HOVERHAWK Propeller and Fan Tip Speed Calculator

Determine Propeller RPM Redline
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.

REMEMBER, .88 to .92 mach is a redline.  This is NOT the most efficient tip speed range for your propeller to operate.

If you want the quietest and most efficient thrust propeller  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 degrade the performance of your propeller.

The tip speed of the multi-blade fans used for air cushion pressure and thrust is limited to about 460 FPS or 314 MPH !

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).


Propeller and Fan Tip Speed Calculator

Compensation for outside temp in Celsius. Speed in Mph.


* Prop Diameter. In inches.

* Engine Rpm. ( Max )

* Engine Gear. Example. 2,58:1 set 2.58, with no gear use 1.

= Prop Tip Speed in Mph.

* Outside Temp. in Celsius ( Normal is 20 Celsius. )

= The Speed of sound in Mph. Calculated using outside temp.

= Prop Tip Speed in Mach. Best performance between 0.8-0.92 Mach.

A propeller does not work well just under and over Mach speed.
Just under Mach (0.92+) the propeller will vibrate, makes excessive noise and will have poor efficiency .


Theoretical Speed Calculator For Aircraft


* Prop Pitch. Measured at 75% of the prop disk radius. (Use right "GO"-button for input. I.e. inch=40, metric=1.016m)

* Engine Rpm. (In cruise or test)

* Engine Gear Ratio. (If direct drive put 1)

* Aircraft drag. 85 to 75%. If the aircraft is very aerodynamically clean use 0.85 . Default id 75% (0.75)

= Speed in Km.

= Speed in Mph.

= Speed in Knot.