Mooney 231 Slow Climbout

[natdm]

Yep, the annual shop was great. Where did you move to?

[LANCECASPER]

On 10/10/2022 at 8:48 AM, Ricky_231 said:

I've never left it for too long, but what I've seen it climbs a little faster (800 - 1000fpm? I really never left it there long enough to give you a precise, stable number) while burning 22-24gph and the engine isn't as cool. At 33" I can close the cowl flaps most days and still get a really good climb with low temps, a little less fuel burn.

By the way, after writing this post, I paid a little more attention to my climb out yesterday, and I was doing 750fpm with 33"/2600RPM, 2 pax, full tanks + bags (55oF)

Mooney proved when they developed the 231 and 252 that full power climbs were more efficient than pulling back power in the climb. However to do this the cooling has to be correct on your airplane, meaning that your fuel flow has to be set up correctly and your cowling seals have to be tight. The old material they used would get "lazy" and would lay back at the top of the cowling and let the air pass over the top rather than being forced down to cool your cylinder fins.

Make sure you reference your POH under normal procedures for climb. Very likely you don't want your cowl flaps closed during climb. On most days a turbo charged engine with cowl flaps, the cowl flaps should be open until you reach your cruising altitude. On a 231 if everything is set up correctly (cowl seals, fuel flow) you may be able to fully close your cowl flaps once you level off. However, it's more important that all of your CHTs under 400, so if it's a hot day you probably won't be able to close them all the way. (Even at all the way closed they are designed to be open slightly to allow better cruise speed). Be much more conservative than what the red line is. The last 40+ years have shown that if you keep those cylinders under 400 they make actually may TBO.

[Pinecone]

With my 252, I climb with everything fully forward and cowl flap fully open.  I also climb at about 125 KIAS.  CHTs are nice and cool in the lower 300s.

At level off, I leave the power up to accelerate.  Pull the throttle and prop back, do a Big Mixture Pull to LOP and fine tune.  Then close the cowl flap.  Most times the highests CHTs run around 360 -370.  My goal is below 380.  If one goes over 380, I crack open the cowl flap or maybe tweak the mixture a 1/10 GPH leaner.  If I open the cowl flap, after the temp goes down, I try closing it again.  Sometimes I can, sometimes not.

I need to see what cowl flap setting is about 1" open.  According to Bob Kormer, that is the best cruise setting for low drag on K or earlier models.

[hubcap]

3 hours ago, Pinecone said:

With my 252, I climb with everything fully forward and cowl flap fully open.  I also climb at about 125 KIAS.  CHTs are nice and cool in the lower 300s.

At level off, I leave the power up to accelerate.  Pull the throttle and prop back, do a Big Mixture Pull to LOP and fine tune.  Then close the cowl flap.  Most times the highests CHTs run around 360 -370.  My goal is below 380.  If one goes over 380, I crack open the cowl flap or maybe tweak the mixture a 1/10 GPH leaner.  If I open the cowl flap, after the temp goes down, I try closing it again.  Sometimes I can, sometimes not.

I need to see what cowl flap setting is about 1" open.  According to Bob Kormer, that is the best cruise setting for low drag on K or earlier models.

Although I have a 231, this is pretty much the same as what I see. I did have my cowl flaps adjusted to 1" open and that made a noticeable difference. Sometimes I can run them closed and sometimes I have to run them in "trail", it depends on the temperature and altitude. I climb with the cowl flaps fully open, and descend with the cowl flaps fully closed. If I have to run with them trailing I lose 3 or 4 kts but the CHT's stay ~340 degrees.

[kortopates]

I need to see what cowl flap setting is about 1" open.  According to Bob Kormer, that is the best cruise setting for low drag on K or earlier models.

This doesn’t really apply to the 252, Bob is referring to the 231 closed position after much testing was done by Mooney and the TCM engineer. The 252 is very different.
Mine are never entirely closed except in descent, even in cold air aloft.

In winter though, climbing at 120KTs i can close CF half way which reduces stress on the CF door and still keep CHTs cool.


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[Aerodon]

On 7/13/2023 at 6:25 AM, Pinecone said:

At level off, I leave the power up to accelerate.  Pull the throttle and prop back, do a Big Mixture Pull to LOP and fine tune.  Then close the cowl flap. 

I set my JPI 'shock cooling' to 40 degrees per minute.  It's almost impossible to trigger during approach and landing (I must manage it well), but very easy to do in the levelling off process.  Rapid increase in speed (more cooling), reduction in power (less heating).  In fact this is the point that the cylinder will 'grab' the valve stem and fail catastrophically if it's too tight.  I can confirm that the EGT and CHT drops to zero and the bits not only go through the turbo but can get pumped upstream into the intake manifold to cause damage in the other cylinders.  TSIO360FB.

Experiment with this a bit, maybe start closing the cowl flap sooner as the speed is increasing. 

Aerodon