Electric Controllable Props

[Avtech]

Hi , bit of an interest of mine, 1950 B35 Bonanza with a Flottorp electric controllable prop. The prop pitch was driven by a small electric motor mounted on the engine, thru a squash plate and rods. The control was by up/dn switch and constant speeding by a radio type valve driven electric controller mounted below the instrument panel (quite large) it was superseded on later models by the Hartzell hydraulic prop, simpler and reliable for the time. A little research and the Mooney Mite M18 came to light with a identical setup but manual. You simply turn a knob to change pitch. With the advent of reliable powerful DC motors and modern electronics, I believe these concepts have a lot of potential for propeller control on LSA aircraft.

[skippydiesel]

I think you will find many examples for light aircraft applications.

 

When I looked into this a few years back for my Rotax 912 ULS I was surprised at the weight of some of these offerings and that most used a slip ring system on the prop hub plate (or similar) rather than something going through the hollow prop shaft.

[Kyle Communications]

Airmaster is a very popular one..it adds about 12kg to the nose though

[Thruster88]

Variable pitch or constant speed versus fixed pitch.

 

For low hp, slow, low flying aircraft the advantage is small. When the Piper Cherokee six was launched with its 260hp engine a fixed prop was standard, cs optional. This is the performance difference

 

Empty weight. FP 765kg CS 777kg

Cruise speed 75% power FP 139knots CS 139knots

Rate of climb at S/L FP 760fpm CS 850fpm

Take off to 50 feet FP 415m CS 378m

 

The Cessna 172, the worlds most produced general aviation aircraft retains a fixed prop to this day, there was a higher hp CS model the R172k but they only sold in small numbers probably because the extra cost to buy and maintain did not outweigh the small performance gain.

[M61A1]

Airmaster is a very popular one..it adds about 12kg to the nose though

I have had some experience with the Airmaster on a friend’s aircraft. It’s simple to operate, very effective and adds considerably to the performance. I’d love one, but I can’t justify the price.

[Flightrite]

Ground adjustable is another choice for some airframes, find the sweet spot?All props are a trade off really.

[Avtech]

A C172, F172XP or C172RG perform nothing like a modern LSA aircraft, the knowledge attained by Beech, Mooney and Flottorp was lost. Cessna and Piper didn't evolve into much.

I believe the developments by Airmaster, Pipistrel, Risen and many others have aviation evolution back on course. My opinion is that ground adjustable prop provides simply a choice.

The auto transmission in my car has been improved over the last 40 years, firstly with hydraulics and recently with electronics. I feel that should happen with aircraft transmissions.

[skippydiesel]

Airmaster is a very popular one..it adds about 12kg to the nose though

Plus 12 KG over the nose of a small aircraft is a lot!!! There are some reputable makers that are sub 10 kg (eg MT)

[Avtech]

the 2 blade airmaster is 9kg, complex design and it feathers too.

good up to 120hp

[Kyle Communications]

Bolly were developing a inflight manual adjusting hub using the through the gearbox hole in the Rotax...I would love one of those...much lighter on the nose and basically just 2 positions if you want..takeoff pitch and cruise pitch...you could of course put it anywhere you like. But I believe they never finished it for some reason

[M61A1]

Plus 12 KG over the nose of a small aircraft is a lot!!! There are some reputable makers that are sub 10 kg (eg MT)

12 kg is the whole prop, you can subtract the weight of the fixed prop to get the difference. Having flown with one, I think the performance gains are certainly worth the weight.

[Kyle Communications]

[skippydiesel]

12 kg is the whole prop, you can subtract the weight of the fixed prop to get the difference. Having flown with one, I think the performance gains are certainly worth the weight.

 

Okay but every gram out on the distant points (nose & tail) of the fuselage makes a disproportionate difference (principal of moments) be very careful and re do your W&B measurements.

 

As far as the gain in performance - I admire you for "bucking" the conventional wisdom which strongly argues not.

Like so many statements this requires qualification - If you happen to fly in/out of nice long strips with good approach characteristics, a well" tuned" fixed prop can deliver the same cruise/top speed as in flight adjustable.

On the other hand if your home is a dodgy paddock with steep approach/departures, your prop better be set for advantage climb - your cruise will inevitably suffer.

No doubt an in-flight adjustable would give you the best of both BUT at a hefty cost penalty. When I looked into this about 5 years ago everything (worth considering) was pretty well north of $10k. Something to be pondered about, when contemplating fitting to an aircraft designed for recreation.

[skippydiesel]

Bolly were developing a inflight manual adjusting hub using the through the gearbox hole in the Rotax...I would love one of those...much lighter on the nose and basically just 2 positions if you want..takeoff pitch and cruise pitch...you could of course put it anywhere you like. But I believe they never finished it for some reason

 

I would love to find out - looked great in the video and other than the 3 blades (I prefer two) very KISS for a in flight adjustable.

[Downunder]

I like the idea of a lightweight and cheap IFA prop with a simple cable and spring arrangement.

Stops to set fine. Pull cable against spring tension to coarsen to another stop at max-course.

The Bolly setup looked good. ...

[Kyle Communications]

Heard back from Peter at Bolly about their IFA. They have a couple out there being tested now on aircraft. Only electronic control version at the moment. I would like to see the manual version. He says also it wont be cheap...will have to wait and see I suppose. I know a lot of people with IFA and all have had issues with the electric motor. One local guy here has had 3 of the motors..they burn out. I think its a european one as its on a Bristell. Heard of a few skymasters that have had issues too. Electric adjustable its hard to find a lightweight strong brushless motor that can take the bashing they get. This is why most GA stuff is hydraulic. Far less to go wrong with a manual version..its a vernier cable..much more reliable

[facthunter]

I think the vernier cable only goes to the governer. You need a bit of force to hold and move prop blades in flight. That's probably why the electric motors are short lived. they get overloaded. When engine oil is used if you lose it you can't feather the prop, which is critical on a multi.. Large stuff has an (electric) feather pump and it's own extra oil reservoir Curtis _(Wright) Electric props are on some of the biggest piston engines ever built..

With extra weight and cost unless you are cruising above say 125 knots you can't justify one. Nev

[kgwilson]

In flight adjustable just isn't worth the cost and weight penalty let alone another thing to go wrong in a light aircraft. I do like the Bolly ground adjustable pitch 2 blade prop I have though. It took me about 4 adjustments to get it right for good climb performance with excellent cruise. If I ended up landing at a short strip and I had concerns about taking off again, I only need a couple of 7/16 spanners & philips screwdriver to adjust it fine to improve takeoff & then I can easily reset it when I get home.

[Paul davenport]

I think Hugh’s Aircraft had a VP prop it fitted through hollow shaft on gearbox and had a vernier cable to adjust. Anyone know how it went

[facthunter]

The Rotax 912 is good in that respect. (hollow final drive shaft). There are aerodynamic turning forces and centrifugal ones acting on a rotating prop. They act in opposite ways so some fine tuning in the design and the forces might be manageable with light loads on the actuating mechanism. Nev

[Sam the Swiss]

How about a DUC propeller, variable, light (but of course not cheap)?

[Kyle Communications]

Yes looked at them today... I like that carbon hub but the price nah....out of the ballpark here..thats why Airmaster currently has the market here on IFA

[mkennard]

Does anyone know how they do it in the Tecnam Twin? I haven't looked at the manual. I can only afford to fly it in a sim.

[Thruster88]

Does anyone know how they do it in the Tecnam Twin? I haven't looked at the manual. I can only afford to fly it in a sim.

 

Certified MT Propeller, hydraulic control. A twin is not the place for dinky electric stuff.

[skippydiesel]

Certified MT Propeller, hydraulic control. A twin is not the place for dinky electric stuff.

 

Back when I looked into IFA props it was the MT that stood out for me.

 

I learned a lot from this bit of reserch - After purchase price there are two on going cost areas to take into account:

 

Time to overall/inspection - propeller manufactures vary greatly in this area from about 2 years to 6 years plus.

 

Local service agent - MT have a service agency in Bankstown (Sydney) so local for me. Not great if you have to send the prop back to Europe or USA for service /repair