1. Estimating % Power using Flight Test Data, Thrust HP, and Equivalent Flat Plate Drag

2. Objective The Objective is to generate a Chart that relates: RPM
% Power Output
True Airspeed
Fuel Flow
Range
Cruise Altitude

3. Methodology
Gather Flight Test Data for a variety of RPM settings (WOT thru economy cruise)
For each RPM, record True Airspeed (TAS) at SL, 4000’ and 8000’ density altitude
Calculate % Pwr for S.L. data
Use the relationship between Density Altitude (DA) and Power Available to estimate % Pwr for 4000’ and 8000’

4. Assumptions Max BHP = 77 HP Prop Efficiency = 75%
I don’t think I’m getting 80 HP based on my maximum RPM of 3300
Prop Efficiency = 75%
Equivalent Flat Plate Area (fe) remains constant
Changes in TAS are due to changes in engine power (% Pwr)
Fuel Flow is proportional to % Pwr

5. 130 mph & 58 THP intersect at fe=4 sq ft
RPM = 3300, TAS = 130 mph
% Pwr = 100%
130
130 mph & 58 THP intersect at fe=4 sq ft 58
THP = 77 BHP * 0.75 = 58

6. RPM = 3200, TAS = 125 mph
125 50 58
% Pwr = 50/58 = 86%

7. RPM = 3100, TAS = 120 mph 45 58
% Pwr = 45/58 = 77%

8. RPM = 3000, TAS = 115 mph
115 40 58
% Pwr = 40/58 = 70%

9. RPM = 2900, TAS = 110 mph
110 35 58
% Pwr = 35/58 = 60%

10. RPM = 2800, TAS = 105 mph
105 32 58
% Pwr = 32/58 = 55%

11. Findings Equivalent Flat Plate Area (Fe) = 4 sq. ft. RPM TAS % Pwr

12. Findings (cont) Measured WOT Fuel Flow = 5.7 gph
Calculate fuel flow based on % Pwr
RPM TAS % Pwr Fuel Flow

13. Effect of Density Altitude on Power Output

14. Findings (cont) Power Output falls with DA
At 4000’ DA, max power output is 87% of S.L. output
At 8000’ DA, output is 77% of S.L.

15. Conclusion
From here, we can do the math and complete the % Power Table