ARC propellers and MOSAIC.. and Hello!
 

Hi all,

My name is Jesse. I work for a small propeller manufacturer in Germany. We are currently working on bringing a new constant speed composite propeller design to the US market ahead of the upcoming MOSAIC rules changes and I thought it might be fun to open up a discussion and see what kind of questions / comments / concerns you might have.

Particularly (potentially?) interesting is the blade geometry of the new ARC propellers vs more traditional (NRC / TRC) propellers (namely: the forward- or advanced- curvature of the blade, as opposed to scimitar or straight blade types), and I would be happy to answer questions or go into detail if anyone’s interested.

We are also looking to gather feedback from pilots who’d be interested in comparing this type of propeller against their current setup in real-world flying.

So don't be shy and I will do my best to answer any questions..

Cheers!

PS.. for what kind of post is the fish icon suitable?

Welcome Helix,

Propeller discussion will be great, but within the rules of PPRuNe, no direct advertising please...

Understood- is the post ok as it is or should I change something?

The post is okay, as long as PPRuNe rules about [no] advertising are respected.

I was curious and found a little more here - https://helix-propeller.de/propeller...rc-propellers/

Not sure I'd want to abandon my Hartzell Trailblazer but a bit curious as to what ARC prop would replace it and in what respects it would be better. (Lycoming YIO-360).

I fly off short unprepared surfaces so particularly interested in static thrust and resistance to erosion and chipping.

HelixCarbon

I see a photo of a Stampe with your prop.
Interested to know how it compares to Hoffmann in a Stampe SV4 with Gypsy 10/2.

I would love a modern technology propellor on my Piper Archer but sadly I'm tied to using the Sensenich prop listed in the aircraft manual. EASA/CAA Part 21 aircraft are poorly served by current legislation. We could be saving fuel and operating our engines more efficiently.

Good luck with your venture anyway.

As you mention MOSAIC, are your props intended for S-LSA market? If so, you may want to direct your initial efforts toward the LSA manufacturers as altering these aircraft with a new prop will require authorization to perform the replacement, which currently can only come from the manufacturer. There is a sub-group of LSAs under E-LSA (experimental-LSA) in the US that do not require that authorization to install, but it is small in numbers when compared to S-LSA numbers.

From my experience approving STC'd propeller changes, I'm aware of the possible effects of "more" blade area than the propeller being replaced. In the case of an engine failure, it can noticeably change the glide characteristics of the plane. I observed this after changing from a Hartzell two blade to am MT three blade on my flying boat. The power off, fine pitch glide rate of descent went from 1100 FRM (difficult, but doable) to 1600 FPM (very difficult to land from, particularly on the water). Selecting coarse pitch upon power loss returns the glide to being 1100 FPM, and it's okay. When I flight tested the RED diesel Beaver, I found a similar high rate of descent with the windmilling propeller, other than with the the FADEC set up, I did not have a propeller control, so I could not reduce the rate of descent, other than to slow the plane to the point where the prop would stop entirely, then the glide was okay again.

This is an awareness thing, if you understand how the plane glides with the prop of your choice, and can be okay with that, that's fine. But, if I'm doing an STC to approve the prop on a type certified airplane (pre MOSAIC), I might be test flying it to assure that in the case of engine failure, the airplane will glide somewhere near what the flight manual says it will. My flying boat would have been a severe "no" in that regard after the change, other than the procedure to select coarse (which is not a flight manual procedure for that type) which made it acceptable.

Thrust is great, but you have to know how it will be if it quits too!

Are folk aware that drag is least with a non feathering prop is when the prop is stopped?

Well I was. The Trailblazer on my aircraft stays in full fine pitch at best glide speed even with the prop lever pulled to full coarse. Stopping the prop gives a significant improvement in glide ratio.

Yes, I have tested for this, and did mention it with respect to the RED diesel Beaver flight testing I had done. That principle is simply understood as to why autorotation works for a helicopter. It will descent very much faster if the rotor stops!

Hey! Sorry I am responding so late- Got caught up at work.. and now I'm on my way out for the weekend- but I will do my best to answer everyone on monday..

Hi! We work a lot with STOL aircraft but don't yet have anything endurance tested on lycoming. We are considering it if there it enough interest.. it would be more a matter of if the internal mechanics of the hub hold up to the vibrations, than anything to do with the ARC profile.. if you want to get in touch with someone more involved in the development and certification stuffs, feel free to hit us up.. ask about the H60A or H62A- one of those would probably be the one we would put on a lycoming.

Ooo- if we're both talking about the same picture- that is a fixed-pitch NRC propeller on a Kiebitz, I would have to dig around a little to find out exactly which one. The ARC's (at least- our ARC blades) really require a constant speed hub for best performance, and while that's technically possible- it may be a while before we go down that road : )

I feel your pain... especially here in Germany- you're not allowed to sneeze without first getting it certified by three different government agencies : )

JMB, Aerospool and Alpi have already begun a partial adoption of our props- they haven't put us on all of their planes yet : ) but fingers crossed. We are also pretty active with experimental aircraft.

What is your potential timeline to establish your market in the US? For example, the EASA LSAs you mention above still have restrictions on their importation into the US and it won't be until July 2026 the new Part 22 LSA certification rules are released. If your timeline is shorter than a couple of years, you may want to contact current US based LSA manufacturers so that your props can be considered before the new rules go live.

As to the amateur-built market, any new prop usually requires a return to the Phase 1 flight testing requirement. Have you started any testing with Lycoming or Continental engines which are the predominant engine in that market? If not, you may want to start that sooner than later if that is also a target market. Good luck.

We haven't done any significant testing with lycoming / conti.. we've been focused on a rotax for a long time (German UL market, for example), but lycoming at least is on the horizon for us, and we have a couple propellers that would be well suited to larger direct drive engines (including a brand new monster prop that- on paper- can handle up to 1000hp.. we'll be officially unveiling it at the AERO Friedrichshafen end of April)..

I will have to ask our engineers and the sales team about specific details, but the plan as far as I can tell is to reach individual owners first and use that as proof of concept for the manufacturers.. If we were just selling another propeller- timing might be more of an issue.. but we have seen over and over how our ARC's perform compared to competing setups, and how people react to flying with them and I am confident that they will be widely adopted- even if not immediately..

You may want to readdress that plan. The individual owners of an S-LSA in the US will not be able to install your prop on their aircraft unless the manufacturer provides the acceptable data as it is considered a major alteration. Now if the owner elects to convert their S-LSA to an E-LSA in order to install your prop then it would not need the mfgr. data, however, they may run across a different problem similar to what an amateur-built (E/AB) owner would face installing your prop. And at the E/AB level a new prop install with no engine history behind it, will probably push the aircraft major change required Phase 1 flight testing beyond the typical 5 hours and possibly out to the 25-40 hour requirement. Something to think about.

Alright- I am trying to wrap my head around everything real quick.. I do not personally handle certification so I am asking the guys here and getting an information overload.. Let me see if I can correctly regurgitate what I am being told:

We are ASTM approved (approved? certified? compliant? one of those words) for Rotax engines. As I understand it, under the new rules, a manufacturer can take a look at our data and decide that the propeller meets their airworthiness requirements, in which case no further testing is required. They may, however, as you said, wish to see performance data specific to their aircraft, in which case flight testing would have to be done. Full disclosure- I am the "marketing guy" here, and an American, and I am trying my best to understand what my very technically minded German colleagues are explaining to me (in German!), and then pass that along here.. there is bound to be something lost in translation, and for that I apologize in advance. I have also passed your question to our American partner (who has been in the aviation business for longer than I have been alive) and as soon as I hear back from him, I will hopefully have something smarter to say : )

In my certification work, I do not [yet] work with the ASTM nor MOSAIC standards. I'm not familiar with those standards, nor the standards applicable to non certified airplanes. But, I do know that physics don't change because of how the airplane has been authorized to fly. The Part 23, 33, & 35 certification standards are very well thought out, and the result of some painful and expensive lessons. If you need to "do it differently" from those standards, you really want to consider all of the implications.

While doing flight testing for propeller change STC approvals on GA airplanes, I have found a few things which were pretty important to understand, and could be an indicator of a reduction of safety, if not correctly compensated or mitigated. In my flight testing of a Bellanca Scout, I found that replacing the metal propeller with a composite propeller allowed airframe and in particular, horizontal stabilizer vibration which was worrisome. I researched this and found a report of similar observations with a composite propeller change to a Citabria in England in 1992. That could be an unsafe condition, as on those airframes, the metal propeller acted as a "harmonic balancer" for the whole airplane, and when it was taken away, undesirable vibrations were possible.

As I have mentioned, a propeller change can dramatically change the gliding characteristics of the plane. If the characteristics have been changed, this needs to be understood from results of good flight testing, so that pilots know what to expect, and how to handle the plane in the case of engine failure

Composite propellers (including wood) are generally not subject to installation limitations to engines the way metal propellers are, though having a good understanding of any vibration vulnerabilities is still important. There have been a lot of hard lessons learned, some over longer than obvious periods of time, in the realm of propeller vibration, so it's worth understanding well for the combination you propose.

In general, what word used depends on the aircraft category and whether it falls under a Standard AWC or Special AWC. For an S-LSA, it would need to be compliant to an FAA accepted ASTM standard. However, that level of compliance is determined at the aircraft level under their Letter of Compliance to the FAA.

They do that now under the current rules. My point is you stated your plan was to approach the individual owner before the manufacturers. However, without the OEMs acceptance first, the owners cannot install your prop per the old or new rules without additional requirements or authorizations.

Not quite. You are intermixing requirements between different aircraft categories. Perhaps research the different requirements between an S-LSA, and E-LSA, and an experimental amateur-built (E/AB) aircraft, or discuss this with your American partner. All have unique requirements to use your new props.

That is something that I- being woefully underqualified to make such determinations- must leave up to our engineers and test pilots.. To the best of my knowledge- we have not experienced any such issues with this particular propeller yet. We have been manufacturing propellers in multiple fields for over 30 years (EVTOL, UAV, paramotor, trikes, gyros, UL & LSA aircraft, etc..)Naturally, we do significant testing with all of our propellers. I can say that with our long history with experimental EVTOL's and UAV's, we are particularly well versed in vibration mitigation- it is a topic that comes up often when talking about vehicles that must withstand rapid changes in direction and acceleration (also worth noting that those propellers are often 2-3 meters in diameter). Long story short: I may not personally have the technical expertise to address your concerns- but this is not Helix's first rodeo.

I've got a meeting with one of our engineers and our american partner this evening. I will bring all of this up with them. I am 100% certain they are both very aware of the challenges, but if it helps me understand and give better answers, then it's worth discussing. I will be sure to update you.. probably on monday.. nope- dangit.. all these german holidays.. tuesday! I'll be back on tuesday- hopefully smarter than I am today : )

Just wanted to drop a quick update- I must once again apologize for not being the most knowledgeable when it comes to certs, etc.. but our American partner in this particular venture is Bill Canino. He is both FAA DAR, and on the ASTM committee responsible for submitting the rules proposals to the FAA. That is only to say that he is well versed and aware of what is happening and what needs to happen.

Many apologies for the delayed response- I needed to make sure it was ok with Bill before I mentioned him by name.

Then perhaps sit down with Bill and educate yourself on the requirements to install your prop on US based LSA and amateur-built aircraft. MOSAIC has the potential to reverse the decline in the Part 91 sector here plus provide an opportunity for EU based LSA centric companies like yourself to expand here as well. However, you only get one chance to make a 1st impression and some of your comments in this thread, and on other websites as I understand, may "tarnish" that impression. Regardless, best of luck with your endeavor.

You are welcome to contact Bill directly if you want to chat with him about requirements. Send him an email at [email protected]

Let me know if you'd like to test out the propeller (no promises- but maybe we can set something up), or just want to talk about our current performance test results.

No need. My comments are only suggestions specific to your marketing posts here and on other forums concerning how you plan to introduce your props to the US market. I think you are underestimating your target market and why they fly LSA or E/AB aircraft especially when you bring up “certified” installers or changes to aircraft Phase 1 requirements into the mix. While you did gain traction with your proactive marketing approach, you have created more questions than answers at this point and not all positive I’m afraid. So while I have no requirement for your props, I have heard and been questioned on them which led me to reply to you here with what I have seen and heard in other places. How you use that info is up to you. Again, best of luck.