Aeromatic Prop

[Psmith]

Does anyone have any experience with an Aeromatic prop on a C145 170? I ran into a fellow with a Aeromatic prop on a O-320 powered Clipper. He had a great deal of experience with regards to setting it up properly and performance increase. He could not say enough good about it and thought it would be the ticket for a 170.


Pete N1320D '51 170A

[GAHorn]

I've not personally flown one, but Cleo Bickford tells me his experience is that they are sensitive to density altitude and that if you have it set up for your local area they are frequently out of your selected performance range when you are off on a cross-country to a higher or lower elevation area.
Personally, I'd sure like to see a ground-adjustable prop that would still fit in our regular spinners. Guess I'll not hold my breath.

[doug8082a]

I've always liked the thought of this, but have never seen one. I read an article about a guy with a Clipper on floats (same guy?) who has one and swears by it. Although, what George says about the need to keep readjusting it based on density altitude could be a pain after a while. I'd love to see one and fly it.

Tarver Propellers (http://www.aeromatic.com) has the type certficate now. Their website has been down for a while, so I don't know where he stands, but last I knew he was trying to get FAA approval to resume production of these props.

The 170 Type Certificate has them approved on the C-145-2H engine (as opposed to the C-145-2). Someone (Eric?) posted not too long ago something about the translation/redesignation of the Continental engine models when they went to the "O" designation. If I remember right the C-145-2 became the O-300A and the C-145-2H became the O-300B??? Did I get that right? Can anyone comment on the difference between the C-145-2 and the C-145-2H and whether the C-145-2H became the O-300B? I'm curious about that. If that's the case then I suppose those of us with C-145-2/O-300A engines would not be able to use the Aeromatic prop.

[Bruce Fenstermacher]

Not sure of the 0-300 designator but the Aeromatic prop requires the 2H which is the dampend crank. I think that any 0-300 with a dampend crank regardless of model would be eligable.

I have a friend who is currently flying a Aeromatic prop on his Great Lakes replica with a Ranger enging which he used primarily for aerobatics. He likes it.

If I had a dampend crank, I'd be looking for one.

[GAHorn]

Doug, that is not the correct lineage of the C-145 engines. Check the differences of these engines under the post I made about it earlier this year. (The -2H did not become the O-300-B).

[zero.one.victor]

There might be a little confusion going on here. Some people refer to a "dampened crank" as one which has the balancing counterweights. These engines have a D in the serial number.The very early C-145's did not have the counterweights,the later ones all did.
A "dampered crank" is one which can be used with a hydraulically-controlled prop. This would be the crank used on the C-145-2H and the O-300B engines.
According to the TCDS,item 4 "propeller--Koppers Aeromatic",: "... C145-2H engine with dampered crankshaft are required when this propeller is installed". The only thing is,the Aeromatic is NOT a hydraulically controlled propeller,to the best of my knowledge it is controlled by adjustable counterweights, air density and propeller speed(centrifigal force).Requiring a C145-2H engine doesn't make sense.

Eric

[zero.one.victor]

Doug, that is not the correct lineage of the C-145 engines. Check the differences of these engines under the post I made about it earlier this year. (The -2H did not become the O-300-B).

George,the following description of the O-300B is in the front of my O-300 overhaul manual.
"The O-300B engine is identical to the O-300A except for provisions for use of a manually controlled hydraulic propeller".
Since the O-300A is pretty much the same as a C145-2,the description of the O-300B souinds like it's the same as the C145-2H to me.
What are differences?

Eric

[doug8082a]

George, I agree with Eric. I found a post from you in the MX Library regarding O-300 Differences which reads as follows:

"... The O300A is the standard engine (derived from C145-2) with improved cam/lifter materials and minor case changes. The O300B has provisions for a hydraulic prop. (Uses a remote gov.) The O300C is identical to an O300A except for a 6-bolt prop flange on the crank. The O300D is identical to a C except for provisions for an angle-drive (so-called "key start") starter motor and a vacuum pump."

From what I'm reading it sounds like the C-145-2 lineage is: C-145-2 --> O-300A --> O-300C --> O-300D and, given the provision for a hydraulically controlled prop, the C-145-2H lineage is: C-145-2H --> O-300B???

I'm confused. Also, to Eric's point, since the Aeromatic is not hydraulically controlled, why the requirement for a engine with that provision and no allowance the the C-145/O-300A?

I'm going to stop now... I'm starting to go cross-eyed.

[funseventy]

I would imagine that the crank had to be hollowed out for the transmission of oil to the constant speed propeller; this would make the crank weaker. Now when you hang a heavier prop out front you have a disaster in progress. So I would imagine that crank was dampened to help eliminate vibration to extend the life of the crank to tolerable limits(TBO). The Aeromatic is heavier because of the hub, but the blades are lighter. Maybe they specified the dampened crank because the weights act as a flywheel since the prop isn't as effective for this. Who knows, my point is, that there is more to the b crank than just being able to flow oil to the prop. There must be other considerations.

I am sure you are all talking about the same clipper-man, Eric Preston. He is very experienced at getting the most performance for the dollar, and extensive experience around antiques, of which Aeromatics fit.

[GAHorn]

It sounds as if there's confusion about what makes each engine a different "dash" number.
It isn't the crank that does it. At least not all by itself.
The dampened crankshaft was an improvement to tolerate higher orders of vibration occuring with the use of later-designs accessories. One example is the 35 Amp generator. When that generator was used on the earlier (non-dampened) crankshaft it's increased load demand created higher, unacceptable vibratory stresses. That's why a dampened crankshaft is required for a 35 Amp generator installation. It's also why the dampened crank is req'd for the Aeromatic. (A prop is a very sensitive candidate for imparting unacceptable vibrations to a crank, and vice-versa, and undampened crank can impart unacceptable vibrations to a prop. There are numerous props that cannot be used on this engine as the result of unacceptable vibrations, and in fact, the Sensenich prop can have certain rpm ranges to avoid for any length of time. But back to engine diffs....)
The O-300-B has provisions for a hydraulically controlled prop. This is more than just a crank change. It includes internal passageways for oil transmission within the crankcase. None of the C-145-2 or O-300-A engines can handle a hyd. prop just because a dampened crankshaft is installed.
While the C-145-2H engine also can operate a hyd-prop, that engine did not directly lead to the O-300-B. There are numerous other internal engine parts that differ between the two engines. I can see why it might be easier to think of the -2H engine as the predecessor to the -B engine (because of the obvious prop similarities) but technically the -B is not a direct descendant, like it is of the -A (again because of the numerous other internal parts improvements.)

[doug8082a]

Aaahh... the eyes are beginning to un-cross now. Thanks George. Just one more question. Since the Aeromatic is not hydraulically controlled, why was is specifically approved for the C-145-2H but not the C-145-2? Based on that, there would seem to be precious few C170's legally capable of using that prop.

[GAHorn]

By specification, (and coincidentally) the -2H had a dampened crank and could handle the vibration levels. The -2 didn't and couldn't (with it's original specified crankshaft.) It had nothing to do with hydraulics.
There are so few Aeromatics out there in airworthy condition that this is currently a moot issue. Tarver is wishing (and it may only be a wish) to go back into production with that prop. I'll not bet on it though. And even when the Aeromatic was in production, there weren't that many people so in love with it that they kept it. There is more than just the issue of changeable pitch to consider with that prop. For one, it's blades are wood. (Think of why all-metal props became popular: Balance, thinner blades are more efficient, rot, stone-damage, ability to repair damage with a file and crocus cloth, etc.) For another, it's blades are attached to the metal hub with moveable ferrules. (Think about constant speed props and their weaknesses: Hub cracking, ferrule wear, bearing falure, need for repetitive tear-down inspections, not to mention the problems of blade retention.)
Tarver might consider recertifying that prop with composite or metal blades. (But that would be tantamount to a new model and then there'd be wt/bal issues, and none of the aircraft Type certificates would be applicable anymore, and you're not likely to get Cessna or anyone else for that matter to re-certify obsolete, no-longer-in-production aircraft for a new propeller. That means an STC will be required and Tarver's costs will skyrocket beyond recognition should that be tried.)

Even if that prop were magically on the market, it would cost between $4K and $8K by modern estimates. How many out there are willing to toss their present all-metal McCauley and spend that kind of money on a prop that will only improve their situation in 2 or 3 % of their airfield performance situations? After the new wonder-prop was available, I'd bet that I'd still live with my present prop and accept the present performance limitations in favor of the present performance compromises I've already learned to live with.

(Leave 2.5 hours of fuel off the airplane and it'll outperform a variable pitch prop conversion with regard to airfield performance and the savings will pay for a lot of fuel stops. After all, ...how many of your takeoffs are really crying for a short-field prop? If you answer "a lot", then you probably should be buying a climb prop anyway, right?)

[doug8082a]

... After the new wonder-prop was available, I'd bet that I'd still live with my present prop and accept the present performance limitations in favor of the present performance compromises I've already learned to live with.

(Leave 2.5 hours of fuel off the airplane and it'll outperform a variable pitch prop conversion with regard to airfield performance and the savings will pay for a lot of fuel stops. After all, ...how many of your takeoffs are really crying for a short-field prop? If you answer "a lot", then you probably should be buying a climb prop anyway, right?)

Or a different airplane... Right you are George. I'm not flying out of any areas that require true "short field" performance. The idea has always intrigued me (relatively "inexpensive" C/S type performance), but I'm sure I'll be staying with my existing setup (O-300A/McCauley 7653).

Thanks for clearing up the engine designation bit.

[N170BP]

(Leave 2.5 hours of fuel off the airplane and it'll outperform a variable pitch prop conversion with regard to airfield performance and the savings will pay for a lot of fuel stops. After all, ...how many of your takeoffs are really crying for a short-field prop? If you answer "a lot", then you probably should be buying a climb prop anyway, right?)

Lately? About 8 out of 10 takeoffs have me yearning for more
performance (and I already have a "climb" prop on my airplane....).

Bela P. Havasreti
'54 C-170B N170BP

[zero.one.victor]

Bela,quit riding in 180's and that yearning for more steam from your 170 will gradually go away........
(been there,done that)
Where were all you & all the other guys who missed the 170 lunch at Bremerton Sunday? Hope to see y'all at McMinnville this coming weekend.

Eric