CS Prop overhaul in non-commercial ops

[alaskaflyer]

When does the typical constant speed propeller need an overhaul? I'm looking mostly at Hartzell and McCauley props on various horsepower upgrades on Cessna 170s and 172s. The plane would not be in any kind of commercial service.

I see a lot of planes in the 600-700 hour SPOH range for sale, in my profession we might call that a clue But I'm trying to confirm my suspicions.

 

[alaskaflyer]

Alaskaflyer, are you making a distinction between a prop "overhaul" and a prop "reseal"? Or, are you considering them to be the same for all practical purposes? -- Mike

Well, I'm just looking at practicalities since I am part 91...my "adviser" mechanic is out of town right now and I am looking at a couple different planes with SPOH times in the 600s, and want to know if I will be stuck with a large prop overhaul bill sooner instead of later.

I suppose if I knew how much the "typical" (if there is such a thing) overhaul bill would be...if it's less than two ASUs then I suppose I would be less concerned....

 

[Henning]

Well, I'm just looking at practicalities since I am part 91...my "adviser" mechanic is out of town right now and I am looking at a couple different planes with SPOH times in the 600s, and want to know if I will be stuck with a large prop overhaul bill sooner instead of later.

I suppose if I knew how much the "typical" (if there is such a thing) overhaul bill would be...if it's less that two ASUs then I suppose I would be less concerned....

It depends on the prop and AD. Lot's of the Hartzels on the O-360 lycs have a 5 year 500 hr AD on them, so watch out there. I recall going through mine for $500 a piece.

 

[alaskaflyer]

So, after much searching I found a reference for a McCauley prop on one plane I am researching (STC for engine upgrade produced model # of prop authorized) with a TBO of 1200 hours or 5 years whichever is first. This partially answers my question, at least in general terms.

I realize that part 91 doesn't have to follow TBO recommendations, so if it is only a little more than half way to its TBO by hours I should probably not be concerned (even though it is past its calendar TBO by 2 1/2 years.) NO AD's on that model either according to the FAA database

Of course I would have the A& P doing the pre-purchase examine it for corrosion and fluid leaks.

I would still be curious as to the typical price for a "base" overhaul. Would $500 quoted by Henning above for an AD inspection be a common price for a tear down/inspection/governor overhaul, assuming a blade or other expensive part doesn't need to be replaced?

 

[poadeleted20]

A CS prop overhaul will run more like $1500 than $500 -- I think that $500 was just for the AD inspection. In any event, other than an AD requirement, overhaul for Part 91 ops is required on an "on condition" basis only, although the factory TBO's (operating hours and calendar time) are a good starting point for making a risk reduction decision.

 

[Steve]

fwiw,

I had the CS prop on my plane overhauled the first week in January. A few of issues prompted me to get it overhauled even though it only had ~300 hrs on it when I purchased the plane in September. The main driver was Hartzell recommends a 60 month TBO for this propeller and it was past that point on the calendar. It is a Hartzell 2-bladed prop. Also, because it has a steel hub it is subject to a 500 hr AD for corrosion inspection. Another reason for getting the OH was I felt there was an unusual amount of vibration related to engine speed, confirmed by an attempt to balance it dynamically. After the prop was in the shop it was determined that the blade clamps were mismatched by the previous overhaul facility in 2000. Any time you buy a plane you better be prepared for a few surprises, despite how thorough your pre-buy is.

Hartzell aluminum hubs are not subject to that AD per the tech staff at Hartzell. I had called them to inquire about the possibility of changing to a 3-bladed prop. They sent me a list of "allowed" blade/hub configurations for various engines and there was one listed for my IO-540. A new 3-blade was going to run $12k-$14k, so I opted to overhaul this go round. If the prop ever becomes unserviceable (the blades on mine are rather unique, lead time to fabricate new ones is 14 weeks), I still might go 3-bladed, or at least go with an aluminum 2-bladed hub to avoid the 500 hr AD. We'll see where we are in 500 hrs.

I got several quotes before I decided on R and D Propeller in Pearland, TX, ranging from $1200 to $3000 for an overhaul. Special parts extra. The low end was basically disassemble, inspect, and reassemble. The high end included the basic inspection plus replacing all parts recommended by Hartzell (no reuse of threaded fasteners, etc.). Mine ran $3900 which included $1600 for new hub clamps. The old clamps could not be reused per Hartzell instructions. I was skeptical that I was being sold some snake oil, but after I got the prop back it didn't require any re-balancing to be within allowable limits when we checked vibration levels after installation. And the prop response during run-up is much smoother now.

I am very satisfied with the work done by R and D Propeller. Prop condition is often overlooked imho, considering it's probably the most highly stressed component on the plane (except possibly the crank, or the pilot, who some consider to be a crank), I feel I have a small measure of assurance that the one on my plane is in as good a condition now as can be reasonably expected.

Attached is Hartzell's recommendations on TBO.

 

[alaskaflyer]

Thanks guys, food for thought!

 

[wsuffa]

For Hartzell props, I urge you to check the TCDS on the FAA site.

Apparently Hartzell went back a few years ago and changed the type data with the FAA blessing. The TCDS for SOME Hartzell props now specify as an Instruction for Continued Airworthiness that you comply with the TBO and Calendar TBO limitations in the Hartzell service instructions (which Hartzell can chage without FAA approval).

By this move, Hartzell has made the TBO/Calendar Time MANDATORY for all users, including Part 91.

Not all props are in this fix. You can figure it out by checking the Type Certificate Data Sheet for your prop on the FAA site.