Ground Run Up

[201Steve]

Here’s my Sunday afternoon day dreaming thought of the day. 

People talk about ground runs as if they do not correctly mimic in flight power output. I understand this in the sense that, it’s impossible to put enough load on the engine to make it “work as hard” on the ground. However, we always talk about this in terms of temperature. “Can’t get the operating temps high enough”. Think about it in terms of the theory in which camp A would say, if you’re not flying enough, at least give it a good ground run to circulate the oil. Camp B would say, a ground run will do more harm than good in terms of not vaporizing the water/ creating more moisture inside the engine. It’s always argued against temperature. 
 

Conversely, I’ve had old timers watch me troubleshooting my engine or looking for oil leaks, whatever, that’ll rush over and say “you shouldn’t ground run your engine with the cowling off, it’ll get too hot and overheat it.”

and then finally, I’d like to introduce the availability of our handy engine monitors, which measure CHT’s per cylinder. For paragraph one I would ask, How can you say the engine is not getting hot enough as actually flying it, when I can look at the head temperatures and see 380 degrees Fahrenheit. For paragraph two I would ask, how are you risking overheating the engine when I’m looking at a CHT of 380 degrees Fahrenheit? 
 

The two scenarios conflict with one another, yet they are commonly regurgitated. That said, what am I missing here? In either scenario it would seem that you have the ability to control either scenario to your desired outcome simply by utilizing the engine monitor. What say you?

[Hank]

It seems that a long ground run without the cowling is risking overheating, because the baffling is designed to force cooling air over & through the cylinders, and without the cowling the cooling air won't go where it's supposed to go in the amount desired. Your engine monitor should let you know before you overdo it, if you're watching it.

Ditto for the ground run instead of flying. But to eliminate water, the oil needs to be at temp for more than just a few minutes--if you've got time for an extended ground run, you've got time for a couple of laps around the pattern . . . . And that is also much more fun! 

[carusoam]

With the instrumentation you can monitor lots of things...

+1 for Hank’s input...getting the oil hot enough to drive out the moisture of combustion takes as much time as going flying...

 

When doing engine break-in runs... things get a bit extra sensitive.  The cylinders typically want to heat up faster than you can get them cooled down on the ground... and without the cowling on, it gets worse....

 

So... some of what the old guys are saying makes a lot of sense...   some gets out of context...

But... when it comes to instrumentation... we are only measuring single points and not complete assemblies....  our limits are tracked using these single points, while we are flying with it’s the cowl in place...
 

And then... there are those that have a few extra AMUs and don’t mind using up cylinders while flying in flaming dragon mode...  

PP thoughts only, not a mechanic...

Best regards,

-a-

 

[chriscalandro]

There are a lot of people with more “experience” with what they’ve been doing the last 30-40 years than sense to take into account modern monitoring, engineering, and logic that has advanced in that time. 
 

just because you have done or practiced something for a long time, does not necessarily mean you’re good at it. 

[MooneyMitch]

1 hour ago, carusoam said:

 

And then... there are those that have a few extra AMUs and don’t mind using up cylinders while flying in flaming dragon mode...  

 

 

I loved taking off the 310HP Ovation in “flaming dragon mode”, and settling back to 2550 or so, soon after that. 

Ocassionally I’d 2700 RPM it in cruise too...... above 8500’ though..... that was a fun time too!!  

[skydvrboy]

3 hours ago, 201Steve said:

That said, what am I missing here?

Uhh... Flying!?  It's kind of the whole reason to own a plane in the first place.

[201Steve]

15 minutes ago, skydvrboy said:

Uhh... Flying!?  It's kind of the whole reason to own a plane in the first place.

Theories of Mx. it’s just something I’m into.