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So the operator manual suggest that generally the descent and approach phases of flight should be sufficient to allow for immediate shutdown after landing. It also says that in hot conditions a 2min cooling run should be considered. 

 

Does anyone have some goal figures for this cooling run? - Done at idle?, 2000RPM? 2500RPM?

What oil temp should we be looking for? 

I operate my aircraft hot and high for the majority of the year and it’s not uncommon to have oil temps in the high 70s Celsius following descent and taxi. Isn’t the purpose of a cool down to allow turbo to return to the lowest possible idle before starving it of oil?

 

Mike

  • Re: 914 Cooling prior to shutdown

    by » 5 weeks ago


    The cool down period is to allow the turbocharger to cool down to the point that residual oil in the turbocharger does not coke after shutdown, and should be done near idle.Turbocharger oil temperature is not monitored, so looking at the oil temperature gauge won't give you much information.

    Watch the turbocharger oil system video for more information. If you don't want to watch the whole thing, the cool down part starts at about 11:45.

     

    https://www.rotax-owner.com/en/videos-topmenu/rotax-minute/461-914-turbo-oil

     

    Mike


  • Re: 914 Cooling prior to shutdown

    by » 5 weeks ago


    Hi all

    About the only thing a pilot has to go on is the oil temperature.  The owner's manual say do not take off unless you have at least 50C in the oil.  As a general rule you want to cool the engine down to near that level if possible.  The turbo and the engine block have a shared oil system so watching this works fine.  The lower the RPM the less energy you put into the oil therefore it will cool faster after you land.  The best idea is to watch oil temperature after landing and if it is not cooling enough be sure that the nose (oil cooler intakes) are facing into any wind and allow some time at idle speed to let the oil temp drop.  Even in some very tight installations that will rarely take more than 5 mins at most.  The turbo engines should never use petroleum oil only for this reason, they simply do not do well at high oil temps.  Semi synthetic, like the Shell Sport plus 4 or even a fully synthetic (best if you are using fuel without lead in that case) work the best to resist carbon formation in the centre section of the turbo.  

    While I agree with what Rotax says about a decent and taxi are perhaps enough I personally like to be sure that the oil temp is as low as possible before shutdown.  

    Cheers


  • Re: 914 Cooling prior to shutdown

    by » 4 weeks ago


    Thanks… 

    I have looked through my engine data for many of my previous flights - I’ve never had engine oil temp <65 on shutdown - I think my install is quite tightly cowled (Sling 4). My typical taxi to my hangar is about 5min and it has to be done at idle because it’s essentially downhill.. Yesterday, I sat facing into the wind for about 5min in front of the hangar with the engine idling and the temp wouldn’t drop below 68. Eventually I simply shut down. OAT approx 12 Celsius at the time… 


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