General info:

Kool is a ground-adjustable air propeller intended for Ultralight and Homebuilt aircraft and other uncertified recreational light machines with internal-combustion and electric engines (airboats, hovercrafts etc).

Prop blades are hand-made with high-strength carbon-fiberglass-epoxy composite. Each blade has integrated stainless steel leading edge protection. Some models have antivortex blade tips. Prop hub is made with aluminum allow, CNC machined and anodized (polished). Bolt pattern is standard used for Rotax engines. Usually the hub has 2 pilot holes. 1” for 503, 582 etc, 47mm for Rotax 912-914. The basic set included blades, hub, blade covers, pitch protractor and hardware.

There is a serial blade number at each blade root. If you need a replacement, you can provide this number so replacement blade(s) can be balanced to fit exactly to your propeller.

Technical data:

Max prop RPM 2800 (3500 for some models) rev/min

Recommended pitch adjustment +/- 5 degrees (using pitch protractor)

Warranty against manufacturer’s defects 100hours for 1 year

Some numbers for 7 standard Kool models (3-blade). Special reinforced blades can be ordered for more powerful engines.


R / L42

R / L62(64)

R / L83 Scimitar

R / L81(82)

R / L 104

R/L 106 Scimitar

R / L 102 (103)









Pitch R=0.75D degrees +/- 5








Appr. engine power HP








Appr. moment of inertia








Appr. weight kg










Assembling and installation:

Recommended for Pusher layout. For Tractor layout another pitch protractor can be recommended, or it is necessary to adjust the pitch before the prop installation on the engine hub and remove the prop from the engine hub each time you have to change the pitch

1.     Disassemble prop hub.

2.     Install propeller blades into their positions between the hub halves (be careful, drilled points inside the halbes must be positioned in front of each other). Install outer bolts with lock nuts and tighten slightly to hold blades in place.

3.     Install the prop hub (with spinner base, spacer if necessary) on the engine (gearbox) flange with the six 8mm metric bolts and washers.

4.      With all bolts slightly tightened, you should be able to easily adjust the pitch on the blades. Make sure at this time that the leading edge of all blades are facing in the right direction and are not backwards.

5.     Set the scale on the protractor to 0 or about the recommended by engine manufacturer pitch. Due to variations in gearboxes, etc. more adjustments are usually required to dial in the “perfect” pitch setting. Clamp the scale with a side clamp Cleco or small C-clamp

6.      Fit the other sheet metal end of the protractor into the center hole of the prop hub so that the sheet metal ears are both touching the flat face of the hub.

7.     Place the notch on the other end of the protractor against the trailing edge of the prop blade.  Rotate the blade until the leading edge side just touches the protractor scale surface. Ensure that sheet metal ears are both touching the flat face of the hub and there are no gaps between the scale part, blade leading and trailing edge surfaces. Torque the two outer bolts to 3-4 foot lbs. to hold this blade at this setting. Then repeat the procedure for the other blades.

8.      When all blades have been set, torque the lock outer bolts sequentially with 5 ft. lb. increments to 12-14 ft lb. This will help to insure proper tracking. Check the pitch of all blades again, and once satisfied, begin torquing the inner Hub bolts sequentially, opposing and with 5 ft. lb. increments to 15-17ft lb.
WARNING!!! DO NOT OVER OR UNDER TORQUE BOLTS! NEVER START ENGINE WITHOUT PROPER TORQUE ON BOLTS!!!                                                                                                                                                                      

9.     Install the six lock nuts on the ends of the protruding prop bolts and torque to
approximately 13-foot lbs. If your bolts have the drilled heads (if not you could drill them), secure them appropriately with steel wire. If your bolts have the drilled shaft and castle nuts, you can add a thin washer to line up the cotter pin holes, but DO NOT UNDER OR OVERTORQUE! A static check of rpm must be performed before flight. Refer to engine manual for specific instructions. NOTE: DO NOT FLY UNTIL YOU HAVE CHECKED AND RECHECKED YOUR PROPELLER FOR PROPER MOUNTING AND PERFORMED A STATIC CHECK OF RPM.  If you cannot reach recommended RPM, you may be Over/Under Pitched. Do not run in this condition or engine damage may result. Install the spinner fairing (if you use spinner) after the static RPM test.

10. Re-check torque of prop bolts after first hour of operation and as routine maintenance. Never over torque or  “STRETCH” prop bolts!  The standard prop bolt for this propeller is a Grade 8 metric and will fit the Rotax 75mm bolt pattern. AN 5 prop bolts will fit the ROTAX 912 application, use the same torque.

If you have any questions - contact Air Trikes Enterprises. E-mail: info@airtrikes.net Phone number: 450-202-7772  Website www.airtrikes.net or one of our local dealers closest to you.