Prop Selection

[409tonner]

I posted this back in may when you asked the same question.

 I have run this cs unit for the last five years and couldn’t be happier with it. See below again!
I run an airmaster with warp drive blades on my 912uls Sting and the performance is exceptional. In take off mode the engine revs to 5700 rpm and the acceleration pushes you back into the seat . I switch it to climb mode 5500rpm about 100 ft off the ground and put the flaps away as it will quickly accelerate through max flap speed 77knts and climb out solo at 80knts at 1300 -1500 ftpm depending on the day And fully loaded it will climb out at 1000 + and temps stay in the green . In the cruise mode 5000 rpm at 24in manifold pressure I get about 115ktas at 15-16l hr and at 26in I get about 125 ktas at 18lhr I plan on 115knts and 18lhr. It is also very good slowing down the aircraft when I put it back to climb mode when I am setting up for landing on down wind . I have also had the misfortune of using the feather mode when I had an engine failure due to oil pump drive pin breaking and locked the engine during my BFR of all things we were 5 miles to the SW of the airport at 2500 agl and made it back to airport with ease . Passed my BFR ? and rotaxs do break. It is also very easy to service . Hope this helps again.

[skippydiesel]

Great to hear from you 409tonner - Sorry but I have no clear recollection of your previous reply (will try & find it).

 

At any rate, a first class answear, full of relevant information, addressing the manufactures credibility (great), the type of prop used (also great)

 

Are you using the disk type slip ring or the mini?

 

Have you ever considered another Airmaster prop or another manufacturer & their prop? If so perhaps you would tell why you didn't go in that direction?

 

 

[skippydiesel]

33 minutes ago, 409tonner said:

I posted this back in may when you asked the same question.

 I have run this cs unit for the last five years and couldn’t be happier with it. See below again!
I run an airmaster with warp drive blades on my 912uls Sting and the performance is exceptional. In take off mode the engine revs to 5700 rpm and the acceleration pushes you back into the seat . I switch it to climb mode 5500rpm about 100 ft off the ground and put the flaps away as it will quickly accelerate through max flap speed 77knts and climb out solo at 80knts at 1300 -1500 ftpm depending on the day And fully loaded it will climb out at 1000 + and temps stay in the green . In the cruise mode 5000 rpm at 24in manifold pressure I get about 115ktas at 15-16l hr and at 26in I get about 125 ktas at 18lhr I plan on 115knts and 18lhr. It is also very good slowing down the aircraft when I put it back to climb mode when I am setting up for landing on down wind . I have also had the misfortune of using the feather mode when I had an engine failure due to oil pump drive pin breaking and locked the engine during my BFR of all things we were 5 miles to the SW of the airport at 2500 agl and made it back to airport with ease . Passed my BFR ? and rotaxs do break. It is also very easy to service . Hope this helps again.

 

Found your, again very comprehensive,  response in May - my question at that time related to a single aircraft & propeller system, a Europa fitted with an Airmaster CS 3 blade Warp Drive, that I came very near to purchasing - only pulling out  at the disappointed in TIF, last minute.

 

Did the Airmaster come with the aircraft or have you "optioned up"?

 

My current question spreads the net far wider - I am interested in obtaining the best information I can regarding a number of CS/IFA propeller suppliers and the performance of their propellers, with a view to making a purchase sometime in the next 3-6 months (if aircraft rebuild goes to plan).

 

If you read my erlier comments - I would consider Airmaster using a 2 blade Sensenich prop (AP420CTF-SNR70E) to be the leading contender (at this time).

[409tonner]

Mine runs the disk it uses alternator type brushes and I have never had to replace them and still plenty of length left. The prop was fitted by the previous owner just before I bought the aircraft off him as the woodcomp had time expired and no longer a dealer in Australia. The airmaster was purchased second hand with low hours and actually came off a tecnam which was going to be used for training and converted back to fixed pitch for simplicity so it wasn’t even specced for the Sting . I never few the aircraft with woodcomp In flight adjustable but previous owner reckoned the airmaster was much better. He got approval off TL ultralights to fit the prop.

Everyone that flys with me is impressed by the performance over a fixed pitch.

Hope this helps  with your decision . I don’t think you would be disappointed with the performance increase for the extra money spent.

[skippydiesel]

1 hour ago, 409tonner said:

Mine runs the disk it uses alternator type brushes and I have never had to replace them and still plenty of length left. The prop was fitted by the previous owner just before I bought the aircraft off him as the woodcomp had time expired and no longer a dealer in Australia. The airmaster was purchased second hand with low hours and actually came off a tecnam which was going to be used for training and converted back to fixed pitch for simplicity so it wasn’t even specced for the Sting . I never few the aircraft with woodcomp In flight adjustable but previous owner reckoned the airmaster was much better. He got approval off TL ultralights to fit the prop.

Everyone that flys with me is impressed by the performance over a fixed pitch.

Hope this helps  with your decision . I don’t think you would be disappointed with the performance increase for the extra money spent.

Better & better.

 

Now that you have broken the damn, I hope there will be a flood of correspondents in a similar vein - thanks again

[facthunter]

There may be a flood of damned correspondents and I hope it's not all in vain... Nev

[skippydiesel]

Hi Nev - With all your experience,  I would have thought you might have an opinion on potential CS propeller suppliers and their props.

 

In addition to those already mentioned  - have just written to Kaspar Propellers - at this , early,  stage looks like they do a range of In Flight Adjustable's, that can be adjusted by several means including a magic electronic box that may give a CS type control.

[facthunter]

It's a pretty dynamic market, changing all the time . They are costly and are not an inconsiderable weight especially when located so far forward and LESS safe than a "solid" prop... Prop failure is not a welcome event and it's not as rare as it should be.. They all need to be serviced and inspected. IF your pitch setting goes too fine it's not safe nor is the engine able to keep you in  the air..  I'm not anti C/S props. Most of my piston flying has been behind them. I like retract gear too but not on everything. . Horses for courses.. Everything is a compromise... A C/S prop blade has twist in it that only right for one pitch angle because all sections of the blade have a design helix with a radius and angle relationship that is MATCHED for only ONE particular pitch figure.. Nev

[old man emu]

Isn't there some performance line in the sand where a CSU is no better than a fixed pitch prop after all factors have been taken into account? Cross that line and the CSU wins. I would have thought that the factors one would look at are engine torque and airframe Vne. Then one would consider the weight trade off and the extra maintenance costs.

 

 

[RFguy]

Skippy, have you had a look to  see what  the extra weight on the front will do to you W&B CoG MAC % ?

 

Nev- good point about the optimal (and likely)  pitch angle where I guess best efficiency is (cruise?).  Nev - do take a look at what E props are doing- everyone else's blades just look like me-too, but the Eprop blades look like a new development direction for props.

----

 

for a J170C, the extra 8kg on the front would be quite welcome. (since there is 4kg ballast there usually, and the extra weight will assist bringing the usable loads more into the desirable  range at MTOW) .  (putting aside a J170C would be best off with the 3300...).

 

 

 

 

[dlegg]

Airmaster and rotax are a good match. Sling aircraft seem to use them exclusively with good results, never hear of Airmaster problems. There is a Europa with 912 and Airmaster prop on my field, this thing cruises at 145kts and stalls around 39...very slippery aircraft. You are very likely to gain your 125kt cruise that you are after, with good takeoff performance. I would use them as local to our area with a good reputation. Might be costly but cheap and unknown is not the place to get a cs prop from.

[facthunter]

Higher revs make the blades want to be driven to finer pitch (Centrifugal turning moment) Some flexible blades can use that principle I suppose and if it works it, works.. Doesn't need a complex hub taking great centrifugal loads in bearings and needing large diameters to be strong enough to keep the blades attached to the hub. The prop blades will also have natural harmonic frequencies that can be destructive. The CTM means you need a strong mechanism to drive it into Coarse and feather it . Electric (heavy motor and gears) and Hydraulic (usually engine oil which can't be counted on always and does sludge up in the dome). Direct via linkage can "hunt" if there's any appreciable looseness in the linkage and if it disconnects your prop will go to the finest pitch it can move to. Nev. .

Edited October 25, 2020 by facthunter
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[Yenn]

Skippy. I sympathise with you, even after explaining what you want, none of us has given an answer. You will just have to live with it. I have C/S endorsement, but haven't used one for years although I did fly an RV10 as a passenger and found it really great to use. My experience with suppliers is that they are very hard to track down and get answers from.

[facthunter]

Much advertising will make comparisons with a fairly "ordinary" prop.. Wood is generally 10%less efficient although a very safe material in practice and easier on the engine if a contact with something solid happens. Nev

[skippydiesel]

2 minutes ago, Yenn said:

Skippy. I sympathise with you, even after explaining what you want, none of us has given an answer. You will just have to live with it. I have C/S endorsement, but haven't used one for years although I did fly an RV10 as a passenger and found it really great to use. My experience with suppliers is that they are very hard to track down and get answers from.

 Hi Yenn - thanks for the sympathy. I guess I thought there would be a whole lot of CS/IFA drivers of  600 kg aircraft out there - but may be not.

 

So far your observation on suppliers & their product(s) is correct. I am passing on, to the Thread,  the recommendations as they come in but so far nothing has come with anything much in the way of a justification ((all a bit "snake oil")

[skippydiesel]

Hi Nev -

 

Would you have some thaughts on:

 

Why are hydraulic CS props so much lighter than electric?

 

With the exception of Kaspar, all of the CS props I have looked at seem to locate the pitch control mechanism in the hub. I can understand this for solid propeller shaft systems but not for the hollow Rotax. Kaspar seem to have the idea - locate the actuating (hydraulic/manual) system on the top of the engine, change pitch by way of a rod, through hollow shaft, acting on a cam arrangement in the hub, which changes blade angle/pitch - your take?

 

How would you compare the efficacy (I understand the mechanical differences); a manual IFA pitch change,  with a CS type system ? (Kaspar offers both)

[facthunter]

The Rotax is especially suited for a direct through the shaft actuator. operating through linkages and essentially push pull. I've  examined them installed, and probably flown at least one.  Enough to know they work ok. and only possible in a practical sense with the Rotax gear box set up or something similar on some other R Drive

   I've commented on pitch locks and their function but NEVER got any response or questions which does concern me somewhat. It's obvious that not all U/L people will need to know  about  issues as they won't be involved. 

  Re the IFA  I don't believe the governed set up is necessary. Incrementing the PITCH of the prop up and down is enough for most operations. and an engine changing it's power won't be masked. Airspeed changes give RPM changes as one is used to..

 In a hydraulic prop most of the parts can be of light alloy. It's only a (largish) piston, a spring   and two short link rods.

  The electric has slip rings brush holders a motor and extensive reduction gears to others on the end of each Blade. The common (larger ) ones are Hamilton Standard Hydromatic and Curtis- Wright Electric. There would be plenty of information on those on line. If you want pitch control complexity, auto corsening and pitch locks look up the Prop s on the C  130 Alison engines. A runaway prop on those is a real big deal. Prop failures are worse than just engine failures Nev

[skippydiesel]

I have a small electric  linear move, for want of a better word, ram - seems a perfect concept for the pitch actuating device.

 

If that doesnt do the job , how about an electric step motor, doing the same thing. To my untutored mind  far lighter & simpler than what is currently on offer in the electric pitch adjustment market.

[facthunter]

You only need a lever. Anything extra is just something else to fail. There's no great force involved. Nev

[old man emu]

17 hours ago, skippydiesel said:

how about an electric step motor,

But with that you will need a stepper driver for precise movement. Not a weighty thing, but something more to erode MTOW and to require maintenance.

 

Remember KISS, and not the mob made for lovin' you.

[skippydiesel]

2 hours ago, old man emu said:

But with that you will need a stepper driver for precise movement. Not a weighty thing, but something more to erode MTOW and to require maintenance.

 

Remember KISS, and not the mob made for lovin' you.

I hear you but have sort of fallen in love (become irrational) with the idea of a CS/IFA. So in a few months when aircraft rebuild complete I will be taking what I have learned from this conversation, combining that with my limited GA CS experience and purchasing a CS/IFA prop.

 

As for my question on CS/IFA systems - seems to be that there is a tendency to overcomplicate (particularly for Rotax 9 engine applications). Hence my observation that off the shelf linear actuators are available and if that isn't the go, a step/stepper motor, coupled to a "jack" screw, located on top of the crankcase & driving through the hollow prop shaft to came in the hub, seems like a fairly simple way of moving the blades.

 

I appreciate Nev's comment about a lever  however  electrical wires are much easier to "pass" through a firewall then levers or cables. I note that Kasper offer a "Borden Cable" or lever or electric variously direct acting or through a hydraulic system.

 

So far I have found only a very small number of CS/IFA pop makers.

Have asked all to give me a costed recommendation, delivered to NSW.

Sent a detailed description of my aircraft, its performance as is and aimed for improvements

I have expressed a preference for a 2 blade prop but have made a point of not ruling out a 3 blade (if that's what they strongly recommend)

Asked all to give me the rational behind their recommendation (seems to be a big ask)

[facthunter]

IF you value safety, and reliability, you wouldn't consider electric actuation in this application. it's wasted money and heavier and fails if you have an electrical problem. It goes straight over the top of the engine in the centre from the dash.  Simple as and a pitch lever is intuitive with throttle and mixture (if fitted)  and carb heat. You could notch or graduate it to use proven adjustments or ranges like Take off range and cruise range. Nev

[Kyle Communications]

Ye I am certainly more partial to the mechanical lever one for sure. Simpler and much less to go wrong..and of course MUCH cheaper

 

 

[skippydiesel]

21 minutes ago, facthunter said:

IF you value safety, and reliability, you wouldn't consider electric actuation in this application. it's wasted money and heavier and fails if you have an electrical problem. It goes straight over the top of the engine in the centre from the dash.  Simple as and a pitch lever is intuitive with throttle and mixture (if fitted)  and carb heat. You could notch or graduate it to use proven adjustments or ranges like Take off range and cruise range. Nev

 

17 minutes ago, Kyle Communications said:

Ye I am certainly more partial to the mechanical lever one for sure. Simpler and much less to go wrong..and of course MUCH cheaper

 

 

 

 

You both have my attention.

 

I would point out that  all of the CS/IFA manufacturers supplying the LSA market (that I have been able to find so far) offer electric control. Airmaster offers only electric and have built an enviable reputation doing so. Most of the others offer hydraulic and electric (MT-Propeller), at least one offers electric over hydraulic (Alisport Idrovario) and Kaspar offers Bowden, linkage, hydraulic and if I understand correctly, electric versions of the Bowden & hydraulic.

 

It has been suggested to me that Airmasters mini slip ring system can take the maintenance/reliability, of at least this part, to 800 hrs plus - not too shabby!

 

So the demand would appear to be there for electric - seems that attraction of relativly easy installation and the allure of CS is defying your logic.

[facthunter]

CS is a different matter where you need something doing the work of a governor. You asked about IFA.   That's why I replied.. .. Nev