Avoid shock cooling on decent

[Tommy]

 Hi everyone!

 

What power setting (MAP/RPM/Mixture) do you guys use for a M20J on long decent (500 to 1000fpm) to keep CHT high as to avoid shock cooling?

 

I tried 23' / 2400 and sometimes my TAS can go above 190knots (!)

 

Thanks

[Tommy]

Sorry double post!

[donkaye]

 Hi everyone!

 

What power setting (MAP/RPM/Mixture) do you guys use for a M20J on long decent (500 to 1000fpm) to keep CHT high as to avoid shock cooling?

 

I tried 23' / 2400 and sometimes my TAS can go above 190knots (!)

 

Thanks

 

See my answer here:

 

http://mooneyspace.com/topic/13596-avoid-shock-cooling-on-decent/#entry176040

[EDNR-Cruiser]

I don't have a fixed power setting... - depends on my cruise altitude, ETE and traffic situation at the airport. What I do as a general rule of thumb is that I reduce MP no more than 2' every 2 minutes to avoid shock cooling, not sure if that is an existing problem at all with our Lyco IO-360 but just making sure that it doesn't get a cold...  

I start every descent by reducing MP by 2" before I even trim down a little and sometimes I bring her in at 21" and sometimes at 16"MP... - no fixed rule. All I try to avoid is a CHT cooling of more than 50°F per every 2 minutes and holding patterns... 

[chrisk]

First, I have a "K".  Which means I am starting my decent at 20,000 ft and 100 miles out.  I typically fly conservatively, at about 55% power.  I just push the nose over and don't touch the throttle (Well, I reduce it as I go down, to keep the mp at the same value).  I don't worry about shock cooling.  I just don't let the engine get too cold.  Typically I don't get into the yellow arc, but if I really need to loose altitude the speed breaks come out and the throttle comes back.    I am also careful about adding power to a cold engine.

 

Anyway, I suspect you could come back to 20 inches with out the prop driving the engine.  And it is not your true airspeed that matters, its what shows on the ASI.   Were are you on the yellow arc?

[stevesm20b]

The yellow arc on the B models is 150mph. I'm in the yellow arc cruising. Any power setting above 15in and I'm going to be well into the yellow arc in a descent. I just stay under 186mph. Vne is 186mph or about 162kts indicated in the B model.