tom Baker Posted October 3, 2014 Report Share Posted October 3, 2014 We know roger, but both Tom Baker and I mentioned in another thread that we had an engine that didn't like to hold compression until warmed up. Mine was below 35 psi until I took her out and warmed up, and compression spiked all the way to 80/80 psi. That's why I was asking CharlieTango to give it a try. Maybe he doesn't hold as much compression while cold, and that's where the little extra stiffness comes from. I know my engine feels kinda limpy, but after a flight there's definitely a difference. Since we don't keep pushing air until pressure tops out (we stop at 80 or 86, but it might go way beyond that), it might just be that CharlieTango has an engine that holds good pressure even while cold, but holds phenomenal pressure while warm. I was just suggesting having a look to see if it even registers with normal testing. Mine was just a one time thing on one cylinder. Link to comment Share on other sites More sharing options...
Anticept Posted October 3, 2014 Report Share Posted October 3, 2014 Yeah it was just one cylinder with me as well, but I was making a point Link to comment Share on other sites More sharing options...
fevlok@mmhs.co.za Posted October 4, 2014 Author Report Share Posted October 4, 2014 Roger Yes i am much wiser now thanks for the future tip here The Ct is also now due for her anual and then I have to learn to trust her again , or is the opsite better ? Long trip coming up next week Kiewiet Link to comment Share on other sites More sharing options...
Roger Lee Posted October 4, 2014 Report Share Posted October 4, 2014 During compression checks I have had on 1-2 occasions a low cylinder. I just hand rotate the prop 4-5 times and re-check it and it has always been back to normal. The manuals well tell you too if you have a low cylinder run the engine and then re-check it. Link to comment Share on other sites More sharing options...
Anticept Posted October 4, 2014 Report Share Posted October 4, 2014 Nothing i did short of warming up worked. It was so weak i could pull the prop through with little effort while i had the air on for that cylinder. Link to comment Share on other sites More sharing options...
swiss_cheese Posted October 5, 2014 Report Share Posted October 5, 2014 There was a similar incident in Switzerland in July 2013: http://www.sust.admin.ch/pdfs/AV-berichte/HB-WYS.pdf "Après le décollage le moteur a subi une perte de puissance. Le pilote a effectué un atterrissage d’urgence dans un champs." Translated into: "After takeoff the engine had a power loss. The pilot made an emergency landing in a field". Link to comment Share on other sites More sharing options...
FastEddieB Posted October 5, 2014 Report Share Posted October 5, 2014 I cannot recall the aircraft type right now* (basic homebuilt ROTAX-powered fabric taildragger) but the fellow in the hangar next to me at 57GA suffered an engine out after takeoff and had to land in a field, causing substantial damage to the plane but no significant injury that I recall. I don't think they ever definitively nailed down the cause. On reflection, pretty sure it was a Zenith 701. Link to comment Share on other sites More sharing options...
IrishAl Posted October 5, 2014 Report Share Posted October 5, 2014 This incident - a 300ft power out during climbout - is notable for the crashworthiness of the CT. Departure took the pilot over a densely populated city (Manchester) and he crashed in a built-up area between a row of houses. The plane was absolutely wrecked, but the two guys walked away 'without a scratch' according to a fire fighter. Unbelievable, when you look at the accident pics. (I hope it's not out of order to post pics like this on the forum - ?) The incident is also notable because no cause was found. Maybe the expertise of the forum could venture a 'best guess' as to the cause. The report can be accessed here: http://www.aaib.gov.uk/cms_resources.cfm?file=/Flight%20Design%20CTSW,%20G-CERA%2006-10.pdf Newspaper report here: http://www.manchestereveningnews.co.uk/news/greater-manchester-news/plane-crashes-into-garden-923094 Link to comment Share on other sites More sharing options...
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