Would you like to know how fast your propeller tips are traveling? Enter some different combinations of prop diameter and RPM setting below to find out. Note: Ambient temperature is needed to determine the speed of sound for a particular day. The speed of sound varies according to air temperature.Try different temperatures then you will see just how much the speed of sound can vary. This calculator can be very useful when trying to determine the ideal propeller speed reduction ratio. You may want your propeller to reach its redline (.88 to .92 mach) at the same time your engine reaches its maximum rpm limit, its redline. To calculate this ratio, divide the maximum prop rpm, as you have determined by using this prop tip speed calculator, into the maximum engine rpm. REMEMBER, .88 to .92 mach is a redline. This is NOT the most efficient tip speed range for your propeller to operate. This calculator is provided courtesy of P. Ponk Aviation. Visit their website at www.pponk.com. USE THIS CALCULATOR AT YOUR OWN RISK
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| Over .92
mach the airflow begins to detach from the propeller which decreases efficiency and
dramatically increases noise. To improve performance and public relations you should
consider reducing RPM so your tip speed will be below 0.92 mach. To convert MPH to feet per second multiply by 1.4667. To convert feet per second to MPH multiply by 0.681818. If you have a propeller speed reduction unit (PSRU) divide your gear ratio (i.e. 2.58) into the maximum engine RPM (i.e. 6800 rpm) to determine your propeller RPM (i.e. 2636 propeller RPM). To determine how fast your propeller can theoretically push or pull you through the air at a given rpm and pitch, multiply your propeller's pitch in inches (usually measured at 75 percent of the prop disk radius) times the RPM. Then multiply that figure times .000947 which gives you your speed in miles per hour. Then multiply this figure by .85 if your aircraft is reasonably aerodynamically clean or by .80 or .75 if your aircraft is somewhat "draggy". This last operation compensates for propeller slippage and some aircraft drag. The end result should be a reasonably accurate estimate of your aircraft's airspeed potential. Use this process to help determine the amount of propeller pitch you need for your particular aircraft. If
you want the quietest and most efficient propeller propulsion system, select a prop
configuration (and reduction drive ratio) that will keep the tip speed for your cruise rpm
at or below 700 feet per second or 475 mph. Above this speed
"compressibility" of the air in front of the prop leading edge begins to occur
which begins to rapidly degrade the performance of your propeller. |
The pitch selection guide below
uses pitch in inches and does not include prop slippage. It shows the
"theoretical airspeed." To convert degrees of pitch as measured with a
protractor go to the page linked here and use the converter to find your blade pitch in
inches.
Degrees Pitch to Inches
Pitch Converter
Pitch Selection Reference Guide
Prop RPM |
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| Cruise Air Speed | 1100 | 1200 | 1300 | 1400 | 1500 | 1600 | 1700 | 1800 | 1900 | 2000 | 2100 | 2200 | 2300 | 2400 | 2500 |
| 220 | 106 | 101 | 97 | 93 | |||||||||||
| 210 | 106 | 101 | 96 | 92 | 89 | ||||||||||
| 200 | 106 | 100 | 96 | 92 | 88 | 84 | |||||||||
| 190 | 106 | 100 | 96 | 91 | 87 | 84 | 80 | ||||||||
| 180 | 106 | 100 | 95 | 91 | 86 | 83 | 79 | 76 | |||||||
| 170 | 106 | 100 | 94 | 90 | 85 | 82 | 78 | 74 | 72 | ||||||
| 160 | 106 | 100 | 94 | 89 | 84 | 80 | 77 | 73 | 70 | 68 | |||||
| 150 | 106 | 99 | 93 | 88 | 83 | 79 | 75 | 72 | 69 | 66 | 63 | ||||
| 140 | 106 | 99 | 92 | 87 | 82 | 78 | 74 | 70 | 67 | 64 | 62 | 59 | |||
| 130 | 106 | 98 | 92 | 86 | 81 | 76 | 72 | 69 | 65 | 62 | 60 | 57 | 55 | ||
| 120 | 106 | 97 | 91 | 84 | 79 | 73 | 70 | 67 | 63 | 60 | 58 | 55 | 53 | 51 | |
| 110 | 106 | 97 | 89 | 83 | 77 | 73 | 68 | 65 | 61 | 58 | 55 | 53 | 51 | 48 | 46 |
| 100 | 96 | 88 | 81 | 75 | 70 | 66 | 62 | 59 | 56 | 53 | 50 | 48 | 46 | 44 | 42 |
| 90 | 86 | 79 | 73 | 68 | 63 | 59 | 56 | 53 | 50 | 48 | 45 | 43 | 41 | 40 | 38 |
| 80 | 77 | 70 | 65 | 63 | 56 | 53 | 50 | 47 | 44 | 42 | 40 | 38 | 37 | 35 | 33 |
| 70 | 67 | 62 | 57 | 53 | 49 | 46 | 43 | 41 | 39 | 37 | 35 | 34 | 32 | 31 | 30 |
| 60 | 58 | 53 | 49 | 45 | 42 | 40 | 37 | 36 | 33 | 32 | 30 | 29 | 28 | 26 | 25 |
| 50 | 48 | 44 | 41 | 38 | 35 | 33 | 31 | 29 | 28 | 26 | 25 | 24 | 23 | 22 | 21 |
| 40 | 38 | 35 | 32 | 30 | 28 | 26 | 25 | 23 | 22 | 21 | 20 | 19 | 18 | 18 | 17 |
| 30 | 29 | 26 | 24 | 23 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 14 | 13 | 12 |
| 20 | 19 | 18 | 16 | 15 | 14 | 13 | 12 | 12 | 11 | 11 | 10 | 10 | 9 | 9 | 8 |
| 10 | 10 | 9 | 8 | 8 | 7 | 7 | 6 | 6 | 6 | 5 | 5 | 5 | 5 | 4 | 4 |
This reference guide is courtesy of www.culverprops.com |
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Prop RPM |
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| Cruise Air Speed | 2600 | 2700 | 2800 | 2900 | 3000 | 3100 | 3200 | 3300 | 3400 | 3500 | 3600 | 3700 | 3800 | 3900 | 4000 | 4100 | 4200 |
| 220 | 89 | 86 | 83 | 80 | 77 | 75 | 73 | 70 | 68 | 66 | 65 | 63 | 61 | 60 | 58 | 56 | 55 |
| 210 | 85 | 82 | 79 | 76 | 74 | 71 | 69 | 67 | 65 | 63 | 62 | 60 | 58 | 57 | 55 | 54 | 53 |
| 200 | 81 | 78 | 75 | 72 | 70 | 68 | 66 | 65 | 62 | 61 | 59 | 57 | 56 | 54 | 53 | 51 | 50 |
| 190 | 77 | 74 | 72 | 69 | 67 | 65 | 63 | 61 | 59 | 57 | 56 | 54 | 53 | 51 | 50 | 49 | 48 |
| 180 | 73 | 70 | 68 | 66 | 63 | 61 | 59 | 58 | 56 | 54 | 53 | 52 | 50 | 49 | 48 | 46 | 45 |
| 170 | 69 | 66 | 64 | 62 | 60 | 58 | 56 | 54 | 53 | 51 | 50 | 49 | 47 | 46 | 45 | 44 | 43 |
| 160 | 65 | 64 | 63 | 58 | 56 | 55 | 53 | 51 | 50 | 48 | 47 | 46 | 44 | 43 | 42 | 41 | 40 |
| 150 | 61 | 59 | 57 | 55 | 53 | 51 | 50 | 48 | 47 | 45 | 44 | 43 | 42 | 41 | 40 | 39 | 38 |
| 140 | 57 | 55 | 53 | 51 | 50 | 49 | 46 | 45 | 43 | 42 | 41 | 40 | 39 | 38 | 37 | 36 | 35 |
| 130 | 53 | 51 | 49 | 47 | 46 | 44 | 43 | 42 | 40 | 39 | 38 | 37 | 36 | 35 | 34 | 33 | 33 |
| 120 | 49 | 47 | 45 | 44 | 42 | 41 | 40 | 38 | 37 | 36 | 35 | 34 | 33 | 32 | 32 | 31 | 30 |
| 110 | 45 | 43 | 41 | 40 | 39 | 37 | 36 | 35 | 34 | 33 | 32 | 31 | 31 | 30 | 29 | 28 | 28 |
| 100 | 41 | 39 | 38 | 36 | 35 | 34 | 33 | 32 | 31 | 30 | 29 | 29 | 28 | 27 | 26 | 26 | 25 |
| 90 | 37 | 35 | 34 | 33 | 32 | 31 | 30 | 29 | 28 | 27 | 26 | 26 | 25 | 24 | 24 | 23 | 23 |
| 80 | 32 | 31 | 30 | 29 | 28 | 27 | 26 | 26 | 25 | 24 | 23 | 23 | 22 | 22 | 21 | 21 | 20 |
| 70 | 29 | 27 | 26 | 25 | 25 | 24 | 23 | 22 | 22 | 22 | 21 | 20 | 19 | 19 | 18 | 18 | 18 |
| 60 | 24 | 23 | 23 | 22 | 21 | 20 | 20 | 19 | 19 | 18 | 18 | 17 | 17 | 16 | 16 | 15 | 15 |
| 50 | 20 | 20 | 19 | 18 | 18 | 17 | 17 | 16 | 16 | 15 | 15 | 14 | 14 | 14 | 13 | 13 | 13 |
| 40 | 16 | 16 | 15 | 15 | 14 | 14 | 13 | 13 | 12 | 12 | 12 | 11 | 11 | 11 | 11 | 10 | 10 |
| 30 | 12 | 12 | 11 | 11 | 11 | 10 | 10 | 10 | 9 | 9 | 9 | 9 | 8 | 8 | 8 | 8 | 8 |
| 20 | 8 | 8 | 8 | 7 | 7 | 7 | 7 | 6 | 6 | 6 | 6 | 6 | 6 | 5 | 5 | 5 | 5 |
| 10 | 4 | 4 | 4 | 4 | 4 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 |
This reference guide is courtesy of www.culverprops.com |
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