Raptor Aircraft

tspear said:
I think they will be very close:
1. Documented CFD based testing.
2. Built prototypes.
3. Built and tested composite structures to determine weight and strength.
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People seem to have forgotten that the Raptor project did at least two of those as well. :rolleyes:
Simply taking these actions means virtually nothing, it's all in how you set up the problems/experiments and how the results are interpreted.

Nauga,
and colorful fluid drawings
 
steingar said:
I truly do wonder who's going to buy it.
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I have a deposit down.

nauga said:
People seem to have forgotten that the Raptor project did at least two of those as well. :rolleyes:
Simply taking these actions means virtually nothing, it's all in how you set up the problems/experiments and how the results are interpreted.
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What are your latest thoughts on how DarkAero is progressing?
 
Katamarino said:
What are your latest thoughts on how DarkAero is progressing?
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I freely admit my latest thought was "Oh, those guys are still at it?"
I've seen next to nothing on their aero/perf/S&C analysis or systems development. If you or anyone can point me to details or even just a summary of their CFD analysis and/or any parameter ID or other aero work they've done with their flying models I'd be interested in poking through them.

Nauga,
and a non-advocate review
 
nauga said:
People seem to have forgotten that the Raptor project did at least two of those as well. :rolleyes:
Simply taking these actions means virtually nothing, it's all in how you set up the problems/experiments and how the results are interpreted.

Nauga,
and colorful fluid drawings
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I very well could have missed it; however I never saw any of these steps taken by Raptor. However, you point about the problem statements and related is still valid.

Tim
 
nauga said:
I freely admit my latest thought was "Oh, those guys are still at it?"
I've seen next to nothing on their aero/perf/S&C analysis or systems development. If you or anyone can point me to details or even just a summary of their CFD analysis and/or any parameter ID or other aero work they've done with their flying models I'd be interested in poking through them.

Nauga,
and a non-advocate review
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You will have to dig through the videos. Here is a sample of one:

Tim
 
nauga said:
People seem to have forgotten that the Raptor project did at least two of those as well. :rolleyes:
Simply taking these actions means virtually nothing, it's all in how you set up the problems/experiments and how the results are interpreted.

Nauga,
and colorful fluid drawings
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While Peter did do some CFD analysis, I'm not sure he was qualified to really do so. And I don't think his little model was a very good test of anything. I saw video where a guy made a leaf blower fly. Doesn't mean it would scale.

At least with the DarkAero kids one of them has a degree in aerospace engineering.
 
In my 50 some years in the aircraft development business, there was one totally inviolate rule when evaluating a new design on paper, to wit, “Paper Airplanes ALWAYS Beat Real Airplanes”. Never once did the design numbers come true when the final product rolled out. Sometime the design never made the real metal/plastic/unobtainium stage, sometimes the miss was substantial, rarely a very small miss but never on initial projections.

True across everything from the F-111 to the F-35 and all in between.

Cheers
 
X3 Skier said:
True across everything from the F-111 to the F-35 and all in between.
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To be fair, though, I imagine getting a military aircraft design from paper to production would be like dragging a sheet of flypaper through a cow pasture. It's going to pick up an awful lot of excess stuff along the way.
 
midwestpa24 said:
I think the same could be said for nearly every aircraft builder since the Wright Brothers!
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A Lancair 320 has a listed empty weight of 1,040 lbs, the DarkAero guys are planning on 750, which is lighter than an RV-12.

I don't doubt the materials available today are better, but they're not that much better.
 
DaleB said:
To be fair, though, I imagine getting a military aircraft design from paper to production would be like dragging a sheet of flypaper through a cow pasture. It's going to pick up an awful lot of excess stuff along the way.
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The same thing happens with all the add-ons. Adding a new gee wizz gizmo that “improves” something never achieves the promised performance/weight/cost and just contributes to the end miss amount. If by some miracle it does (very rarely in my experience), the delta is added/subtracted from the promise and the total shortfall still exists.

The way Commercial Aircraft Makers address this is to underpromise the guarantees to the airlines with enough pad to not go bankrupt. Still they sometimes pay out not unsubstantial cash to launch customers and adjust guarantees for later buyers. Since rarely is an all new commercial design launched, incremental change is easier to judge than clean sheet designs. OTOH, the KC-46, a derivative of the 767, has been a nightmare for Boeing. They won the liars contest with Airbus and are losing a boatload of money.

Cheers
 
FormerHangie said:
A Lancair 320 has a listed empty weight of 1,040 lbs, the DarkAero guys are planning on 750, which is lighter than an RV-12.

I don't doubt the materials available today are better, but they're not that much better.
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About six years ago now, when I was looking at the Velocity kits, I talked to the factory and asked about switch to Carbon Fiber. The answer was the plane would be about 150lbs lighter, and add 200K in cost.
And that was just for a straight switch, no optimization.

Tim
 
X3 Skier said:
In my 50 some years in the aircraft development business, there was one totally inviolate rule when evaluating a new design on paper, to wit, “Paper Airplanes ALWAYS Beat Real Airplanes”. Never once did the design numbers come true when the final product rolled out. Sometime the design never made the real metal/plastic/unobtainium stage, sometimes the miss was substantial, rarely a very small miss but never on initial projections.

True across everything from the F-111 to the F-35 and all in between.

Cheers
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I wonder if it was different working for Kelly Johnson. You think they were trying to make the sr71 go Mach five and just missed it or they promised the u2 in 6 months and ran long taking a whole year to first flight? Not trying to be a prick. Just asking because I don’t know.
 
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Tarheelpilot said:
I wonder if it was different working for Kelly Johnson. You think they were trying to make the sr71 go Mach five and just missed it or they promised the u2 in 6 months and ran long taking a whole year to first flight? Not trying to be a prick. Just asking because I don’t know.
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Since those were "Black Ops" aircraft, there were probably considerably less hands in the design cookie jar. Scope creep is usually what drives up costs, timelines, and weight while killing performance. Its not enough that the aircraft is good at mission A, but it also needs to do B, C, D, and E, and maybe F if we can fit it in.
 
The SR-71 and U-2 were before my time but similar Black Programs (F-117 and B-2) I was directly involved with had the same overpromise and underdeliver as White World programs. Main reason were really bad guesses as to what could be done on schedule with new technology. In the end, enough money and time was spent that both came close to the original requirements but still not as promised.

Cheers
 
X3 Skier said:
The SR-71 and U-2 were before my time but similar Black Programs (F-117 and B-2) I was directly involved with had the same overpromise and underdeliver as White World programs. Main reason were really bad guesses as to what could be done on schedule with new technology. In the end, enough money and time was spent that both came close to the original requirements but still not as promised.

Cheers
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Thanks for the response. Interesting to ask people actually around.
 
X3 Skier said:
In my 50 some years in the aircraft development business, there was one totally inviolate rule when evaluating a new design on paper, to wit, “Paper Airplanes ALWAYS Beat Real Airplanes”. Never once did the design numbers come true when the final product rolled out. Sometime the design never made the real metal/plastic/unobtainium stage, sometimes the miss was substantial, rarely a very small miss but never on initial projections.

True across everything from the F-111 to the F-35 and all in between.

Cheers
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Interesting. I have talked to a number of engineers over the years that differ from your perspective. As long as there is no "new technology", aircraft designs are very predictable and final specs are usually within a few percent. When I tried to debate the performance vs paper concept and pointed to F35, F16.... The counter argument was look at how many companies build the first plane and multiple "conforming" prototypes to get through the FAA faster; and all conforming prototypes are eventually sold to customers. Now, this is all commercial aircraft; Citation, Gulfstream, Boeing....
Basically, known tech, with well defined requirements, has allowed modern computer design to be extremely reliable and predictable. The problem is when you leave the well known.

Tim
 
tspear said:
Interesting. I have talked to a number of engineers over the years that differ from your perspective. As long as there is no "new technology", aircraft designs are very predictable and final specs are usually within a few percent. When I tried to debate the performance vs paper concept and pointed to F35, F16.... The counter argument was look at how many companies build the first plane and multiple "conforming" prototypes to get through the FAA faster; and all conforming prototypes are eventually sold to customers. Now, this is all commercial aircraft; Citation, Gulfstream, Boeing....
Basically, known tech, with well defined requirements, has allowed modern computer design to be extremely reliable and predictable. The problem is when you leave the well known.

Tim
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The “few percent” are seldom if ever on the right side of the initial SWAG that the design is supposed to achieve, according to the marketeers hawking the plane. I would wager a beer that every sale includes a pad in the numbers that the bean counters require to protect the company from having to make good on guarantees for fuel burn, maintenance hours / flight hour, Dispatch Rate. etc. That pad is reduced the more planes produced.

There’s more requirements to meet than max speed, altitude, and similar performance factors that are amenable to modern rigorous analytical techniques.

Finally, it relatively simple to predict what a derivative 737 or Gulfstream will be like after you’ve produced a thousand or so. Even the F-111F met the predicted performance after production of the F-111A/B/C/D/E models.

As you say, easy to do with known technology and designs but much harder with true advancements of which there are very few in commercial aircraft. A “new” 737 design isn’t much different than the thousands before them. The first 737’s were a different story, I suspect.

Most performance advancements are driven nowadays by engines (pun intended) which are usually developed ahead of the airframe. A notable recent failure was the geared fan from Pratt & Whitney and also their JT-9D for the 747 that almost bankrupted both Pratt and Boeing.

Cheers
 
tspear said:
Basically, known tech, with well defined requirements, has allowed modern computer design to be extremely reliable and predictable. The problem is when you leave the well known.
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With the emphasis on the last sentence. Using your last design as a basis and modding that is much more likely to result in accurate predictions than a wholesale new design. Add to that the modding analysts themselves generally know where the weaknesses are and there's a history of *model validation* and analytical & empirical corrections meaning the analytical models aren't starting from scratch with each new airplane. It's not just an improvement in the predictive technology, it's the foundation the models are built upon that makes the accuracy possible.

Nauga,
who plays with building blocks
 
I think the P-51 was done in time and ahead of performance, if the legend is more or less correct. They were promised something better than the P-40, and they got it.

Most of the time I think things don't make the specs is because there isn't a lot of consequence. Outside of aviation, when contracts have penalties for being late and/or bonuses for being early, magically quick things happen. Like cleaning up the Iraqi oil well fires.
 
Albany Tom said:
Most of the time I think things don't make the specs is because there isn't a lot of consequence. Outside of aviation, when contracts have penalties for being late and/or bonuses for being early, magically quick things happen. Like cleaning up the Iraqi oil well fires.
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The P-51 wasn’t really useful until the original Allison engine was replaced by the Rolls Royce Merlin. No clue if it met the original requirements for the Brits who first ordered the Allison version.

As far as meeting contract requirements causing better performance to promise, three more recent examples had little influence and resulted in major financial pain to Boeing (Pratt & Whitney in the first case). 747/JT-9D, KC-46 and 787.Two were clean sheet designs and the KC was supposed to be based on an existing airframe but had some really new technology involved.

Another semi truism. “Never buy the A model of anything”:D

Cheers
 
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I believe they used the Allison as a compromise requirement from the British. And the big limitation of the Allison was the single speed supercharger, as I understand it. But even with that, as a low level aircraft I'm pretty sure it was faster than anything the British or Germans had at the time; and as the original request was for a P-40, it beat probably every spec for that aircraft. Now, was that because NA took advantage of more modern information? Sure. That's how you do it.
 
I think we can all agree the Raptor beat all my predictions! 1. It flew. 2. Didn't kill the most hated airplane builder. I will eat crow now.
 
I only watched about 30 seconds worth but it sounds like he’s planning to go 300kn on 90 hp.
 
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