zkvii
Well Known Member
Hi,
Things are beginning to settle down with the 7A and I'm now trying to get the most bang for $$ on fuel. How do I find the "best/most efficent" RPM speed?
For example - this weekend I had an hour X-Country at 10K which allowed a bit of data collection, but I'm no further forward with my understanding.
I have a 7496 Blended airofoil Hartzell prop - is there a single 'best' rpm for it - or does it depend on DA and speed for the optimum speed? If so how do I find that and or work it out.
Second linked question - I was able to maintain 21.2" MAP at 11500' DA @ 50F which gives me about 75% at 2650 rpm and 65% at 2350.
If I want to get a good fuel burn 63% seems about right with just under 28 lph and 161 TAS @11.5K DA, but I have to pull the MAP back to 20.8" with 2350. (BSFC of about 0.39 )
Down lower obviously this is magnified even more - so am I better pulling RPM back to 2000 or just the MAP back further? Somehow restricting air into the engine goes against what feels like the best option.
I've got all the raw data, but it is difficult to graph / visualise when I have 3 input variables - MAP, RPM, Fuel F -> IAS.
Thanks for any pointers,
Carl
Things are beginning to settle down with the 7A and I'm now trying to get the most bang for $$ on fuel. How do I find the "best/most efficent" RPM speed?
For example - this weekend I had an hour X-Country at 10K which allowed a bit of data collection, but I'm no further forward with my understanding.
I have a 7496 Blended airofoil Hartzell prop - is there a single 'best' rpm for it - or does it depend on DA and speed for the optimum speed? If so how do I find that and or work it out.
Second linked question - I was able to maintain 21.2" MAP at 11500' DA @ 50F which gives me about 75% at 2650 rpm and 65% at 2350.
If I want to get a good fuel burn 63% seems about right with just under 28 lph and 161 TAS @11.5K DA, but I have to pull the MAP back to 20.8" with 2350. (BSFC of about 0.39 )
Down lower obviously this is magnified even more - so am I better pulling RPM back to 2000 or just the MAP back further? Somehow restricting air into the engine goes against what feels like the best option.
I've got all the raw data, but it is difficult to graph / visualise when I have 3 input variables - MAP, RPM, Fuel F -> IAS.
Thanks for any pointers,
Carl