Percent HP charts

[tomn]

Does anyone have performance /  %HP charts for an IO-360 A3B6 that they are confident is correct.  After reading the Red Box thread last night I began to wonder if the data I have is actually correct.  My E had the A3B6 installed and I have not found updated performance charts specifically for it although I have not looked through older paperwork.  

 

Thanks, Tom

[Bob - S50]

Our '78 J has an IO360 A3B6D, and according to the MAPA safety foundation booklet about flying 'by the numbers' we use the target number.  For our J and engine if we add the MP to RPM/100:

 

50 = 75%

47 = 65%

44 = 55%

 

For example 2400 RPM/100 = 24 + 23" MP = 47 = 65%

 

For an E they list the numbers as:

48 = 75%

45 = 65%

42 = 55%

 

Comparing that with the performance section of our POH it is right on the money.  Might be different for your E.

 

Bob

[gsxrpilot]

I had the same question.  I'm flying a C with the O360.  Would the numbers be the same?  I'm wondering how to calculate 65% power or 75% power.

 

Thanks,

Paul

[orionflt]

the lycoming engine manual has all the data to do the calculations, I'll see if i can find mine and post the info

[Andy95W]

First, fInd an RPM your engine likes, typically around 2400. Lowest vibration is best and will be easiest on your engine.

17" = about 55%, 9.0 gph

20" = about 65%, 9.5 gph

23" = about 75%, 10.5 gph

Works for me, and besides I can't read the gauges any more accurately than that anyway.

Fuel burn numbers are rough. Over about 1000 hours of flying M20Cs, I have burned 10 gph +/- 2%. Honest. Tach time X 10 = fuel burn at the gas pump. I don't even need a fuel flow gauge, I just have to write down tach time at fill up.

[Bob - S50]

I had the same question.  I'm flying a C with the O360.  Would the numbers be the same?  I'm wondering how to calculate 65% power or 75% power.

 

Thanks,

Paul

Paul,

 

According to the MAPA Safety Foundation manual, for a C the numbers are:

 

75% = 49

65% = 46

55% = 43

 

Was that what you wanted?

 

Bob

[Andy95W]

Paul,

 

According to the MAPA Safety Foundation manual, for a C the numbers are:

 

75% = 49

65% = 46

55% = 43

 

Was that what you wanted?

 

Bob

Bob,

I tried to make the numbers work from the M20C POH, but couldn't get a clean result.

i.e., 2400 rpm 22" mp = 46. POH says 74% power.

2300 rpm 21" mp = 44. POH says 66% power.

So I just went back to my old standby of

17" = about 55%, 9.0 gph

20" = about 65%, 9.5 gph

23" = about 75%, 10.5 gph

Oh, and I always use flaps for takeoffs.

[gsxrpilot]

Paul,

 

According to the MAPA Safety Foundation manual, for a C the numbers are:

 

75% = 49

65% = 46

55% = 43

 

Was that what you wanted?

 

Bob

 

Thanks Bob, that's exactly what I needed.

 

Cheers,

Paul

[Bob - S50]

Bob,

I tried to make the numbers work from the M20C POH, but couldn't get a clean result.

i.e., 2400 rpm 22" mp = 46. POH says 74% power.

2300 rpm 21" mp = 44. POH says 66% power.

So I just went back to my old standby of

17" = about 55%, 9.0 gph

20" = about 65%, 9.5 gph

23" = about 75%, 10.5 gph

Oh, and I always use flaps for takeoffs.

Whatever works.

 

What RPM is that?  2700/20" is more power than 2400/20" is more than 2000/20".  However, if you fly LOP, then fuel flow will be a pretty good indication of power.

 

It isn't important that we set exactly 55%, 65%, or 75%.  2345/22.8" and 63.364% is just as valid for cruise.  The idea is to get us in the ballpark and then adjust it as the mission dictates.  For me, since I'll usually cruise at 7500' or above, setting WOT and 2400 RPM will keep me at about 65% or less.  If your POH shows a different number then you should definitely use that number to get you in the ballpark.

 

However, whatever we do, we should have fun!

 

Bob