The Question LSA and CSU specifically of the Jab 230 d and Airmaster CSU.

[facthunter]

You need to set the pitch stops appropriately. A MUST, not an" I will if I get around to it." Having the best engine around won't count for anything if the prop brings it undone.  THIS should be hammered in any CSU  endorsement or installation. Nev

[walrus]

Agreed Nev, there is always the possibility of the regulator (electronic or hydraulic) failure. The regs call, I think, for the ability to climb on full coarse and the fine pitch stop gives you the same.

 

There is a lot of tosh talked about CS props but they are a trade off - performance vs.  complexity and weight. A fixed pitch prop is also a trade off. 

 

In my case I want more than usual range and a CS prop appears to be the way to et it and still keep within 600kg.

[skippydiesel]

5 hours ago, Kenlsa said:

More weight, complexity and cost.
Reduced useful load.

Followed by further cost at service intervals.

Further followed by more paths for failure.

And further followed by immediate stress selecting your out landing spot.

Ken

All true - doesnt stop me lusting after one - as I said its about want not need.

[skippydiesel]

Should I ever have the $$$$ I will purchase a CS prop for my ATEC. Therefore the question is not is this a logical sensible decision but what CS propellers are most likely to give me the best return on my hard earned dollars.

 

Best return on $$ in this context is:

 

Most likely to give a significant performance enhancement - Reduced ground role - Increased climb out - Increased speed for fuel consumed OR  reduced fuel consumption for same cruise speed. Suggestions/Recommendations welcome ?

Minimal increase in maintenance requirement. There will be some increase in maintenance (annual greasing/inspection, etc) but I would like to minimise this by selecting a manufactures that does not require the return of the CS prop in some ridiculously low interval (some are as low as 2 year, others 6 , some have no return policy. Comments?

Maximum reliability /safety. Reliable service history and on board system that will accommodate a CS partial/total failure. Comments?

Minimum weight penalty. I have noticed that, at least some, hydraulic units are very much lighter than electric ones - I dont know why this would be - any suggestions?

Minimum complexity. I fancy a two blade unit but most manufacturers are offering three. With a bit of digging some are also offering a two blade. Why the bias toward  three blades?

[Blueadventures]

Skip I personally would not bother with a CS on your aircraft.  The electric I have seen need attention to the commutator surface and brush dust deposits etc. I reckon a 3 place e-prop is the go and good while they have a return policy if not happy. Will no doubt provide improved service. I plan to get one next July. Will be superior to the Fiti prop. IMHO.

Edited October 4, 2020 by Blueadventures

[skippydiesel]

15 hours ago, Blueadventures said:

Skip I personally would not bother with a CS on your aircraft.  The electric I have seen need attention to the commutator surface and brush dust deposits etc. I reckon a 3 place e-prop is the go and good while they have a return policy if not happy. Will no doubt provide improved service. I plan to get one next July. Will be superior to the Fiti prop. IMHO.

I refer you to my previous comment: All true - doesnt stop me lusting after one - as I said its about want not need.

[skippydiesel]

Okay:

 

It has been thoroughly established and accepted by me, that the fitting of a CS prop to an RAA type aircraft is a foolish thing to do BUT I still want one and would like to have some assistance in the direction/selection of said foolish acquisition - anyone willing to provide recommendations/comments  as listed:

 

• Most likely to give a significant performance enhancement - Reduced ground role - Increased climb out - Increased speed for fuel consumed OR  reduced fuel consumption for same cruise speed. Suggestions/Recommendations welcome ?
• Minimal increase in maintenance requirement. There will be some increase in maintenance (annual greasing/inspection, etc) but I would like to minimise this by selecting a manufactures that does not require the return of the CS prop in some ridiculously low interval (some are as low as 2 year, others 6 , some have no return policy. Comments?
• Maximum reliability /safety. Reliable service history and on board system that will accommodate a CS partial/total failure. Comments?
• Minimum weight penalty. I have noticed that, at least some, hydraulic units are very much lighter than electric ones - I dont know why this would be - any suggestions?
• Minimum complexity. I fancy a two blade unit but most manufacturers are offering three. With a bit of digging some are also offering a two blade. Why the bias toward  three blades?

[walrus]

Skip, it’s not necessarily foolish. In my opinion what counts is the size of the aircraft performance envelope in terms of stalling speed to maximum cruise. Something like a C172 has a max speed of a little over twice stall (roughly 45 Vso and max 110)  However a Savannah has a much bigger envelope about three times stall (30Vso and max about 90). Then you get to RV’S etc and the range is even bigger. 

 

On U.S. aviation boards you can read endless discussions from people trying to find a suitable compromise pitch setting with their ground adjustable props. A CS prop gets rid of that problem.  Then there are all these new engines, but some of them have useless torque curves because you have to set pitch to avoid the possibility of over revving on takeoff. They advertise huge horses at high rpm, but you can’t use the power without a CS PROP.

[Kyle Communications]

Skippy...buy an Eprop then you will have similar performance with 1/5th the weight 👀

 

[facthunter]

Even a CS prop is not  perfect at varying speeds and loads. You could design a fixed pitch that was more efficient at a PARTICULAR speed and LOAD. The twist along the blade could be more tailored to the defined condition.. A CS is still a compromise and the BLADE is inevitably weaker as it's a round section where it starts, as it must rotate on it's own axis in bearings designed to take high centrifugal loads, to function. Making a 3 or more blade hub is not that difficult to design  and usually done to reduce diameter  but IS a highly loaded component that must not fail.. Props require inspections quite regularly. The more complex the more costly. Nev

[walrus]

True

[skippydiesel]

Thank you for your alternative suggestion (Kyle)  and technical comment (Nev) however it would seem that there is so much resistance to the idea of having a CS prop on an RAA class aircraft that I will not be getting any answers to the questions I posed.

[Paul davenport]

I too lust after an air master type CSU for exactly the reasons you want one Skip . Short field opps in my 230. I cannot seem to find anyone who has done this before and I am reluctant to jump to purchase one . At a recent agricultural seminar an instructor suggested that if you want to try out a new product first convince your neighbour to try it to see if it works, same principle applies here

[APenNameAndThatA]

On 28/9/2020 at 11:43 AM, SSCBD said:

FT A lot of CSU's are being fitted to RAA  LSA aircraft these days specifically with Rotax engines. My Question is why I cant see any on GEN4 engines. 

And as I stated - the performance increase Quoted by  - Airmaster Propellers CSU state that:

 

Performance tests have shown up to:

• 33% shorter ground roll

• 10% better climb than fixed pitch prop

• 20% improvement in cruise and economy

Also provided was an Endorsement Specifically  J430 which is the 4 seat VH version

 

Sohrab Ghasimi - Jabiru J430There were some significant improvements in performance as follows: 20-30% reduction in ground roll, Higher climb rate, Smoother running and an increase of cruise speed to of 15 - 20%.

PDF from Airmaster of above information.

http://www.gap.aero/pdf/airmaster/Airmaster_propeller-systems-332-420.pdf

 

 

SO if you operate in say far nth QLD and tight strips in a Jab 230 for example - and you had the money WHY NOT Have the extra performance. 

 

 

 

 

I think that if a CS prop actually gave a 33% shorter ground roll AND a 20% improvement in cruise then you would get much less argument from people. I bet the performance improvement would be nowhere near that good. I think the disconnect in the convo is that no one believes those figures.   

 

To get a 20% improvement in cruise, you need to effectively have 1.73 times more power. I the efficiency of your standard prop is 0.6, then that is not possible. IIRC, the average prop has an efficiency of 0.8. (By efficency, I mean converting engine power to prop power/work. (1.2 cubed = 1.73)

 

(As for the mighty Foxbat: revs just below yellow on takeoff and just below yellow full throttle at 8000 ft cruise!) 

[RFguy]

short field TO performance in a J230 is pretty good already I thought.

The cruise performance of the J230 prop is pretty well matched to the airframe and the engine. yep you can go fast with more throttle but efficiency wont change too much (actually falls because of high prop RPM)

 

Best suggestion I have for increasing the short field performance Paul would be to increase the number of blades . this way the blade loading is lower and they're not working as poorly in TO roll.

Wait for the direct drive E props maybe. 

But yep - fixed pitch prop - can't have it all.....

 

I reckon the most recent Gen4 is ripe for a little bit of turbocharger...not sure how you would plumb it thought.

Edited July 2, 2022 by RFguy

[Paul davenport]

Still waiting for some one to give real world figures . Actual demonstratable  real world  numbers from someone who has one on his 230 up until then is all speculation, and then ask the question would you do it again or is it not worth the cost. 

[Blueadventures]

1 hour ago, RFguy said:

short field TO performance in a J230 is pretty good already I thought.

The cruise performance of the J230 prop is pretty well matched to the airframe and the engine. yep you can go fast with more throttle but efficiency wont change too much (actually falls because of high prop RPM)

 

Best suggestion I have for increasing the short field performance Paul would be to increase the number of blades . this way the blade loading is lower and they're not working as poorly in TO roll.

Wait for the direct drive E props maybe. 

But yep - fixed pitch prop - can't have it all.....

 

I reckon the most recent Gen4 is ripe for a little bit of turbocharger...not sure how you would plumb it thought.

When E-Props have sorted a direct drive prop suitable for Jabs; I recon they will make available 1 or 2 demo props and they will promote them to purchasers if there other props are an indication of their quality and performance.

Edited July 3, 2022 by Blueadventures

[APenNameAndThatA]

2 hours ago, APenNameAndThatA said:

I think that if a CS prop actually gave a 33% shorter ground roll AND a 20% improvement in cruise then you would get much less argument from people. I bet the performance improvement would be nowhere near that good. I think the disconnect in the convo is that no one believes those figures.   

 

To get a 20% improvement in cruise, you need to effectively have 1.73 times more power. I the efficiency of your standard prop is 0.6, then that is not possible. IIRC, the average prop has an efficiency of 0.8. (By efficency, I mean converting engine power to prop power/work. (1.2 cubed = 1.73)

 

(As for the mighty Foxbat: revs just below yellow on takeoff and just below yellow full throttle at 8000 ft cruise!) 

The above only takes into account the blade efficiency. So it’s basically wrong. What you could do is compare the revs at WOT on cruise and takeoff. If the WOT RPM at takeoff is higher than at WOT RPM at cruise, you will be able to calculate the engine power difference from charts that show power at full throttle at different density altitudes and different RPM’s. From the difference in power, you will be able to calculate (speculate about) how much extra power you will have from a CS prop. 

 

Are you allowed to cruise at WOT in a 3300? (can in a Rotax). Is max RPM for takeoff same as max RPM in cruise (higher in a Rotax, which is a reason for CS props in a Rotax.)

 

Another factor is that if you move your C of G forward with the 8 kg on the nose, you will reduce your efficiency because your elevators will need to produce more downforce. I don’t know if significant. Stall speed higher, too, IIRC. Don’t know if significant. I suppose your Cof G envelope will tell you if it is too far forward.  

Edited July 3, 2022 by APenNameAndThatA

[APenNameAndThatA]

On 4/10/2020 at 3:10 PM, Blueadventures said:

Skip I personally would not bother with a CS on your aircraft.  The electric I have seen need attention to the commutator surface and brush dust deposits etc. I reckon a 3 place e-prop is the go and good while they have a return policy if not happy. Will no doubt provide improved service. I plan to get one next July. Will be superior to the Fiti prop. IMHO.

There is a guy on here who has carefully tested props and reckons that they all perform about the same. Truth — I have no clue. 

[facthunter]

Unless you crise above 120 knots you can't justify it Cost weight and added unreliability. If your pitch control mechanism fails at any point other than optimum you are worse off. IF it fails to full fine pitch you may only be able to fly near stall at full revs. It's also more likely to throw a blade than a two bladed wooden prop. Nev

[RFguy]

I'm not even sure the Jabiru engine permits it.
"A maximum moment of inertia of 0.30 kgm2 is recommended for the propeller assembly for 3300 engine variants."

Airmaster is about 0.5 - so NO.

 

and... J230 would get too nose heavy IMO with 9kg hanging off the front .

standard  : two up (150kg), and 10kg of fuel lands the MAC at 11%. limit is 10%.... lots of work for the elevator to do...

then add 9kg to the nose, that puts the MAC at 8%... .. 12kg in BAGS-B fixes it. .. now the aircraft weighs 21kg more....

 

Edited July 3, 2022 by RFguy

[Blueadventures]

36 minutes ago, APenNameAndThatA said:

There is a guy on here who has carefully tested props and reckons that they all perform about the same. Truth — I have no clue. 

Have read those test results, I respect his efforts; however I'm in disagreement as the E-Prop is giving 6 to 8 knots better WOT performance and increased speed at rpm settings and better economy from my flying seat in the Nynja.  With Pitch setting although not at best getting 108 kts and in  UK achieving 113 Kts under a strict, planned test regime.  The prop shape works the air different and I had to adjust rudder trim as soon as prop fitted and very noticeable taxi speed at idle as have to brake slightly now.  As time and some long trips are made I will be able to look back over my fuel usage figures.  At this point I am very very happy with the prop.  Have also flown the 4 blade version on a Skyranger for about 3 hours and very good also.  There is a demo one 3 blade available at times from Mark Kyle so worth a try and make your own observations.  

[Paul davenport]

And still no real world figures from a j230 owner with a CSU prop , all speculation and guess work , which maybe correct but until it’s actually confirmed speculation nonetheless 

[RFguy]

there isnt any CSU that is light enough that you can buy that you can put on a 3300 unfortunately. 

IE there is not one.  

that's why there are no real world figures. Hang out of the direct drive Eprop, see how that goes. 

the only CSU props on Jabiru airframes are on rotax engines...

 

I'm looking to get more economy rather than speed.  tidy up around the main gear ( I reckon there is 6HP in drag at 120 kts to be got there) , control surface joins , cowling exit 5HP, 0.5 HP for the strut mounted light etc. 

 

[Thruster88]

1 hour ago, Paul davenport said:

And still no real world figures from a j230 owner with a CSU prop , all speculation and guess work , which maybe correct but until it’s actually confirmed speculation nonetheless 

The performance gains mentioned in your original post are BS. There is nothing special about a j230, it is an aircraft that will cruise at 120 knots just like a current model piper archer or cessna 172. These two aircraft have always had fixed pitch props. Would they go faster with a constant speed, no because they can all ready cruise at 55%, 65% or 75% power with their fixed pitch props. They have power charts in the POH to show rpm to use at various altitudes to achieve this. Would the takeoff performance increase,  yes but only by about 5-10% based on data from aircraft that have a fixed or constant speed option propeller.

 

All aircraft fly in the same fluid and are subject to the same physical laws.

 

Flywheel retention is an issue for the jab engine, do you want to fit a different propeller that may increase the risk?

Edited July 3, 2022 by Thruster88