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Dobson Convertiplane Prototype 11

119 Sleet01  4.3 years ago
Auto Credit Based on Sleet01's Dobson Convertiplane Prototype 7

Updated version of proof-of-concept Dobson Convertiplane:

  • More accurate wing size
  • More accurate weight
  • Reduced bizarre fuel consumption issue via engine power multiplier hack
  • Closer to prototype ship's color scheme.

!Landed on the USS Tiny

Spotlights

General Characteristics

  • Predecessor Dobson Convertiplane Prototype 7
  • Created On Windows
  • Wingspan 16.7ft (5.1m)
  • Length 21.3ft (6.5m)
  • Height 9.0ft (2.8m)
  • Empty Weight 947lbs (429kg)
  • Loaded Weight 1,124lbs (510kg)

Performance

  • Power/Weight Ratio 139.908
  • Wing Loading 9.8lbs/ft2 (47.9kg/m2)
  • Wing Area 114.5ft2 (10.6m2)
  • Drag Points 2484

Parts

  • Number of Parts 68
  • Control Surfaces 3
  • Performance Cost 407
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    45.9k 50CalChicken

    @Sleet01 yes, now that I look, it does!

    4.3 years ago
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    119 Sleet01

    @50CalChicken It's good of you to say, especially since it looks like an upside-down AMC Pacer :)

    4.3 years ago
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    45.9k 50CalChicken

    Cool.

    +1 4.3 years ago
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    119 Sleet01

    This was a real aircraft! Or, at least, my attempt at representing one. A group of us on Reddit's r/weirdwings have been trying to track down details and information about whether it ever flew; see this thread for more info.

    Details:

    The little delta, which may fly this year or early in 1954, will be a two-place job powered with twin McCulloch 4318 target engines developing 70 h.p. each. It will incorporate a coaxial propellor-rotor mounted in a nose shaft that will swing from vertical position -- for vertical helicopter take-off -- to a horizontal position for airplane flight altitudes.

    The twin rotors each have three blades mounted rigidly, with unusual -- and secret -- gearing to permit the shaft to swing from vertical to horizontal and return.
    ...
    Performance estimated by Dobson, who formerly was chief of the Helicopter Division of Aeronautical Products, Inc., is:

    max. speed, emergency power, 187 m.p.h.;
    max. climb, 1950 ft./min.;
    range, 225 miles;
    min. sinking speed, power off, 21.2 ft./sec.
    The Dobson convertiplane will have a high wing of 112.5 square feet area, a useful load of 440 pounds including two persons and 20 gallons of fuel; a gross weight of 1100 pounds, and a rotor diameter of 16 feet. Control surfaces will comprise two vertical fin-rudders at the wing tips, each with a skid on the underside.

    This version has:
    - Working elevons,
    - Cyclic input is suppressed above 150kph for smoother flying in aircraft mode.
    - While hovering, rudder uses differential torque to rotate the correct direction (but the rotation sticks, so you have to manually counteract it).
    - Camera is oriented for horizontal flight, while the cockpit is oriented for landing (if you are brave).

    4.3 years ago
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    119 Sleet01

    Take-off procedure 1:
    1. Use Trim to rotate prop-rotors to point perpendicular to the ground. The hinge is too strong so do this slowly!
    2. Set throttle to 100%.
    3. Use VTOL to slowly increase collective until the nose just begins to lift up; drop VTOL by one click once this starts.
    4. Smoothly raise Trim lever to ~95%; this will lift the nose further due to torque.
    5. If the ship is generally upright, the shaft is generally perpendicular to the ground, and the plane is mostly stable: increase VTOL to 90% ~ 95% and take off. If not, you will probably crash and burn immediately.
    6. Smoothly nose down to horizontal flight. Cyclic inputs to the prop-rotors phase out at 150kph.
    7. Throttle down to ~50%. Trim Pitch using the Trim lever: lower is nose-up, higher is nose-down. Manage velocity using VTOL lever: less is slower, more is faster.

    Take-off procedure 2:
    1. Use Trim to rotate prop-rotors to nearly horizontal. Avoid letting the rotor tips touch the ground!
    2. Throttle up to 100%.
    3. Increase collective to ~95% using the VTOL lever.
    4. Once in the air, immediately increase Trim to ~95%.
    5. Follow steps 6, 7 as per procedure 1.

    Landing procedure:
    1. Approach landing point in horizontal flight; get to within about a kilometer at about 500 meters altitude (less with experience).
    2. Decrease engine throttle to ~33%. Decrease VTOL to about 25%.
    3. Extend landing gear.
    4. Set Trim to about 90% (decreased thrust will change the Cg / Ct balance so try to find a stable point)
    5. Pitch up to about 60-70 degrees on the Attitude Indicator ball. You will rise quickly while bleeding off airspeed; decrease VTOL to lower VSI until you begin sinking towards your landing area.
    6. To speed up, pitch down; to slow down, pitch up. I find it easiest to land from the orbit view, but it is possible to land from the cockpit view.
    7. Try to maintain a positive forward speed and negative VSI using cyclic, rudder, and VTOL controls only.
    8. When the rear skids touch down, decrease VTOL slightly until the nose starts to drop slightly.
    9. Smoothly reduce Trim to 0 and VTOL to 0.
    10. Reduce throttle to 0%.

    4.3 years ago
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    119 Sleet01

    Issues:
    1. Too much VTOL will lead to blade stall while maneuvering. Do not exceed 95% VTOL in horizontal flight.
    2. Adding VTOL and Trim too fast during takeoff will cause the ship to flip on its back and explode.
    3. Power-out landings are tricky because the rotor has a tendency to over-speed and explode, which somehow changes the Cg enough to make gliding landings impossible. Good luck.

    4.3 years ago