Hartzell Propeller

(This letter from Hartzell was provided by Steve Dortch)  Thanks Steve !!!


There are two basic propellers available from Hartzell for this aircraft. These are the HC-A2MV20-4A1 and the HC-D2MV20-7. These propellers are very similar to the HC-A2(X,V)20-4A1 and the HC-D2(X,V)20-7. The HC-D2 prop also had an earlier variant, the HC-12X20-7.


Basically, the story is like this: The HC-A2MV20-4A1 prop, and it's earlier versions, the HC-A2(X,V)20-4A1 props are constant speed propellers. These propellers use an engine mounted governor, a "T"-drive and and oil transfer unit to supply oil to the propeller. The HC-D2(X,V, MV)20-7 propeller is a controllable propeller that uses engine oil pressure via a hydraulic unit to control the propeller. This propeller is often referred to in the field as "the diaphragm prop" because it employs a large rubber diaphragm to control the propeller.


The "big AD" on these props is 97-18-02. There are others, but this one is the latest and the biggest. The MV props are exempt from this AD, and any others that affected the earlier versions. Obviously, if you can find an "MV" propeller, this is your best choice.


If you cannot find an "MV" prop, your next best choice is to find an HC-A2(X,V)20-4A1  or HC-D2(X,V)20-7. There are two distinct advantages to buying one of these props. They have the newer style hub (as indicated by the alpha character immediately following the - (ie "A" or "D"). 97-18-02 requires a 500 FH/5 yr. inspection on these props, as opposed to a 250 FH/5 yr. inspection on the older hub versions (indicated by a numeric character immediately following the - (ie "1"). The props with the newer style hubs can also be converted to (or fitted with) the MV clamps and blades, exempting them from the AD's. Conversion of these propellers requires new (MV) blade clamps, and modification of the existing blades (if they pass inspection), and/or purchase of new "MV" blades. I would not recommend buying an HC-12(X,V)20-7, as they cannot be converted and have the shortest time between inspections.


If you are thinking about buying one of these props, check the blade clamp serial numbers per 85-14-10.  Blade clamps with serial numbers 0-D5293 basically need to be removed from service, while D5294 through K6336 need only comply once, and clamps with serial numbers higher than K6336 require no compliance.


Please note that no AD requires these props to be overhauled. The requirements are for inspections, but not overhaul.


If you are looking in the used market, these props were installed on the Beech Bonanza and the Navion. If you would like to buy the constant speed propeller (the HC-A2(MV, V, X)-4A1 prop), make sure you get the governor, the "T" drive and the oil transfer unit.


The HC-A2(X,V)20-4A1 propeller can be converted into an HC-A2MV20-4A1 prop and be AD free. You need new clamps and a decent set of blades to accomplish it, but it can be done. 


If you purchase a used HC-D2(X,V,MV)20-7 propeller, it is in your best interest to change the diaphragm before installing the propeller. The diaphragm should be replaced every two years, as they can leak and cause a loss of engine oil. Also note that this propeller is basically a "two-piece" unit, the propeller and the hydraulic unit. The prop won't work without the hydraulic unit, but they are sold without them as the AD is on the prop, not on the hydraulic unit. Even Hartzell sells them in this manner.


If you purchase an HC-A2(MV,X,V)20-4A1 prop, please contact us before you attempt to install it. This prop is very easy to damage on installation unless you know exactly how to install it.


If you have any further questions, or would like to contact us again before you make a purchase, feel free to do so.



Kevin M. Ryan

Hartzell Product Support.

email: techsupport@hartzellprop.com