New pics on Eggenfellner site

[rv6ejguy]

The current crop of electric C/S props have relatively slow transit times so they are not suited for aerobatics but are entirely workable for the flying most of us do. It would not be too hard to change motor rpm or gear ratios within the hub to speed up response time.

Slip rings are on all heated props and are well proven in many other electric props. There are advantages to each design. It just does not make sense to add the complexity of a drive design to use a prop system not suited to the engine/ drive package. I don't see Eggenfellner changing their designs any time soon to appease the people looking in from the outside. Current users seem happy with the electric solution. What hydraulic prop would you then use? There are only two lightweight designs available and they cost about the same as an MT.

Rotax also offers a cool manual prop setup as used on some CT Design aircraft. Really simple, reliable, light and cheap. You leave full throttle on and just adjust rpm/ power with the prop control.

[gmcjetpilot]

Electric props have been around a long long time, on air transports from the 30's and 40's and even on GA planes like early Beech Bonanzas.

The most infamous was the Curtiss C-46 "Commando". An electric motor was used to alter the angle of the prop blades. With a little corrosion, the electric contact could be lost, resulting in the prop moving into fine pitch and the engine over speeding. This was particularly serious on take off from high altitude fields. They got a bad reputation, needless to say. Today, the FAA will not allow Curtiss Electric props on anything. The C-46 was called the widow maker for the props. Now today's electric props on your RV are not going to be as critical, but on a twin, one engine at full thrust and one at idle at a critical phase of flight could get ugly fast.

The 1940's Beech electric prop had good service, but of course electric props went away in favor of Hydraulic for a reason.

I would disagree that today's electric props are near or on even par with hydraulic ones or super reliable. You use an electric prop because you have to.

Hydraulic props are better in almost every way, especially maintenance, cost and response time (ie RPM control). The same electric prop problems of yesterday, still exist today to some extent. Wires, slip rings, small motors spinning in a hub, all have some challenges operating a prop on planes.

The twins I flew freight years ago had HOT PROPS. The heat elements and slip rings and where always doing weird things. The mechanics cursed them. We flew in known icing and had to have them working. The hot props worked, but it was another thing to go wrong.

Hydraulics, once set up are pretty bullet proof if you don't have a hose leak, but it is a possibility. Lycs had aluminum gov lines and fittings up till the late 80's. There where a few aluminum tube gov line failures, that caused engine failure due to loss of oil, so the FAA let an AD fly, replacing all lines with flex lines or stainless steel lines / steel fittings. After 30 years they decided the aluminum tube and fittings where not good enough. I had to replace two of them on my old twin. It was a pain and about $300-$400 in parts.

It was not the ridged aluminum pipe or fittings fault as much as mechanics who did not reinstall them with the proper clamps and supports. Fatigue took over and cracks happened. Nothing is perfect. Everything has pros and cons.

Bottom line electric props are a compromise, but its also a needed compromise with most auto engine conversion. It's all about compromises. There is no need to deny the limits, they are there and probably always will be with electric props. Aerobatics is not the Selling point for Elec props, nor is the wires and controllers. Also electric props COST more...... So the money you save on your alternative engine will be partly or completely eaten by the prop.

[rv6ejguy]

Naw, don't buy it. I've seen and heard of quite a number of problems with aluminum, hydraulic props over the years, even check this forum. Leaks, cracks, governor problems . Hot props not a big issue on PA31s or E90s in my experience. Gotta have them anyway for these aircraft unless you want alcohol. In any case, very high amps required for a hot prop compared to running a DC motor to turn the blade angle. Todays DC motors are way more reliable than what we had even 20 years ago. Slip rings are used on many types of equipment with excellent reliability at surface speeds equal to or in excess of those found on aircraft propeller systems.

One of the high time canard MT electric flyers has 2600 hours on his I think now. One set of brushes at 1400 hours, no other problems to date. The Avio/ Quinti props used initially by Eggenfellner gave good, reliable service by most accounts as well.

A great number of US WW2 transport, bomber and US fighters had electric props, both Curtiss and Hamilton Standard. We are talking hundreds of thousands of props here. Post war, many American transports used electric props. They worked just fine or they wouldn't have used them in these numbers.

Most of the latest US military aircraft have dumped hydraulic control surface actuation now for electric gear. Lighter more reliable. Electric gear is starting to replace hydraulic steering gear on upper end autos like BMW as well. Lots of progress on this front in the last decade or so.

BTW I could have used a hydraulic prop with my combo. More weight, similar cost, more to go wrong. Didn't make sense. Doesn't make sense for most auto engine conversions for the same reasons.

Makes sense for a Lyco but that's not what this thread is about.

[cjensen]

I agree with you Ross. There is no need to spend development money to replace something that is giving fine service. The costs are close, with the electric being a little higher.

There was a guy in here a few weeks ago with an old V-tail, and still had the elcetric prop on it. He said he would never change it. Works flawlessly.

The slip rings for the hot prop on our King Air have been trouble free for years. We have more problems with the governers than anything.

The electric props are slower to respond, but people that want them, are not buying them to do aerobatics...hence the auto conversion. Well, they could be switched off to resemble a fixed pitch prop for a loop or roll here and there. Don't see why that wouldn't work...

Point is, if electric props were so problematic, there WOULD be a push to replace them with hydraulics. They aren't, and there is no need for a provision.

[osxuser]

Wow, didn't mean to spark another controversy, but here are a few things:

First, George, close on the Curtiss Electrics, but I know some Grumman Albatross' that still fly with them.

I've worked as an A&P for a few years now, and I am one of the ones that curse the slip ring/brushes system. It may work fine, but I don't want it on something CRITICAL like pitch change. Reliable, yes, but no where NEAR as infailable as the Hydraulic system. Hot props don't run as much as pitch change mechanism would.

Numbers wise, you might see as much problems with hydraulic CS setups, but percentage wise, I promise there at at least 4x the number of Hyd CS here than Elect. CS. I just don't like the setup from my experience, on the maintence side. And I don't like how they fly, as mentioned before.

That has been the reason for me eliminating the Egg from my list of possibilities. Still considering a Chevy V6 or maybe rotary... Of course, Lyc is leading my list still.

[Rotary10-RV]

I believe the reason most of the aftermarket PSRU makers don't use Hyd control is different than what everyone is saying. Most of the units are stand-alone sumps. At least Eggenfellner's is. To run a PSRU that uses rolling element bearings AND a plain bearings is costly and complex. Plain bearings want high pressure/low flow and rolling element bearings want low pressure/high flow so most of the manufacturers just don't bother. Lycs and Conti's use a bypass hole on a plain bearing to pass the high pressure oil to work the prop. Mistral's unit is beautifully made, and costly, but since they are really trying for certification they really need that option. Marcotte makes a long shaft version of their unit using a separate pump and tank, but I 'll bet they haven't sold many. The best unit for conversion would be Tracy Crooks since he uses a plain bearing on the prop shaft, but he hasn't done it so far. Tracy also uses a common sump with return lines so his would be ideal. I can't think of any of the makers that says hard core aerobatics is OK, most simply aren't set up for it.

Bill Jepson