Hartzell Overhaul cost, Smooth metal props
penguin said:
I recently paid $2800 to overhaul a McCauley 2-blade prop. However, if the MT & Hartzell TBOs are both 6 years for new props where's the difference? A metal prop can only be overhauled a certain number of times (3 I think) before the blades are too thin. Where as a composite prop does not have that limitation as the blades do not have to be ground down. My preference is for an MT or Whirlwind because they are lighter and much more smooth. Pete
I paid $1,500 for a Hartzell HC2YK overhaul. I asked the shop if there are common problems which they see and the answer was most come thru overhaul with no problem or extra cost. The fatigue life of a Hartzell, depending on model of prop and engine (electronic ignition or HC pistons) is between 8,700 hours to 20,000 hours! Taking the low limit and 200 hours a year, which would be over 43 years! The high limit 100 years worth if flying. What would a Wood based MT prop with composite cover be like in 40 or 100 years? No one knows, since MT has only been in business since 1981. Of course I will not care about props in 100 years. Also, even though MT has certified props, many of their props are not approved on any cert aircraft. This is not a put down of MT, but credit must be given to Hartzell for supporting the experimental market and testing their props on experimental airframes with experimental engine configurations.
As far as smoother, I am not sure how you know this Pete, since it is subjective.
May be you have never flown a smooth metal bladed prop, and the metal props you have flown don't reflect all metal props. I understand the new Hartzell blended airfoil prop is very smooth. Also it does not have a RPM "range" restriction as some state. The limitation is a single power setting when using electronic ignition and/or HC pistons, "do not operate above 22" below 2350 RPM," which is not a "range" or affect normal operations.
My HC-C2YK/F7666-4 is very smooth and I am happy with it, but I did need to get it balanced. After getting a proper ballance, I was very happy with the feel. Any "wood" based blade, like the MT composite covered wood core blades are going to be ?naturally? smoother. Wood has natural dampening qualities. However how much smoother? I know a good tracking prop, well-balanced, even with metal blades, is going to be pretty smooth. You are not going to totally tame engine vibrations with the prop alone. With metal blades, you can feel some RPM's are smoother than other RPM's, due to harmonics. I don't find it objectionable, but if you are paying attention you can detect subtle difference. It is very easy to avoid these narrow RPM bands. Not sure if vibs are all prop or the combo of engine/prop vibrations. The Wood based prop will be smoother over a wider RPM range, but metal props are not as bad as people make out, especially when you take cost and availablility of service for the Hartzell into account. George