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  1. Onemorechance

    Propeller efficiency versus efficiency losses.

    When you say that a propeller has an efficiency of 51%, does it then mean that the efficiency losses with respect to the ideal propeller are 49%? My answer would be NO! Why? Because the ideal propeller will have an efficiency lower than 100%! Therefore the losses with respect to the ideal...
  2. Onemorechance

    One prop governor for two propellers

    I don't know if I can describe it in detail, but the problem is basically as follows: We have a gas turbine engine (420 shp turboshaft engine mostly used in helicopters). We want to use it in an experimental aircraft. The engine would drive 2 counter rotating constant speed propellers (probably...
  3. Onemorechance

    When dry sump oiling is preferred over wet sump systems?

    I have a splitter bevel gearbox with shaft rotation 6000 rpm and gear pitch circle rotation speeds above 30 m/s, transmitting a power of 400 HP. According to me it would be necessary to use a dry sump oiling system with jet spray lubrication to both the gears and the bearings. With such high...
  4. Onemorechance

    Representing turboshaft engine in integrated torsion vibration study

    For a preliminary study on torsion vibrations of the integrated system engine-transmission-propeller I need information on both propeller and engine. The propeller is not such a problem, I can easily find the information I need in order to model it, but that is not the case for the engine. The...
  5. Onemorechance

    Allison Model 250 C20 Turboshaft Operational range

    Hi, Any RR or Allison engineers or others that could help me with these 2 questions? 1. I know that in a MD-520 Helicopter the engine (Allison Model 250 C20 Turboshaft) is installed with engine axis under 45° compressor up, while the same engine is installed in many other helicopters and...
  6. Onemorechance

    Operating a gasturbine in different positions or attitudes

    This may be too vage of a question, but anyway. I would like to know if a gasturbine engine can be operated in any position for any length of time. For example, if I would like to use a gasturbine engine with its axis in vertical position for x time and then bring it in another position, say...
  7. Onemorechance

    Kevlar fibers in Rubber matrix?

    Hi there, I need to make a very light reservoir, the differential pressure should be 30 atmosphere, it should be very flexible and foldable when empty. I was thinking of using a combination of Kevlar tissue in a Rubber matrix . Is this a good idea? Would it be possible (instead of using Kevlar...
  8. Onemorechance

    Output Mass and Stiffness matrices from NASTRAN?

    I make a simple beam model in which only stiffness and mass properties are attributed to the beams. I would like to extract the mass and stiffness matrices for this model. How can I do this? If possible I would like to have this data available in the F06-file?
  9. Onemorechance

    Using Accelerometers for stability of aircraft.

    Can anybody prove me wrong or right when I claim the following statement: Accelerometers can be useful in measuring rotational accelerations, but it is absolutely impossible to measure translational accelerations because of the unknown direction of the gravitational field. Onemorechance

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