A slight design change 6

[Sparweb]

Meet Alice. She's had a facelift and a new wardrobe. I guess she needed to look pretty for her date with DHL.

2018:

2021:

 

[3DDave]

Why ever would one not want to put a weighty pod on the tip of a thin and apparently greatly flexible wing? And make it have a large gyroscopic component on top of that. Not sure which is the topper - the ever so racy choice of the V-tail or the tiny butt-prop.

I thought those design choices had been thoroughly exhausted in the 1930s Italian aircraft industry with echos going into that strange collection that Germans built for WWII.

In unrelated, but somehow similar news, Peter Sripol did a 30 foot span foam-board airplane with 50 electric motors and matching props across the wing leading edge, but lack of stiffness (and colliding with the launch vehicle) made flying itfor more than a few seconds to almost an entire half minute more interesting than it should be.

https://www.youtube.com/watch?v=3aee2qDauTQ

 

[SWComposites]

Sigh. Alice 2018 was likely designed by someone who had never certified an aircraft. When they got around to the one engine out case the configuration was doomed.

 

[btrueblood]

How are wingtip-mounted motors better than the tail-mounted motors for an engine-out scenario?

 

[rb1957]

"Why ever would one not want to put a weighty pod on the tip of a thin and apparently greatly flexible wing?" ... never seen an F104, or a Learjet 31 ?

yes, I know something to be done carefully, but there are reasonable reasons for doing this (and for being very careful about doing it).

I find it "funny" that the original design supposedly took advantage of wing tip vortices, and was a new creative solution to a problem. Only to revised itself to a much more traditional design. To be sure, if we don't try new things we won't learn.

One issue they may have had is the weight a cables from battery (or whatever) to motor.

why to the engine nacelles have large inlets (where they had none before) ?

another day in paradise, or is paradise one day closer ?

 

[MintJulep]

https://www.eviation.co/aircraft/#Alice

If we imagine that the fuselage aft of the wings is full of battery and power electronics then the CG change from empty to fully loaded looks pretty dramatic.

The horizontal stabilizer and elevator look small.

why to the engine nacelles have large inlets (where they had none before) ?

Because even electric motors need cooling.

 

[rb1957]

A logical placement for the batteries is under the cabin floor. Mind you the "terrible" energy density of batteries means either you don't go far, or you have blister like an A380 under floor !?

Another option might be H2 fuel (instead of batteries) ... but that of course brings a Whole bunch of different problems with it.

and where'd the windows go ? DHL wouldn't be interested in pax, so now maybe a freighter ?

another day in paradise, or is paradise one day closer ?

 

[BrianPetersen]

The absence of windows is likely specific to DHL's application. Seems that this could be either a commuter or freight aircraft.

 

[GregLocock]

I expect DHL will get rid of the pretty tapered rear fuselage and go for a cylinder plus fairing...

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[3DDave]

The problem with doing anything with wing tip vortices is they are fundamental to the generation of lift - like inescapable. Anything clever one comes up with is just a patch that makes the flow look like it comes from a longer span - which is usually much cheaper to do unless, like large passenger/cargo jets the space at the airport is the thing limiting span.

Observe winglets - the greatest gift to stupid ground handling accidents ever. Watching one wing tip that would have passed over or under a wing or horizontal stabilizer instead slash its way to 10s of thousands in damage because the operator didn't want to pay a couple of ramp workers to keep an eye on clearance during pushback or taxi on the ramp tickles me in a way that only that famous truck-scalping bridge can approach.

 

[verymadmac]

So what are those inlets on the engines for?
Demonstration of an ignorance of blockage factor maybe, they look way too big for engine cooling, and its a terrible place for a heat exchanger.

I suppose the tapered fuse doesn't matter if they are hand loading parcels or if the hold is a constant section and gap between the tapered skin and the hold is filled with battery's (not a completely silly idea).
Look at the waste space in that fuselage

https://www.eviation.co/wp-content/themes/eviation/images/bg-takealook-3200-20210625.jpg

The payload difference between freight and passenger seems small (100 lbs) a bit of gillliner, carpet tape and a couple of cargo nets doesn't add up to much compared to 8 seats and interiors (plus the ducting and electrical plus the other passenger related bits and pieces).

Apparently pitching to Fedex with windows on your plane pictures is a big no no, guess the same might apply to DHL.

Observe winglets - the greatest gift to stupid ground handling accidents ever

nah everyone just needs to put their pitots on their wing tips (la F27) then ground handling issues just leave neat round holes in everything.

 

[SWComposites]

Wingtip engines are NOT better for a one engine out condition.

 

[rb1957]

"Wingtip engines are NOT better for a one engine out condition."

did anyone think they were ?

whilst worst position for engine out there "could" be other redeeming factors that off-set this and make it a reasonable design solution.

another day in paradise, or is paradise one day closer ?

 

[btrueblood]

Sorry, the renderings' quality made it look like the wingtip motors were the "new" design, and the OP didn't specify...

The new configuration looks a lot more conventional...which is not a derogatory term, people have looked at wing/tail/engine configurations for over a century now, and certain configurations just work better.

Though, a rotor strike on tail mounted fans might be an issue for takeoffs?

 

[rb1957]

the new location looks better for "prop ground strike" than the previous ...

though maybe they'd've added a ventral fin (a la Do335) ...

(edit) ... oh, I notice the "tail dragger" config ... the "prop ground strike" not so much of an issue with the earlier design ... maybe why they went this way ?

another day in paradise, or is paradise one day closer ?

 

[Ng2020]

Same issue as the proposed Embraer regional airliner configuration in the other post... Is the cargo door next to the prop?

 

[Sparweb]

It seems that some have not followed the "Alice" from Eviation with quite the same point of view that I have, or not followed it at all. I don't blame you - it's always been a foolish paper-airplane right form the get-go and has yet to look like it has the potential to be a successful design. This post is perhaps another example of poking fun on the internet. If you see it that way, then no worries, ignore me. This is only meant for fun.

The 2018 model's tip-pod engines were hilarious. To see them actually built was amazing and raised the prospect of seeing video someday of a dramatic ground loop engine blow-up. Since that could have caused some fatalities, it was ironically fortunate for Eviation that instead they had a battery fire which destroyed their prototype.

The current concept is profoundly flawed, but less obviously so. The tail cone is sleek but extremely flexible, being so narrow. It once again demonstrates that the designers are artists, not bounded by engineering. There are other details that will be very difficult to master with the proportions they show, such as directional stability, one-engine out, landing speed, aeroelasticity of the wingtips and tail. Perhaps others I haven't yet noticed.

Striking any deal with DHL by showing them that concept is a new level of amazing.

 

[verymadmac]

I was just struck by the thought, if that is the best of their airframe design, what on earth does the electrical system architecture look like?

 

[Ng2020]

Yes, the few images I've seen look doubtful, but for GKN to be involved as a supplier of both major structural assy's and wiring harnesses, it does their reputation no favours if the project were to fail. For that reason I would hope that they have done their homework in assessing the project's viability and technical feasibility.

 

[Sparweb]

They seem to be getting somewhere, now.
The proportions still don't look right, but better than the original.

That's an airspeed probe on the nose. That's always seen on flight test aircraft. Expect a flashy announcement, soon.