Recent content by Jean Claude

  1. Jean Claude

    Gyro Warning System

    John, There is a slight asymmetry between the left crosswind and the right crosswind: The non-uniformity of the induced speed produces a transversal flapping angle and, in case of divergence, the impacts against the flapping stop will not occur exactly at the back point, (relative to the...
  2. Jean Claude

    Imagine. Too much HP.

    it seems to me you are forgetting two points: 1) it takes a bit of time for the rpm to change with rotor load, due to the rotational inertia of the blades: 3 to 5 s are needed to close 2/3 of the gap with the steady Rrpm. 2) The rotor load during the vertical climb of a loop is far from zero...
  3. Jean Claude

    Rolling drag of aircraft wheels on a grass runway

    Title: The rolling friction of several airplane wheels and tires and the effects of rolling friction on take-off Author: J. W. Wetmore NACA report n° 583 naca-report-583 - Abbott Aerospace Canada Ltd Comment: Interesting measurements of the variations of rolling coefficient according to the...
  4. Jean Claude

    Rolling drag of aircraft wheels on a grass runway

    Title: The rolling friction of several airplane wheels and tires and the effects of rolling friction on take-off Author: J. W. Wetmore NACA report n° 583...
  5. Jean Claude

    Imagine. Too much HP.

    In this situation, you can still increase the number of blades and so you will have more thrust with more power input
  6. Jean Claude

    Some thoughts on cross wind takeoffs.

    Mike, The thrust curves obtained by JavaProp are accurate, even if the plane shape of the blades is a little different. But we must at least enter the aerodynamic pitch at 3/4R, which is difficult to exactly measure
  7. Jean Claude

    Imagine. Too much HP.

    Yes, but this video shows 18 seconds of run before the T.O. The maximum thrust of 145 Hp is clearly not used in this phase.
  8. Jean Claude

    Imagine. Too much HP.

    More power can always give more thrust. For that it is enough to increase the pitch of the blades (to take into account the additional of induced speed), and their surface (not to reach their stall) But there are unfortunate side effects: - An excessive acceleration of the takeoff run may...
  9. Jean Claude

    Some thoughts on cross wind takeoffs.

    Mike, Don't worry. It's not the wear of your engine. It's just that the fit of propellers to engines is rarely perfect and I not know how it is unperfect. So, a shorter chord will require a larger pitch setting, which will result in less static thrust. Their thrusts, however, can be just as good...
  10. Jean Claude

    Some thoughts on cross wind takeoffs.

    It is a pity that the manufacturers do not specify in their flight manual the takeoff procedure in case of a downhill runway (just the new recommended pre-launch rrpm, depending on the slope)
  11. Jean Claude

    Some thoughts on cross wind takeoffs.

    As I said, extrapolating too far can be dangerous. Thus 115 hp already gives almost too much forward acceleration with the nominal pre-launch of 220 rpm Increasing it further by a downhill slope of the runway, reduces the distance only a little, because the autorotative torque not improves in...
  12. Jean Claude

    Some thoughts on cross wind takeoffs.

    Where do you get this distance from? Is this an actual measurement on your sloped runway? The shortened take-off distances due to the downhill runway, or to the headwind, or to a more energetic pre-launch, or to a stronger prop. thrust may possibly be equal, but the margins for the flapping...
  13. Jean Claude

    Some thoughts on cross wind takeoffs.

    Yes, 105 -(6.8* 10.3*Cos(45)) = 56 m
  14. Jean Claude

    Some thoughts on cross wind takeoffs.

    John, I calculated the takeoff run without wind for an ELA 07 S 115HP at 450 kg and a static propeller thrust of 2200 N. I get a distance of 105 meters at S-L . Then I redid this distance calculation with a 20 kts wind and I get 37 meters. So, if you want the take-off distance of this ELA at...
  15. Jean Claude

    Some thoughts on cross wind takeoffs.

    In flight, the angle of the disc can reach about 30 degrees, for which the cL of the disk is maximum, Moreover, the thrust of the propeller comprises then a component of lift which relieves as much the rotor. Hence the possibility of a very slow flight, if the propeller thrust is sufficient to...
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