For all you knuckheads that only visit the site through tapatalk, or just visit the forum only through the site, the new Featured Bush Plane Article is up on the Double Ender. https://www.backcountrypilot.org/features/category/featured-bush-planes/the-prototype-double-ender

Go check it out. The article is written in a way that speaks to us directly (the backcountry/stol crowd), and the video is mind blowing. The DE is an awesome machine. This is the most in depth reporting on the Double Ender to date, in my opinion. Thank you Zane for spending the time developing this type of content. (You lucky bastard)

Thanks Evan! I'll have to check it out later.

Awesome work, Zane! I would have had to change my underwear after some of those approaches.

Oregon180 wrote:Awesome work, Zane! I would have had to change my underwear after some of those approaches.

It helps to just look through a lens and pretend you're watching a movie.

Zzz wrote:

Oregon180 wrote:
It helps to just look through a lens and pretend you're watching a movie.

Sly dog...

That was awesome, Zane!

Looking forward to reading it after work!

There is only one of these right?

It looks like they totally did away with those custom-designed wings which it was using originally, this looks like a whole new set?

The time and energy which has gone into developing this aircraft must be unbelievable.

Battson wrote:There is only one of these right?

It looks like they totally did away with those custom-designed wings which it was using originally, this looks like a whole new set?

The time and energy which has gone into developing this aircraft must be unbelievable.

They are certainly custom, but yes, I believe this is a new wing from what it had originally. It's pretty active with the slats and spoilers.

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Amazing Video ..Great job ZZZ ! Music sounds fab ! Breitling...look out..there is new competition for best promos !..

The DE has two modified 914 Rotax engines bumped from 115 to 130 hp each.

The recently announced Rotax 915 puts out 135 and I suppose the DE team could possible massage that a bit more as well, say bumping it to 150 hp.

Now envision this thing in ZZZ's future videos leaping and landing with 300 hp available. It's almost criminal
.

Denali wrote:
Now envision this thing in ZZZ's future videos leaping and landing with 300 hp available. It's almost criminal

Any idea how efficient the inline-twin setup is? I can't imagine that the rear engine is converting fuel into thrust as well as it would if it didn't have another engine in front.

Cool plane and awesome to see someone putting their ideas into reality. Nice work on the article and video Z.

TradeCraft wrote:Any idea how efficient the inline-twin setup is? I can't imagine that the rear engine is converting fuel into thrust as well as it would if it didn't have another engine in front.

In a very, very basic sense - the energy added to the airflow (power delivery) of the propeller is a function of the difference in the air's velocity on each side of the prop, airspeed off the back less the airspeed coming in, among other things.

For the aft prop to lay down the same power as the front prop, it needs to accelerate the already fast moving air to higher speed again, which is less efficient because drag varies with the square of the airspeed - so there is additional drag. Then you have all the turbulence from the front prop, which I don't remember how to account for numerically... but it's certainly adding more drag (and stress on the prop).

So yes, the airflow coming off the front prop is definitely going to reduce the performance of the aft prop, the fuel burn per thrust delivered won't be as good.

Battson wrote:

TradeCraft wrote:Any idea how efficient the inline-twin setup is? I can't imagine that the rear engine is converting fuel into thrust as well as it would if it didn't have another engine in front.

In a very, very basic sense - the energy added to the airflow (power delivery) of the propeller is a function of the difference in the air's velocity on each side of the prop, airspeed off the back less the airspeed coming in, among other things.

For the aft prop to lay down the same power as the front prop, it needs to accelerate the already fast moving air to higher speed again, which is less efficient because drag varies with the square of the airspeed - so there is additional drag. Then you have all the turbulence from the front prop, which I don't remember how to account for numerically... but it's certainly adding more drag (and stress on the prop).

So yes, the airflow coming off the front prop is definitely going to reduce the performance of the aft prop, the fuel burn per thrust delivered won't be as good.

Interesting. So, aside from the "safety" associated with the twin engine redundancy, what other advantages are there?

I guess it's structurally lighter / simpler than a conventional twin, which have very beefy wing sections to support the engines (which also can't be used for spoilers / flaps around the engine nacelles) while still having more power and redundancy, and none of the single engine out yaw issues.

Battson wrote:

TradeCraft wrote:Any idea how efficient the inline-twin setup is? I can't imagine that the rear engine is converting fuel into thrust as well as it would if it didn't have another engine in front.

In a very, very basic sense - the energy added to the airflow (power delivery) of the propeller is a function of the difference in the air's velocity on each side of the prop, airspeed off the back less the airspeed coming in, among other things.

For the aft prop to lay down the same power as the front prop, it needs to accelerate the already fast moving air to higher speed again, which is less efficient because drag varies with the square of the airspeed - so there is additional drag. Then you have all the turbulence from the front prop, which I don't remember how to account for numerically... but it's certainly adding more drag (and stress on the prop).

So yes, the airflow coming off the front prop is definitely going to reduce the performance of the aft prop, the fuel burn per thrust delivered won't be as good.

I'm not nearly as up to speed on this as I should be, but here's a shot at some engineering talk from the helo side of the house. At some climb rates, the induced power is actually less than in a hover on many helicopters, and it's supposedly that on a coaxial helicopter the lower rotor is more efficient since it's always in a "climb." But momentum theory isn't complex enough to wrap this up. I'd have to pull out my notes from the discussion we had on this last year to get more detail.

There's definitely the chance for losses due to turbulence as the aft prop encounters the vortex sheet from the forward prop and the opposite rotation of the air from the forward prop. I'm curious if double-ender's set-up has more of the benefits or detractors or if they all come out in a wash.

Cool. I don't get it, but I don't have to. Hats off to the innovation and pioneer spirit.

I'm curious...

On a push pull, are the props generally the same (or can they be different?) because of the turbulence, air velocity differential, and other factors? I figure you really can't have too big of a torque difference front vs rear because that would create some roll wouldn't it? I am also not sure about harmonics and other vibration factors relating to the use of different props, rpm settings, and for that matter even different engines, for inline twin configurations.

Also the video and article in the link note that one of the 914 engines is carb, the other fuel injected. Is that for redundancy ie, the carb is a tad simpler with no complex injectors and related electronics, whereas injection does not suffer from carb icing issues? Anyone know?

I've seen Cessna C-337 Skymasters flying above me, but have never actually approached one on the ground to have a closer look. Sort of a rare bird, at least around here.

You know, the thing about this website backcountrypilot.org, the more you read, the more you begin to realize how much more there is to know about almost everything. Humbling actually.

That Double Ender is some kind of cool plane ! In a weird sort of way it somehow also reminds me of the Oscar Meyer Wiener Mobile. Not sure why?

Zane,
Great video and documentation of this cool airplane.

I totally dig the double ender!

I intentionally avoided being too detail oriented for this piece, opting instead to try to just put you guys in the cockpit and share my experience going for a ride. I didn't have the footage nor the time to interview Alec more about the technical details. I think if I wanted I could do a highly detailed profile of the aircraft, but I know there's still a little discretion on their part regarding some of the design. I'm still wondering what he's doing for cabin heat, because the day we flew it was really warm so the topic never came up.

gbflyer wrote:Cool. I don't get it, but I don't have to. Hats off to the innovation and pioneer spirit.

Live and let live for sure, but I can't see how you'd not "get" a wide open view in front of you while flying. It is so cool. The wing is undeniably effective for STOL, though another question I didn't think to ask was why the increased dihedral?

As for me, I'm loving this role. The time to do these features is now more scarce than ever, unfortunately. I didn't even get to finish the Alaska/CubCrafters trip series. If only I could quit the day job...

Zzz wrote:I intentionally avoided being too detail oriented for this piece, opting instead to try to just put you guys in the cockpit and share my experience going for a ride. I didn't have the footage nor the time to interview Alec more about the technical details. I think if I wanted I could do a highly detailed profile of the aircraft, but I know there's still a little discretion on their part regarding some of the design. I'm still wondering what he's doing for cabin heat, because the day we flew it was really warm so the topic never came up.

No worries, it's fun just talking about the possibilities of the details sometimes. I still haven't gotten a chance to read/watch (too much going on at work), but I'm looking forward to it.