Ironflight

Ironflight

VAF Moderator / Line Boy
Mentor
I got a private email with one of the simplest questions anyone has asked me - yet I had never really thought to post - "So Paul, what kind of cruise performance/endurance do you find with different power settings?"

I am slightly embarrassed to say that while I collected tons of data during my phase 1, I have been so busy flying (and when not flying, working at the day job), that I have yet to build a lot of nice performance tables. And I have been so happy flying along at 8,000', wide open at 70% power and leaned out, that I really haven't used much else. But in answer to the question, I quickly dug out a few numbers, and I might as well share them with everyone. I just computed three conditions at 8,000', computing speed, endurance, and range. These are test numbers, without a lot of fine-tuning for DA, temperature, etc...but representative of what you can get in the real world. The RPM was set at 2500 for these three test points, and I can't tell you the MAP - I set my power by % on the EFIS (the MAP is in the records, I'm just too lazy tonight to pull them....). Endurance is absolute to dry tanks at 42 gallons.

8,000'

% HP = 70
TAS = 174 kts
FF = 8.5 gph
Endurance = 4.9 hours
Range = 860 miles


%HP = 60
TAS = 164 kts
FF = 7.3 gph
Endurance = 5.7 hours
Range = 943 miles

%HP = 50
TAS = 147 kts
FF = 6.3 gph
Endurance = 6.7 hours
Range = 980 miles


As usual, your mileage (and speed, endurance, etc...) will probably vary! I'm ready to stretch my legs after 3 hours anyway!

Paul
 
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Also, what are your specific power settings (MP, RPM) to achieve those power percentages?

Thanks,
Mike
 
I recently did the exact same thing for my Rocket. I flew at 7,500' and 9 different MP/RPM settings. For each, I ran 50 dF ROP and LOP and logged the KTAS and FF.

Very interesting stats for my own use regarding where to run when I want to maximize speed or endurance. I put them on a laminated card that I carry in my map box.
 
Leaned to as low a fuel flow as I can get without roughness...which amazingly turns out to be very, very close to the Lycoming number for minimum fuel flow versus % power. (It is also slightly LOP according to the EGT graph on my GRT EFIS)

As I stated in the original post, RPM was 2500, MAP was whatever was required to get the %power I wanted - my EFIS displays %pwer, and it closely matches the Lyc power curves.

Obviously, these are just three datapoints out of a huge amount of flight test data...I just picked those becasue someone asked for those conditions, and since I had them handy, I posted them.

Paul
 
Ironflight said:
As I stated in the original post, RPM was 2500, MAP was whatever was required to get the %power I wanted

Paul
Click to expand...

Sorry for my question.... I somehow scanned over the above sentence in your original post.

Mike
 
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