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.

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

Has anyone found a good replacement spring for the Atkinson Pitch Trim? The True Value spring no longer is available. Thanks, Brian

HI there, Installed the B&C starter. Without changing anything else the prop roared around. Problem solved. Nothing wrong with the Skytec, it's just higher torque at higher current and struggles with the setup. Have flown one flight since. All CHTs 390F, Oil topped out at 180F. OAT was 73F. I need to get slightly better airflow through the NACA inlets for cylinders. They are dedicated 5" x 1.5455" inlets through dedicated diffusers and dual plenums. I'll increase flow with some tiny 1/4" VGs. I need to add some piccolo tubes in and under the plenums and get some solid pressure data with and without VGs. Topped out at 190KIAS at 4000ft with the Hertzler Mk IV cozy prop. This reflected the first flight. I've refinished the Lightspeed Berkut prop and have had it painted. I need to balance it and check top end. It used to give me 206KTAS, but I expect to get approx 215KTAS now. The new Hetzler prop probably isn't far off either with more pitch which should be a match for the lightspeed top end and have much better takeoff performance. I removed cowls and all is well. The plenums seal against the crankcase cylinder flanges which I thought might me a problem. None observed. Tg not an issue without load. I see no difference in MAP from the previous config. The old Berkut centreline inlet spilled a lot of air. I am staggered the new little 5" wide centerlne flush inlet diffused once for induction with spilled air diffused a second time for oil is working so well to provide induction and oil air. I'll take measurements in time, but I'm getting textbook performance in line with calculations. I think I can do even better. The throttle oil outlet works well in controlling airflow, and has a direct affect on MAP when closing. Re-routing of the rudder cable conduits has put my rudders about 1/4" to 3/8" actuated at the tops. I can see them still delfected against the fixed upper winglet portion when I'm flying. Have to fix that. For anyone who is cutting your rudders full length, like I've always said, good luck seeing an in trail position from the cockpit! Not a good idea. I'm done with mods for a while! My recommendation to all building is just get it finished and go fly! Having my plane out of the air was awful. Now that it is going, I haven't had much time to fly, but it's there when I want to and that is COOL. Cheers

Hi Wayne, How did your downdraft turn out? Are you selling kits? I'm looking for downdraft for an IO-360 installation. Thanks, Brian