Oil temperatures in the winter

[AlanKoz]

I found out yesterday when flying around 5000 ft with the OAT reading 23 F, that Ms. Dynon was not happy, as the oil temperature dropped below 120 (cowl flap closed) and the “engine speed” complaint was issued.  After powering back and descending to 2000 ft all was good again.  I was thus wondering if folks flying the Phoenix in cold climates are taping off part of the radiator, which is what I did with the Pipistrel Sinus I had.  Any suggestions?

[mikeschumann]

That's why you have the cowl flap.  Just partially close it if the engine temp drops to low.  Even in Florida, when I am descending from altitude to land, with the engine at idle, I usually have to partially close the cowl flap to make sure my engine temp is >120 when I am on final.

[Foley]

Wide open on climb. Closed on decent. I’ve never messed with cowl flaps this much on any plane before. I don’t even mess with props or mixture as much in complex aircraft. Close them when soaring with engine off. Half closed when idle soaring. Overheating can happen quickly if you don’t pay attention. Watch Rpm’s and oil temp on cruise.

[Jim Lee]

Some early Phoenix had 75% coverage cowl flaps.  The factory was worried that with 100% coverage people would overheat their engines.  I finally convinced them that we needed 100% coverage, and all subsequent planes had this.  I can't remember when they made the change.  But Foley is right, you have to monitor the temps to avoid overheating.  Thankfully the Dynon lady does a nice job of warning you before any damage is done.

I do my best to keep the oil temp around 190f.  The engine runs cleaner when it is at a hotter temperature.   Check your cowl flap when fully open.  Sometimes the cable slips and the knob setting is at full open, but the flap has actually moved beyond open to partially closed.  It doesn't take much, only a slight angle will disturb the airflow enough to prohibit full cooling on climbs or in hot weather.  On my plane, one notch out on the knob is full open.  Until I remove the lower cowling and readjust it.

For minimum drag while soaring, open the cowl flap all the way.  Most of the air will enter the cowling and exhaust out the rear of the cowling, which is much lower drag than a flat plate diverting all of the air around the front of the cowling.  After 15 minutes of soaring, it doesn't matter if the cowl flap is open or closed in regards to the non-running engine temperature.

The Sinus (and Lambada, and many other Rotax planes) does not have a cowl flap and so aluminum tape on the radiator is warranted.  I've never had a need to do that with the Phoenix with the cowl flap.  You just have to stay a little ahead of the game.

[Barry.h]

Hi Jim,

 

Is the difference between the 75% and 100% flap coverage the size of the flap or did they change the geometry? i.e. if I have a 75% coverage can I extend the flap to get closer to 100%

[AlanKoz]

Nice…. Thanks for all the advice.  

 

I kept the cowl flap closed on take off and no problem.  Yesterday with ground temps at 35 F in the UP of Michigan and 22 F at 5000 ft, and with the cowl flap totally closed on descent, the oil temp dropped below 120 and Ms. Dynon was not happy….barking engine speed, engine speed as the rpms yellow lined.  But no big deal since I was coming in to land.  

 

My cowl flap does not provide total coverage of the opening, so maybe, as Jim wrote, its the older version.  I will take a photo to share.

[AlanKoz]

 

 

 

 

 

 

 

Is this the 75% coverage flap as there is still an opening for airflow at the top?  

 

Is t

7 hours ago, AlanKoz said:

Nice…. Thanks for all the advice.  

 

I kept the cowl flap closed on take off and no problem.  Yesterday with ground temps at 35 F in the UP of Michigan and 22 F at 5000 ft, and with the cowl flap totally closed on descent, the oil temp dropped below 120 and Ms. Dynon was not happy….barking engine speed, engine speed as the rpms yellow lined.  But no big deal since I was coming in to land.  

My cowl flap does not provide total coverage of the opening, so maybe, as Jim wrote, its the older version.  I will take a photo to share.

Is this the 75% coverage flap>

[mikeschumann]

That looks like the 75% flap.  I suspect that you could easily swap out the flap for a 100% version.  I would check with Jim Lee to make sure.  That would definitely solve your problem.

I always want to land with engine temp >120 in case you need to go around.

[AlanKoz]

Mike:

For sure its the partial cowl flap.  The X-plane model Phoenix U15 for my flight sim clearly shows full flap cowl.  Jim has confirmed this is the 75% coverage flap.  I wrote to Ed Babovec to see if I can buy one.  Indeed, the temps drop below 120 on approach to landing and this would not be good if a go-around is needed.

Thanks

Alan

[AlanKoz]

JIM LEE suggested to build my own cowl flap…. Did just that, only took a couple of hours with a wee bit of help from my A&P….  

All is now perfect with the oil temps in the snow UP of Michigan!