Cobalt Valkyrie

I want this plane to succeed. It's very pretty. (Well, except for the mock-up interior which is horrid.)

There are engineering points on this aircraft that I just don't understand, though.

* The twin tails is the biggest one. That's a lot of added weight, complexity, and drag for an aircraft that is supposed to be fast, go far, and carry lots. I'd love to know what they thought they were gaining with that other than, "it looks cool!"

* The canopy. The ridiculous opening mechanism must weigh piles. How do you get into the thing? I see a fat bar pulled right across where I'd like to put my feet as I get in. How about getting into the back seat? Is it air-conditioned? Because with that much glass and no opening windows, it's going to be a sauna in the summer.

* Twin wheels on the nose. Again, why? Yes, canard designs rest a bit more weight on the nose. But what did that extra weight and complexity gain you in such a small aircraft?

* Winglets? Again, sexy, but pointless. A Boeing-style blended tip would be more efficient and lighter when you don't need to worry about wingspan limitations. This plane is too small for wingspan limitations.

I want this thing to work. So amazingly sexy. Those design decisions do make me question its viability, though.
 
The twin tail is a good point, there is no good purpose for it. The twin nose wheel I can forgive, I don't mind the idea of redundant nose wheel on a canard where if the nose goes down my heals may grind. :lol:
 
Henning said:
The twin tail is a good point, there is no good purpose for it. The twin nose wheel I can forgive, I don't mind the idea of redundant nose wheel on a canard where if the nose goes down my heals may grind. :lol:
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I'm guessing the CG is located relatively far aft since that's where the wing and engine are. That means there is a relatively short moment arm between the CG and the vertical surfaces, necessitating large vertical surfaces.

So instead of one huge surface, they designed it with two smaller ones.
 
kyleb said:
I'm guessing the CG is located relatively far aft since that's where the wing and engine are. That means there is a relatively short moment arm between the CG and the vertical surfaces, necessitating large vertical surfaces.

So instead of one huge surface, they designed it with two smaller ones.
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Which is less efficient.
 
A little bit about the designer.

David has a Master of Science in Aerospace Engineering from the Georgia Institute of Tech in aircraft design as well as a physics and economics degree from the Ecole Nationale Supérieure des Mines de Nancy. He received his private pilot license in 2001, and started his career at Altran, a global leader in innovation and high‐tech engineering consulting, where he focused on aerospace consulting.
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But I guess we all know better.
 
SkyDog58 said:
A little bit about the designer.



But I guess we all know better.
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You obviously have never worked on a French or Italian machine before, it's all about beauty.:lol: You would not believe the arguments I have commissioning yachts from Southern Europe. "You can't put that there, we need to be able to fix that thing, and right now I have to cut the boat up to get to it." "But look how beautiful it is there, it fits perfectly!":rofl::mad2::rofl:
 
Henning said:
You obviously have never worked on a French or Italian machine before, it's all about beauty.:lol: You would not believe the arguments I have commissioning yachts from Southern Europe. "You can't put that there, we need to be able to fix that thing, and right now I have to cut the boat up to get to it." "But look how beautiful it is there, it fits perfectly!":rofl::mad2::rofl:
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Actually I had an Italian girl say exactly that.
 
SkyDog58 said:
A little bit about the designer.



But I guess we all know better.
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Robert McNamara had a great resume and that didn't turn out well. This is a really neat project, but after 5 years and 5 prototypes, plus some of the compromises inherent to the configuration, it ain't exactly on the fast track to success.
 
So instead of one huge surface, they designed it with two smaller ones.
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Henning said:
Which is less efficient.
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It worked pretty well on this:

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Yeah and on this one as well.

aa2kqfxbxyx3qtzwiohm.jpg


But they were both designed by some guy named Kelly Johnson who obviously did not know that it was a poor design.
 
Or the b-70, f-15, f-18, mig 25, SU 27, F-22, etc.

Single vs multiple vertical surfaces is a compromise. A single surface will be more aerodynamically efficient, at the cost of higher point loads and a bigger (taller) overall aircraft.
 
kyleb said:
Or the b-70, f-15, f-18, mig 25, SU 27, F-22, etc.

Single vs multiple vertical surfaces is a compromise. A single surface will be more aerodynamically efficient, at the cost of higher point loads and a bigger (taller) overall aircraft.
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Also, I imagine that with a pusher configuration, you have a lot less airflow over the rudder at low speed...
 
kyleb said:
Or the b-70, f-15, f-18, mig 25, SU 27, F-22, etc.

Single vs multiple vertical surfaces is a compromise. A single surface will be more aerodynamically efficient, at the cost of higher point loads and a bigger (taller) overall aircraft.
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For anyone to say a single vertical is more efficient requires knowing the size and shape of a single vertical for equivalent directional stability over the same range of AOA and sideslip. I can think of a number of possible reasons that two might be more efficient than one on a configuration like this.

Edit: one obvious one is that if a centerline vertical is masked,my the fuselage at higher AOA two smaller verticals canted outboard can be more efficient than one single one tall enough to be effective in the fuse wake.

Nauga,
Whose tail is part of the whole
 
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kyleb said:
Or the b-70, f-15, f-18, mig 25, SU 27, F-22, etc.

Single vs multiple vertical surfaces is a compromise. A single surface will be more aerodynamically efficient, at the cost of higher point loads and a bigger (taller) overall aircraft.
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F-22 and SR-71 have twin, canted tails for reduced radar cross-section. Many of those have twin tails to increase maneuverability, including all the fighters without increasing height. In particular, the Navy planes. For the twin-boom aircraft, there isn't the same weight penalty as single fuselage aircraft due to the added reinforcement needed to put it in the center (and complication).

Each of those has a really good reason to go with the twin tail. There may be one for this aircraft as well, but I don't know what it is. I doubt it's masking: other pusher aircraft with similar body forms work great with one vertical tail. They also have no issues with the prop location. It may be structural. With the engine in the back, for access, there may not be sufficient structure atop the engine for the tail.

I still think it was done because it looks cool.
 
arnoha said:
I still think it was done because it looks cool.
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Might very well be. Certainly worked for Mooney and Beech. I just took issue with the 'single is more efficient' POV.

Nauga,
and form over function
 
nauga said:
Might very well be. Certainly worked for Mooney and Beech. I just took issue with the 'single is more efficient' POV.

Nauga,
and form over function
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Other than the blanketing issue (and vortex impingement), isn't a single fin going to have more authority, given the same shape and total area? Lower tip losses, less effective area lost to the boundary layer, etc...Allowing you to shrink the surface somewhat if you choose?
 
arnoha said:
I doubt it's masking: other pusher aircraft with similar body forms work great with one vertical tail.
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Remind me of a couple of successful pushers of that planform (or body shape) with a single tail. I honestly can't think of any.
 
kyleb said:
Other than the blanketing issue (and vortex impingement), isn't a single fin going to have more authority, given the same shape and total area? Lower tip losses, less effective area lost to the boundary layer, etc...Allowing you to shrink the surface somewhat if you choose?
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I think nauga's point was that that is true in ideal case, but the real world may pop some of those balloons. First, a longer fin means more cantilevered length. More length means more structure means more weight. At some point, the weight savings of having only one structure is overcome by the savings of having two weaker structures. This is one of the reasons why Air Force fighters often have twin tails. Two short tails means pulling more G's before breaking without unduly fattening the fin. The Navy gets the added bonus of being shorter so it fits on a carrier better.

Another factor is roll/yaw coupling. Since the vertical fin only extends up and not down, there is always some roll introduced with rudder input. A longer rudder puts in a greater lever arms means more roll with your yaw. It could be done to ease the flying characteristics.

The last issue is the blanketing. Sticking the fin out in cleaner, faster air could be the last reason for all the complication of two tails.

And, granted, carbon fiber construction massively reduces the penalty for the structure of twin tails.

Still. None of that seems to apply to this aircraft at first read. I could definitely be wrong, but that's my read on it.
 
kyleb said:
Remind me of a couple of successful pushers of that planform (or body shape) with a single tail. I honestly can't think of any.
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Not sure what you're including in the planform as criteria, but how about:

  • All the Bede aircraft.
  • All the Lake aircraft.
  • Icon A5
  • Seabee
  • Prescott Pusher
The Bede come closest to the planform. I was unable to find any canard pushers with a single tail, granted. I find it hard to believe the canard makes much of a difference here, but I won't stake my life on it.
 
FastEddieB said:
Not sure what you're referring to as platform, but...

8707706826_00613f2e8e_z.jpg
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Planform is the general arrangement of the airframe. The single engine Cessnas share a common planform ( high wing, tractor, monoplane). Most of the fighters in WWII shared a common planform - low wing tractor monoplane.

A canard pusher effectively defines a planform. Seabees, Icons, and Sky Arrows share a planform. But not with canard pushers.
 
SkyDog58 said:
Yeah and on this one as well.

aa2kqfxbxyx3qtzwiohm.jpg


But they were both designed by some guy named Kelly Johnson who obviously did not know that it was a poor design.
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You're talking completely different function that a little put put fractional-sonic plane doesn't need addressed on the SR-71, and I don't see where this Cobalt thingy has two engine nacelles.

Are you guys really this stupid?
 
Here's another winner from the same Kelly Johnston:

image.jpeg

Single tail. Kelly Johnston used a twin tail when it was advantageous and served a purpose.
 
Henning said:
You're talking completely different function that a little put put fractional-sonic plane doesn't need addressed on the SR-71, and I don't see where this Cobalt thingy has two engine nacelles.

Are you guys really this stupid?
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Yes henning we are that stupid. Not all of us are an expert on everything like you seem to be. We are all in awe of your superior intellect and your vast experience in designing and building aircraft as well as you vast knowledge of all other things. I am particulary impressesd with your deep undertanding of all of the social economic ailments of the world and of your plans to cure them. I bow to your superiority.
 
It's pretty, doubt I'll see one on a flight line anytime.
 
"It is very likely that it does not need any further discussion and thus bumping it serves no purpose. If you feel it is necessary to make a new reply, you can still do so though."
...so, I thought it did because their website now is claiming that you can order one for a 2018 delivery.. $15K deposit.. since it is now 2018 I wonder if we'll see this go from vaporware to flying model? Its price is competitive with Mooney and Cirrus..

I'm dubious since the site looks dormant since about 2016 though. Anyone else hear anything?
 
Henning said:
The twin tail is a good point, there is no good purpose for it. The twin nose wheel I can forgive, I don't mind the idea of redundant nose wheel on a canard where if the nose goes down my heals may grind. :lol:
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Now the bonanza lovers are going to be upset.
 
Tantalum said:
"It is very likely that it does not need any further discussion and thus bumping it serves no purpose. If you feel it is necessary to make a new reply, you can still do so though."
...so, I thought it did because their website now is claiming that you can order one for a 2018 delivery.. $15K deposit.. since it is now 2018 I wonder if we'll see this go from vaporware to flying model? Its price is competitive with Mooney and Cirrus..

I'm dubious since the site looks dormant since about 2016 though. Anyone else hear anything?
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Considering that this thread and their website has been dormant for the last couple of years. I'm curious as to what made you think of this.
 
FormerHangie said:
Considering that this thread and their website has been dormant for the last couple of years. I'm curious as to what made you think of this.
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Lately YouTube has been giving me recommended videos that are YEARS old. An old valkyre video popped in my recommended feed and it made me think to do some googling and I saw on their site that they are claiming 2018 deliveries. But the POA trust has been silent so was curious if there was some back story to it

zaitcev said:
The test accident was in September 2017
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Wow... I had no idea they had an accident. The write up (quoted below) sounds like there could be some serious aerodynamic issues with the design of the airplane. Planes have accidents in testing, but if basic controllability is suspect then this doesn't bode well for them


"The pilot stated that immediately after rotation, he experienced extreme difficulty controlling the airplane. As the airspeed increased, he began to attain some controllability and climbed to about 1,000 feet above ground level. He determined that the ailerons were ineffective but was able to use the rudder for directional control. The pitch stability was sporadic with him experiencing intermittent pitch up and down movements. After about 20 minutes of manipulating the flight controls and practicing climbing and descending using the trim, he managed to stabilize the airplane around 90 kts."
 
Tantalum said:
Lately YouTube has been giving me recommended videos that are YEARS old. An old valkyre video popped in my recommended feed and it made me think to do some googling and I saw on their site that they are claiming 2018 deliveries. But the POA trust has been silent so was curious if there was some back story to it


Wow... I had no idea they had an accident. The write up (quoted below) sounds like there could be some serious aerodynamic issues with the design of the airplane. Planes have accidents in testing, but if basic controllability is suspect then this doesn't bode well for them


"The pilot stated that immediately after rotation, he experienced extreme difficulty controlling the airplane. As the airspeed increased, he began to attain some controllability and climbed to about 1,000 feet above ground level. He determined that the ailerons were ineffective but was able to use the rudder for directional control. The pitch stability was sporadic with him experiencing intermittent pitch up and down movements. After about 20 minutes of manipulating the flight controls and practicing climbing and descending using the trim, he managed to stabilize the airplane around 90 kts."
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I think they're doomed. Eight years and they don't have a viable design. Plus, the marketplace they're selling into is small. Aircraft design has progressed past the point to where the first flyable prototype crashes during normal maneuvers, so I have to question their design team's competence.

If I were an investor in this enterprise, I'd pull the plug. But then, this is not a project I would have put my money in.
 
Tantalum said:
The write up (quoted below) sounds like there could be some serious aerodynamic issues with the design of the airplane. Planes have accidents in testing, but if basic controllability is suspect then this doesn't bode well for them.
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Several ways to look at that incident exist. They brought a new test pilot, who promptly crashed the prototype. Previous test pilots found nothing untoward with it, so what gives? Maybe the new guy was not Len Fox. Or there was a downtime and someone decided to try something out. Or a technician forgot to put a cotter pin into a crown nut.
 
90 kt rotation. :oops:
 
13 years later and they're still afraid to put the gear up? Clearly not on a fast track.
 
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