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Jabiru Variable Pitch and C.S. Props

Discussion in 'Engines and Props' started by ROM, Nov 1, 2007.

  1. ROM

    ROM Guest

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    The discussion so far has been on fitting adjustable and inflight variable pitch props to Rotax engines.
    Has anybody fitted the Sensenich 2 blade ground adjustable prop or any other type of ground adjustable prop to a Jab 3300 engine or an inflight variable or constant speed prop to the same engine?
    If so what prop type and what were your experiences, the results and your thoughts on doing this?
    And what are the drawbacks and points to watch?
    We are keen to get experiences and opinions here as we are glider towing with a J230 and need to get the maximum out of a limited engine power.
    i believe that the Canadians and British Jabiru owners are throwing away the Jab props and installing the Italian GT props for better performance.
    We will also need to get any prop changes through Jabiru's system as it is a certified aircraft.
  2. facthunter

    facthunter Well-Known Member

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    certified prop.

    ROM, with regard to your last point, I don't like your chances. A wooden prop avoids the harmonics (vibration ) problem that can cause sudden blade failure, from vibration within the prop.(like a tuning fork which has a natural frequency) It is not caused by out of balance forces that can be felt externally, so you are not aware of them. Nev....
  3. ROM

    ROM Guest

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    Yes, I am very aware of the cyclic and harmonic frequencies that arise from direct drive engines and that wood props can handle these.
    As an example, the Italian GT fixed, VP and CS props are all wooden bladed props so they probably don't have the harmonic susceptibilities that the composite props do.
    There are also other manufacturers with wood cored and composite covered blades on their VP and CS props.
    There are a stack of propeller makers out there and in the usual manner of all things ultralight, there will be a few makers whose products are tested, tried and completely acceptable.
    The rest could be anything from excellent to, politely put, very suspect!
    Unfortunately, as I discovered when I first started to explore the buying of an ultralight /LSA for our gliding club, the ultra light movement runs on a fairly heady mix of myth and rumour.
    If you want the nuggets of truth out there you really have to go digging with that proverbial, very large back hoe.
    So, I am digging for those nuggets, this time on the subject of propellers.
    I hope and would really appreciate it if some of the very knowledgable participants in this forum can supply me with those propeller information nuggets.
  4. Captain

    Captain "THE RAT"

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    ROM

    Good post and it's a very interesting issue since the loose flywheel bolt issue was sheeted back, to some degree in some cases, to prop types.

    I too have been watching the OS J websites and forums on this subject and look forward to seeing the replies that are posted here.

    BrentC triggered a reasonable exchange on this issue when he went to a carbon fibre 3 blade a short while ago. Did you see those?

    Regards Geoff
  5. ROM

    ROM Guest

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    Yes, I had a look at those posts Geoff and was very interested in the experiences that a few people have had with these props on the Jab engines.
    Our real problem, club wise is that we have to conform with Jabiru's certification requirements but if the info can be put together then there could be a good case for some changes to Jabiru's certfied aircraft propeller configurations.
    Cheers. Max
  6. High Plains Drifter

    High Plains Drifter Guest

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    Rom, What are the difficultys of getting a CAR 35 "one off" approval. HPD
  7. ROM

    ROM Guest

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    Haven't even thought of that yet! The thought of the paper work makes me shudder.
    Besides, we still have to find the prop make and type that is fully compatible with the Jab 3300 engine, will be very reliable, perform as advertised, has good back up, has a long TBO, is easily maintained, is easily repaired, and has no long term deleterious effects on the engine or airframe.
    There's a prop maker and prop out there somewhere that will do all of this on a Jab motor.
    The problem is to find it.
    This is where you guys come in!
  8. High Plains Drifter

    High Plains Drifter Guest

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    ROM, The British or Canadian Jabiru owners may have gotten the GT approved in some way. That may simplifie the CAR 35's approval if needed. Their helpfull chaps and I find are always more than happy to take a quik phone call.
  9. Flyer40

    Flyer40 Member

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    Hey ROM, I don't know anything about this subject and I don't know how helpful this is, but I noticed Lightning advertise the following prop options for use with the Jab 3300.

    Sensenich W58Fk-64
    Sensenich W64ZK-51
    Sensenich WC56FJ-56
    Sensenich Carbon Fibre Ground Adjustable
  10. facthunter

    facthunter Well-Known Member

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    Possibilities.

    Sensenich have been around for ever. Carbon fibre may be less of a problem than metal which is the most critical. You can end up with a prohibited RPM, even in an approved engine/prop combination.. Nev...
  11. High Plains Drifter

    High Plains Drifter Guest

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    I imagine tow plane operations would have a prop constantly working in a load and rev range that is not normaly imposed on it. HPD
  12. facthunter

    facthunter Well-Known Member

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    Harmonics.

    It's usually a small rev range that is prohibited. There can be more than 1 ,generally, only with big stuff. The POH will state them . AVOID operating the engine in the range(s) specified.. This relates to the propeller properties, (stiffness & mass distribution) and how it is affected by the pulses originating in the engine. They don't have to be direct drive always either. Whilst this information is not provided in general to RAAus type aircraft, the principles apply to all. There's a bit on the Hartzell site. Personally I wouldn't like to be a propeller builder. Nev...
  13. ROM

    ROM Guest

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    Glider towing usually is a full throttle operation but the towing airspeeds of around 70kts and engine revs are about the same as any normal full throttle climb out speed that would be typical for the type of aircraft normally used in towing.
    The time period for full throttle operation to the normal release height of 2000 feet AGL using say a low powered tug [ "low powered" compared to a say a Pawnee tug! ] is around the 6 to 7 minutes with a total tow time, ground to ground of around 9 to 10 minutes for a 2 seat glider.
  14. facthunter

    facthunter Well-Known Member

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    Glider towing.

    A fixed pitch sensenich with finer pitch and a bit more blade area (dia with CF) might be the go as your speed range is minimal, and if you got it right you would not need to vary the pitch after that. Still have to get max. revs though. They say it's easy to end up with a lot of nice unsuitable props on your shelf. Good luck Nev..
  15. ROM

    ROM Guest

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    Yeh! A lot of nice unsuitable props, that's what worries us and that is the reason for this thread. We also have training and long distance flying as well as the glider towing so whichever prop, it has to cover a big operating range.
  16. High Plains Drifter

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    At least the superceded two blade wood props make nice wall fixtures - I keep an "Arrowprop", a "Catto" and a "Henry" hanging in the lounge room.
  17. rodknee

    rodknee New Member

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  18. ROM

    ROM Guest

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    Been talking with Jabiru about propellers for quite a while including today!
    The Sensenich and MT props listed there have not been cleared for certified aircraft, ie. those that are factory produced and are used for training, glider towing and etc.
  19. Ross

    Ross Member

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    Looking at the newest J230C at Narrandera recently and noticed that its Jabiru wooden propeller appears to have a leading edge insert quite different from the props on the other two J230Cs in the hanger.

    Does anyone know any more about this insert?
  20. TechMan

    TechMan Member

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    That probably because Jabiru don't want to authorise the use of other propeller brands on their aircraft.
    Being LSA, it is up to the manufacturer to authorise any modification on the aircraft. CAR35 engineers cannot be used for approval of modifications on Light Sport Aircraft.

    If you decide to say stuff it and operate the aircraft our a GT (for example) without the manufacturer's approval, then you are operating outside of the Special certificate of airworthiness and CASA undoubtedly has a whole range of penalty units that can be applied to that. Remember that the SCoA is a CASA issued document and has nothing to do with RA-Aus. If you breach the conditions of the SCoA, then you deal with CASA.

    Chris

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