ul and lsa performance

[Dan Grunloh]

Those weight tables can be a bit misleading because of items not included. The installed weight of a Rotax 447 is 82 lbs with B-reduction drive, recoil starter and exhaust. The 618 will weigh 126 lbs with electric start (needed), and a heavier reduction drive (also needed). That total does not include the 25 lb battery to crank it, and the coolant! The difference in installed weight is close to 60 lbs. The 30 HP electric motor on Mark Beirle's Thundergull weighs 16 lbs. Most planes can cruise on half the engine needed to takeoff and climb. For the 618 you are carrying 60 lbs that you don't need for most of the flight. Jeron plans to run the same prop with both engines. You need a reduction drive anyway but will have to add a sprague clutch. Plenty of room in the cowling for the electric motor the new ones are tiny. Look at the Thundergull electric motor in the photo album for August 2011 Light Plane World. Hybrid designs may not replace ordinary aircraft real soon but you are going to see them flying pretty soon at airshows

http://www.eaa.org/lightplaneworld/issues/1108.html

[steveinindy]

Hybrid designs may not replace ordinary aircraft real soon but you are going to see them flying pretty soon at airshows

I just think the added weight and complexity of trying to rig an electric motor into the propeller, etc is not worth the trouble.

you are going to see them flying pretty soon at airshows

Eh. I see a lot of things flying around and I don't necessarily give them anything but a passing glance. Whatever floats your boat my friend. All I ask is that you do whatever interests you in a safe and effective manner.

Most planes can cruise on half the engine needed to takeoff and climb.

Can they do it safely at the altitudes the guy who started this thread is talking about? Especially during high DA settings? I am simply looking at this as the most effective way to do it.

Jeron plans to run the same prop with both engines. You need a reduction drive anyway but will have to add a sprague clutch.

Like I said, I have questions of whether the supposed power loading benefit is outweighed by the risk of applying new technology and more complicated systems into a group of aircraft where construction and maintenance at times leave something to be desire. If the idea here is to make this as minimally difficult to build, operate and maintain so we can get more people flying as easily as possible, then adding complexity is not necessarily the best approach.

[Ron Blum]

Although our original poster is probably gone, the couple bits of good information that he got were the people that did fly like he wants to and the fact that electric motors don't degrade with altitude (to a point).

Electric power storage is still too heavy. Electric motors are always lighter than gas engines; electric fuel is always heavier than gas fuel ~16:1 (but decreasing :o)

Burt has mentioned several times about flying an electric aerobatic routine. This is the most sensible (he knows the limitations). That would be high power for very short durations.

I am curious how a hybrid powerplant would be advantageous? Car and airplane power requirements are completely different. The car needs lots of high, varying power in town and little, continuous power on the interstate. An airplane needs high, continuous power all the time (except for the airshow routine).

I am also willing to take this conversation off the forum (since it is no longer the original post topic).

Always wanting to learn more ...

Thanks, Ron

[Bill Berson]

Ron,
Electric has no advantage if your mission, as stated, is to fly on "high continuous power". The hybrid advantage is for folks that cruise at near best L/D.
In this case, additional power is required for climb. Since climb is short duration, a brief output from an electric system makes sense.
Really, the same as a hybrid car that uses electric to pass or climb a hill.

Electric has some "new" possible advantages such as increased flexibility in motor location, for example. And some disadvantages. Try to use the advantages and minimize the disadvantages.

Van (RV designer) has an electric motorglider. (I think Van knows what he is doing most of the time, and has a blog about this)
But Van doesn't have an electric airplane.

Electric has some niche applications.
Bill

[steveinindy]

The hybrid advantage is for folks that cruise at near best L/D.

Which I don't think many ultralights do especially when you figure in high density altitude. Most of them are pretty draggy aircraft because of the very nature of the designs that are used. A pusher proper (the most common configuration I have seen in UL aircraft, at least around here) is already at a disadvantage because of operating in the disrupted wake. If memory serves, I think Ron's a trained aerospace engineer with a specialization in aerodynamics. He could probably discuss your argument in much greater detail than I could.

Electric has some niche applications.

It does. I don't think anyone is saying that it does not. The discussion is over what precisely those niches are and the technical limitations of the technology at the present happen to be. One of the big problems in experimental aviation is that folks latch onto what works in a carefully controlled setting (such as product development or under the guidance of the likes of Rutan or another great) and try to apply it to their own work without realizing that there are a few issues that don't tend to be as well publicized in such situations.

[Ron Blum]

Bill, thanks for the thoughts.

There are so many people out there that think electric is the right way to go (which it may be, but we are not there yet with storage ... as you mentioned earlier). For an automobile the electric motor makes tons of sense: constant, high, low-end torque and zero fuel usage when stopped. Big city driving.

The torque curve for an airplane on the other hand is set by the propeller, a simple 2nd-order exponential curve (which actually mates to a gas engine fairly well). Successful electric airplanes (to date) have been very high altitude; very long winged; very, very, very low power applications. But still way cool.

Another thing that people do (like with automobile engines) is to use the rated horsepower ... continuously. One can do that in an airplane engine (it's certified to do that), but a "typical" 150 Hp automobile engine putting out 150 Hp continuously would exploxed in a matter of a few hours. Most of the larger electrci motors that I have looked at will run continuously at about 50% rated power. And, cooling is an issue ... ask Sikorsky on their Firefly.

We need to continue to ask questions and push the status quo ... lest nothing will ever get done.

Thanks,
Ron

[Jon Ferguson]

I like the old answer best. They figured this out in WWII, just add a supercharger to force more air into the engine at high altitude, simple and effective.

[Bill Berson]

Even simpler is to increase the compression ratio for a high altitude engine.
Then the engine must never be used at sea level with full throttle.
This was done in the old days.