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Thread: MT - Propeller for Sierra's

  1. #1

    MT - Propeller for Sierra's

    Sierra owners,

    As some of you know, we are interested doing a STC for a MT-Propeller installation on the Sierra. According to the local FSDO (Scottsdale, Az), there is no field approval for this type of modification. Therefore, a one time STC or a full blown STC will be necessary. I am in contact with MT-propellers and they are willing to support us on this project. If there is enough interest, we would be willing to do the full STC for the Sierra and provide the STC and MT-propellers to BAC members at a 10% discount. It is still uncertain if the propeller they suggested would be suitable for our use. The options were 2 different 3 bladed and one 2 bladed prop of diameters of 72 to 74 inch. There are still some questions that need to be addressed and the FAA is holding those answers at the moment. But, if there is enough Sierra owners that will commit to buying the MT-Propeller, we will proceed.

    The suggested propeller/spinner combos will save 17-18 lbs off the nose. There will be no yellow arc on the tach and take-off/climb should improve significantly with the 3 bladed prop. There are no ADs on these props, in-fact MT-Propellers hasn't a listing in the FAAs AD file under appliances. I think cruise will increase some with the 2 bladed prop due to the more efficient blade design, but MT-Propellers doesn't think the 3 bladed prop will provide any cruise speed increase. Flight testing will tell. These propellers retail around $8500 (3 bladed) with another $1K for the composite spinner. I'm not sure what the total delivered price price for the prop will be to a member, but I think it would be something under $9000, except for Alaska, Hawaii and outside the USA. So if you have serious interest in getting this prop, let me know and we will decide on how to proceed. Also, let me know if you are interested in the 3 bladed or 2 bladed prop (~ $700 less)

    Thanks in advance for your input.

    Marty Vanover
    Phoenix, Az.

  2. #2

    MT - Propeller for Sierra's

    >As some of you know, we are interested doing a STC for a MT-Propeller
    >installation on the Sierra.

    The Grumman community went through this about 5 years ago. No C/S prop was
    available to fit the Tiger. Solid crankshaft like the Sundowner (same
    O-360-A4K engine), and no provision for an oil controlled prop.

    MT to the rescue. They got the 3 blade electric prop approved in Germany
    under the European JAR standards, and then used that data to convince the FAA.

    The exchange rate became unfavorable, and the prop was never bought in the
    US, except for one owner of a New Tiger (2002). To this day, there is one
    in Germany, and one in Oklahoma, and that is it. Seems the MT folks were a
    little upset that the Grumman owners didn't buy when the price went up.

    It was $12,000 plus installation.

    >The suggested propeller/spinner combos will save 17-18 lbs off the nose.

    The MT is lighter than the oil controlled Hartzells, of this there is no
    doubt. It is also a quiet, smooth prop with a different sound than you are
    used to if you fly behind a metal prop.

    >These propellers retail around $8500 (3 bladed) with another $1K for the
    >composite spinner. I'm not sure what the total delivered price price for
    >the prop will be to a member, but I think it would be something under
    >$9000, except for Alaska, Hawaii and outside the USA.

    Are you comparing the Experimental version for your pricing? The Certified
    version for the Grumman was vastly more (about twice what a Hartzell HC
    prop could be bought on the street for -- $6000).

    Another issue was that they limited the engine RPM to 2500 instead of 2700
    to meet JAR noise standards in Europe. You can manually override the
    electric controller to get 2700 out of it for take-off, but you don't get
    the Constant Speed function in the override mode, so you have to control
    the engine RPM manually. Not a problem at altitude, but it can be a
    handful on T/O as the engine is spinning past redline and you have
    rotation, gear and flaps to deal with.

    Bob Steward, A&P IA
    Birmingham, AL

  3. #3

    MT - Propeller for Sierra's

    Bob,

    What you say is true. I was interested in getting a Tiger before deciding on the Sierra. I new we would need a C/S or controllable pitch prop for our normally high density altitudes. When I found the MT-Prop STC for the Tiger, I was really stoked. Then I found out the cost.

    The first quote I got from from MT-Prop for the three bladed prop was: MTV-12-B/183-59b for USD 8,330, Composite Spinner USD 1,050. Shipping will be about USD 350 and assembly another USD 350.

    This hydraulic prop has already been certified on the -A1B6 engine at 2700 for TO and max continuous power on the Australian Vulcan P68 Observer 2 (see attached photo) The FAA type certificate number for the MTV-12 is P25NE. They quoted 45 lbs inclusive of the spinner for weight (my equipment list shows 58.1 lbs for my Hartzell prop and 4 lbs for the spinner assy). The diameter is 72 inches (183cm).

    I would prefer the 74 inch (188 cm) three blade MTV-12-B188-53b prop for our application, but haven't had a response to my inquiry on that blade. The last I heard it was only JAA certified on the TSO-360-C1A6D on the P68C.

    Nope not cheap. But, I'd pay a premium to get some T/O & climb performance. The 17.1 lbs weight savings combined with 6.2 lbs for a light weight starter and 4.5 lbs for a light weight alternator just about solves the forward CG issue for the Sierra AND provides 27.8 lbs of more cabin load. Hey, that's a extra small suite case right where it does the most good!

    Marty Vanover
    Phoenix, Az.

  4. #4
    I would be interested in the MT prop and I have looked into the feasability of field approval. If someone is going to go through the project in a reasonable time I would sign on to buy one. But if I wind up buying a new Hartzel prop this fall I seriously doubt I would buy another prop when the MT becomes available.
    Is this a project being considered by BAC with costs/ risks and savings shared? Or is MT interested in selling directly once approval is done? Or a private shop/individual taking this on? All are good, just want to know where we are heading. I think this would be a great use of BAC resources and with an STC to sell could return it's costs in time.
    I would think that with the weight savings a 3 blade would be worth looking at. Whatever is certified in the other I360A1B6 applications would make sense to me.

  5. #5
    I am cautiously interested, but all the certified MT applications I have seen so far have been starting in the $12K range. I am looking at a new 2-blade Hartzell for around $6K, with a good trade-in (assuming I move before the offer expires near the end of this year). I could not justify doubling the cost. I will be watching for more refinement on the pricing structure, for the prop, STC, and shipping. I can do my own installation.

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