Airplane 05 - A new airplane design

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by drstress, May 27, 2019.

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  1. May 27, 2019 #1

    drstress

    drstress

    drstress

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    This is the first installment of an airplane design that I have been working on for about a year. This is intended to be a group-effort learning experience about how to design an airplane, not to produce a real airplane detail design. This is not an inexpensive airplane nor would it be easier than any other airplane for a homebuilder to produce. Except for the tractor-pusher engine arraignment it is not particularly innovative. I am following known, safe design practices. It uses standard, proven engines. All design efforts take several iterations to get it right. This is the fifth iteration, and not the last, of my original concept.

    I will present the design over several posts. This is a rough outline:

    Specification and conceptual design
    • Expected performance
    • Cockpit and fuselage layout
    Preliminary design
    • Wing sizing
    • Engine selection
    • Fuel requirements
    • Weight estimates
    • Control surface sizing
    • Performance estimates
    • Stability estimates
    Structural analysis of the preliminary design
    • Conversion of the preliminary design into a working structural model
    • Loads estimates
    • Strength estimates
    There will not be any detail design.

     
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  2. May 27, 2019 #2

    drstress

    drstress

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    Specifications for Airplane 05:

    Design Mission:
    The airplane will be capable of carrying one pilot and one passenger with baggage for a usable distance. Safety and occupant comfort will be the primary goals. It will have modern (glass cockpit) flight instruments. It will have twin engines. It will be capable of maintaining a high rate of climb in hot, humid (Florida summer) conditions up to the cruising altitude.

    Payload:
    • Pilot - 190 lbs
    • Passenger - 190 lbs
    • Baggage - 80 lbs
    Performance:
    • Cruise altitude – 10000 feet
    • Service ceiling – 15000 feet
    • Range – minimum of 4 hours @ cruise speed with 1 hour reserve @ best endurance speed (at least 650 statute miles, approximately 150 knots cruise). In addition to fuel for this range, fuel will include warm-up, taxi, climb to cruise altitude, descent and landing/taxi.
    • Minimum rate of climb – 1000 feet/minute @ 100 knots TAS to cruise altitude
    • Vstall, flaps – 45 knots maximum
    • Vstall, clean – 60 knots maximum
    Design Features:
    • Twin turbo-charged engines
    • In-line tractor/pusher configuration
    • Constant-speed propellers
    • VOR/ILS/GPS navigation with on-board maps
    • Limited auto-pilot with heading and altitude hold
    • Electric plain flaps
    • Utility category
    • Compliance with FAA CFR 2011, Title 14, Vol 1, Part 23 as much as practical
     
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  3. May 27, 2019 #3

    pictsidhe

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    Well this makes a pleasant change, somebody designing an aircraft using engineering methods. The forum would benefit from seeing how you have gone about it. Perhaps you could start a member project blog and drown us in details.
     
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  4. May 27, 2019 #4

    drstress

    drstress

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    I would like to invite everyone to participate in the design discussion. Please follow these rules:

    I need critiques from knowledgeable people. All critiques must be accompanied by references to available test data or references to verifiable analysis techniques. (“Extraordinary claims require extraordinary proof.” - Occam's Razor)

    I will not provide accurate dimensions. This is to prevent someone from using my data to actually build an airplane. (“Those who can make you believe absurdities, can make you commit atrocities.” - Voltaire)

    I do not have a lot of experience with aerodynamics or stability, so don't believe anything that I show here until it has been verified by you or someone that has the necessary experience. (“The more I read, the more I acquire, the more certain I am that I know nothing.” - Voltaire)

    Please keep personal opinion out of this. If you know there is something wrong or there is a better way, please provide references that can be checked by everyone. There is no guarantee I will incorporate your input into my design, so don't get pissy if I don't. (“Opinions have caused more ills than the plague or earthquakes on this little globe of ours.” - Voltaire)

    I have a sign that hangs above my desk:

    “If I get this right, a beautiful bird rises into the air. If I get this wrong, people die.”
     
  5. May 27, 2019 #5

    pictsidhe

    pictsidhe

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    I'd say that I like your quotes, but that would violate rule 4 ;)
     
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  6. May 27, 2019 #6

    drstress

    drstress

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    If this was a movie it would be titled, “There Will Be Math”, but don't worry you won't be “bloodied” by it. I am a retired aircraft structures engineer, so this presentation will be from an engineering viewpoint. Most of the math will be simple algebra with a couple of matrix or simultaneous equation solutions. If I throw in some calculus it will be used to make the presentation more understandable, but not absolutely necessary. This is not an engineering course where you are expected to derive or even understand a complicated derivation of a formula.

    I will try to adhere to the following:
    • Airframe Guide for Certification of Part 23 Airplanes, FAA AC_23-19A
    • Systems And Equipment Guide For Certification Of Part 23 Airplanes And Airships, FAA AC_23-17C
    Aircraft design is heavily dependent on spreadsheets. There will be several MS Excel spreadsheets presented, including some with VBA macros. My version of Excel is from MS Office 2007. I also use Mathcad for almost all of my calculations. I started using this software in the late 1980's obtaining a reduced price license when I was taking a graduate class. I updated this over the years, stopping at Mathcad 2001 Professional which still works well for my needs.

    OpenVSP and VSPAERO will be used. OpenVSP (Vehicle Sketch Pad), “is a parametric aircraft geometry tool. OpenVSP allows the user to create a 3D model of an aircraft defined by common engineering parameters. This model can be processed into formats suitable for engineering analysis.”

    VSPAERO is a vortex lattice CFD program bundled with OpenVSP that will calculate the aerodynamic coefficients and stability derivatives we will need. A large part of this effort is an exercise about learning to use VSPAERO. In Raymer's, “Aircraft Design”, there is a chapter entitled, “Stability, Control and Handling Qualities”, where he presents various equations for hand calculations. Quoting Raymer, “Note that these methods are considered crude by the stability and control community and are only suitable for conceptual design estimates and for student design projects.”

    OpenVSP is available for free from NASA. See: http://openvsp.org/

    The loads and stress analysis will be accomplished using both hand calculations and NASTRAN finite element analysis. The shop where I was a DER will let me access their PATRAN/NASTRAN license. I have fifty years experience with computers, during thirty of which I performed hand analysis in conjunction with computer assisted analysis including a lot of FEM modeling. I do believe, with the software and computers available today, that an accurate FEM analysis must be used to verify all hand analysis. Also, all analysis must be validated with hardware testing to destruction if necessary.

    In the early 1990's drafting tables either disappeared from aircraft engineering departments or were taken over as desks for CAD terminals. I believe this improved the accuracy of the designs many fold. If you join EAA you get access to the Solidworks CAD Learning Edition. I am not sure at this point that I will use Solidworks since I am not presenting a detail design. I use 3ds Max 2010 as a graphic design tool. I got a license for 3ds Max when I was doing some 3d modeling for a game and it still works for me. (Don't ask me about that gig. I don't want to talk about it.)
     
  7. May 27, 2019 #7

    drstress

    drstress

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    I will try to not disappoint you. I hope I haven't taken on too big of a project.
     
  8. May 27, 2019 #8

    Vigilant1

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    Thanks for coming back, drstress. I was afraid we'd lost you.

    I'm looking forward to seeing your work.

    Will you be using constant speed props for this little bird? In the similar (but more modest) centerline thrust concepts we've most extensively discussed here lately (the "Beetlemaster" and the "Micromaster") we have generally assumed fixed-pitch props (for economy purposes and due to limitations on crankshafts and front bearings of the proposed engines--VW derivatives and small industrial engines, respectively). Controllable pitch props certainly reduce the tradeoffs required between acceptable single engine climb performance and two-engine cruise speed. But, Burt Rutan was able to get good single-engine performance and cruise performance with fixed-pich props on his Defiant, so it is possible.

    Thanks for letting us peer into the processes you've used.
     
    Last edited: May 27, 2019
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  9. May 27, 2019 #9

    pictsidhe

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    Looks good to me. I'll be investigating VSP. I'm just getting into checking stability for my own design.
     
  10. May 27, 2019 #10

    drstress

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    Thank you for the welcome and feedback. In my dream airplane world cost is no object, so yes Airplane 05 uses constant speed props. I will discuss this when I show the engine selection.
     
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  11. May 27, 2019 #11

    drstress

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    My conceptual, aerodynamic and stability design techniques are from the following:

    Books:
    • The Advanced Pilot's Flight Manual, Kershner, 1985
    • Flight Theory for Pilots, Dole, 1989
    • General Aviation Aircraft Design, Gudmundsson, 2014
    • Airplane Aerodynamics and Performance, Lan & Roskam, 1980
    • Aerodynamics for Engineers, Bertin & Smith, 1989
    • Synthesis of Subsonic Airplane Design, Torenbeek, 1986
    • Aircraft Design: A Conceptual Approach, Raymer, 2012
    • Aircraft Design: A Systems Engineering Approach, Sadraey, 2013
    • Airplane Design, Parts I-V, Roskam, 2002
    Course notes:
    • AOE 3134, Stability and Control, Virginia Tech, Lutze
    • M&AE 5070, Introduction to Aircraft Stability and Control, Cornell University, Caughey, 2011
    Other:
    • ESDU 94009, Symmetric Steady Manoeuvre Loads on Rigid Aircraft of Classical Configuration at Subsonic Speeds, 1994
    • ESDU 67036, Geometric and Kinematic Relationships for Various Axis Systems, 1967
    • ESDU 67004, Conversion Formulae for Rotation and Translation of Body Axis, 1967

    My structural analysis techniques are from the following:

    Books:
    • Analysis & Design of Flight Vehicle Structures, Bruhn, 1973
    • Airframe Structural Design, Niu, 1988
    • Aerospace Vehicle Structures, Southworth, 1986
    • Calculating the Aerodynamic Loads and Moments on Airplane Wings, Koffeman, 1986
    • Formulas for Stress, Strain, and Structural Matrices, Pilkey, 1994
    • Failure of Materials in Mechanical Design, Collins, 1981
    • Stress Concentration Factors, Peterson, 1974
    • Formulas for Stress and Strain, Roark & Young, 1982
    • Advanced Mechanics of Materials, Cook & Young, 1985
    • Concepts and Applications of Finite Element Analysis, Cook, 1981
    • Finite Element Modeling for Stress Analysis, Cook, 1994
    Course notes:

    AE 421, Airplane Detail Design, Embry-Riddle Aeronautical University, Ritchie/Eastlake, 1981

    Other:

    Eight large loose-leaf binders filled with notes from thirty years as a structural engineer. The method and techniques in these notes are from, among lots of others, the Boeing Design Manual, the McDonnell-Douglas Structures Manual and the NASA Aerospace Structures Manual.
     
    Last edited: May 27, 2019
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  12. May 27, 2019 #12

    bmcj

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    One thing to keep in mind is that the dual verticals will likely lose a little bit of effectiveness due to interaction between the two inner surfaces. In other words, when yaw induces a lower pressure on one inner surface and a higher pressure on the opposite inner surface, there will be some cancelation of the two pressure fields as they try to equalize. That means that the stabilizing effect will probably fall in between that of a single rudder and two rudders each acting at 100% effectiveness.

    Of course, proper choices of distance and chord combinations can help mitigate some of the loss.

    Just don’t be surprised if two are not twice as effective as one at twice the size.
     
  13. May 27, 2019 #13

    Pops

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    I also thought of the Beetlemaster. If I had more time and energy I would like to built the Beetlemaster. Vigilant , I'm waiting for you to start construction.

    Looking forward for this thread. Hope is not to deep for this redneck . Already like the looks of it.
     
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  14. May 27, 2019 #14

    drstress

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    We are a long time away from discussing the tail surfaces. Please hold that thought until we get to discussing the vertical tail. In the meantime maybe you could put together an example from wind tunnel testing or CFD analysis. Also an illustration of what you are describing would be appropriate.

    p.s. You are very right about the issues you raise concerning the tail. I'll show my solution when we get there.
     
    Last edited: May 27, 2019
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  15. May 27, 2019 #15

    drstress

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    Everyone,
    Please understand the two illustrations I have posted are very much "cartoons". The exterior illustration is for sizing the cockpit. There are several other models for the CFD and stability analysis. I will present those in time. We will iterate to a preliminary design solution.

    The airframe illustration is even more of a "cartoon". In this illustration there is only a vague idea of where, how many and what size the structural members would be. The illustration is mainly for packaging purposes. It shows where the door frame, control surface attachments, etc. might go. Also this illustration allows a better guess at the weight and CG of the airframe components. Again, we will iterate to a preliminary design solution.
     
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  16. May 27, 2019 #16

    Vigilant1

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    These (rational) rules are going to get quite a workout. I might tape a cheat sheet to my monitor so I can tell who is being called out for what (me included). :)
     
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  17. May 27, 2019 #17

    drstress

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    Oh wow man, you make me sound like a school mar'm. I'll try to be gentle, but I want "Just the facts, ma'am, just the facts." Help me make sure that my posts aren't "calling out" anyone. I truly want this to be a group effort.
     
  18. May 27, 2019 #18

    Vigilant1

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    No, I'm just having a bit of fun. It will be good to keep the discussion as fact-based as possible, but that's a higher "standard of proof" than is normal here.

    It is hard to herd cats! Still, you've obviously put a lot of work into this, and it deserves a disciplined discussion. And if you've got analysis to go behind your design choices (single rudder or two, to cite a recent example), I'll learn a LOT from that.
     
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  19. May 27, 2019 #19

    Retiree

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    I look forward to the progress of your project. If you do not provide basic dimensions and performance targets, how can we judge what you are doing is reasonable?
    Doug
     
  20. May 27, 2019 #20

    drstress

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    You are right. Like the examples I am asking others to show, I will need to provide enough information so you can see what I am doing. As we go along, I will have to develop a method to satisfy my need to keep someone from actually building this airplane. I have been debating for awhile whether I have the time or am qualified to do what I am attempting. I do not want anyone depending on my design as a real airplane.

    If anyone is serious about a detail design, it would take a consortium of several qualified individuals to pull this off. They would need to legally agree to structural static load tests, DER and DAR approval, and to a rigorous flight test program.
     
    Last edited: May 27, 2019

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