A

alpinelakespilot2000

Well Known Member
How to calculate % of power for break-in while flying

My Aerosport Power break-in handout instructs staying less than 7000 ft and using 70-75% power. Mahlon's instructions say 65-75%. Regardless of which I use, what's the easiest way to calculate % of power that will give me a figure I can count on?

Will the % of power indicator on my Dynon be close enough? My Dynon has both rpm and manifold pressure, OAT, and fuel flow (though I have no idea how accurate the fuel flow is yet). I've set 2700 rpm and 160 hp in the Dynon menu, as that's what's listed on my Aerosport data plate.

If my Dynon will not be close enough, is there a simple primer for how to calculate it the old fashioned way? I've read earlier threads on % of power but didn't follow them all that well.

Thanks.
 
Last edited:
plehrke said:
Search function works great.
Click to expand...
Gee, I never knew one existed.:eek:

Since I have looked through the archives, let me rephrase the question:

Given that I'm not a good enough pilot to both fly the airplane and do complex calculations (or read very hard-to-read-fine-print charts) all at the same time, I'm hoping that either I can count on:

A. The Dynon % of power to be pretty close; or, if that's not the case,
B. That there is an easy way to make sure I'm in that 65-75% range WHILE flying. What's a good strategy for doing this?

If there's a thread that has already covered it, and I've just missed it, please point it out. Most of the threads I found contain a very complex set of calculations.
 
Last edited:
alpinelakespilot2000 said:
Gee, I never knew one existed.:eek:

Since I have looked through the archives, let me rephrase the question:

Given that I'm not a good enough pilot to both fly the airplane and do complex calculations (or read very hard-to-read-fine-print charts) all at the same time, I'm hoping that either I can count on:

A. The Dynon % of power to be pretty close; or, if that's not the case,
B. That there is an easy way to make sure I'm in that 65-75% range WHILE flying. What's a good strategy for doing this?

If there's a thread that has already covered it, and I've just missed it, please point it out. Most of the threads I found contain a very complex set of calculations.
Click to expand...

If you keep rpm/100 + map equal to 47, this will guarantee power between 70 and 75% at all altitudes up 8000 feet. Temperature has an effect, about -1% per 10 degrees F below standard temperature.

Formula is complex, I actually have it programmed into a programmable calculator for in flight usage.... but I never use it.

Running lean, it's determined soley by fuel flow and BSFC of your engine.
 
Steve,
There is a reprint in the '21 Years of RVator'
by Van on setting power by simply adding the
MP and RPM together. It's under 'Performance',
Page-292.

Email me at:
[email protected]
if you need a hard copy.

Tom
 
Thanks Vern and Tom. Really helpful. It sounds like you're both talking about a very similar rule of thumb. I have 23 Years of RVator so I'll check there.
 
Unless I am mistaken, and I could be, the Dynon seeks cruise rpm, not max. So it uses this to calculate TACH TIME, you select the std Lycoming compression ratio or whatever and it loads data tables.

Use the % power and that works fine.

Now..... Time for a quick tech lesson, and if in doubt contact me directly.

Horsepower on the RICH side of peak EGT is determined by MASS AIRFLOW, and if you chose to run in on the LEAN side of peak EGT, which you should if you can, then HP is determined by FUEL FLOW only.

The Dynon is pretty darned accurate in my experience.

If you can't get your head around this, and I do not blame you, none of us learned this in flying school, then contact me. Happy to help.

Just be aware most people only know Old Wives Tales, that is all they know, so They Know. Understanding the Science is another matter.

Cheers,

David Brown.
 
You must log in or register to reply here.