# Scaled Jets (F-16)

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

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1. Jun 7, 2016

### Acrojet

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2. Jun 7, 2016

### BBerson

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Well, it's good to have all that BD-5j experience.
But a two seater is another matter where the risk to the passenger needs to be considered, if this is for sport.

I don't know what the planned span is, the drawing shows around 5000 (millimeters, I guess?) or around 17 feet?
17 feet span and 2100 pounds is 123 pounds per foot span loading.

3. Jun 7, 2016

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4. Jun 7, 2016

### Acrojet

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BBerson,
Don't know you from Adam.... I sense a cavalier attitude in your written tone. Your little comment about my BD-5jet time.... I actually have 23,000 hrs most in jet aircraft. I fly jets for a living. So I kinda have that thing sorted out. Are you a moderator seeking to squash people's ideas or dreams? I wonder? Risk to the passenger? How about risk to the pilot? Your comment would imply that I would somehow "hijack" a person and force them to fly in my personal jet? Seriously? So I'll let that slide just this one time....
I'm not on here to defend what I'm trying to do. If the aircraft is too hot for you (or anybody else) so be it. Don't like it, don't buy it or even comment. Move on to the next thread. I'm looking for people who are interested in what I'm trying to do, not negative Nellies who sit back and try to squash ideas and efforts being put forth. Keep the negativity at bay. I will freely admit I'm not an aeronautical engineer and I haven't done the math on it personally (I was smart, I hired someone to do that) but I do know a bit about what I'm talking about and while on the surface it appears too good to be true, everyone said the same thing about the UL-39 ducted fan and the PJ-11 and they've both proved the doubters wrong. So you can be part of the solution or part of the problem, the choice is yours.
So now that that is out of the way, the span is 18 feet, giving it a 116 per foot span loading with 180 sq ft of wing area. Yes it will have some high wing loading when fully loaded, but that won't be the norm, used only for long x-country flights when range is an issue. I don't anticipate anyone flying like that unless they absolutely had to. Otherwise the per foot span loading would be closer to 89 for most local acro flights with two people onboard. Remember this is a jet aircraft that will require training (ground school and flight) in order to fly one and then the appropriate type rating will be issued after all requirements are met. This aircraft isn't going to be for everyone, but for many it will be just what they're looking for.

Peter

5. Jun 7, 2016

### Acrojet

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6. Jun 7, 2016

### DangerZone

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7. Jun 7, 2016

### DangerZone

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Your project sounds really interesting, are there any more details about the engine modification and the original wooden plans?

8. Jun 7, 2016

### Jay Kempf

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There are tons of nice stable large model airplane versions of the F16 and every other fighter for that matter. The F16 is NOT statically and dynamically unstable unless the CG is put in a bad place. FBW is used to go beyond normal attitudes and for advanced mixing of controls for torturous maneuvering at the limit beyond a normal pilots ability to keep himself safe. Normal stuff. Speed kept within limits, normal control volumes, normal CG, docile airfoils, yadda... and it is a pussycat of a design, and fairly low drag. So built light and with a normal amount of thrust and no afterburner should be pretty straightforward assuming the engine controls and starting are all automated. Should be easier to fly than a large prop stuck on the nose.

9. Jun 7, 2016

### rv6ejguy

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Proved wrong about the UL-39? I never saw any performance/ fuel flow numbers from flight testing which supported the original claims being made about BSFC or speed/ ROC. I might have missed them however... The UL-39 was a magnificent accomplishment for sure but physics and reality of engine design and performance don't take a holiday for anyone.

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10. Jun 7, 2016

### Lucrum

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At the risk of high jacking the other guys thread

It's a GE T-58-8B with the power turbine completely removed. I then removed most of the angled trailing edge of all the turbine nozzles that were immediately in front of what is now the nonexistent power turbine wheel/blades. Since the added swirl would only diminish thrust. The engine is now effectively a 10 stage axial flow compressor turbojet weighing in at 240lbs incl. starter. I plan to use one of the now unused tach drives to turn an alternator for electrical power. Fortunately I have copies of both the training and maintenance manuals for the engine.

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11. Jun 7, 2016

### BBerson

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Nope, not a moderator.
If you don't want comments you should have said that. Or start a members log where comments are not possible.
I was just looking at your general numbers.
Since you seem to take simple questions negatively ... that's all from me.

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12. Jun 7, 2016

### BoKu

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BBerson raises a good and valid point of ethics, one that is lost on many homebuilders and kit developers: For a single-seat aircraft, you can be pretty sure that everyone on board has made an informed decision to partake in relatively risky activities. You can also be fairly sure that they will moderate those activities according to their favored level of risk acceptance. For a two-seater, not so much. There is a good possibility that one of the people on board has not made an informed decision to so partake, and were not fully informed of the risks. There is just as good a possibility that a passenger is not even capable of an informed decision. On that basis, the developer of a multiplace aircraft has an ethical duty to design and build to a higher standard of care than they might for a single-seater.

13. Jun 7, 2016

### Acrojet

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Not at all, that's what this is all about!

14. Jun 7, 2016

### Acrojet

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No, not a problem. Have a great day

15. Jun 7, 2016

### VAPORTRAIL

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I stand corrected! My eyeballs did think there would be a 36" tall cockpit at 60 percent.

Sign me up for 1 plane and 1 shoehorn!

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16. Jun 7, 2016

### Acrojet

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Boku,

In closing, "EXPERIMENTAL AIRCRAFT ARE INHERENTLY DANGEROUS" if you can't get that, then buy a certified aircraft and go fly it. Do you need to tell your passenger that it is what is? Of course, but to say it's the kit makers responsibility is just ridiculous. Dont like it, seems too dangerous for you? don't buy it. Every airplanes flight characteristics will be different and this one will be no different. Testing will tell in the end. It may imdeed be too much for the average flyer, that will have to be dealt with accordingly.
I'm done with this "ethics" and "morality" issue.

Oh what the heck, you've convinced me to make it a single seater now, screw it!

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17. Jun 7, 2016

### Acrojet

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Ya it's gonna be tight, but if I fit in a BD-5 at 6' and 220lbs with helmet and parachute then that is a pretty good size.
Again, it won't be for everybody, but if you're under that you should be fine. It's been said "It's not ones size that determines wether or not one will fit in a BD-5, but rather their desire to do so......"

I'll put you down for one..... ;-)

18. Jun 7, 2016

### Wanttaja

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One of the reasons I fly a single-seat airplane. The only neck at risk from my piloting skills or wrench-turning ability is my own.

While I wish the effort the best of luck, there are a few items of concern.

What the category is certification expected? People who have hundreds of thousands of dollars to spare for a single-seat jet kit are NOT the kind of people with 5,000 spare hours to build the aircraft. They'll hire someone. And if the plane is licensed Experimental Amateur-Built, that's fraud. A business plan based on customers willing to commit a felony is not a good one. I presume you're planning for Experimental Exhibition? But that's got more limits....

Next, there's the completion. Why would someone pay all that money for a kit, and the salary of someone to build it, when they can buy a flying L-39 for less?

Finally, there's the weight of history: Aviation is littered with unsuccessful homebuilt jets. The Zipper, the Javelin, the Maverick, the BD-10, and a couple more that I can't remember their names. The BD-5J is the closest to a successful design, but we're still not talking a lot of aircraft.

Ron Wanttaja

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19. Jun 7, 2016

### Acrojet

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Jay,

Couldn't have said it better myself. You get it! Took me a while to get that, but the RC large replica F-16's are very docile.
(I'm scaling up an RC F-16 more than I'm scaling down a real F-16)
The key is keeping it light. Once it starts to get too heavy, that's when it gets dicey when we ran the numbers. The powerplant will be our key. And fortunately that's looking really good. The next "available" engine class is the GE-T-58 (modified) and then the Marbore ll, these engines are too heavy for what we want and burn a ton of fuel, etc, etc.

I'll put you down for serial number 2. ;-)

Peter

20. Jun 7, 2016

### Acrojet

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Ron,

Thanks for chiming in. We're at the early design/fabrication stage. At this point, we're going to be very similar to the FLS Microjet and the SubSonex except a little bigger (x2). Again, any jet aircraft requires a Type Rating and of course that comes with training. If one has the time to build one on their own then it will certainly be "amateur" category. If they have someone else build it for them, it would be experimental exhibition Catagory. And then there are legitimate builder assist programs that we could certainly set up. Time and testing will tell. You made a good decision about your skills as a builder and pilot and have made a decision to fly accordingly and that's good.
This (60%) F-16 is almost a two place BD-5j (or SubSonex) it's twice the size in weight and we've tried to match the powerplant to suit our needs. Keeping it light (powerplant is the key) and simple (KISS). I'm obviously very familiar with the BD-5J (I own and fly one of Jim Bede's original BD Jets, N152BD. It's 43 years old now and is still running strong!!) and that has kinda been my starting point for this two-place F-16. Being very careful in keeping the weight and sizing down.

With all those "other" jet kits you listed they were riddled with issues almost from the start, Im trying not to have those issues, at least not intentionally.
They (Viperjet, BD-10, maverick, Javelin, etc) are in a total different class - complex, too heavy, large expensive fuel thirsty engines. As I've stated several times, our powerplant will be the key. If it doesn't work, then I won't proceed until the engine technology catches up. But we're almost there. The core engine is a 250lb thrust turbojet (very similar in size and rating as the PBS TJ-100) that weighs a whopping 50lbs and is up and running very well, ceramic bearings and all. The added fan and gear box will increase the weight by 45lbs and the increases the thrust by almost a factor of 3 @ roughly the same fuel burn. Very similar to the Williams EJ22.

As far as who's in the market? That's not my primary concern. The important things is that I want one! Otherwise I wouldn't do it. But having said that, I know lots of guys who will buy one, trust me. I have a buddy of mine who's paying $230,000.00 for a FLS Microjet and he's going thru their "builder assist" program now, and it's got only one seat! So I know there are people out there who will buy it. I'm not doing this to sell hundreds of kits, I mean that would be nice, but that's not why I doing it. I fly with a lot of frustrated former fighter jocks at my airline job and they are all with me! There's not much out there that really turns them on. Sure there were some hopefuls, but they never panned out for various reasons. I must qualify that by first saying that I'm building this because "I" want one and if it goes well I will offer it to people who can and will buy one at a price-point that is fair for what they are getting. L-39 comparison - there is none. That's a total different class of jet fun. A decent L-39 will run you ~$200-300,000.00 then there's the operating cost and hanger cost, maintenance costs on a foreign military jet. Remember this designed to be a fairly econimcal jet, simple in design from the start and cheaper to operate than any other military jet available. This scale jets engine is small and very fuel efficient. 30/40 gal of JetA per hour. The L-39 burns that amount just taxiing to the runway. I have a buddy who owns one of those too and he says it's fun, but exspensive to operate.

In your travels did you get a chance to ever fly the BD-10, Viperjet, BD-5J, SubSonex? If so, what was your assessment of them? I'd be curious to know. Great reading your articles.

Peter

Last edited: Jun 7, 2016
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