TwinEZ

[Kent Ashton]

I see that a chap named Ashton (no relation) is planning to build a Twin-engine EZ using two Aeromomentum engines.   https://www.facebook.com/groups/25741482604/  He has the engines and posted a pic if his idea so I guess he's pretty serious about trying it.  I wonder if this fellow has read up on the previous efforts at twin-engine EZs?  

http://forum.canardaviation.com/showthread.php?t=2139  http://stargazer2006.online.fr/derivatives/pages/twin-ez.htm  http://forum.canardaviation.com/showthread.php?t=5252
They have not been very successful AFAICT.  His two engines appear to weigh 185 each _dry_ (pic 2), then there is the weight of watercooling X 2, extra structure to support the engines, extra mount, cowl, and prop.    Maybe he's an aeroengineer and has it all figured out but I suspect it will suck up hours of work and then prove a costly mistake.  Why am I writing this?  In the hope that he will stumble across TwinEZ in a google search and study what has been tried before.  Or maybe we have some FB members here who will link to this.

Google and the forums have preserved a wealth of canard pics and discusson over the years but it appears to me that half the people posting on FB are not aware of what's there and what has been attempted before.  The first URL above says it was reengined as a single.  I don't know what happened to the second airplane.   The 3rd URL airplane was bought by our friend Zubair Kahn who rebuilt it as a single and crashed it.

tags: twin engine Long-ez  twin engine longeze twin engine longez coscio ivan shaw

Edited July 31, 2018 by Kent Ashton

[Voidhawk9]

Not sure why a person would do this. A LOT of extra work for no real increase in safety or reliability (single vs twin safety statistics are clear).

The Aeromomentum engines are interesting though, I will watch the AM20T with interest (260hp at o-360 weight).

[mquinn6]

Better get more rudder - this will flat spin like a saucer with only one engine.

[ashtonb]

Hmmm... where to start...

Voidhawk... keep studying aerodynamics. A well-designed twin is safer... hands down. After over 35 years of flying, I'll take the well-designed twin with an engine down over crashing into the wilds of Alaska any day (no brainer).

Mquinn6... Talk to the guys that actually built and flew the first two attempts and you will learn that rudder authority was amazing... all the way to canard stall, with one engine shut off with prop still spinning (max drag). doesn't get better than that... for a well-designed twin. Nonetheless, we added even more rudder... because we could.

Kent ... Yes, I did talk (in person) to those available, that tried before (of course... how could one set out to do something as daunting as this without being thorough in determining why it did not work before, in order to create a punch list of things to solve). In talking to Mike Melville about Ivan Shaw's build (Ivan stayed with Mike when he was building it. The aircraft aerodynamics were solid... just didn't have enough thrust and fuel burn was high with the engines he used.

Yes, I have a few engineers backing up the build, so it will fly safe (enough rudder, weight and balance, structural loads... and thrust... lots of thrust).

I purposely kept quiet (mostly) and off these forums in order to not have armchair quarterbacks (that have not done the research and are not engineers) from draining my Mojo with coffee shop conjecture. It's a challenging enough undertaking than to add that to the mix. I did reach out for assistance from those qualified to assist.

I will say this about the previous attempts. Those that tried it before did very good work and the concept was and is, very solid. The technology was simply not there yet to pull it off. It is now. Their reasons for trying this, opposed to the center line thrust design, was also well thought-out.

I won't elaborate any further as the community can come and touch it and discuss the actual performance at airshows, when it is finished. It has been an awesome adventure to take on such a challenge. It has been amazing to work with the qualified advisers that have stepped up to assist.

Brian

[Todd Stock]

I believe Voidhawk was speaking to outcomes versus the usual list of advantages cited for ME versus SE.  Worth reviewing both the last 27 NALL reports and other analyses of non-airline aviation accidents to understand the data on SE vs. ME accident and injury/fatality rates related to mechanical failure.  Summary: pilots injure or kill themselves in engine loss/shutdown situations at a significantly greater rate (2x to 4x, depending on how the data are parsed) when an engine fails/is shut down on a ME versus SE.  Lots and lots of reasons for this, including mission profiles, higher speeds at landing/impact (w/related V^2 effect on energy to be dissipated), variables in training and proficiency, the conditions into which a ME airplane driver is comfortable launching versus SE, and the usual ADM issues which a second engine adds when the first one fails, etc.  This is not aerodynamics, but instead acknowledgement of the same realities which generate all those notes, cautions, and warnings in POH/AFMs, -10's, -1's, and NATOPs, as well as yearly injury and fatality numbers in the NALL and regulator reports (FAA, TC, CAA, etc.).

On yaw authority...every aircraft will depart controlled flight given the right set of flight/aircraft conditions and driver input, but at least for this discussion, what we should be concerned with is at what airspeed in level flight, zero power generated by critical engine &  max on the other,  and landing configuration we must operate to avoid that loss of control.  I suspect it's not too difficult a task to calculate a ballpark number for Vmc, and then to verify that number during flight test...pretty sure it's been done before at least a few times.  Yes - it may very well be higher than the minimum level flight airspeed either in a glide or with both engines operating, but it's unlikely to be anywhere near cruise.  And yes, the airplane might 'spin like a top' if things get too slow, but competent ME pilots tend to try to maintain enough airspeed to avoid that particular corner of the flight envelope.  

Interesting discussion/project which illustrates just how diverse our expectations can be re: building our own dream aircraft.  Might be interesting to discuss what mods might be desirable to avoid making Vmc higher than it absolutely needs to be.

Edited December 2, 2019 by Todd Stock

[ashtonb]

Hi Todd,

I agree that reviewing the data is important and your ME/SE summary concludes why I decided to do this project. The design of most light twins is what realizes the data  you are speaking to. And, this is why I said :"well designed twin". I'm not a fan of conventional, small under-powered twins that can turns things more deadly when an engine drops out.

Yaw... After the data has been calculated, then its time to test fly. As I mentioned, the test flight of one of the twins that were made, had rudder authority, with an engine down and still spinning (worst drag configuration), to canard stall speed... which is another reason I took up this challenge, with this configuration of aircraft. Even with demonstrated stability and rudder authority to canard stall, we are running our rudders to the top of the vertical fin.

With VMC at, or below canard stall, I think we have a robust flight envelope for a new light twin.  This is not a new revelation...  Velocity Twin.

Of course, any aircraft design project should be undertaken with adequate research and engineering... even more so with the complexities of a twin. 

It is very rewarding to be a part of our general aviation community, where we can still collaborate and, leveraging the knowledge from those that came before us, try new things.