Scaled Jets (F-16)

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Acrojet, Jun 6, 2016.

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  1. Jun 6, 2016 #1

    Acrojet

    Acrojet

    Acrojet

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    F-16 (60% scale)
    image.jpg

    Statistics and performance:
    Empty wt: 700-900lbs
    MTOW: 1900-2100lbs
    Max speed:350kts red line
    Criuse speed:250kts
    Stall speed:~70kts clean (normal landing wt) 65kts landing config
    G loading:+6 -3 min aerobatic category
    Range: @FL250 900NM w/VFR reserves
    fuel capacity:120 gallons (wing and internal center tank fuel)

    Engine:
    Turbofan rated at 700lbs thrust at TO
    weight:90lbs
    fuel burn: 42gal/hr at max rated thrust
    cost:$55-60,000 USD

    Airframe:
    -2-place all metal construction
    -"all-flying" tail stabilator
    -non-pressurized (limited to FL250, non-RVSM)
    -pneumatic landing gear and speed brake, hydraulic brakes
    -mechanical manual control system (no computers or advanced actuators)
    -plain flaps
    -all balanced flight controls
    -S8052 airfoil for best compromise between acro and cruise wing performance:
    image.jpg

    The goal is to create an "affordable" representation of an F-16 (60% scale) for two people to bore holes through the sky in without breaking the bank. While it won't be cheap, the goal will be to "kit" this aircraft once all development is complete at a price-point that should be on par with a high performance experimental kit aircraft presently available on today's kit market.

    I will post here as things develop further. I presently operate one of only a few BD-5J (James Bond jet) aircraft and will use my knowledge and experience with this aircraft in developing the F-16 aircraft.

    Peter Reny
    Dream Scheme Designs© microJET Airshows
    email: acrojet@aol.com
     
  2. Jun 6, 2016 #2

    BoKu

    BoKu

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    To heck with the airplane; if you can supply engines that meet that spec and price point the aviation world will beat a path to your door.
     
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  3. Jun 6, 2016 #3

    Acrojet

    Acrojet

    Acrojet

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    Boku,

    Yup, I know what you mean. I've been working on this engine deal for about 8 years now. Finally seeing a light at the end of the tunnel (no it's not a train coming the other way) and the core is already up and running and the price point should be pretty close to that. ;-)

    Peter
     
    Last edited: Jun 6, 2016
  4. Jun 6, 2016 #4

    Lucrum

    Lucrum

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    This is essentially my intended design though not an exact scale F-16. Just using the overall layout as a guide and a modified GE T-58 for propulsion.
    Are there any 700 lbs trust engines out there with a sfc of 0.4 lb/lbt/h ?
     
  5. Jun 6, 2016 #5

    Acrojet

    Acrojet

    Acrojet

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    Are you making it from metal or composite? Yes there is an engine that fits that performance. I'm having it made. It will be available for the F-16 first and then other aircraft once the F-16 slots are filled. These will be essentially custom built engines and made by a very small company, so while it may take a little longer to get one, the company has a very small "overhead" so they have to make them efficiently to keep the price low....

    Peter
     
  6. Jun 6, 2016 #6

    BoKu

    BoKu

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    Veering toward off-topic territory, but a valid cautionary tale: The engine described is essentially the Williams EJ22, which was barely possible in 2002 when I was interviewing at Eclipse. What it wasn't was practical, as the article describes:

    History, Travel, Arts, Science, People, Places | Air & Space Magazine

    When I was interviewing there, they were pretty cagy about the pricing they were getting, but it sounded to be around $150k per unit. And, again, that was 14 years ago, so the price could only have headed uphill.

    Thanks, Bob K.
     
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  7. Jun 6, 2016 #7

    Acrojet

    Acrojet

    Acrojet

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    Bob,

    Yup it's very similar to the EJ22 motor. But it's simpler (if you can believe that) Its not made here in the US and as a result it doesn't carry all,the legal "red-tape" that would be required here. And it's not "certified" so again less red tape. What I can tell you, is that it's based on an existing turbojet that has been modified with a fan. These will be all new engines not modified existing engines, but based on existing turbojets. That's about all I can say at this time... ;-)

    Peter
     
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  8. Jun 6, 2016 #8

    Lucrum

    Lucrum

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    welded steel frame with wood skin for the fuselage All wood wings. Originally planned on all wood vert & horiz stabs but I didn't like how they turned out.
    So I think I'm going to redo them in aluminum.

    I'm not disputing your engine specs But they are way better than anything already in production that I'm aware of, in terms of both sfc and dry weight, let alone cost.

    Smaller turbine engines generally have a higher sfc
    A sfc of .40 for an engine that size would be phenomenal Even for an experienced turbine engine designer using exotic materials and manufacturing Technics.
     
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  9. Jun 7, 2016 #9

    Acrojet

    Acrojet

    Acrojet

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    I know. Just remember Williams made the EJ22 and it weighed 88lbs and was rated at 750lbs of thrust.
    And that was many many years ago. Well, times have changed and the technology and tools to fabricate such an engine have come a very long way. Williams is a pretty big company with a pretty high overhead cost and huge liability cost that are factored into the price of their engines. This new motor will be a little bit heavier (90-100) lbs and 40-50gal/hr burn rate for 700lbs of thrust. It was originally configured with an aft fan but was later scrapped in favor of a front fan because the loss of pre pressured from air to the compressor was too great. You be amazed at how simple the engine is. High tech ceramic bearings and all!!
     
  10. Jun 7, 2016 #10

    Lucrum

    Lucrum

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    I certainly hope it works out for you.
    There are only a few examples of others modifying the engine I'm using into a pure turbojet. I have no way of knowing how accurately they measured their static thrust.
    I only know how the final stator blades were modified in one of those cases. I cut away a lot more of the curved trailing edge then they did. So presumably I'll get better thrust. I just won't know for sure until I run and measure it. Anticipating at least 800lbs static, possibly something approaching 1,000lbs according to one engine model anyway.
    Based on their fuel flows I'll be burning 120 gal per hour at T.O. thrust. I'm planning on a 100 gallon fuselage tank. 21 ft fuselage length and 18 ft wing span.
    I also have an X-Plane computer model of it flying. I currently plan on limiting Vmo to 270 KTS You probably already know this but RVSM starts at 29K. Consequently I plan on cruising as high as 28K for cross country flying. Air frame is stressed for +9 / -3 G
     
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  11. Jun 7, 2016 #11

    Acrojet

    Acrojet

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    Yup, well versed on RVSM, but I'm limited to FL250 because it's non-pressurized. So I assume yours will be pressurized? Anyway, sounds like you've done a lot of research and development. Good luck as well. Keep me posted on the modified engine. That was my second choice if I couldn't get mine built

    Peter
     
    Last edited: Jun 7, 2016
  12. Jun 7, 2016 #12

    Matt G.

    Matt G.

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    I'm curious what changes you've made to enable safe, acceptable handling qualities of a replica of a fighter jet that is both statically and dynamically unstable and requires FBW controls to be controllable by a human pilot. A few years ago I started running numbers on a scale T-28 and found that the horizontal stabilizer area had to be increased to provide an acceptable CG range for a two-seat, tandem aircraft, and the full size version of that is stable. You will be in a far worse position, as you are scaling an aircraft that is, by design, both statically and dynamically unstable. Inquiring minds want to know...:)
     
  13. Jun 7, 2016 #13

    Acrojet

    Acrojet

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    Matt,

    Great question. And a common one....
    I said (asked) the same thing of an engineer friend of mine. His initial response was " you ever see a scale RC f-16 fly? I said "yup". He said "do they have fancy computers to control it?" I said " not to my knowledge" he said "exactly". You see you first have to understand a few things about the real F-16 with my scale F-16.


    Real F-16 Scale F-16
    Weight: Really friggin heavy. 2100lbs
    Thrust: Whole bunch of it. 700-800lbs
    Airfoil: Supersonic with LE devices. Subsonic fatter wing
    CG: Aft (because of engine) Balanced for normal flight

    I'm being funny here, but seriously the big difference with the F-16 is what it's slated to do (mission) my mission isn't going supersonic (not enough thrust, among many other things)
    I think because I say "F-16" people think it's gonna be a "real" F-16 but smaller and it's not, it only looks like an F-16 with not hardly the performance or capability of the real thing. Once you get past that preconceived notion, then you can start to think logically about going forward with the project. I had a hard time about getting past that, until I keep seeing all these RC F-16's scooting all over the place with "direct" inputs to those "albeit" strong servos. And the darn things fly very very well, and very stable. You need to think of my jet more of a "scaled-up" RC F-16 than a scaled down "real" F-16. When you can wrap your brain around that, then you can get the engineering done. Trust me it took a long time to get that through my head. Now don't get me wrong, we still have to "tweak" some stuff to make the CG work, but to the naked eye, you won't (shouldn't ) be able to tell. I even have the full operating "scale" gear being made (machined) and its identical to the real jet except it's smaller and a whole lot lighter. Anyway, trust me the numbers work (albeit with some minor tweaking)
    I will keep you posted as time goes on and more things can be shared. We finally live in a time where technology is catching up with our dreams. I've had this dream in my head for about 16 years now and I can finally see all the pieces coming together.
    For now I'm gonna have to be satisfied flying my BD-5J:
    image.jpg

    Peter
     
  14. Jun 7, 2016 #14

    VAPORTRAIL

    VAPORTRAIL

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    Peter, wishing you all the success possible. BUT are you like 4 feet tall?

    How can you scale an F-16 60 percent, make it reasonably accurate looking and still have room for a human?

    The full size version is pretty tight you know.
     
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  15. Jun 7, 2016 #15

    Acrojet

    Acrojet

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    Umm,

    I'm six feet tall, weigh in at a lean 220 and wear a helmet and a parachute in my BD-5j. I "will" fit. Remember it won't have an ejection seat and all the side equipment, etc, etc. Listen, it's gonna be tight, but I'm not making this thing to fly x-country in. And yes we've made some tweaks to the canopy and cockpit area, but you'll never notice it with the naked eye. If you're a fat guy you probably won't fit, sorry my jets not for you. If you won't fit in a BD-5, then you probably won't fit in my F-16. Sorry. ;-)

    Peter
     
  16. Jun 7, 2016 #16

    Glider

    Glider

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    How many cycles (starts) will the engine support before overhaul?

    Best Wishes!
     
  17. Jun 7, 2016 #17

    Doggzilla

    Doggzilla

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    I would actually be happy with a fraction of the performance, and since 235 knots is as fast as production prop aircraft go, and for $550k, I think most of us would be happy matching the 235 knots even for 6 figures.
     
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  18. Jun 7, 2016 #18

    Acrojet

    Acrojet

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  19. Jun 7, 2016 #19

    Acrojet

    Acrojet

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    Well, I'm not going to be so bold to give a total price for the kit which will include the engine (and possible avionics and instruments, yet to be determined) because it's too early in the program, but I can see this in the $150-200,000 for a full kit. Yes that includes engine and avionics. Now things could go up (or even possibly down) as things get added it could increase but I'm pretty set on what the kit will include so I don't expect a huge change.....
    Have to wait and see....
     
  20. Jun 7, 2016 #20

    BBerson

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    I would be interested in some comments about the span loading.
    Without ejection seats, what is the plan for sink rate after engine failure?

    And the stated 700 pounds thrust with a gross of 2100 pounds is a 1/3 ratio.
    What is the RC models thrust ratio?
     

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