Question for those smarter than me

Ventucky Red

Ventucky Red

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Jon
Which is just about 99.9999999999% of the others here..:p

What is the purpose of the third pusher prop on the tail, and why are the motors mounted at end of the wing.. seems to me that it would make it a little harder to control should they lose and engine err.. excuse me a motor

Full article here https://www.cnbc.com/2019/02/20/siemens-to-provide-electric-motors-for-start-up-eviations-plane.html


105748220-1550607284989eviation.jpg
 
The third motor is easy - they need three to get the thrust they want/need. As for the location of the wing motors, you're right about the differential thrust issue. Maybe with three motors the loss of one of the outboard ones isn't as big a deal.
 
Maybe if you lose thrust from one of the wingtip motors, you should shut down the other wingtip motor, and let the centerline one carry you to the scene of the crash?
 
Conceptual design art from companies that have never built an airplane before is always fun. You may be smarter about airplanes than 99% of the people who work there.

Doesn't look like they thought about prop clearance on T/O and landing either.
 
Ventucky Red said:
....seems to me that it would make it a little harder to control should they lose and engine err.. excuse me a motor....
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This is purely speculation on my part, but it seems like it would be relatively simple to have a FADEC-type controller that would throttle back the opposite wingtip motor to some preprogrammed percentage of thrust if you lost a wingtip motor. With the tail motor running at full thrust, it might be enough thrust to fly you to an uneventful landing somewhere without causing a loss of control due to yaw forces. This could be done quicker than your brain could even process the motor loss. Again, just speculation to possibly explain the design decision to place the wing motors where they did.
 
If they made the V tail even bigger they could make the wings smaller and it would be more efficient.


/sarcasm
 
Fallsrider said:
This is purely speculation on my part, but it seems like it would be relatively simple to have a FADEC-type controller that would throttle back the opposite wingtip motor to some preprogrammed percentage of thrust if you lost a wingtip motor. With the tail motor running at full thrust, it might be enough thrust to fly you to an uneventful landing somewhere without causing a loss of control due to yaw forces. This could be done quicker than your brain could even process the motor loss. Again, just speculation to possibly explain the design decision to place the wing motors where they did.
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Yeah, because computers never get faulty data, or misinterpret data. Having them make all the decisions is better. In fact, a computer wrote this post.
 
I guess slipping in for a crosswind landing is out now, huh?
 
As depicted, I'm not convinced you could rotate the aircraft for takeoff without striking the rear propeller. It would only be a matter of time that anyone flying this thing in a crosswind would also strike the other two props. High school daydream engineering.
 
I'd almost bet the prop in the rear is to produce renewable energy to power the props on the wing tips. Everything's got to be green now.
 
Salty said:
I'd almost bet the prop in the rear is to produce renewable energy to power the props on the wing tips. Everything's got to be green now.
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@Salty you must not have studied engineering! Clearly the two wing tip props are simple windmill-like generators to generate the power to turn the pusher in back. If they were behind the pusher it just wouldn't work because the relative wind will be from the front. They're probably mechanically geared to the rear prop so they can run when there's a total loss of electrical. Plus this design allows them to land like a Osprey with a simple modification to allow wing rotation.
 
Mycroft17 said:
The third motor is easy - they need three to get the thrust they want/need. As for the location of the wing motors, you're right about the differential thrust issue. Maybe with three motors the loss of one of the outboard ones isn't as big a deal.
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Might be the plane was designed by marketing folks, not people with any practical experience. Or they may consider that loss of a single electric motor is less likely than if it was a recip or turbine.

Interesting to consider what the VMC would be, in a case like this. Back when I was a kid, I made a U-Control airplane with two Cox 0.49s on the wingtips. Had to start the outboard one first to ensure it ran out of gas first. Even so, the thing did an incredible demonstration of VMC roll....

Ron Wanttaja
 
chemgeek said:
As depicted, I'm not convinced you could rotate the aircraft for takeoff without striking the rear propeller. It would only be a matter of time that anyone flying this thing in a crosswind would also strike the other two props. High school daydream engineering.
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How do we know those are not puller props and it flies backward?
 
Don't understand what the benefit is of having pusher props. Tractor props on the wings would put them in less disturbed air ahead of the airframe.

There's a reason every other tri-motor has the props out front. ;)
 
The motors are on the wingtips because the battery weighs 7,000 lbs. The wing loading has to be distributed to offset the fuselage weight of more than 9,000 lbs when the passengers are considered, much like a zero fuel weight restriction does.

That's my uneducated guess, anyway. :D
 
wanttaja said:
Might be the plane was designed by marketing folks, not people with any practical experience. Or they may consider that loss of a single electric motor is less likely than if it was a recip or turbine.

Interesting to consider what the VMC would be, in a case like this. Back when I was a kid, I made a U-Control airplane with two Cox 0.49s on the wingtips. Had to start the outboard one first to ensure it ran out of gas first. Even so, the thing did an incredible demonstration of VMC roll....

Ron Wanttaja
Click to expand...

Ronno:
This is an 8-th grade wet-dream. >049s driving 6x3s (how did you "peak" outboards with inboards up and "peaked?" Guess you coulda run golden-bees inside; I dunno. Please post something on engine-out performance and handling. I absolutely loved .049 C-L. Best
 
wanttaja said:
Might be the plane was designed by marketing folks, not people with any practical experience. Or they may consider that loss of a single electric motor is less likely than if it was a recip or turbine.

Interesting to consider what the VMC would be, in a case like this. Back when I was a kid, I made a U-Control airplane with two Cox 0.49s on the wingtips. Had to start the outboard one first to ensure it ran out of gas first. Even so, the thing did an incredible demonstration of VMC roll....

Ron Wanttaja
Click to expand...

Similar experience with a "Hey Bubba hold my beer" home design/built RC plane.
The take off was exciting, and the finish was nothing short of spectacular.
Even counter rotating props didn't help.
 
The wing tip props probably have some sort of positive effect on the wing tip vortices thereby reducing the associated induced drag.
 
GRG55 said:
Don't understand what the benefit is of having pusher props. Tractor props on the wings would put them in less disturbed air ahead of the airframe.

There's a reason every other tri-motor has the props out front. ;)
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I don't either, but the Rutan Voyager back engine did all the work after takeoff iirc. Front one stayed feathered.
 
SkyDog58 said:
The wing tip props probably have some sort of positive effect on the wing tip vortices thereby reducing the associated induced drag.
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I would bet so. Too bad Vmc is around 400 kts!
 
The front end looks somewhat like a BD-5....is Jim Bede involved with this project?
 
Note that since there's no fuel tank in the wing, they actually get some benefit to putting some weight out at the tip. It's a similar reason why I can stick 20 gallons in my tips without it counting against the overall gross.
 
  • “Several challenges remain before battery-powered flights take off, including battery weights.”
See, they have obviously thought all those things you guys have brought up. Clearly “flying after the Paris Air Show” will happen at a time TBD after these very minor issues are worked out:rolleyes:

Cheers
 
keen9 said:
Conceptual design art from companies that have never built an airplane before is always fun. You may be smarter about airplanes than 99% of the people who work there.

Doesn't look like they thought about prop clearance on T/O and landing either.
Click to expand...
Thank you for the validation that I am not the only one thinking this way.

To expand on your thought: the artists drew a futuristic airplane that looks cool. They they tried to find an aeronautical engineer who would make it work. They were getting "no" and "hell no" everywhere until they found 1 guy who was willing to go with the farce. We now have a nice new concept that will need an engine rebuild every time it lands properly with high AOA. :)
 
the third one in the tail is actually a wind powered mechanism for the margarita machine.
 
BigBadLou said:
Thank you for the validation that I am not the only one thinking this way.

To expand on your thought: the artists drew a futuristic airplane that looks cool. They they tried to find an aeronautical engineer who would make it work. They were getting "no" and "hell no" everywhere until they found 1 guy who was willing to go with the farce. We now have a nice new concept that will need an engine rebuild every time it lands properly with high AOA. :)
Click to expand...

So.... is it a requirement to tear down an electric motor after a prop strike..??
 
3393RP said:
The motors are on the wingtips because the battery weighs 7,000 lbs. The wing loading has to be distributed to offset the fuselage weight of more than 9,000 lbs when the passengers are considered, much like a zero fuel weight restriction does.

That's my uneducated guess, anyway. :D
Click to expand...

I bet you could convince the designer that it would be lighter if he didn't fully charge the batteries.
 
I'm currently flying 2 R/C twins. They are both P-38's. One 55 inch wingspan, the other 14 inch.
They both have counter rotating props. Single engine is pretty tame.
 
I have the UMX Commander. Only flown it once so far with a hand launch and spot landing in a wet and sandy baseball infield. Like 6” bounce stop. The wing glue separated. Hoping to fly soon from an improved surface.
 
"Several challenges remain before battery-powered flights take off, including battery weights."

Battery technology only improves 1.5% per year, which means we will be dead before this thing works.
 
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