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New Hartzell Prop for 912 Series Rotax Engines

PostPosted: Tue Apr 14, 2015 12:42 pm
by av8rps
Looks like we may have another good choice for a prop...

Hartzell Awarded TC for Two-Blade Bantam Prop for Rotax Engines

April 9, 2015 - Hartzell Propeller has received an FAA type certificate for its new two-blade Bantam propeller for use with the Rotax 912 and 914 four-stroke engines series, the most prevalent powerplants in use by light-sport and ultralight (non-U.S.) aircraft.

The recent approval covers installation of Hartzell’s two-blade Bantam propellers, featuring carbon fiber structural composite blades, hard nickel leading edges, and composite spinners.

The new propellers are available in various diameters ranging from 67-77 inches through Hartzell’s Top Prop performance conversion program. Bantam two-blade props are approved for 912iS Sport (100hp), 912 (80hp), 912 (100hp), and 914 (115hp) engines. Lightweight Bantam two-blade propellers weigh only 25 pounds, including spinner.

“The Rotax 912 and 914 series of four-cylinder, four-stroke engines perform even better with Hartzell’s new two-blade Bantam prop,” said Hartzell Propeller’s Joe Brown. “This will become the propeller of choice for many light sport and ultra light aircraft.”

Superior strength of the carbon fiber structural composite material enabled the Hartzell Propeller engineering team to design blades with wider chords and thinner airfoils, ultimately leading to higher performance and durability.

Learn more at

Re: New Hartzell Prop for 912 Series Rotax Engines

PostPosted: Tue Apr 14, 2015 10:37 pm
by Av8r3400
"Only" 25 pounds? I wonder who approved it? Definitely not Rotax...

Love to see the MMOI test numbers on that pig...

Re: New Hartzell Prop for 912 Series Rotax Engines

PostPosted: Wed Apr 15, 2015 11:29 am
by FlyerChief

I just got a reply back from Hartzell and their response to the MMOI question was:
For a two blade prop at 74” diameter, the polar moment of Inertia is approximately 0.435 slug*ft^2 (estimated). For reference, the 77” diameter of the same design is 0.447 slug´ft.2 (measured).

Slug-Square Foot (slug-ft2) is a unit in the category of Mass moment of inertia. It is also known as slug square foot. This unit is commonly used in the UK, US unit systems. Slug-Square Foot (slug-ft2) has a dimension of ML2 where M is mass, and L is length. It can be converted to the corresponding standard SI unit kg-m2 by multiplying its value by a factor of 1.35581794859.

Therefore it would appear the MMOI in understandable terms is 0.435 x 1.355818 = 5900... just within the Rotax limits for the 74" prop and 6060 for the 77 inch... just over the Rotax specified limit.

It appears that a lot of the mass is close to the hub and therefore doesn't impact the MMOI as much. Still that's a lot of extra weight to hang off the front of the plane, and since Highlanders like to have a slightly rearward CG, I'll stick to a prop under 10 lb.


Re: New Hartzell Prop for 912 Series Rotax Engines

PostPosted: Tue Apr 21, 2015 11:19 am
by kenryan
25 pounds seems pretty light for a constant speed prop. What do the alternatives weigh?