Hartzell prop overhaul: metal or composite prop?

[agmolnar]

Hello all,

I am one step closer to closing escrow on the 2007 DA40. The aircraft is due for a prop overhaul, and I may have the option to upgrade from its current Hartzell metal prop to a composite one. My understanding is that the metal prop overhaul is about $3-5k while a composite prop is closer to $15k (new). I may have the opportunity to pick up an overhauled composite prop for closer to $8-10k, so the questions are:

Has anyone upgraded form metal to composite and what has been your experience?
Have you seen a speed increase or general better engine/prop operation?
Has the investment been worth it? (less cost to overhaul over the longer run)
Anything else to consider?

I also have been reading about the weight/CG issues. This craft has a 905lb useful load, 50-gallon tanks, and a relatively forward CG of 97.05 so I don't think I'll run into too many aft CG issues and therefore probably don't need the weighted plates in the front. (If I am mistaken here, please let me know!)

If there's an existing and similar thread on metal vs. composite, please point me there (I searched...but did not find).

Best,
Arpad

[Rich]

If you replace the Hartzell with the composite (or a MT), your empty CG will move aft. The aluminum Hartzell is hanging right on the nose of the plane and is considerably heavier than the composite.

[Chris B]

Has anyone upgraded from metal to composite and what has been your experience?
Have you seen a speed increase or general better engine/prop operation?
Has the investment been worth it? (less cost to overhaul over the longer run)
Anything else to consider?

Hi Arpad -

Welcome to DAN!

There are several good prop threads on DAN, which you probably have already perused. If not, the most notable is "Hartzell Aluminum Propellor" (sic) - link

Based on my discussions with Hartzell at OSH, my personal experience with the aluminum prop, and various threads on DAN, here is my take on the trade-offs (in alphabetical order):

• Climb - composite (marginal)
• Cost - aluminum (no contest)
• Durability - wash? (nickel is tough, but aluminum is easy to file)
• Ground clearance - aluminum (marginal)
• Noise - wash? (though aluminum is shorter, and tip speed is usually the noise problem...)
• Overhaul - wash (the governor drives overhaul issues, and is identical)
• Sex, er... Ramp appeal - composite (IMO)
• Speed - aluminum (marginal)
• Vibration - composite (no contest)
• Weight - composite (no contest)

Both are very good props. So it all depends on what is important to you!

Separately, note that the overhaul situation on the prop is very similar to Lycoming's 2000 hour overhaul recommendation. For Part 91 operators, time-based overhaul is not required. Some people (raises hand) are OK with this, and some are not...

FWIW, Hartzell's technical reps at OSH indicated that - barring strike damage! - the aluminum prop (my interest) should last through several engine overhauls with regular 100 hr lubrication, plus periodic (7-10 year) inspection, cleaning and hub seal replacement. Presumably the same is true of the composite prop.

Chris

[Antoine]

Hello all,

I am one step closer to closing escrow on the 2007 DA40. This craft has a 905lb useful load, 50-gallon tanks, and a relatively forward CG of 97.05 so I don't think I'll run into too many aft CG issues and therefore probably don't need the weighted plates in the front.

905 lb useful is a fantastic number for a 2007. It is an XL or the base version? If it has the whistles and bells you need, dont miss it!
As a comparison my 2007 -XL (admittedly with lots of avionics, but no metal prop) was at 827 lbs useful.
So if it is an XL, I suggest you double check the change history of the W&B report.

[agmolnar]

Thank you Chris for the welcome to DAN and Rich & Antoine for the thoughts - appreciated.

The 2007 about to close escrow is a "hybrid", meaning it's a base version but with the GFC700. I really liked this small group of hybrids that were made (just before upgrade to XL) since it has a number of features that were really important to me: AP, forward CG, high useful load, but didn't include other features in the XL and XLS series that were not so good for me (extra weight and of course price . The S/N is 40.695 (built very late 2006, but 2007 model year).

Putting the composite Hartzell on the plane would push useful load to 921lbs (from 905lbs) but push the CG to 97.8 (from 97.05). If I did go with the composite, I would likely add ballast because I value the CG more than the useful load given my mission profile (two pre-teen kids...). Then again, I have read about the case of not taking the aft CG issues too seriously (ignoring the law for a moment, no pun intended) driven by 50g tank spin certification issues. If I am not thinking clearly about this, please let me know!

Other factors I am considering (please weigh if you have any insight):
- the pre-2008 models like this one have less clearance so -1 for the composite
- composite less likely to go out of tolerance, and my existing metal prop has been filed (therefore lower lifetime costs?)
- there does seem to be lots of disagreement on noise, speed, and overall performance

(Finally, if I ever added Powerflow, I might be more than halfway to upgrading the base model to an XL model, but for a lower price than buying the XL outright. )

On the margins, given a good deal on the composite that I have in hand ($8k vs. $14k new), I am leaning that way. Although I scratch my head at why the composite is valued at 2x metal if the advantages are marginal as Chris and others have noted. Balanced by favorable reports from Tommy, however...

Best,
Arpad

[rwtucker]

Welcome to DAN Arpad. I concur with all of the very good advice you already received above.

Two additional issues from an MT owner who has always before flown behind aluminum props.

- The "worry factor." The wood is very thin at the tip. I don't know about the other DAN members but I am close to paranoid when I park my XLS in a crowded guest parking area. Shortly after I bought the XLS, I caught one idiot flexing my blade "to see what it was made of!" While the MT is durable in flight, I have seen with my own eyes how an identical MT blade (not mine and not on a DA40) snapped like a twig when it caught the edge of hangar when being pushed very slowly by hand. An inadvertent bump at just the right angle and place can render a blade useless . . . then there are birds.

- It seems like your CG change will be minimal. As suggested above, I would verify. The aft CG issue with the MT on the XLS is by no means insignificant, especially if you or someone else who might fly the aircraft is a low time pilot.

[carym]

Congrats on your new plane. It really sounds like you looked into this much more than I did and will be making a smart "investment".

I just want to add one more consideration for you. We all want more speed out of our planes, and one way of achieving that is to move the CG as far back as you can tolerate (speaking from a safety standpoint). With an aft CG you need less down elevator to maintain altitude and that adds up to faster TAS, a phenomenon well known to transport pilots. Antoine posted in another topic that when he is in an updraft he finds that his TAS is greater because he has to put the nose down. While he attributed that to error in the pitot static system going to the G1000, I suspect that part of the increase in TAS is real because there is less down elevator needed.

[agmolnar]

- It seems like your CG change will be minimal. As suggested above, I would verify. The aft CG issue with the MT on the XLS is by no means insignificant, especially if you or someone else who might fly the aircraft is a low time pilot.

I just want to add one more consideration for you. We all want more speed out of our planes, and one way of achieving that is to move the CG as far back as you can tolerate (speaking from a safety standpoint). With an aft CG you need less down elevator to maintain altitude and that adds up to faster TAS, a phenomenon well known to transport pilots. Antoine posted in another topic that when he is in an updraft he finds that his TAS is greater because he has to put the nose down. While he attributed that to error in the pitot static system going to the G1000, I suspect that part of the increase in TAS is real because there is less down elevator needed.

Thank you Robert & Cary. Interestingly, our local flight club flies its DA40s with 40 lbs of removable ballast in the extended luggage area. This seems to serve two purposes: 1) reduces the chance of a prop strike when training with medium/large size pilot + instructor and no one in the back seats, and 2) creates some TAS speed increases in single pilot operation.

So many things to consider, so little time!

[Chris B]

905 lb useful is a fantastic number

+1

That turns the DA40 into a real 4-place aircraft. And with a GFC 700. Wow. Great find!

Chris

[smoss]

Wow! I didn't realize I had the very first XL made--40.696. Aluminum prop has served me well with no complaints.