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Aero News Network Video - Terrible Raptor 1st Flight Review

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Mad MAC

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The raptor project offers us an incredible opportunity of numerous worked examples. Perhaps to get the best value out of it going forward we need several threads (flight test, structures, power plant and cooling) to make it easier to find the information later and for the Mods to be able to keep this wiggling can of worms under control.

He is running a glycol mix isn't he, rather than straight glycol, either way temporarily switching to straight water should improve heat transfer a bit for testing purposes (if it doesn't make a differance than its probadly the radator being completely ineffective).
 

rv6ejguy

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Water has better heat transfer but a lower boiling point at a given pressure. The Specific Heat of 50/50 EGW is about .88 and boiling point at SL is 225F.

I run 30/70 EGW as I feel is the best compromise between boiling point, freezing point, pump lubrication, pumping ability (EG is more viscous) and corrosion resistance. This won't buy Raptor much since it was nowhere close to dissipating the required heat at climb power.
 

wsimpso1

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So, watched the Aero News Network video segment, and getting caught up here after being away since the end of July, are these all correct?
  • Raptor has done a first flight.
  • Peter did the first flight himself, after all.
  • Low acceleration, low ROC, all the evidence of an underpowered aircraft.
  • Coolant temperatures climbing throughout the flight, including after power reduction for approach and landing.
  • Visible pitch excursions on final and flare, possibly mid-flight as well. Whether these are pilot-, wind-, or aircraft-induced (or a combination thereof) is undetermined.
Is that a fair summary of the first flight, as shown in this ANN video report?
Oh Topaz, am I going to have bounce your post because it is old news, repetitious, etc? JK.

Your summary is pretty close actually. He had pitch, yaw, and roll oscillations all moving with the same period. this oscillation is visible by watching the FPV and chevrons on his ADHR in the flight video, with pitch and roll being big and yaw being smaller and apparently coordinated with bank.

Bill
 

Topaz

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Mod Note: Let's keep this thread focused on Raptor. Another thread would be more appropriate for documenting other projects, even for purposes of comparison.
 

Dana

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Interesting. For a Mechanical Engineering program to maintain accreditation currently, it must have a full semester course each of Thermo, Fluids, and Heat/Mass Transfer. My bet is the chapter on heat transfer is ignored because there is a whole semester on the topic elsewhere in the curriculum. My copy of Van Wylen and Sonntag does not have any chapter on heat transfer, and it was the basis for the then required two semesters of Thermo. 1970's.
Same here, though for Aero engineering in the 1980s; it was one semester of thermo, one of heat transfer, and "propulsion" which was subtitled applied thermo (mainly the thermodynamics of jet engines, I think we spent day on piston engines to my great disappointment).


So, watched the Aero News Network video segment, and getting caught up here after being away since the end of July, are these all correct?
  • Raptor has done a first flight.
  • Peter did the first flight himself, after all.
  • Low acceleration, low ROC, all the evidence of an underpowered aircraft.
  • Coolant temperatures climbing throughout the flight, including after power reduction for approach and landing.
  • Visible pitch excursions on final and flare, possibly mid-flight as well. Whether these are pilot-, wind-, or aircraft-induced (or a combination thereof) is undetermined.
Is that a fair summary of the first flight, as shown in this ANN video report?
That pretty much sums it up as I see it.
 

pictsidhe

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I like the way he now has better acceleration than a Cirrus. He forgot to mention a couple of minor details, though. The Cirrus was going uphill and was not at full throttle until well into the run.
At full throttle, an SR22 is 50' in the air before the Raptor was halfway down its maiden flight takeoff roll.

It's really, really hard not adding a snarky or cutting comment to facts like those.
 
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rbarnes

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I still counted 25secs and 2,000' to get to 80kts and still not flying.... not to mention he's comparing the acceleration between a plane loaded within 200lbs of gross with a plane that is at gross with 1 person and 10 gallons of gas.... and we have now officially moved on to taping over the wheel wells with "real strong tape" 🤦‍♂️
 

rv6ejguy

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Peter should compare apples to apples and that would be with the turbocharged SR22T with 315 hp. Takeoff run about 14-16 seconds with 2 aboard, unknown fuel, let's say 2800 pounds, Vr is 70-75 kts. from several videos I watched on YT.

Power to weight ratio 8.88 pounds/hp for the SR22T. Raptor would need around 405hp to match this performance and I calculate he's around 293hp now from the latest run. Ditto with 4 people and 620 pounds of fuel aboard, Raptor needs around the same 405 hp to have the same power to weight ratio as an SR22T at gross.

The 1000 pounds extra that Raptor weighs over the Cirrus hurts every performance parameter and it will require extra hp to make that up which means higher fuel burn. The turbocharged Conti 550 has pretty fair BSFC when running LOP in cruise. The Audi will be thrashing to make the required hp at high rpm and well outside it's optimal BSFC island and that is before the mods which Peter did to it which will certainly increase the BSFC over the stock Audi diesel specs. While .34 might be achieved at 2000 rpm stock, it's likely more like .38 at 4000rpm to develop 300 cruise hp. With Peter's mods, possibly more like .40 which is really close to what the Conti can do LOP.
 

pictsidhe

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With the very high backpressure from the turbos, there is no way he is as low as 0.4. With properly matched turbo(s), then a little under 0.4 at 4000 is possible.
 

cblink.007

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How about getting a review from somebody that is actually familiar with test flying aircraft. The climb rate was probably kept very shallow for a purpose.
as far as the instability goes nobody really knows because nobody else was in the cockpit. The long takeoff roll could have also been done intentionally the check stability and high speed on the ground just before liftoff. The landing that appeared to be less than stellar can also be due to the fact that they were not trying to set it on the ground in the first quarter of the runway and again they may have been checking for ground effect issues. The opinions on there by the media are basically standard for how the media actually understands anything they report on.
That flight was a demonstration in how not to test fly.
1. He started his narration by mentioning how he was 'in a rush to get airborne' due to rising ambient temperatures. With a known problem like that, a first flight attempt that time around should have been aborted. You do not do a first flight with known issues, such as engine cooling, ever.
2. The long takeoff roll was a result of an overweight and underpowered machine.
3. The aircraft exhibited significant flying quality deficiencies. Without proper instrumentation, it is very difficult to characterise and solve. However, he asked his followers and subscribers for input. Very amateur.
4. He did not land it how he did to characterise ground effect handling. He landed it to get on the ground.
5. He has no test plan; taking it up and seeing what happens while flying off the 40 hours is not the way to evaluate and characterize an aircraft intended for production. The test plans we write for our test work often exceed 100 pages (appendices included), because they cover everything, and for good reason.
 

bmcj

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Is that a fair summary of the first flight, as shown in this ANN video report?
Yes to all, except maybe the last point. There was some speculation that the pitch and/or roll oscillations may have been due in part to a side effect of the camera’s image stabilization protocol.
 

Victor Bravo

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The original video "news report" is far less of a hatchet job than some of us might have expected. It seemed almost completely factual and without a lot of "spin", but there were a few words thrown in here and there that took a little jab at the company.

I hope it is conidered relevant with the new restrictions on this subject, mods feel free to shoot at will:

Has anyone looked into the possibility that some bizarre airflow patterns and large vortices (shed off of the canard root, wing strakes, or upper fuselage curvature) are simply not allowing enough mass airflow or ram pressure into the upper fuselage intake air scoop?

That would account for some or all of the cooling and heat exchange problems... regardless of whether the radiators and fluids were designed optimally or performing as well as they could/should.

The cooling system is clearly not thought out really well, even from my amateur untrained point of view. Some sort of flow visualization "clown puke" pressure and velocity map, etc. etc. might show that the air is simply not getting into the scoop. The scoop is on the wrong side of the airplane for darn sure, but I'm speculating that the parts forward of the scoop could be just "swirling the air out of the way", or creating some bizarre reverse flow, etc. This has happened on several conventional cooling systems, so I can easily imagine it could happen on a weird one like this.
 
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Voidhawk9

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Wings and canard are far enough outboard that they're not going to affect the scoop. It is on a retreating portion of the fuselage though, so the bouundary layer will be thick, and there is no diverter or anything to encourage flow into it.
Plus, on the flight he had the scoop in the closed (half open) position and inadequate internal ducting to prevent the air flowing almost entirely around rather than through the rads.
Some Velocity canards have a pair of BIG NACA scoops up there, sometimes with VGs to encourage flow into them. Seems to work, but I suspect they also have good ducting internally to use that flow efficiently.
 

JayKoit

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Just watched the newest video above. Can someone confirm/clarify the following:

1 - In regards to the takeoff comparison, The Cirrus SR20 run is over 1000' higher in elevation, and we don't know OAT/DA either...given these variables it would seem that you can't make a fair comparison, correct? Plus it seems very apples to oranges to compare a naturally aspirated SR20 with an IO360 to his turbo setup...

2 - Can someone weigh in (objectively and appropriately) on Peter's new horsepower calculations? He's now stating he's getting over 300HP based on the changes he's made. Is his method for calculating that accurate, or not?
 

pictsidhe

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Peter is calculating his hp from fuel flow. He is using a BSFC figure attained by factory engines around 2000rpm and 90% throttle. I think 0.33? Owing to the tremendous back pressure from his turbos, his engine will not hit that BSFC anywhere.
The BSFC, like all diesels, will be somewhat higher at his 4000 max power rpm. Quite a lot higher in his case. I'd estimate up around 0.5 compared to a stock bsfc of around 0.38 up there. That would mean he is only getting around 2/3 of his claimed power.
A YouTube commentator recently said that the engine was dynoed a long time back. It made around 200hp. Peter explained that the dyno was broken and he didn't have time to go back. Any of us see that?
 

rv6ejguy

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Just watched the newest video above. Can someone confirm/clarify the following:

1 - In regards to the takeoff comparison, The Cirrus SR20 run is over 1000' higher in elevation, and we don't know OAT/DA either...given these variables it would seem that you can't make a fair comparison, correct? Plus it seems very apples to oranges to compare a naturally aspirated SR20 with an IO360 to his turbo setup...

2 - Can someone weigh in (objectively and appropriately) on Peter's new horsepower calculations? He's now stating he's getting over 300HP based on the changes he's made. Is his method for calculating that accurate, or not?
See my post #51 above. I don't think Peter considered all the variables for comparison. During the first flight video and from the tower video of that flight, the initial ROC and angle of climb looked downright scary before the power reductions. We know the weight is high already so that is a given, the other possible factors are:

Lack of thrust (power)
Low lift coefficient
High drag
 

aeromomentum

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A complete redesign of the cooling system (aircraft?) basically from scratch will be required to make a maybe minimally viable aircraft. That being said, the 30/70 antifreeze to water mix will help as Ross suggested. The type of antifreeze also has an impact on the heat capacity. The addition of Water Wetter will help. These changes, along with spray bars, may just allow for a full pattern flight before overheating.

My guess is that even with a 400+HP engine working correctly the Raptor will not meet the performance goals by a wide margin.
 
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