Poll: Van's Twin

[jrichichi1]

Make it a knockoff of the Wing Derringer. Two-seater with a larger baggage area. Retractable. Have a variety of engines available for it. O-320 up to the new IO-390-EXP119. If you really wanted it to be a high performance twin, go with two UL Power UL520T engines (220 HP). Not only are they much lighter, the turbo-normalizing gets you power up high (S.L. power up to 15,000 MSL), and they even come in a counter-rotating version (no critical engine...). However, I would never expect Van's to go with a UL Power engine. It would be an impressive aircraft if they did.

I'd make a similar to the -14 but with either doors like the -10 or a combination slider/doors (slide the canopy back, open a low-height door forward and step in). I'd probably do four tanks like a Glasair Sportsman but make them "wet" like RV's. Lots of fuel for range. You use a Facet pump to transfer fuel from the outboard tanks to the inboard tanks. How much fuel? As much as you can get!! Just like other aircraft, you can offload payload to fill up with fuel or vice versa.

No pressurization. Too complicated and too heavy. Keep it light and simple (if you can call a retractable twin simple...).

Due to the increased utility of something like this, some sort of deice would be great. Again, I wouldn't expect Van's to go out on a limb for a deice system. A "weeping wing" or a "thermal" system would be nice. Each have their respective advantages and disadvantages. If you make the leading edge "bolt-on" similar to how the tanks are attached, you can swap out leading edges with or without a deice system. It would probably be best to have the wet fuel tanks in between the front and rear spars if that was the case.

Anyway, I've wasted too much time typing about this.

Jeff

[David Z]

Jeff, I quite like where you're going with this. Nice big tail and rudder for single engine controllability. Big engines for single engine performance. It needs to be so good on one engine that the saying "second engine takes you to the scene of the crash" doesn't apply.

If we're sticking de-ice systems on this plane, then it needs big engines to keep performing when the icing gets bad too. The turbo UL520 sounds wonderful.

4 seats though, need the seats.

Would it sell? Would people build it? I'm guessing not many. Same problem as described the 6-seater thread. The plane would simply be too big and complex.

[sprucemoose]

Only too big and complex if we make it so.

2 seats
Moderate engines- O-320
Fixed gear. Retracts are a waste under 200 kts. Also improves Vmc.

Need boots or 4 seats? Go buy a Baron or 310.

[jrichichi1]

Originally Posted by David Z

Jeff, I quite like where you're going with this. Nice big tail and rudder for single engine controllability. Big engines for single engine performance. It needs to be so good on one engine that the saying "second engine takes you to the scene of the crash" doesn't apply.

If we're sticking de-ice systems on this plane, then it needs big engines to keep performing when the icing gets bad too. The turbo UL520 sounds wonderful.

4 seats though, need the seats.

Would it sell? Would people build it? I'm guessing not many. Same problem as described the 6-seater thread. The plane would simply be too big and complex.

Yep, I agree with you David. I understand the Derringer had pretty good engine-out performance. Like you said, big engine, big tail, and you also need to be lightweight (read: high HP to weight ratio) to get good single engine performance. To help out on the S.E. performance, just don't load up with fuel and payload and stay light if you're worried about an engine-out scenario (mountains, night, etc.). Once you're out of the "danger zone" you can land, tank up and fly heavy, with a lower S.E. service ceiling.

That's one of the main reasons I said to have huge fuel tanks. So that even with half full "main" tanks you still have good range in the aircraft. You're going to want to have around 180 gallons total fuel capacity with this aircraft. 30 gallons in the outboard tanks (each tank) and 60 gallons in each inboard "main" tank. The UL520T typically burns 8-11 GPH so full tanks should give you about 9 hours before you're a glider. That's a LONG flight!!! With 30 gallons in each main tank, you're talking a 2 hour flight with a 45 minute reserve. The Derringer supposedly had a 184 kt cruise speed. I would expect with the more powerful engines you would be going faster but this still gives you about a 350 nm range with a 45 minute reserve. That can get you past a lot of "bad" territory.

Maybe a compromise on the seats would be to do what is done on the Sportsman 2+2. You have two, full size seats in the front and two aft facing seats in the back. The aft facing seats share a common seat back that can be easily removed via four bolts to make room in the back if you want to pack the back with cargo. The rear seat "bottoms" are attached to the seat back via piano hinges and are removed with the seat back (it's all one big assembly). The piano hinges allow you lift up the seat bottoms to store small items under the seats when they are installed. It's a really nice setup. The seats in the back can easily fit a couple of kids or small adults. Plus, they work great for tossing baggage on them. Just Google "Sportsman 2+2 aft facing seats" and look at the images. Some people had forward facing seats in the back but the head room was limited as was the allowable load due to C.G. concerns.

The aft facing seats have some good qualities to the design.

1) It keeps the C.G. close to the front seats when you put people in the back.

2) You get more head room for those in the back since the fuselage has a larger cross section there.

3) Both the front and rear seats, seat belts, headset wiring, etc. tie into the same bulkhead. You don't need to make two, relatively heavy, complex bulkheads with this arrangement.

Let's face it, most of the time you probably won't be flying with someone in the back seats. If you do, they will be facing backwards. Some people won't like facing aft during the flight. For them either put them in the front seat or leave them on the ground...

Would it sell? Yeah, I'm sure it would sell a few. How many? Who knows. A lot of people talk. Very few take action unfortunately... If Van's had something like Glasair's Two Week To Taxi (TWTT) program, then you'd probably get more takers. With the TWTT program, you're essentially trading cash for time. Also, the people who would most likely be purchasing an aircraft like this have the cash but not the time. The people who don't have the cash for a TWTT program wouldn't be purchasing an aircraft like this anyway.

It would be nice but again, I don't think Van's would do this. Maybe someone else will...

Jeff

[JDeanda]

I’m not a big believer in the concept of the light twin. Universally poor single engine performance on takeoff and added complexity are too hard to fix. By the time those issues are handled, it’s not a light twin any more. As I’ve said before, I’ve seen the Comanche, Arrow, Tiger and others transmogrified into twins. I don’t think any of those became better airplanes from that, they just became multiengine trainers. Light twins designed from a clean sheet (Crusader, 310, Baron, Travel Air, Apache… ) all those, did not do much better. Worst example of course, is the Lancer (twin Citabria,) an interesting but truly useless curiosity of an airplane. I don’t see that Vans has any magic to address these problems, nor do I think a Vans twin would “pencil out” as Greg Hughes might say. I for sure would not buy one or encourage anybody else to.

[David Paule]

Originally Posted by sprucemoose

Only too big and complex if we make it so....

Given the innate complexity of having two engines, can you imagine a homebuilder NOT loading such an airplane up with gadgets and systems?

Fortunately the poll, right now, is running 10 to 1 against the concept.

Dave

[rocketman1988]

Against Van's devoting resources to a twin...

Maybe someone else will step up...

[MacCool]

Originally Posted by rocketman1988

Against Van's devoting resources to a twin...

Maybe someone else will step up...

If I was one of the many would-be builders out there that was watching my kit and parts shipping dates slip farther and farther, I’d be a little miffed at Vans devoting resources to anything other than current supply chain, manufacturing, and shipping issues, and I include the RV-15. I can’t imagine how that theoretical airplane isn’t years away from shipping its first empennage kit.

[sprucemoose]

Originally Posted by David Paule

Given the innate complexity of having two engines, can you imagine a homebuilder NOT loading such an airplane up with gadgets and systems?

Fortunately the poll, right now, is running 10 to 1 against the concept.

Dave

I can imagine all sorts of scenarios that would keep me up at night if I were Van’s. There is a difference between complexity added by the builder by larding it up, and complexity in the basic design (fixed gear vs retract for example) but yes, I get your point and I agree.

FWIW I don’t think Van’s will do a twin, and I’m not sure I’d want them to anyway. But for a fun little thought exercise, yes I would sure love to build one if they did!

[sprucemoose]

Originally Posted by rocketman1988

Against Van's devoting resources to a twin...

Maybe someone else will step up...

The practical side of me agrees with you. The dreamer on the other hand…

If Van never put a little time into dreaming and R&D then the RV fleet would consist of a few dozen RV-3s and very few of us would be enjoying this hobby. Just sayin’.

Maybe we need another poll- “which is the worse idea, a 6-seater or a twin?”