FlyingMonkey Posted September 12, 2013 Report Posted September 12, 2013 My CTSW has pretty minimal engine instruments, all in small analog gauges: Tach, CHT, Oil Pressure, Oil Temperature, Volts. Normally all these indicators stay in the green, but in a WOT climb on a hot day (hot here is 90-95° OAT), the oil temp starts getting high. CHT stays good, usually does not break 220°. But the oil temp will creep up into the 230-240° range. It comes down a few minutes after I level off, reduce climb angle, or throttle back, so I think this is normal. My question is what is an acceptable oil temp to maintain for a long climb, versus "too hot to let it stay there"? The yellow on my gauge starts at 230° so I usually start thinking about taking action if it stays above that level for more that a few minutes. Is that too conservative? Too aggressive? I read Roger's suggestion in another thread on this topic to ensure the rubber "skirt" is forward and not folded back under the cooler, I'll check that before next flight. Any other suggestions to make sure my bird's blood doesn't boil? Thanks!
sandpiper Posted September 12, 2013 Report Posted September 12, 2013 Some days I have to step climb or cruise climb at about 95K. Yesterday was an example, 87F on ground (175'), full power climb to 3500 msl at 95K. OAT at 3500 was 81F. At time of level off I had 245 oil temp and it would only cool to 230F at 5200 RPM. That's bottom of yellow. Finally when I reduced to a 5000 RPM cruise the oil temp came down to 220. CHT is never a problem. The temp was still climbing slowly as I leveled 3500. What would have happened if I needed 7000 msl. Guess I would have needed to pray for a more rapid OAT decrease. To me, this is a major PITA and is a design flaw. In the winter, you get to tape up the radiator if you ever want to see 190F. Even here on this part of Oregon where this is needed with OAT 40F to about 50F. So, lets see, is this a 1, 2 or three piece of tape day? OOPS! Guessed wrong, only needed 2, now it's running too damn hot. Cow flaps would cure this, maybe even the summer problem.
FlyingMonkey Posted September 13, 2013 Author Report Posted September 13, 2013 Sounds like you guys are getting the same temps I am. I'm curious to see how temps change with the change of seasons in autumn and winter.
2FlyAgain Posted September 13, 2013 Report Posted September 13, 2013 Last summer (2012), I had an oil thermostat installed in my CTSW. The work was done at a FD service center and FD approved the alteration for my aircraft. I don't think that there is a blanket LOA. My apology for not providing more specifics. But, the paperwork is with the airplane undergoing annual condition inspection. But, an oil thermostat is an alternative to consider...
2FlyAgain Posted September 13, 2013 Report Posted September 13, 2013 I should add that it doesn't prevent the higher oil temperatures during climb on hot days. But, it does eliminate some of the other oil temperature issues.
FredG Posted September 13, 2013 Report Posted September 13, 2013 I get that our planes show 240 degrees F oil temperature on climb-out on hot days. Where do we find credible information about the effectiveness of lubrication when oil temperatures reach 240 degrees?
CT4ME Posted September 13, 2013 Report Posted September 13, 2013 I've seen numerous references to oil temps being fine at 240 degrees. This Rotax spec sheet shows "normal" temps as "lower than 250", and refers to "occasionally high oil temperature" as being over 248 degrees. http://www.rotax-aircraft-engines.com/portaldata/5/dokus/d04899.pdf Tim
sandpiper Posted September 13, 2013 Report Posted September 13, 2013 Roger - at hose change I re-routed and shortened the one from the tank to the bottom of engine. The other one you mention looked OK when I replaced it. It didn't show any signs of collapse. I'll look at the orientation of the radiators. Anway, this is nothing new. It is a "from day one" problem.
FlyingMonkey Posted September 13, 2013 Author Report Posted September 13, 2013 I've seen numerous references to oil temps being fine at 240 degrees. This Rotax spec sheet shows "normal" temps as "lower than 250", and refers to "occasionally high oil temperature" as being over 248 degrees. http://www.rotax-air...okus/d04899.pdf Tim Thanks for that Tim. It looks like Rotax is unconcerned with temps below 250° and even above that for short periods, when using a synthetic or semi-synthetic oil. I'd still like to run mine cooler rather than hotter, but I won't start to sweat when I see 240° in a hard climb.
Farmer Posted September 13, 2013 Report Posted September 13, 2013 Seeing Red. Less than one hour flight at 5000 RPM, below 2500 MSL, OAT 87 F, landed at Honolulu International. One runway closed, so much taxi time, about 17 minutes, mostly holding on taxiway. At idle 1900 RPM, CHT went to 253, 251. red light on for less that one minute. Turned into wind, set to 3000 RPM, cooled within seconds. Did not kill engine before take off on return flight. Coolent check OK before the flight and after the flight from HNL back to HJR all well no loss of fluid. Never saw that before, have you? Farmer
Jim Meade Posted September 14, 2013 Report Posted September 14, 2013 FYI, When George Braly did the extensive engine heating tests, one of the aspects he tested was the advice to park into the wind on runup. His data showed conclusively that the airplane engine ran cooler when facing downwind than when upwind. His tests were on big Lycomings and TCM. Not sure how a Rotax would respond but the point is don't take the "runup into the wind" as gospel without at least thinking about it. If you get to looking for the reason you park into the wind, it is likely because some CFI told you to and because it intuitively seemed like a good idea. That doesn't mean it was ever tested. Braly tested it.
sandpiper Posted September 14, 2013 Report Posted September 14, 2013 One thing to watch for if you do a downwind run up is anything on the ramp, especially light stuff like sand, may get picked up then blown back into the prop. It happened to me on a slow downwind taxi over some sand on the ramp. Not much sand but apparently enough.
Doug G. Posted September 14, 2013 Report Posted September 14, 2013 Upwind also allows you to look for traffic. Although I suppose you could turn upwind before you cross onto the runway. It depends a bit on where you are I suppose. It is rare that I have anyone in front of me or behind me when I do my runups, I do have to occasionally wait for others landing or departing. I also have never had over temp at those times.
Jim Meade Posted September 14, 2013 Report Posted September 14, 2013 Upwind also allows you to look for traffic. Although I suppose you could turn upwind before you cross onto the runway. It depends a bit on where you are I suppose. It is rare that I have anyone in front of me or behind me when I do my runups, I do have to occasionally wait for others landing or departing. I also have never had over temp at those times. You do runups on the runway? Not a practice that is acceptable at most airports I use. If there is any issue with the runup, you could be sitting on the runway long enough for incoming traffic to be affected. One should have time and space to focus on just doing a good runup and watching the engine gauges, not worrying about blocking a runway.
Ed Cesnalis Posted October 21, 2013 Report Posted October 21, 2013 Jeremy installed a 2nd rubber baffle to cut off any air bypassing my coolers on the top. The seal is impressive but the result is no improvement in oil temps when OAT is 70degrees or above. The new fuel pump didn't help either. Climbing from 200' I hit above 250degrees at 4,000' Interesting, I leveled off at 4,000' and at 92% throttle my egt went to 1400 and when i later advanced the throttle it goes back to 1200. Rich mixture does cool but just EGT. Here's my new theory, I want to try a new radiator taping technique. In the winter I use 2 strips of 3" tape across the bottom. For summer I now want to try taping the radiator where there is no oil cooler behind so the air flow will be concentrated at the oil cooler location.
Ed Cesnalis Posted October 21, 2013 Report Posted October 21, 2013 Roger, My coolant is always cool only my oil reads hot. I got new oil hoses and cleaned the cooler and flushed it till it was like new. No joy there but I will look again for a reduced radius. I'm on my 3 set of hoses now. 70 degrees F OAT is the magic number, below that I stay cool, at 70 or above my oil gets hot in climbs or even a little in level cruise. I think this magic number points more towards lack of cooling capacity than at flow, wouldn't a restricted flow be an issue even below 70? Coolers clean, been there done that on most suggestions.
Ed Cesnalis Posted October 21, 2013 Report Posted October 21, 2013 I'm going to rule out a false reading 1st.
Ed Cesnalis Posted October 21, 2013 Report Posted October 21, 2013 oil temp is my only gauge that jumps around at all. good tip on switching with cht.
207WF Posted October 23, 2013 Report Posted October 23, 2013 Like Ed, I have tried everything on the oil temp issue with no joy, and its been an issue since my '07 was new. I even tried a couple of things not discussed here. Now I am thinking I need an auxilliary oil cooler, mounted separately under the cowl, like we used to do on old VW engines. I wonder if I could get an LOA for that? WF
sandpiper Posted October 23, 2013 Report Posted October 23, 2013 Like Ed, I have tried everything on the oil temp issue with no joy, and its been an issue since my '07 was new. I even tried a couple of things not discussed here. Now I am thinking I need an auxilliary oil cooler, mounted separately under the cowl, like we used to do on old VW engines. I wonder if I could get an LOA for that? WF Ditto!!
Ed Cesnalis Posted October 23, 2013 Report Posted October 23, 2013 Of the three here saying they have a high oil temp all the time in climb who has done this? "If the CHT's stay down that means air is moving over the radiator and coolant is flowing normally. If the oil temp is high then something is slowing the oil flow. You may be correct in some cases, but the way you state this it rules out all other possibilities. For instance cool CHT does show flow through the radiator but it doesn't show good air flow through both coolers, that may or may not be true. It doesn't speak to false readings. And it doesn't explain why I was perfectly cool in 2007 and didn't see my 1st high oil temp for 1 1/2 years.
Ed Cesnalis Posted October 23, 2013 Report Posted October 23, 2013 If you are right that means that my plane developed a reduced radius after 1 1/2 years and then replacing the hoses did not fix it and then at the 5 year change it didn't fix again. We have never removed the fire sleeves and heated it up though. IF FD's routing is a problem and it needs to be changed shouldn't FD get involved? Given how wide spread and long standing this issue is I think they should provide something.
Anticept Posted October 23, 2013 Report Posted October 23, 2013 CharlieTango, there's a mod where the radiator inlet can be enlarged with a little filing for higher air flow. Dave at FDUSA is probably the best person to ask about recommendations for hot climb outs, but how i solved the problem on hot days is just add 10 kts to Vy.
Ed Cesnalis Posted October 23, 2013 Report Posted October 23, 2013 Adjusting speed, rate of climb, pitch, flap settings ...etc all have no effect other than I can prevent temps above redline by leveling off and throttling back. The one and only fix is to get to an altitude where OAT is below 70F. Climbing fast gets me there faster. Roger, given the 'fix' in my current condition is to find air at 69F or below how does that speak to the idea of a reduced radius?
Tom Baker Posted October 23, 2013 Report Posted October 23, 2013 Roger, wouldn't a reduced radius either starve the engine for oil or create a higher oil pressure depending on where it is at?
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