Prop Selection

[skippydiesel]

Hope I will get some great factual criticism to the following:

 

Based on being the propeller of choice for the listed aircraft (or just plain popular) I have narrowed my 2 blade, CS propeller selection, for my Rotax 912ULS, to the following manufacturers:

 

Alisport Idrovario as  fitted to Pioneer aircraft. Available as a 2 blade with  an electric/hydraulic system - 5.8 kg - no weight on actuation/control system .

 

MT- Propeller as fitted to Pipistral Virus SW. MTV-33-1-A. Available as a 2 blade hydraulic only. 8.7 kg. Very reputable company (Au distributer and service) and the Virus SW has class leading, third party verified, performance with this prop.

 

Woodcomp SR 3000.2W N as fitted to ( cant remember) Available as a 2 blade hydraulic & electric control systems. 8.5 kg ( + control system ? ) about E4208 plus GTR & freight. Reputable 

 

Airmaster AP420CTF-SNR70E (Sensenich) - 9.1 kg. Almost local (NZ). Not a prop maker as such. Great reputation. Lots of technical information on web page. About $11 K

[cscotthendry]

Skippy:
I don't have many facts to rely on, but here's some opinion.
My aircraft came with a Woodcomp prop. On our first major cross country, we got a largish chip in the leading edge, beyond the coverage of the metal protector strip. My concern was that having a wooden core, the core would soak up moisture from the air and change dimensionally enough to crack the composite covering. Sooo, I changed to a solid composite prop (Bolly). The Bolly is also locally made and supported which was a big factor in my choice. The other big factor was Woodcomp's policy that any repairs required returning the prop to the factory. That had the potential of almost permanently grounding the aircraft.

Having said that, I think an obvious factor would be price and weight change. If you add a kilo way out at the front of the plane, you're going to have to offset that by adding or moving some other weight.

[skippydiesel]

Thanks Cscothendry - strange!  it would seem you and I are the only forum contributors who have an interest/opinion  about CS props fitted to this class of aircraft.

 

At this early stage, many moths from making any sort of decision/commitment.

 

I favour Airmaster because of they are sort of local, have a great reputation and their "system" is easy to fit to any Rotax 912. Unfortunately it is heavy and costly.

MT is a renowned aircsrew manufacturers but doesnt make an electric CS prop for Rotax

Alisport Idrovario is an interesting hybrid

[Kyle Communications]

Ok my opinion is it is not worth the money or the extra weight for the advantage that you get from a CS unit.

 

[RFguy]

e-prop have one (CS)  in the works

 

https://aircraft.e-props.fr/glorieuse.php

 

Edited October 7, 2020 by RFguy

[kasper]

12 hours ago, cscotthendry said:

Skippy:
I don't have many facts to rely on, but here's some opinion.
My aircraft came with a Woodcomp prop. On our first major cross country, we got a largish chip in the leading edge, beyond the coverage of the metal protector strip. My concern was that having a wooden core, the core would soak up moisture from the air and change dimensionally enough to crack the composite covering. Sooo, I changed to a solid composite prop (Bolly). The Bolly is also locally made and supported which was a big factor in my choice. The other big factor was Woodcomp's policy that any repairs required returning the prop to the factory. That had the potential of almost permanently grounding the aircraft.

Having said that, I think an obvious factor would be price and weight change. If you add a kilo way out at the front of the plane, you're going to have to offset that by adding or moving some other weight.

Nice to hear about the Bolly prop - it’s one I’m considering for a home built.  
 

I assume you put the bolly on the Legend 600 your profile lists as your plane - interested to fine how receptive the manufacture was to your request to change the prop and how easy/hard it was paperwork wise with Raaus and CASA. 

[skippydiesel]

2 hours ago, Kyle Communications said:

Ok my opinion is it is not worth the money or the extra weight for the advantage that you get from a CS unit.

 

Kyle Kyle - this is not about bagging a propeller system its about reviewing what is available in the CS market . The arguments for/against CS props is well known (certainly by me) I do not deny the purely factual argument but as I have said before  this is not a need its a want. If you have some CS experience at this end of the light aircraft world,  please give me the benefit (I still want to try an e-prop before committing to a CS)

[Kyle Communications]

My comment was not based on anything to do with Eprop or anything else other than on a 600kg aircraft the extra weight and W&B effects of a CS unit on a light weight aircraft. I know quite a few guys that are running them and the issues they have had with them as well. No I have never flown with one in a RAA aircraft but I have in GA. That is a different kettle of fish with aircraft weight and penetration and so is flying a much heavier aircraft. So yes I cant comment on my experience in a RAA with a CS but being a facts and figures sort of guy...1 and 1 does usually make 2.

 

[cscotthendry]

Kasper:
I wrote to Aeropilot and they sent me a letter of approval for the prop change. I'm not sure what other paperwork I'll need to do when I go to sell the aircraft. The local dealer made an arrangement with Aeropilot after I fitted my Bolly, to list those props as an official “option” here in Oz.

The Bolly people were brilliant to deal with. They asked me a series of questions and that led to a reccomendation. They shipped the prop, hub and spinner very quickly.

I purchased the reccomended prop and then set it up. It took a couple of gos to get the right pitch for our aircraft, but that's pretty normal.

[skippydiesel]

15 hours ago, cscotthendry said:

Kasper:
I wrote to Aeropilot and they sent me a letter of approval for the prop change. I'm not sure what other paperwork I'll need to do when I go to sell the aircraft. The local dealer made an arrangement with Aeropilot after I fitted my Bolly, to list those props as an official “option” here in Oz.

The Bolly people were brilliant to deal with. They asked me a series of questions and that led to a reccomendation. They shipped the prop, hub and spinner very quickly.

I purchased the reccomended prop and then set it up. It took a couple of gos to get the right pitch for our aircraft, but that's pretty normal.

 

Just checked out the Bolly web page - as I thought,  no mention of a CS prop (which is the primary focus of this conversation). I am fairly sure that they had one under development for many years and  that  Robin Austin used a prototype Bolly CS in his record breaking Rotax 912 ULS Sonerai VH-SGS - economy cruise 165 knots - record breaking 238 knots over a 500 kilometre course. With this sort of third party endorsement, I wonder why they did not put the prop into production.

[kasper]

Skippy,

 

Sorry for the thread drift away from CS props - I of course am considering a Bolly fixed pitch for the my home built - its not even conceivable to consider a CS for a flex wing cruising at 80knts esp. as the cost of any CS is more than I invested in the whole airframe, instrument and second hand rotax engine!

 

Cheers.

Edited October 8, 2020 by kasper

[Kyle Communications]

Bolly have been working on a CS for a long time..recent discussions (maybe 6 months ago) with them about a manually controlled one with them was that they only want to make the electronic controlled version...well they cant find anyone to get it done apparently so a mate tells me after talking to them 2 weeks ago. There is a video on youtube about it I will see if I can find it

 

[Kyle Communications]

When I spoke to them they were not interested in producing the mechanical vernier version which I think is a better way to go anyway...fine for TO and then set what you want for cruise...nice and simple and no motors or electronics to burn out which is a common thing with all of these CS units. This video is 6 years ago..one would think they may have it done by now. They could have been selling the manual one straight away

 

 

 

 

 

[skippydiesel]

5 hours ago, kasper said:

Skippy,

 

Sorry for the thread drift away from CS props - I of course am considering a Bolly fixed pitch for the my home built - its not even conceivable to consider a CS for a flex wing cruising at 80knts esp. as the cost of any CS is more than I invested in the whole airframe, instrument and second hand rotax engine!

 

Cheers.

Don't be sorry - this forum is all about sharing ideas/knowledge/experience - I am impressed with the cost (lack of) your aircraft AND you reminded me of Bolly's success in breaking a few world records

[skippydiesel]

17 hours ago, Kyle Communications said:

When I spoke to them they were not interested in producing the mechanical vernier version which I think is a better way to go anyway...fine for TO and then set what you want for cruise...nice and simple and no motors or electronics to burn out which is a common thing with all of these CS units. This video is 6 years ago..one would think they may have it done by now. They could have been selling the manual one straight away

 

 

 

 

I think I saw this display at NATFLY Temora ? Seems like eons ago. Sounded/looked to be on the very brink of production. I wonder why it has not progressed to public availability

 

[jetboy]

I cant add any crtique for the 4 CS props you have narrowed choice to,

 

for my VP project the powerplant was set up for Airmaster but I wouldnt need a full CS system just inflight pitch change and with 90 SHP to run I think the lower power version of IVOprop would do fine

 

https://ivoprop.com/

 

They have been around for ages and despite them looking like the blades are about to peel off the 2 attach bolts at any moment i've seen no trouble with them. Probably not as efficient as the other types because of the flat taper, the cost and weight is low.

 

 

[skippydiesel]

1 hour ago, jetboy said:

I cant add any crtique for the 4 CS props you have narrowed choice to,

 

for my VP project the powerplant was set up for Airmaster but I wouldnt need a full CS system just inflight pitch change and with 90 SHP to run I think the lower power version of IVOprop would do fine

 

https://ivoprop.com/

 

They have been around for ages and despite them looking like the blades are about to peel off the 2 attach bolts at any moment i've seen no trouble with them. Probably not as efficient as the other types because of the flat taper, the cost and weight is low.

 

 

Thanks for the suggestion Jetboy - checked out the web site. Veeery interesting. Unique approach - a twisting/warpable blade - first impression: a bit scary! So different from all (most) others who follow the convention of rotating the entire blade rather than changing the aerofoil itself.

Certainly follows the KISS principal but as you say may give up some efficiency in doing so.

I wonder a bit about the adjusting/torsion rods fatigue life. Its one thing to use it as a ground adjust but to use the sam system for inflight (regular/constant) adjustment could be a concern.

[kasper]

1 hour ago, skippydiesel said:

Thanks for the suggestion Jetboy - checked out the web site. Veeery interesting. Unique approach - a twisting/warpable blade - first impression: a bit scary! So different from all (most) others who follow the convention of rotating the entire blade rather than changing the aerofoil itself.

Certainly follows the KISS principal but as you say may give up some efficiency in doing so.

I wonder a bit about the adjusting/torsion rods fatigue life. Its one thing to use it as a ground adjust but to use the sam system for inflight (regular/constant) adjustment could be a concern.

Never found the torque rods to be a problem.  My issue with the prop - and the reason I changed it out for a fixed pitch - was it really didn’t seem to do much to the performance. There was not enough difference between fine and course and it just didn’t add enough performance.  

[skippydiesel]

1 hour ago, kasper said:

Never found the torque rods to be a problem.  My issue with the prop - and the reason I changed it out for a fixed pitch - was it really didn’t seem to do much to the performance. There was not enough difference between fine and course and it just didn’t add enough performance.  

This is the sort of feedback I like to see - real life experience & sound logic.

 

Unfortunately I seem to have posed a question(s) that strangely few are interested in or alternatively have no experience in (doesnt usually stop people from commenting). I say strange because most pilots are looking for that little something that may enhance their aircrafts performance and a CS prop will do that. The cost benefit is questionable in most instances but their is no doubt that a CS prop will give you the best combination of TO/Climb/Cruise.

[skippydiesel]

 

Comparison of Fixed and CS propellers corrected.pdf

Okay this may get some interest/conversation going:

 

Its going to be quite a few months befor I must make a decision, but that's a positive, as it gives me time to discuss the matter with you(s) and digest all the feed back (ha!?)

 

At this early stage I favour Airmaster:

 

"Airmaster AP420CTF-SNR70E (Sensenich) - 9.1 kg. Almost local (NZ). Not a prop maker as such. Great reputation. Lots of technical information on web page."  About $12 K (delivered)

 

HOWEVER Airmaster are recommending the "AP332S fitted with blades WWR68W ( or possibly 70w) by Whirlwind". This is their standard/generic Rotax 912 offering. It is a more complicated airscrew and is 2.1 kg heavier than the AP420CTF. Strangely with an extra blade & mechanism it is only slightly more expensive than my choice.

 

Airmaster have referred me to the attached informal propeller testing/comparison test: 

 

From this test, using a Tecnam P 92 (sharing the same engine type but otherwise a very different aircraft, in almost every way to the ATEC Zephyr)  you will see that the AP420CT appears to perform as well as the AP332S with the possible exception being noise generation. The noise issue may be  significant in a sheet metal aircraft but is unlikely to be so in a composite one.

 

I look forward to an avalanche of comments/advise

[facthunter]

A wooden prop is not the ultimate fixed pitch available. Of course all the others would be an improvement on it .Nev

[skippydiesel]

This attached article on CS prop use on Foxbat is, in my mind, a very balanced article:

https://foxbatpilot.com/tag/constant-speed-propeller/

[Thruster88]

22 minutes ago, skippydiesel said:

This attached article on CS prop use on Foxbat is, in my mind, a very balanced article:

https://foxbatpilot.com/tag/constant-speed-propeller/

As per the fox bat article and looking at the 912uls performance curve you will "pick up a bit", maybe 4kw for takeoff and almost nothing for high cruise with a constant speed. If you really need that extra 6 horsepower to operate at a strip it is still going to be marginal.  

[facthunter]

Yes the article is quite reasonable.  It concentrates on getting the max horsepower from the engine by the prop making the engines revs available. (like lower gears in a gearbox).  One point should be made in all of this is even a CS prop blade is a compromise as it's blades twist cannot suit  a wide range of RPMS efficiently,  wheras a properly "tailored" fixed pitch for a particular  speed. CAN  IF this is done for your cruise  speed it will out perform any CS at that speed as well as being lighter and cheaper and more reliable..  Nev

[skippydiesel]

Thanks Thruster - I have been "operating" from my paddock/strip for about 11 years now. Every TO/Landing is "short field" and  just a bit nerve wracking. 

 

With full fuel & just me (always), TO role is under 100 m, climb out 1500 ft/min, from  a 1100 ft ASL grass strip, with my ground adjustable prop adjusted for what I call advantage TO/Climb (not fully optimised).  This is pretty good by most standards but of course my cruise speed 100-110 knots, 5000-5200 rpm 13-14 L/h is compromised. By how much????  

 

Well it has been suggested to me that if I was in a position to optimise my ground adjustable prop for cruise I might be able to achieve a max cruise  (5400 rpm) of 125 knots plus, so an economy cruise of 115-120 knots possibly ??????

 

My existing Fiti prop is no more (accident) so must be replaced. I have a few months to make the decision -

 

Go with the  2 blade Fiti Eco  ground adjust, I know so well and have a high regard for OR replace with something else of unknown benefit (CS) that may give a more flexible performance???

 

Decisions Decisions - all help gratefully received.