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  • #31
    Originally posted by Gabriel
    Why can't the Osprey autorotate?
    Due to the design of the rotors it can't autorotate. I'm not familiar with rotorcraft aerodynamics, so I can't give an exact explanation.

    Originally posted by Gabriel
    Can it sustain stationary flight on one engine IGE and OGE?
    It can fly on one engine (and I believe is designed to have one power both, and land that way
    Originally posted by Gabriel
    If not, can it transition from stationary flight to forward flight after an engine failure, and how much altitude would be needed?
    [/QUOTE]

    You can't maintain forward flight without lift on the wings. In rotor mode, all the lift is on the rotors. There may be a way to push the nose over and get it to move forward, but I don't know how easy that would be.

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    • #32
      Originally posted by Bok269
      If you have a dual engine failure in airplane mode, you are (relatively fine). In rotor mode you can't autorotate, which could be a problem.
      I am trying to understand the mechanical/physical reason why it cant autorotate. If instability is the problem ISTM that it should be possible for the computer regulate the collective to ............ AH Does it have variable pitch propellers ?

      Can a chinook autorotate ?

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      • #33
        Originally posted by Gabriel
        Why can't the Osprey autorotate?
        Can it sustain stationary flight on one engine IGE and OGE?
        If not, can it transition from stationary flight to forward flight after an engine failure, and how much altitude would be needed?
        Do penguins have knees?

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        • #34
          Originally posted by flyboy2548m
          Do penguins have knees?
          "Penguins, in common with all birds, have a different arrangement of joints in the legs from those in mammals. However, they do have joints equivalent to our knees - the difference is that these joints are much closer to the hip than on mammals"
          Signature removed by admins.

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          • #35
            IIRC, the Osprey has undertaken a single autorotation test at altitude. While it made the transition successfully, the conclusion was that it's vertical speed was such that contact with the ground would have resulted in a very high risk of fatal injuries to the crew and passengers. The relatively small diameter of the rotors reduce the Osprey's ability to maintain a slow vertical controlled descent. I don't think they have conducted a follow-up test since, and I think the requirement for autorotation for the Osprey has been dropped.

            Apart from this, I understand that there is a concern that the Osprey would respond asymmetrically while transitioning into autorotation. If this occurred, there would be some tendency for the bird to roll with obvious resultant problems, and I don't believe the crew has ejection seats to leave the bird in the event of an emergency. Single rotor helicopters are more stable in autorotation with a single rotor approximately over the centre of mass.

            I am curious about the autorotation capabilities of CH-46's and 53's. It would seem that they might be prone to some asymmetry as well.
            Terry
            Lurking at JP since the BA 777 at Heathrow and AD lost responsiveness to the throttles.
            How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth? Sherlock Holmes

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            • #36
              Originally posted by flyboy2548m
              Do penguins have knees?
              You should ask that question in the OT forum. An Osprey thread in the Aviation Safety forum is not the appropriate place for asking about penguins and their knees. It is, however, the right place to ask about the Osprey's autorotation and single engine capabilities.

              --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
              --- Defend what you say with arguments, not by imposing your credentials ---

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              • #37
                Originally posted by Flying Bear
                If you have a point, would you care to explain what it is?
                All helicopters are affected by Vortex Ring State. The larger the helicopter the more likely it it the event will be found however it is entirely predictable and avoidable. When flying a light helicopter in a descent at slow forward speeds if you feel a sudden vibration through the cyclic, you are entering VRS however the trained pilot response is to increase forward speed and decrease collective. At worst, you abort your approach.
                Don
                Standard practice for managers around the world:
                Ready - Fire - Aim! DAMN! Missed again!

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                • #38
                  Originally posted by Quench
                  Realy? Why is that?
                  I mean what if you run out of fuel? You are saying that you cant put the nacelles into the vertical position and yank the collective at the last minute helecopter style?

                  So if you runout of fuel your dead !?
                  That sucks!
                  First you NEVER SHOULD run out of fuel!
                  However should you be dumb enough to run out of fuel, you leave the nacelles in the forward flight position and glide to a landing. The propellers / rotor's will be sacrificed but you and the aircraft will live to fly another day. The aircraft has many options available for emergencies.
                  Don
                  Standard practice for managers around the world:
                  Ready - Fire - Aim! DAMN! Missed again!

                  Comment


                  • #39
                    Originally posted by Quench
                    I am trying to understand the mechanical/physical reason why it cant autorotate. If instability is the problem ISTM that it should be possible for the computer regulate the collective to ............ AH Does it have variable pitch propellers ?

                    Can a chinook autorotate ?
                    You answered your own question. In the vertical mode the cyclic and collective operate the pitch change mechanisms in the rotor's. Therefore by definition in forward mode, the propellers are variable pitch.

                    In order to auto rotate, the rotors must be capable of moving to a negative pitch. I don't know that they can. The Osprey was never intended to have auto rotation capabilities.
                    Don
                    Standard practice for managers around the world:
                    Ready - Fire - Aim! DAMN! Missed again!

                    Comment


                    • #40
                      Originally posted by FireLight
                      IIRC, the Osprey has undertaken a single autorotation test at altitude. While it made the transition successfully, the conclusion was that it's vertical speed was such that contact with the ground would have resulted in a very high risk of fatal injuries to the crew and passengers. The relatively small diameter of the rotors reduce the Osprey's ability to maintain a slow vertical controlled descent. I don't think they have conducted a follow-up test since, and I think the requirement for autorotation for the Osprey has been dropped.
                      I was unaware of that test, thanks.
                      I didn't think auto rotation was ever a requirement for the Osprey. With twin engines and forward flight capability, auto rotation seems a bit redundant.

                      Apart from this, I understand that there is a concern that the Osprey would respond asymmetrically while transitioning into auto rotation. If this occurred, there would be some tendency for the bird to roll with obvious resultant problems, and I don't believe the crew has ejection seats to leave the bird in the event of an emergency. Single rotor helicopters are more stable in autorotation with a single rotor approximately over the centre of mass.

                      I am curious about the autorotation capabilities of CH-46's and 53's. It would seem that they might be prone to some asymmetry as well.
                      Tandem rotor helicopters are required to have auto rotational capability although I'm not sure if the requirement is for an undamaged aircraft or a survivable event.

                      I know The Piasecki CH21 (Flying Banana) could and did auto rotate regularly due to it's single 450 HP engine design.
                      Don
                      Standard practice for managers around the world:
                      Ready - Fire - Aim! DAMN! Missed again!

                      Comment


                      • #41
                        Originally posted by Gabriel
                        You should ask that question in the OT forum. An Osprey thread in the Aviation Safety forum is not the appropriate place for asking about penguins and their knees. It is, however, the right place to ask about the Osprey's autorotation and single engine capabilities.
                        Yeah but is a post commenting on my asking about a penguin's knees appropriate in the Aviation Safety forum?

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                        • #42
                          Originally posted by Dmmoore
                          I was unaware of that test, thanks.
                          I didn't think auto rotation was ever a requirement for the Osprey. With twin engines and forward flight capability, auto rotation seems a bit redundant.
                          anytime.

                          Agreed about the auto rotation requirement. If they loaded it up with marines and gear, it will probably make the situation worse anyways. IIRC, I think there were also some questions about the glide slope of an Osprey. (noted as being worse than a 707, although I don't know whether that's a bad thing or not.)

                          I know The Piasecki CH21 (Flying Banana) could and did auto rotate regularly due to it's single 450 HP engine design.
                          Thanks in return. Good note about the FB. It would be interesting to know how the 46/53 respond in similar situations.
                          Terry
                          Lurking at JP since the BA 777 at Heathrow and AD lost responsiveness to the throttles.
                          How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth? Sherlock Holmes

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