Aeromatic props

[bagarre]

He seemed pretty confident that it wouldn't be much of an issue to get the other hub approved and gave me a few examples (337's) of Swifts with approval.

An STC would be wonderful tho.

Also, he has a chap out of country that is doing actual performance measurements on a C170.

Even still, I still haven't seen validated performance measurements between the Aeromatic and a McCauley metal prop.
(Let alone the outside storage issue)

IMO, there could be a market for a $5,000 propeller that climbs like a 51" and cruises like a 55" that had bolt on paperwork...if that was actually the case.

[Bruce Fenstermacher]

Right, no one thinks getting an approval will be difficult. But notice he isn't getting one.

[blueldr]

I bootlegged an aeromatic prop on my Stinson L-5G when I was stationed up in Alaska. It provided a nice kick in the butt for take off and seemed some better in cruise too when compared to the standard wooden fixed pitch prop.However, it had to be adjusted for operation at a given field elevation by application of large counterweight washers. Operating from a different elevation required resetting the counterweights. Not the greatest deal in mountainous country.

[GAHorn]

Wow. Very cool.

You have unlocked a mystery as to why the TCDS would require the -2H engine with the Aeromatic Propellor.

To bad they don't support it.

Yes, that was actually mentioned to us several years ago, 2002 according to the thread, ...I missed that too, but... the F200H prop has not been available for many many years.

Baggie, the problem with the Aeromatic is that: 1- it was designed to replace/improve performance upon an ordinary wooden prop, and ...2-it has laminated, wooden blades, which, ...3-are not as efficient as metal blades due to necessary thickness, and .....4-rot/deterioration. (the reason for the AD to check for engagement of the lag-screws which hold the blade to the hub. Those lag screws do not inspire confidence, if you've ever seen one.)

While the metal McCauley fixed-pitch prop is a compromise.... it's a good one....and simple to maintain. (A two-position McCauley prop was offered in the Flypaper recently if you wanted to go to the expense of converting to an "H" type engine. Dave Bengston took me for a ride in his so-equipped 170B at Benton Harbor and I believe I detected slightly better performance during takeoff/climb. That was only my impression..... but presumeably that combination had the intended benefits or it would never have reached production/approval stage. However, it was not the "kick in the butt" bluEldr describes... and doubtless the increased complexity/cost of that setup is why it was not a success and explains why it's such a rarely-found combination. (Keep in mind that even those owners with real horsepower increases (engine conversions to 180 hp and more) with constant speed props can demonstrate a literal leap off the ground.... they still can't overcome the Rule of Drag which states "Drag increases as the square of velocity".... IN other words, even with a trick-prop you will not see worthwhile increases in cruise speeds. Meanwhile you will see increases in maintenance issues.)

[Bruce Fenstermacher]

I also rode with Dave at Benton Harbor. I had the same impression as George. The two speed prop on Dave's airplane, in the very short flight demonstration we had, seemed to perform better than a fixed prop. But, at least on this occasion it was not a WOW moment.

If I had one of these props and it was airworthy I'd have to run it, along with my cross wind gear and I hope Dave can continue to do so for a long time as it seems to be the only airworthy example right now. But between finding, and maintaining the prop and then swapping out to a -2H, it's way to much.

BTW we (my partner really) have two Aeromatic Props (not airworthy at the moment) and a -2H engine in our pile of stuff. And every time I see them it lights a little fire in the back of my mind about how cool it would be to run one of them.

While it will likely never happen I think it more likely a prop company like MT would get a STC for their composite electrically controlled adjustable propellors. Not that would be cool.

[blueldr]

Almost all of the old Bellanca Cruiseairs used to be equipped with the Aeromatic prop, and I seem to remember a number of 108 series Stinsons having them too.
They had a problem with control at altitude and later came out with some sort of "cruise control" to keep the proper pitch at altitude.
The Aeromatic prop that I installed on my L-5 was an experimental, uncertified model that was made for the USAAF, which I managed to liberate from government servitude. The L-5s were being fazed out of the Air Force inventory and the prop would have gone to the salvage yard anyway.
Actually the only difference that I could determine was that it was desigined for the SAE #10
spline shaft on the Lycoming O-435-11 engine of the L-5G rather than the flange shafts of the other engines involved with it.
I suppose that had it been really worthwhile they would still be making them. They must be sort of a cult thing like Swift and Luscombe airplanes. Owners love them, but they just don't sell or they'd still be making them.

[n2582d]

Here's a picture of the F200H hub. The aluminum tube connects the top chamber to the base of the hub where it gets oil pressure. Pressurizing the line drives the prop to low pitch/high RPM.

P1010001.JPG

Aeromatic Hi-Cruise Propeller.png

When I opened up the Hi-Cruise Control cylinder I found that the spring (#13) was missing. Anybody know where I might find one? I'm also wondering about the regulator valve assy. (#31). I hope that it is not required for the C-170 with the O-300B. It seems that it would be redundant with the hydraulic control valve already on the engine. (Edit: The Hi-Cruise model uses the port on the forward left side of the engine but the "crank" valve is removed and another fitting replaces it.) Cessna wants several hundred dollars for the drawings which show the Aeromatic installation. I'll wait until I'm ready to install the prop before buying that.

[bagarre]

I thought I'd share an email thread from Kent Tarver over at aeromatic.com

(the aeromatic propeller is) Really no different from an MT or any other composite prop. Since most people choose black I would suggest using a white prop cover, not silver. That will reduce the temp of the blades considerably in direct sunlight. Moisture in the blades has never shown up as a problem because the wood is essentially protected from moisture intrusion by both the fiberglass covering as well as the wood in the shank area is treated with Nelsonite, a moisture barrier and wood preservative.

There is no documented history of wood decay in an aeromataic prop. When I first started up the prop business in 2000 there was supposed to have been a dry rot blade failure which caused me lits of loss time and money. I sent the failed blade to the world's most authority on wood, the Forest Products Laboratory, a division of the Agriculture Department, in Madison, WI. for analysis. The report came back, "This propeller blade did not fail as a result of any kind of wood decay". Obviously the failure was a prop strike. I think I mention that on my web site.

Yep, many experts on effecienty, no one with numbers however. I have all the original engineering from Koppers. The tip is thicker than metal. The only time that comes into play is when the tip speed approaches Mach .9, otherwise you can forget the argument. 74" prop turning 2800 rpm = M.8125 plus advance ration of 80mph puts the tip speec at M1. Slight loss of effecienty. Cruise rpm of 2400rpm and advance ratio of 120mph put the tip speed of the prop at M.715. Not an issue. The T-28 with the big engine operates the prop tip speed slightly over M1 at takeoff rpm.

I have efficiency curves on the Aeromatic props, they top out at about 83%. All the re-inventing of the propellers over the last 4 or 5 decades by Hartzell and McCauly has not improved on efficiency to any measurable degree. Propeller turning in the 1200 to 1400 rpm range can realize efficiencies of up to a little over 90%. The guy that designed the Piper Malibu and the Venture said that there is nothing in either of those airplanes that was not known in 1932. By the same measure there is nothing in modern propellers that was not know in 1938 and earlier, when the original patents were issued to the Everel Propeller Co. for the Aeromatic. propeller.

The H version of the F200 is not supported except for repairs. The F200 is identical in every way to the F200H except the H version has additional parts mounted on the nose of the hub and of course the control mechanism to the cockpit. The propeller can be installed on you airplane with a field approval, 337. That is if you AMI is up to speed on the regulations. One important document used to support the field approval is their document Order 8900.1. I also can send you a copy of a 337 that installed the prop on a Swift that had an STC 0-300 D engine installed. Engine was STC'd, prop was added by 337.

There are several 6 bolt patterns. Get the assembly number, I can tell if it will fit your engine.

Assuming that the prop is compatible and assuming all parts are or can be made airworthy, I can turn it around for about $3200. That includes complete OH, CAD plating of steel parts, replacing any parts that fail to pass inspection.

What is the assembly number of the prop you found? The Assy number for your C-170 4356H-1. Since I don't make the H version you will use Assy 4356-1.

A guy in Paraguay is using one on his plane and told me he really liked it. But I have had computer crash and lost all old records.

The old props were made from birch and covered with cellulose nitrate sheet. My blades are made from maple and covered with fiberglass. If you have broken screws in a blade I can't match the other one with a new blade, both blades will have to be replaced.

I think the next big question is, will the Baltimore FSDO give me approval to install one. The TCDS doesn't help much as I don't have the right motor and the propeller named isnt supported anymore.

[n2582d]

I'm still looking for "CAA Approved Supplement No. 2 to Airplane Flight Manual (pertinent to Koppers propeller installation)." This is a required sheet of paper to make the installation of the Aeromatic F200-H legal. Any leads would be much appreciated.

The TCDS says that a C-145-2H engine is required to run the prop so I was thinking that I would have to talk the local FSDO into allowing me to use my O-300B (which I have the C-170 Association's STC for). On closer inspection of the STC I now see that it allows for any propeller listed in the C-170 type certificate. Thanks Ron for including that clause. What's the chance of getting the STC amended to include the spinner for the Aeromatic propeller as the prescribed "bullet" spinner won't fit? Might want to include the skullcap spinner in any amendment too.

[GAHorn]

You'll be hard-pressed to fit a skull cap to an Aeromatic, but in any case, Bruce has been working on those amendments.