FlyingMonkey Posted July 11, 2015 Report Share Posted July 11, 2015 My engine usually runs pretty cool. Today I went for my flight review, and everything went fine except my oil temps were running higher than I'm used to. CHTs were fine around 220°F, but oil temps were *well* into the yellow at 240°F to 245°F. I had to shallow our climb out and reduce power to about 5000rpm. Once we leveled off it eventually cooled to the low limit of the yellow arc, but it never ran as cool as I'm used to seeing, and it got hot again when climbing out after a touch and go. Now, it was very hot today, 90°F with high humidity ("heat index" of 103°). Density altitude was 3200ft from a 940ft actual field altitude. And we had a lot of fuel, my 190lb, and my 225lb instructor. So we were probably right at gross weight. These temps are higher than I'm used to, but I'm not prepared to say unusual considering conditions. Opinions? Link to comment Share on other sites More sharing options...
Anticept Posted July 11, 2015 Report Share Posted July 11, 2015 Can't speak for the SW, but for my LS, that is a little high for summer. Link to comment Share on other sites More sharing options...
Roger Lee Posted July 11, 2015 Report Share Posted July 11, 2015 Hi Andy, Full of fuel, an extra person and high OAT's could get you to 240F. Not something I would worry about until you hit 250F. Have you checked that oil hose I put springs in to keep it wide open? It's the one that comes off the top right side of the cooler and then back into the oil pump housing. Another troublesome hose for some is the oil return line off the bottom of the engine back to the tank. FD has put an "S" bend in some behind the engine and in some planes it was too tight and reduced radius too. You could add a coouple springs here or reroute the hose straight out between and under cly. 2&4 then back towards the tank. You would need to remove the straight fitting into the tank to a 90 degree. This makes this hose have a nice easy bend and can't get a reduced radius. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted July 11, 2015 Author Report Share Posted July 11, 2015 Hi Andy, Full of fuel, an extra person and high OAT's could get you to 240F. Not something I would worry about until you hit 250F. Have you checked that oil hose I put springs in to keep it wide open? It's the one that comes off the top right side of the cooler and then back into the oil pump housing. Another troublesome hose for some is the oil return line off the bottom of the engine back to the tank. FD has put an "S" bend in some behind the engine and in some planes it was too tight and reduced radius too. You could add a coouple springs here or reroute the hose straight out between and under cly. 2&4 then back towards the tank. You would need to remove the straight fitting into the tank to a 90 degree. This makes this hose have a nice easy bend and can't get a reduced radius. Thanks Roger. I plan to pull the cowl today and check the hose. I'm flying again today solo so I'll see if this is a trend. Link to comment Share on other sites More sharing options...
gbigs Posted July 11, 2015 Report Share Posted July 11, 2015 My engine usually runs pretty cool. Today I went for my flight review, and everything went fine except my oil temps were running higher than I'm used to. CHTs were fine around 220°F, but oil temps were *well* into the yellow at 240°F to 245°F. I had to shallow our climb out and reduce power to about 5000rpm. Once we leveled off it eventually cooled to the low limit of the yellow arc, but it never ran as cool as I'm used to seeing, and it got hot again when climbing out after a touch and go. Now, it was very hot today, 90°F with high humidity ("heat index" of 103°). Density altitude was 3200ft from a 940ft actual field altitude. And we had a lot of fuel, my 190lb, and my 225lb instructor. So we were probably right at gross weight. These temps are higher than I'm used to, but I'm not prepared to say unusual considering conditions. Opinions? You had extra weight you don't normally have in the plane...And it was hot outside, you are fine... Link to comment Share on other sites More sharing options...
CT4ME Posted July 11, 2015 Report Share Posted July 11, 2015 I'd say, given the circumstances, it should be considered normal. Rotax considers normal to be "less than 250". 240 is a good spot to gain your attention, and maybe start thinking about lessening the climb rate or stair-stepping the climb, but nothing else. Out here in AZ we can see 240 on climb out much of the year. Of course, if this behavior is new or different than previously experienced... Link to comment Share on other sites More sharing options...
FastEddieB Posted July 11, 2015 Report Share Posted July 11, 2015 On the one hand, I guess the engine in a heavily loaded plane has to work a little harder. On the other hand, I have never noticed higher temps at higher weights. In the climb, one would still use roughly rather same climb speed at climb power, so cooling should not be greatly affected - you just have a lower climb rate. And in cruise, the small difference in cruise speed should not greatly affect cooling either. Or maybe I'm just not that attuned to the small differences involved. In any case, I would not be too quick to write off an overheating engine as being due to being a little heavy. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted July 11, 2015 Report Share Posted July 11, 2015 If you climb at a higher power setting due to the extra weight then higher temps would be expected. If your radiator's angle is optimized for a steeper climb and the extra weight requires a reduced pitch attitude then the lower pitch at high power could be a factor. I don't step climb or throttle back if I am in the yellow. I have learned to get to altitude where OAT is less and 75F as quickly as possible. If you are seeing higher temps then you are used to compare the OAT. Link to comment Share on other sites More sharing options...
FastEddieB Posted July 11, 2015 Report Share Posted July 11, 2015 If you climb at a higher power setting due to the extra weight then higher temps would be expected. Sure, but don't most of us little guys climb at full power regardless? Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted July 11, 2015 Report Share Posted July 11, 2015 Sure, but don't most of us little guys climb at full power regardless? Does a CT not use full power for climb? If I'm climbing out of Las Vegas or So Cal and the ambient temps are high (could be over 100F) and I need to climb to 10,000' to clear terrain and my oil temp goes 20 260F+ before my climb is 1/2 way I will be forced to climb at a lower throttle setting. This may be counter productive, I have learned over time. You can step climb, climb at a lower power setting or climb at 264F. It can be hard not to reduce power when you have been 1 degree below redline for more than ten minutes. Different pilots will use different techniques. If you are in excess of 5,500 RPM then a power reduction is required before 5 minutes. Link to comment Share on other sites More sharing options...
gbigs Posted July 11, 2015 Report Share Posted July 11, 2015 If you climb at a higher power setting due to the extra weight then higher temps would be expected. If your radiator's angle is optimized for a steeper climb and the extra weight requires a reduced pitch attitude then the lower pitch at high power could be a factor. I don't step climb or throttle back if I am in the yellow. I have learned to get to altitude where OAT is less and 75F as quickly as possible. If you are seeing higher temps then you are used to compare the OAT. Correct. Extra weight requires the engine to work harder on a given angle of climb. He says he had to lower the nose to lower the degree of climb to shave off his temp...this is what happens when you level off after a climb also, the temp drops... The 90f day in Georgia with humidity with max gross and a Vy (or Vx) climb will increase engine temps, no question. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted July 11, 2015 Author Report Share Posted July 11, 2015 It looks like I'm not going to make it to the airport today. I will fly tomorrow and report. Link to comment Share on other sites More sharing options...
FredG Posted July 11, 2015 Report Share Posted July 11, 2015 This is an empirical question. Attempting to provide answers without some actual testing seems speculative to me. When the airplane is flown again under its usual flight conditions (weight, temperature, density altitude, rate of climb, airspeed, etc) then Andy will be able to assess whether anything has changed from its previous performance. BTW, I don't think humidity has much to do with the heat absorbing capacity of air. For a discussion of this question, see https://answers.yahoo.com/question/index?qid=20100527123829AAQqwTd Fred Link to comment Share on other sites More sharing options...
FlyingMonkey Posted July 11, 2015 Author Report Share Posted July 11, 2015 Density altitude varies with dew point. Dew point an a measure of specific humidity, so humidity does have some effect. Playing around with a DA calculator, it looks like at 90°F and altimeter 30.15 (yesterday's setting), DA increases ~100ft per ten degrees increase in dew point...or 10ft per degree. Link to comment Share on other sites More sharing options...
gbigs Posted July 11, 2015 Report Share Posted July 11, 2015 This is an empirical question. Attempting to provide answers without some actual testing seems speculative to me. When the airplane is flown again under its usual flight conditions (weight, temperature, density altitude, rate of climb, airspeed, etc) then Andy will be able to assess whether anything has changed from its previous performance. BTW, I don't think humidity has much to do with the heat absorbing capacity of air. For a discussion of this question, see https://answers.yahoo.com/question/index?qid=20100527123829AAQqwTd Fred Humidity affects density altitude. Density altitude is a big factor when pushing the plane. Link to comment Share on other sites More sharing options...
FastEddieB Posted July 11, 2015 Report Share Posted July 11, 2015 Density altitude is a big factor when pushing the plane. I'm sure my crew would agree! Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted July 11, 2015 Report Share Posted July 11, 2015 What is the climb power setting for a CT per the owners manual? Are you saying that it's not unusual, on a hot day, to experience excessive oil temps at that power setting, requiring some sort of corrective action? Mine says climb RPM = 4800 4800 @ WOT is a bad idea. The only other thing my POH says about climbs is that Vx=66kts and Vy=78kts Limitations are 5,800 RPM for more than 5 min - 5,500 Continuous Reflex, 0 and 15 are all usefull flap settings for climbs. I do the vast majority of my climbing with reflex flaps. I am saying that some CTs have cooling issues and when temps on the ground are near 100F and initial climbs need to be 10,000' you can quickly redline your oil temps. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted July 11, 2015 Report Share Posted July 11, 2015 What is normal? 5,800 RPM is permissible but no-one with a ground adjustable prop goes that flat. Climb rates are good so we tend to optimize more for best speed. If you can make 5,500 in climb then you will have to throttle back to limit to 5,500 continuous in cruise. This is fine for lower altitude but above 7,500 you will sacrifice some speed and the resulting cruise power setting will be less than 75%. The book says 4800 but its not very helpful, assuming we climb at high power settings 4800 is really lugging a 912. Link to comment Share on other sites More sharing options...
Tom Baker Posted July 11, 2015 Report Share Posted July 11, 2015 When flying a airplane that has a slow stall speed and a relative high cruise speed in comparison, and you can only choose one propeller pitch. When new these airplanes were delivered with the propeller pitch set so about all they would turn when climbing was 4800. Since that point field experience has shown that less pitch is better for climb and engine health. Even with the reduced propeller pitch most don't turn 5500 while climbing, even in a cruise climb. Link to comment Share on other sites More sharing options...
FastEddieB Posted July 11, 2015 Report Share Posted July 11, 2015 Eddie, you should probably carry more fuel reserve. When I want maximum range, I want maximum range! Seriously, the rest of the story... Nice flight. Good landing. Something not right leaving the runway. Flat nose tire. Look closely and you'll make out a wheeled shop chair we called into service as a dolly. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted July 11, 2015 Report Share Posted July 11, 2015 Again, I know nothing about this, but... It sounds like you would want to pitch your prop to achieve 5500 rpm at full power, level flight, at your "normal" cruising altitude. Then to climb you simply raise the nose resulting is reduced rpm and reduced airspeed. However, since this is like going up hill in high gear, you are limited in how high you can raise the nose and not "lug" the engine. The alternative would be lower pitch prop, but you would have to reduce throttle for level flight so as not to exceed 5500 rpm continuous operation. Of course, this is no different than most fixed pitch prop airplanes. These planes really need an in-flight adjustable pitch prop. That's correct. You can block out 2 altitude ranges and in the end most will optimize for best speed somewhere in the 8,000'DA - 11,000'DA range. less than 7,500'MSL call it 8,000'DA there is another limitation. Rotax uses 5,500 RPM but pilots instinctively use 75% power as well. In a light sport where many fly close to the ground 3,000' could be the normal cruising altitude but if you pitched for 5,500 WOT at 3,000 you would end up throttling back to 5,200 for less noise and better economy. That's why the recommendations have creeped up to more than 5,500 because much of the population flies low but optimization for at least 7,500' still makes sense. many light sport pilots are limited to sport pilot privileges and this means the bulk of the cruising is limited to 10,000'MSL Exceptions might be glider towing, banner towing, high altitude ops, ...etc. Link to comment Share on other sites More sharing options...
FredG Posted July 11, 2015 Report Share Posted July 11, 2015 Once you account for DA, there is no additional need to account for (or even know) the humidity. The heat index applies to the thermal experience of humans (and other beings that cool, in part, by the evaporation of sweat) and not to the cooling of objects by moving air. In the case of cooling by moving air, only the air temperature and air speed matter. Link to comment Share on other sites More sharing options...
FastEddieB Posted July 11, 2015 Report Share Posted July 11, 2015 You are one of the best, most aware pilots I know. Thank you. Lord knows I try. Not only that, but who else can get his wife to push his airplane while he video's her pushing his airplane? Sometimes I tell Karen it's good we know who wears the pants in this household. Always good for a laugh! Link to comment Share on other sites More sharing options...
FastEddieB Posted July 11, 2015 Report Share Posted July 11, 2015 In the case of cooling by moving air, only the air temperature and air speed matter. As an aside, for human physiology only pressure altitude matters. Explained to me more than once by people who seem to know. Apparently but the time the air gets to the alveoli, temperature is irrelevant. Or something. Link to comment Share on other sites More sharing options...
FastEddieB Posted July 11, 2015 Report Share Posted July 11, 2015 It's great you caught it and didn't have a prop strike.Ummm... ...a prop strike is pretty unlikely in a Sky Arrow! Unless maybe doing an inverted ribbon cut! Link to comment Share on other sites More sharing options...
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