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10/23 Raptor Video

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BBerson

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Right. They should throw the trainees into some real life operations. Perhaps O'Hare would do.
Trainees could try O'Hare in slow times under supervision. But my training choice would be a normal average tower under supervision and not Valdosta. Valdosta tower is open 15 hours a day to process only 60 operations a day so that's 4 operations each hour. Hardly an efficient learning airport.
My main concern is all these towers at airports that don't need any. The 5 mile radius class D airspace control eliminates the ultralights and Basic Light Sport and other entry level, antiques, gliders and sport aviators from the populated areas people live. If it was non-towered it would have more operations.
 
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rbarnes

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I learned to fly at a Class B airport from day 1 through my instrument rating. No patience for sloppy radio work.
Can't count how many times my instructor would whack me on the back of the head and tell me to quit calling the controllers "Roger" since he was pretty sure that wasn't the guy's name.
 

Kyle Boatright

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Trainees could try O'Hare in slow times under supervision. But my training choice would be a normal average tower under supervision and not Valdosta. Valdosta tower is open 15 hours a day to process only 60 operations a day so that's 4 operations each hour. Hardly an efficient learning airport.
My main concern is all these towers at airports that don't need any. The 5 mile radius class D airspace control eliminates the ultralights and Basic Light Sport and other entry level, antiques, gliders and sport aviators from the populated areas people live. If it was non-towered it would have more operations.
Talk w/AOPA. They "saved" a lot of towers back in the day. Much to my chagrin.
 

Voidhawk9

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PM reporting slight power loss increasing during flight, blaming it for now on redrive tension increasing due to thermal expansion. Redrive pulled apart and oil leak and wearing parts replaced. Belts etc seem OK.
Must be a lot of waste heat going somewhere, OR the problem is elsewhere.
 

BBerson

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Engines lose power as they overheat. My Grob would overheat after about a ten minute climb. I wouldn't expect a long engine life running at high temp.
 

rv6ejguy

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In theory, if he fixes the cooling issues and gets it up high (say 15K') it ought to move along fairly well. Then there's the weight issue...
This would be around 260 KTAS at 25,000 feet burning 21 GPH, would take about about 50% more power and FF to get to his predicted 300 KTAS top speed up there. His FF at 230 KTAS would be around 14.6 GPH which is almost exactly double what he predicted (7 GPH) and almost exactly what I predicted a couple years back here.
 
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rv6ejguy

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PM reporting slight power loss increasing during flight, blaming it for now on redrive tension increasing due to thermal expansion. Redrive pulled apart and oil leak and wearing parts replaced. Belts etc seem OK.
Must be a lot of waste heat going somewhere, OR the problem is elsewhere.
Belt tension couldn't be soaking up 20-30ish HP as they'd get smoking hot and fail in a couple minutes. It's just another wild guess based on zero facts like he's done so often in the past, like with the wheel wells. Most belt drives need a properly tensioned belt via a mechanical spring or gas spring idler. The aluminum pulleys do heat up and expand and the belt can get dangerously tight and fail without one if just relying on a rigid cold tension setting. The trick is getting the right tension so the belt doesn't ride up or skip but not so tight as to additionally stress the belt.

His dry splines won't last long here. If they have to float, they need lube, otherwise splines need a press fit to live.
 

Kyle Boatright

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This would be around 260 KTAS at 25,000 feet burning 21 GPH, would take about about 50% more power and FF to get to his predicted 300 KTAS top speed up there.
I never saw 300 knots as realistic. Nor do I see 25K' as realistic without a complete redesign - the pressurization concept with externally bonded windows isn't confidence inspiring. Just thinking through it, is a single projection made about this aircraft in reach? It isn't unusual to miss a performance goal or two, but hit the rest. I'm not sure the Raptor is even in the ballpark with any of its initial claims - speed, fuel flow, useful load, pressurization.
 

rv6ejguy

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I never saw 300 knots as realistic. Nor do I see 25K' as realistic without a complete redesign - the pressurization concept with externally bonded windows isn't confidence inspiring. Just thinking through it, is a single projection made about this aircraft in reach? It isn't unusual to miss a performance goal or two, but hit the rest. I'm not sure the Raptor is even in the ballpark with any of its initial claims - speed, fuel flow, useful load, pressurization.
I agree, from what we've seen so far in flight testing, Raptor can't reach a single one of the performance predictions made back in 2013. Until Peter can shed something like 1400 pounds, getting down to a similar empty weight as a Lancair IV-P, he doesn't have a hope. That's a very tall order as long as he has the Audi diesel engine in there.
 

lelievre12

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Then you start performing takeoff, landing, stability and stall tests at that CG location, at the lightest weights possible (to keep speeds low early in the test program). Then you start doing these tests at slightly more forward and slightly more aft locations, until you reach CG locations at which landing and takeoff become problematic, which sets your forward limit, and at which stability or deep stall becomes concerning, which sets your rear limit.
Marc,

The straight and level 'landing configuration' CG determination seems logical however I'm wondering if exploration of accelerated stalls and slips is needed as well? (when I say stall I mean canard drop).

Or is it aerodynamically unnecessary and would stall the same way in a sharp banked turn as straight and level?

I note there are folks whom are using full rudder crossed controls to nail steep approaches and can't help wonder if this mode of 'flying' is beyond the tested envelope of those airframes.

In the same way I wonder if accelerated turns with an aft CG might stall the main wing if uncoordinated. Something you'd want test before turning base-->final with 4 aboard.

There is also the landing gear which is bound to affect the landing configuration stall differently. I'm expecting as the center of gear drag is below the ship CG that there will be a nose down moment which stalls the canard earlier than if the gear is up. Or put another way, the main wing would be closer to a stall in a gear up accelerated turn than a gear down flare to land.

The more I think about Raptor testing the longer the program becomes.
 

BJC

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The founder of Cobalt went to Georgia Tech. (Maybe in Tolouse?). The Valkyrie is bound to be successful.

Oh wait...
Yup. As I recall, I questioned his claim wrt GT, since the degree he has was not offered back in the dark ages when I was there. He replied to my email, asserting his degree.


BJC
 

lelievre12

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Dors anyone knoe the operating limitations?


BJC
Well we do now as pretty much the full envelope was 'explored' in the first few flights. I was actually dumbfounded when PM firewalled the aircraft in the circuit to see how fast she would go. So much for careful flutter testing.

Raptor Vs0 looks be be about 85KIAS and maximum straight and level looks to be 139KIAS. The ratio between the two is 1.63 which in case you were wondering is not....not...not good. The last time I saw a flying envelope that bad was when I looked to buy a 1947 Republic Seabee amphibian with an original Franklin engine. Vs0 was around 65MPH and max was barely 95MPH. This was a plane that was barely flying when it was in the air. The ratio? 1.53. Sounds close to the 1.63 above doesn't it?

By way of comparison my current bus (P210) stalls light at 44KCAS and max indicated is around 169KCAS. The ratio? 3.84. Most high performance aircraft should be in the 3-->4 range.
 
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BBerson

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I don't know why this research airframe would get any sort of normal test program. In the last video he mentioned the production model might have shorter and wider fins so it could be a completely different airframe if it gets to that.
The rudder area is split between two. So pushing one rudder to cross control isn't as effective, I would think.
 

Kyle Boatright

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I don't know why this research airframe would get any sort of normal test program.
Depends if he's still convinced this is the pre-production model, moving almost directly into production OR if he's given into the <seemingly obvious> thought that this one is DOA and he needs to reboot this thing from waaay back in the process.
 

Marc Zeitlin

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The straight and level 'landing configuration' CG determination seems logical however I'm wondering if exploration of accelerated stalls and slips is needed as well? (when I say stall I mean canard drop).
Yes. If you don't fly it during the Phase I (for E-AB aircraft) you're not allowed (and it's not smart to) fly it after Phase I. How else would you know what it does, even if the event is unplanned in Phase II?

I did stalls at forward, mid and aft CG's at light, mid and MGW's, at 0, 15, 30, 45, and 60 degrees of bank, and verified that my plane would not do anything untoward in any of those configurations.

Or is it aerodynamically unnecessary and would stall the same way in a sharp banked turn as straight and level?
It does NOT stall exactly the same way. At high bank angles and higher speeds and "G" loadings, the canard bob is more pronounced at rear CG's, and more "mushy" at forward CG's. You can't hold it in the stall for very long at 45 - 60 degrees of bank - the nose just falls off (and it feels like you're inside a clothes dryer, spinning around the wingtip). And that's just MY plane - it's possible that someone else's COZY MKIV would have different characteristics. Hence the need to test.

I note there are folks whom are using full rudder crossed controls to nail steep approaches...
You mean like me?

and can't help wonder if this mode of 'flying' is beyond the tested envelope of those airframes.
No, because I tested slips at various speeds in Phase I, along with slipping turns.

In the same way I wonder if accelerated turns with an aft CG might stall the main wing if uncoordinated. Something you'd want test before turning base-->final with 4 aboard.
Skidding turns are contraindicated, and COULD theoretically lead to a main wing stall at aftmost CG. Slipping turns, however, are not stall prone. I do not recall if I ever tested skidding turn stalls - could be a hole in my test program in 2002.

There is also the landing gear which is bound to affect the landing configuration stall differently. I'm expecting as the center of gear drag is below the ship CG that there will be a nose down moment which stalls the canard earlier than if the gear is up. Or put another way, the main wing would be closer to a stall in a gear up accelerated turn than a gear down flare to land.
The moment change with gear up/down is minimal in a COZY MKIV/Long-EZ - the landing brake has more effect on the nose down moment, and even that's relatively small. In any case, I did all of my stall testing with the gear up.

The more I think about Raptor testing the longer the program becomes.
A REAL test program on a new design aircraft is far longer than a Phase I program for a proven design, such as a Velocity or COZY MKIV, which still take 35 - 45 hours to work through the whole envelope of required tests. I only had 3 increments of CG and weight - with a new design, where the limits of each are unknown, much smaller increments of expansion are indicated, so it's a LOT more flying. Wouldn't surprise me if the plan (if there was one) would call for 150 - 300 hours of flying.

Raptor Vs0 looks be be about 85KIAS ...
I doubt that the stall speed is that high. Since PM doesn't know what a stall is and hasn't tested slow flight, all I can go by is wing loading, which is almost identical to the COZY MKIV, given the GW at which Raptor is flying and the wing area. Although stall speed is also related to CG location, and we don't know that either, it's not a HUGE effect.

In any case, my plane canard stalls at around 61 KIAS at aftmost CG, and maybe 67 KIAS at fwd most CG (both mid-weight). Add a few kts for MGW. So I'd expect Raptor to be in the mid 70's - call it 75 KIAS.

BUT, since we already know that his static ports are in the wrong place and read incorrectly, we actually have no clue whatsoever as to what his KCAS is, or KTAS. We can estimate from GS, if someone wanted to do so, based on the ground track and speeds, but he doesn't really seem capable of holding a constant speed or altitude for any length of time, so that's hard.
 

Kyle Boatright

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In any case, my plane canard stalls at around 61 KIAS at aftmost CG, and maybe 67 KIAS at fwd most CG (both mid-weight). Add a few kts for MGW. So I'd expect Raptor to be in the mid 70's - call it 75 KIAS.
The CAFE foundation's test of a Cozy MK IV pegged the (canard) stall speed between 61 and 71 knots, IIRC, depending on gross weight and CG. Substantially in agreement with your info...
 
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