What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

WHICH HARTZELL PROPELLER MODEL?

Jetmart

Well Known Member
Van's is showing both a 72" and 74" C/S prop for the RV- 14 & 14A for the 390Hp. What are the pros & cons of each option. They are both priced the same?
 
RE: Which Hartzell propeller model?

Glen,

I called Hartzell a few weeks ago with the same question. They had me contact Vans. Essentially, vans stated that the 72" is for both the taildragger and the tri-gear aircraft. The 74" prop is not recommended for the taildragger RV-14. For what it's worth, I ordered the 72" prop.
I hope this helps!
 
I had heard that before but surprised to see both listed on Van?s site for the taildragger. I guess they?re concerned about prop strikes??
 
When only considering an RV14-A (which can use either it seems), any thoughts on pros and cons on choosing one over the other?
 
When only considering an RV14-A (which can use either it seems), any thoughts on pros and cons on choosing one over the other?

All else being equal, at any given RPM, greater blade length will yield greater thrust. I chose the 74" version for my -14A.

FWIW, when I spoke to Mike Seager back in September, he agreed that the 74" Hartzell is the best-performing prop for the -14A.
 
Why not put in on the 14 then? Is 1" less ground clearance really going to be a factor?

Apparently so. With the -14's tail up on takeoff, it won't take much over rotation to place the prop disc in closer proximity to the ground than the -14A's in its normal three-point attitude. Not to mention the tailwheel version's entirely different main gear legs, the springiness/compressibility of which (on, say, a poorly executed wheel landing) might also bring the longer prop closer to the ground than desired.
 
This topic has been covered in the past here on V A. Basically, prop length was reduce for the 14 to satisfy the drop test ground clearance requirements, I believe.
I learned this after I received my 72? prop (14) and was a little pissed. I would have preferred the 74?. I asked Hartzell if I could exchanged my unopened 72? prop and they said once shipped it is considered used.
I advise, if you are a good pilot and feel you will not crash land or over rotate
by an insane amount, go with the 74?. If you are a below average, have a tendency to lose control, wear a watch over 1 lb, and get lost on cross country flights.....go with the 72?.

R
 
Went with the...

72? on my RV-14. As strongly recommended by Vans. I have no way to know what difference another inch of radius would make, but I am completely happy with how it performs. 101 hours now....
 
72? on my RV-14. As strongly recommended by Vans. I have no way to know what difference another inch of radius would make, but I am completely happy with how it performs. 101 hours now....

Why is the 74" listed on Van's website for the RV-14 if it is not recommended ?
 
My Guess is Vans designed and are the experts. As an amateur builder I have far less knowledge than the folks that designed it. My money is on Vans. Just saying
 
We've had a bit of a data display issue here on the web form related to props and RV model numbers, which we're working on today. Expect that to change and be fixed later this evening.

Generally speaking, the 74-inch props are spec'ed for the A-model aircraft and not for the tailwheel aircraft when the risk of a prop strike on the non-nosewheel models is determined to be significant. In the case of the 8/8A, the longer prop is spec'ed as ok for use on the tailwheel model due to that specific design.

Have people used 74 inch props on tailwheel aircraft? Yes. We spec what we spec based on our design. If a builder installs a different prop, he/she accepts any related potential risks/consequences as part of that decision.
 
Last edited:
After consult with many experts, I put a 74" aerobatic Hartzell on my 14. There is plenty of clearance but avoid the obvious.
 
After consult with many experts, I put a 74" aerobatic Hartzell on my 14. There is plenty of clearance but avoid the obvious.[/QUOTE

What is the difference in design of the aerobatic vs standard and what difference in performance would you expect?
 
Movement direction with loss of governor pressure

The primary difference between the aerobatic and non aerobatic versions of the same propeller is the direction of blade travel caused by the governor. In a non aerobatic prop the blades go to fine pitch (high RPM) when there is no regulation supplied by the governor due to the action of internal springs. These "regular" props will be in fine pitch when the engine is shut down. Aerobatic props are the opposite. They are in course pitch with no input from the regulator as they would be seen sitting on the ground. The reason is in the event the governor looses oil supply in a negative G manouver, a non aerobatic prop would be driven to fine pitch by the internal springs potentially causing the engine to dangerously overspeed. With an aerobatic prop, the loss of oil to the governor during a negative G manouver causes the prop internal springs to drive the blades to course pitch, reducing RPM. If both props have the same blade, the performance will be identical for either throughout the positive G flight envelope.
 
The primary difference between the aerobatic and non aerobatic versions of the same propeller is the direction of blade travel caused by the governor. In a non aerobatic prop the blades go to fine pitch (high RPM) when there is no regulation supplied by the governor due to the action of internal springs. These "regular" props will be in fine pitch when the engine is shut down. Aerobatic props are the opposite. They are in course pitch with no input from the regulator as they would be seen sitting on the ground. The reason is in the event the governor looses oil supply in a negative G manouver, a non aerobatic prop would be driven to fine pitch by the internal springs potentially causing the engine to dangerously overspeed. With an aerobatic prop, the loss of oil to the governor during a negative G manouver causes the prop internal springs to drive the blades to course pitch, reducing RPM. If both props have the same blade, the performance will be identical for either throughout the positive G flight envelope.

Thanks, very helpful
 
Which means the prop governor needs to be one specifically designed to work with a aerobatic prop. I found out the hard way.
 
Back
Top