Raptor Composite Aircraft

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Dexacare, Mar 28, 2016.

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  1. Jun 11, 2019 #661

    rv6ejguy

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    The cabin was pressure tested but didn't quite reach the design limit before popping the door seals. He addressed those but never re-tested and it was never tested to limit + 25 or 30%. Initially the windows were BONDED on the OUTSIDE of the frames but some popped the bond during post cure. Peter then decided to bolt through the structure from the outside and seal them with standard Pro-seal (not recommended for use against acrylic as it can cause crazing).
     
  2. Jun 11, 2019 #662

    Andy_RR

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    There's also what Len said and what Len actually thought.

    I think some of his criticisms (as reported by Peter) were a bit suss but fundamentally they were doing the job of polite and slightly technical things to say in order to refuse to fly the thing.
     
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  3. Jun 11, 2019 #663

    Turd Ferguson

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    That sounds like an almost comical approach to problem solving
     
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  4. Jun 11, 2019 #664

    Marc Zeitlin

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    Yeah, that occurred to me after I wrote what I wrote. Who knows what Len said that just went "whoosh"...
     
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  5. Jun 11, 2019 #665

    Marc Zeitlin

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    Which would have still been woefully inadequate. For a composite plane that's supposed to cruise at 25K ft., where an explosive decompression leaves one with a "Time of Useful Consciousness" of 1.5 - 3.5 minutes, a safety factor of 2X - 3X for pressurization would be appropriate, at least for doors and windows. Control system pass-through leaks could be less - maybe 1.5X, but there's so little weight to save there that 2X - 3X would still be recommended, just for consistency's sake during the testing.

    With the pressure at 25K ft. being about 5.45 psi, the differential is 9.25 psi, so the cabin should be tested to 18.5 - 27.75 psi. Good luck with that.
     
  6. Jun 11, 2019 #666

    akwrencher

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    So.....if the target was 60k feet, just out of curiosity, what are the pressures for that?
     
  7. Jun 11, 2019 #667

    BJC

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    The Raptor’s performance specifications list 25,000 feet as the maximum operating altitude.


    BJC
     
  8. Jun 11, 2019 #668

    akwrencher

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    Right, I guess I got my signals crossed from another current thread. Oops....
     
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  9. Jun 11, 2019 #669

    wsimpso1

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    It sure sounded to me like Len did his look-see on airplane details and said to himself "Nope". After that it was an all negative news day.
     
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  10. Jun 11, 2019 #670

    Tiger Tim

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    Were they advertising a sea level cabin all the way up to FL250? If not, a diff of about half that should still give an acceptable cabin altitude.
     
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  11. Jun 11, 2019 #671

    rv6ejguy

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    I think they were aiming for 5.5 psi diff, about like a King Air 90. I can't recall the certification requirements but I thought it was 1.5X safety factor here. Like I said before, so many gotchas on this design.

    The fans are calling to ditch Len and find someone who will be willing to fly it. They just don't get it that probably no professional test pilot is willing to risk flying it as is. They seem to think Len's concerns were trivial and that Peter's design is going to fly well and be far superior to what's already been flying for over a decade, like a IVP.

    Many also believe in the Audi engine coupled to a totally unproven PSRU. The list is long on things that won't work well but the aero stuff is the hardest to solve. The elevator design (s), as we discussed at length here, were nonsense from the start.
     
  12. Jun 11, 2019 #672

    TMann

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    Bottom line ....
    I was really excited to see a new entry into the canard world. The canard design could really use an infusion of enthusiasm.
    I can't imagine how complex this project really is.

    This never came off as a prototype but more as a "Cadillac of the Sky" model. I get what he's trying to accomplish but man, that's a huge chunk to bite off. Combine that with some of the internal vibe associated with the team and it's a wonder they have accomplished as much as they have.

    What I will say is that this project has been the most open effort I have ever seen. The weekly updates have been fun to follow. We have seen it, warts and all, practically live.

    I think every innovator has hit this wall. The question really is how do you react to the situation and push forward.
    Perhaps the best is yet to come.
     
  13. Jun 11, 2019 #673

    BBerson

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    The BD-5 development was also reported occasionally to the public. But sales started before the prsu and unproven engine was fully developed.
    Experts were brought in and couldn't help.
    Being open seems to be a method to get deposits. But it puts the developer in a bind to do the impossible. Bad enough for an airframe, it takes a huge second effort to develop a power plant. Almost like failure was expected.
    I think Burt said he never released any performance claims until after the development. Or at least the first flight.
     
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  14. Jun 11, 2019 #674

    TarDevil

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    Apparently, many of the commenters are experienced aviators. I guess all they do is crank the engines and fly and ignore stuff like sound "aerodynamics" and "aircraft structure. "
     
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  15. Jun 11, 2019 #675

    TMann

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    Very true indeed. I heard Burt say that he doesn't discuss new projects until they reach fruition.
    If it doesn't work out, they moved on to the next one and nobody heard anything about it. (If you need proof of that look at the design number gaps in the list of Rutan aircraft.)

    One of the biggest takeaways from Burt's approach was the entire concept of SC (Scaled Composites.) Not only were the designs "Scaled" but they were strictly a proof of concept. If you look at some of the prototype aircraft that came out of SC, they were pretty rough. It was all a matter of proving the design worked then move on to the next step.

    Imagine where the Raptor would be if they:
    • Used a Lycoming engine.
    • Fixed Gear (and I love retracts.)
    • Scrap the air-conditioning.
    • Scrap the pressurized cabin.
    • No cup-holders....
    They could have been at Oshkosh a year ago...... for a lot less money.
     
  16. Jun 11, 2019 #676

    Steve C

    Steve C

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    These days it seems all too common to advertise wild performance specs on a plane that has either never demonstrated it or never flown at all.
     
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  17. Jun 11, 2019 #677

    BBerson

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    This reminds me of a call I got as a Tech Counselor. The caller said he was a new Aero engineer and wanted to ask me what I thought about his 6 place design powered by a "crate" engine, to use his words.
    I couldn't think of what to say. So I blurted out "what is a crate engine". (I knew what a crate engine was but wanted to let him talk)
    Then I think I said something like: "have you designed anything before"? Or, "do you want your family flying behind a crate engine".... That's all I remember.
     
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  18. Jun 11, 2019 #678

    BoKu

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    I watched as much of the video as I could. I had to stop to give my eyeroll muscles a rest. There should be a picture of Raptor in the Wikipedia article on Sunk Cost Fallacy.

    I thought it was ironic that the guy who thought it would be a good idea to develop a propulsion package from scratch (with turbos, redrive, and systems up the wazoo) thinks it would take a solid year to do an IO550 install. Sure, for an amateur working alone. I know lots of teams of three that could have it mounted, cowled, and running in a month tops.

    But one thing I learned from the vid is that there is actually some sort of method to the madness of the elevator design. Apparently they want to preserve the possibility of having flaps or flaperons on the main wing, and balance the Cl increase with coordinated deflection of a flap-like elevator. I seem to recall that the Beech Starship does something similar, and I've not heard anything to suggest that it's necessarily a bad idea. But that would require more systems, more testing and tweaking, and more mass, in an already unreasonably bloated airframe.

    One thing I get from the Raptor vids that I have managed to watch is that Peter seems deathly allergic to incrementalism. As we've discussed ad nauseum, a sane team would have made a very simple prototype with foam core wings and an off-the-shelf powerplant as a development platform, and iterated from there towards a product that meets their requirements. But Peter wants to do it all, and all at once; one and done.

    I certainly grant that the latter approach makes for better video. Which I guess is fine if you care more about the video than the thing it depicts. Which suggests that Peter might have fallen into an ego-driven value trap in which he has forsaken his stated objective in pursuit of clicks and likes.
     
    Last edited: Jun 11, 2019
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  19. Jun 11, 2019 #679

    Turd Ferguson

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    If I remember correctly, the P210 flew at FL250 on 1.9 psi. Seems Cessna used "just enough" pressurization to get the job done...which should be a clue.
     
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  20. Jun 11, 2019 #680

    nicknack

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    IMHO, the pressurization and Audi engine with non proven PSRU are a complete distraction and recipe for failure. It took Titan that makes the replica T51 years to get their auto-conversion engines to work with the correct ECU programming and reliable PRSU. And even Lanair had issues with the bonded windows in the Lancair Evolution.
    The raptor guys should have just began by proving the airframe aerodynamics, handling qualities 1st and slowly bring it to FL180 and FL250 in stages. If they needed a high altitude engine, please just go turbo-prop
    For something more realistic just look at the horten horten hx-2 that jus flown recently.
    https://www.horten-aircraft.com/en/
     
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