Climb Setting question

[jaylw314]

20 minutes ago, testwest said:

But why is everyone having to work so hard to keep their engines cool in climb, when they are supposed to be able to stay in limits when flown as designed? 

For the IO-360, the CHT limit is 475^oF.  I haven't heard of anyone having problems with temps that are THAT bad.

I think people are going with the idea of keeping temps below 400^oF, on the theoretical basis that aluminum alloys lose about 50% of their strength at that temperature.  I haven't heard of or read any actual data suggesting that makes a difference, but it seems doable for most people.

[ArtVandelay]

I think people are going with the idea of keeping temps below 400^oF, on the theoretical basis that aluminum alloys lose about 50% of their strength at that temperature.

Careful...

 

At 400°F it’s closer to 20%, you need to get to 475° to lose 50%, they drop off quickly after around 425° and that’s for standard aluminum alloys, I assume they use a more heat resistant alloys.

 

Here for quick reference:

 

 

 

Tom

[jaylw314]

Yeah, I can't find the graph I saw, it was one of Mike Busch's webinars, but it was definitely different numbers.  I'll see if I can find it later

8 minutes ago, ArtVandelay said:

Careful...

 

At 400°F it’s closer to 20%, you need to get to 475° to lose 50%, they drop off quickly after around 425° and that’s for standard aluminum alloys, I assume they use a more heat resistant alloys.

 

[testwest]

So, for the OP, the suggestion is, keep the power up, keep the speed up, climb reasonably good and “git on down the road”!

As far as CHTs in the climb go, Mooney and the FAA are (were) concerned with a point design condition. Us owner operators are more concerned about balancing performance and engine durability over the long term. So even though the airplane may pass the cooling climb condition flight test, we can smartly get most of the performance in climb rate and velocity made good, while being mindful of engine durability, by the suggestions here....cruise climb, maximum power, manage cylinder temps with speed and/or cowl flaps (in that order), target EGT. Hope this helps.

[PT20J]

8 hours ago, ArtVandelay said:

8 hours ago, jaylw314 said:

I think people are going with the idea of keeping temps below 400^oF, on the theoretical basis that aluminum alloys lose about 50% of their strength at that temperature.

 

Careful...

 

At 400°F it’s closer to 20%, you need to get to 475° to lose 50%, they drop off quickly after around 425° and that’s for standard aluminum alloys, I assume they use a more heat resistant alloys.

 

Here for quick reference:

 



I believe the numbers that get bandied about the Internet for aluminum strength vs temperature originated with APS and John Deakin originally got if from a Pratt & Whitney publication titled The Aircraft Engine and its Operation.

Th

Since the ordinate axis isn't scaled, and we don't even know if it starts at zero, it is pretty meaningless other than to say not to operate P&W engines above 450-500 deg F CHT.

Lycoming has long recommended 435 F max for high performance cruise and 400 F max for economy cruise.

As a practical matter, keeping temps below 400 F seems prudent. I'm not sure that obsessing on really low CHTs buys anything on a Lycoming IO-360. 

 

[carusoam]

Design and testing are important... to get past the initial FAA requirements to build the plane...

MSers are stuck with longevity and costs after that...

Somebody gives the key temp for cylinder longevity as 380°F... (wish I remembered where that comes from, I expect APS)

Which isn’t too difficult with a well designed cowl.

In 1965 neither the cowl design (dog house) or the instrumentation (JPI or equivalent) were available to the ordinary pilot...

We are so fortunate to be in the collective position that we are in today...

Now i’m Looking forward to reading Norman’s friend’s document...

Best regards,

-a-