Recommendations - UltraProps.com

Suggested Propeller and Engine Combinations for Original Ultra-Prop 1

(Other prop/engine combinations not specifically listed may be extrapolated from this proven list)

Engine (Aircraft)	HP	Reduction Ratio	Prop	Diameter*	Pitch**
R503 DC	52	2.58:1	104	59″	15 or 16
R503 SC	48	2.58:1	104	59″	14 or 15
R447 (best)	40	2.58:1	104	59″	13 or 14
R477	40	2.58:1	104	59″	16
R377 (best)	35	2.58:1	103	59″	13 or 14
R377	35	2.58:1	104	59″	11
R277	28	2.58:1	103	59″	10 or 11

Engine (Aircraft)	HP	Reduction Ratio	Prop	Diameter*	Pitch**
Honda/B&S	13	direct drive	103	36″	13
Honda/B&S	20	direct drive	103	42″	15 or 16
Honda/B&S	20	direct drive	104	42″	14

Engine (Aircraft)	HP	Reduction Ratio	Prop	Diameter*	Pitch**
Hirth F33	28	2.5:1	103	59″	10 or 11
Hirth F33	28	2.5:1	103	52″	17 or 18
Hirth F33	28	2.5:1	102	59″	13 or 14
Hirth F33	28	2.5:1	102	55″	17 or 18
MZ 34	27-32	2.34:1	103	57″	10 or 11
MZ 34	27-32	2.34:1	103	52″	15 or 16
MZ 34	27-32	2.34:1	103	49″	17 or 18
MZ 34	27-32	2.34:1	102	59″	10 or 11
MZ 34	27-32	2.34:1	102	57″	13 or 14
MZ 34	27-32	2.34:1	102	52″	17 or 18

*Increase pitch by one degree for every one inch decrease in diameter.
**A change in pitch of one degree is worth about 200-300 change in engine RPM. Increasing pitch will decrease RPM. Decreasing pitch will increase RPM.
***Other lower reduction ratios are available.

NOTE: If a loud “buzzing” noise is noted at high RPM with high-pitch blocks, it is because the tips are stalling. Do not operate the propeller in this range. Either a lower pitch or smaller dia. prop must be used.

Tests have shown that at and below 52-in. dia., no blade tip stalling will occur with 18-degree pitch blocks below the rated 3100 RPM.

Between 52″ dia. and the full 59″ dia., the approximate tip stalling RPM or onset of buzzing is shown in the table below for various pitches.

Diameter	18 deg pitch	16 deg pitch	14 deg pitch
59″	1900 RPM	2400 RPM	2700 RPM
58″	2050	2450	2700
57″	2100	2700	3100
56″	2250	3100
55″	2400
54″	2550
53″	2800

Ultra-Prop 1 Propeller RPM Limits

Prop Diameter	RPM Redline
59 inch	3100
54 inch	3300
48 inch	3600
42 inch	3950
36 inch	4200
30 inch	4500
24 inch	4200

This information is provided courtesy of Competition Aircraft Inc.

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Ultra Prop Propellers

Suggested Propeller and Engine Combinations for Original Ultra-Prop 1

(Other prop/engine combinations not specifically listed may be extrapolated from this proven list)

Ultra-Prop 1 Propeller RPM Limits