V-22 Osprey stabilization during takeoff.

  1. I have always been interested in the V-22 Osprey u.s. navy aircraft, it can tilt it's rotors to take off vertically.

    Now, say we have a takeoff scenario, a crewmember decides to move to the back of the craft while it is taking off, the change in weight distribution creates a pitch where the craft tilts backwards, now the aircrafts senosors, I assume an inertial measurment unit detect changes in the pitch and now what? what does the system do to stabilize the plain? obviously the two rotors cant shift to counter the pitch, so my only guess is a weight inside the plane that can be shifted on command to fix the center of gravity,

    So the question is, how does the u.s. navy v-22 osprey stabilize it's pitch during takeoff?
     
  2. jcsd
  3. phinds

    phinds 9,372
    Gold Member

    Please keep your seat belt fastened during takeoff.
     
  4. AlephZero

    AlephZero 7,298
    Science Advisor
    Homework Helper

    and also make sure the cargo can't move around, otherwise this happens.
    https://www.youtube.com/watch?v=uIjO0sKBDDw
     
    Last edited: Jan 2, 2014
  5. Seatbelt fastening, that makes sense but what about changing payload distributance(changing center of mass), unless the center of mass is exactly under the axis of the rotors, the force from the rotors should theoretically create torque with the gravitational force, creating spin(pitch) that would make the plain crash,

    Now unless the crewmembers form with the plane a center off mass intersecting the axis of the rotors, the plain should theoretically crash every time.

    I made a spotty picture but I think you should get my point, without stabilization, torque is created

    somehow they managed to avoid this, maybe there is torque but too insignificant to create any substantial pitch.

    In the picture the center of mass is a bit behind the rotors, this can be imagined as a fat passenger sitting in the back.
     
    Last edited by a moderator: Jan 2, 2014
  6. forgot pic
     

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  7. AlephZero

    AlephZero 7,298
    Science Advisor
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    The center of mass is below the position of the rotors. This makes any helicopter stable to a certain extent when hovering, because the body acts like a pendulum hanging the rotor(s).

    Of course if you move the CM horizontally, the plane will "tilt" a small amount and tend to start flying horizontally in some direction instead of hovering above a fixed point on the ground. But making small corrections for that is no worse than compensating for effects of variable wind speed and direction.

    But I don't know if you would want to try flying a V22 like this:
    https://www.youtube.com/watch?v=08K_aEajzNA
     
    Last edited: Jan 2, 2014
  8. berkeman

    Staff: Mentor

    That chopper pilot is having way too much fun! :biggrin:
     
  9. AlephZero

    AlephZero 7,298
    Science Advisor
    Homework Helper

    Hmm ... the problem with that sort of flying is that you might not get to learn from your mistake. Note: mistake, singular. You probably don't live long enough make more than one.
     
  10. Bobbywhy

    Bobbywhy 1,908
    Gold Member

    Here is a description of a radio-controlled (RC) model of the V-22 which is authorized by Bell-Boeing. I assume that means this model mimics the real aircraft, specifically the 3-axis gyro stabilization system:

    Bell Boeing V-22 Osprey ROTORMAST - Scale KIT
    Stability
    Three Gyros are used to stabilize pitch, roll and yaw, the gyro signals are fed from the gyros into the controller and are applied to the appropriate servos depending on the nacelle angles, The gyro operate in all flight modes but their gains are adjusted by the Rotormast V-22 controller as the ship performs a conversion. For this reason the gain setting is not controlled by the transmitter as in a conventional model helicopter and the gain switch on the transmitter is only used to swap between the hold and rate mode on the ground. For rock solid stability only uses high quality MEMS HH gyros with remotely adjustable gain.
    http://www.skyrush.eu/en/Tiltrotor-Aircraft/Bell-Boeing-V-22-Osprey-ROTORMAST-Scale-KIT
     
  11. AlephZero

    AlephZero 7,298
    Science Advisor
    Homework Helper

    This is getting way too complicated - which might explain why the development program cost more than 10 times the initial estimate.

    A "real helicopter" can do a stable back-flip around the tail rotor from hover, without any of that stuff. (The first one is at about 1 minute into the video, and another later on)

    https://www.youtube.com/watch?v=LhB6tX9TT7w
     
  12. Bobbywhy

    Bobbywhy 1,908
    Gold Member

    The V-22 Osprey was not intended to be like “a real helicopter”. The US Marine Corps and Air Force have already successfully deployed the multi-mission Osprey in combat with good success. Future expected users include USN, Israel, Japan, and United Arab Emirates. Our Navy plans to phase out those “real helicopters” used in anti-submarine warfare with the Osprey. New generation dipping sonar systems are larger and weigh more, approaching limits of most helicopters. Also, longer on-station time and faster multiple dip cycle times are possible while tracking submarines can be accomplished with the Osprey’s high-speed ability.

    This from Wiki:
    “It is a multi-mission tilt rotor aircraft that can take off and land vertically (VTOL) and a short takeoff and landing (STOL) capability. It is designed to combine the functionality of a conventional helicopter with the long-range, high-speed cruise performance of a turboprop aircraft.”
    http://en.wikipedia.org/wiki/Bell_Boeing_V-22_Osprey
     
  13. Like with a helicopter, the individual blades of the rotors can pitch about their long-axis.

    [​IMG]

    Electronics use sensor information from accelerometers and navigation to control this in relation to the intended actions of the pilot and to adjust for movement in the center of mass.

    [​IMG]

    This gives a lot of control both during take-off and landing, and during transition to forwards flight.
     
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