Efficiency as Creativity

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I'm sure most of us complain bitterly about the price of avgas, but our usual response is to simply fly less. Other factors contribute to that so fuel becomes the easiest and most convenient excuse. At some point, we'll have to decide to fish or cut bait and exit the game entirely, I suppose. But there is a third option and that's to fly a more efficient aircraft. In my travels and in interviews, I broach this subject often because as a skinflint—also known as a cheap bastard—it interests me. But I'm always surprised that most owners I know don't give a whit about aircraft fuel mileage.

So I'm right at home here in Ajdovscina in Slovenia where Russ Niles and I are visiting with Pipistrel Aircraft. The company's founder, Ivo Boscarol, has staked out the hyper-efficient side of flight and just as most of the rest of the industry hasn't even given lip service to efficient flight—exceptions are Diamond, Rotax and Thielert—Pipistrel is just the reverse. The first item in its design brief is the most speed for the least fuel. That's why it has won the NASA Green Flight Challenge going away for a couple of years. On Saturday, we got a look at one of their airplanes, the Virus SW, and collected some flight data and impressions.

First the name. It's a bit of an inside joke, says Taja Boscoral, Ivo's energetic and impressively able daughter. Some years ago, when the company was having great success selling its airplanes, would-be customers came back from demo flights with smiles and the staff joked that they had caught the Pipistrel virus. The name stuck and, well, there you are. I'm not sure it would be my first choice for an airplane name because for an English speaker, the word connotes either a trashed computer or forced visits to the lav. But the Virus is a lot more pleasant than that. Once you've flown it, you won't think about what it's called, other than blazingly fast.

It's a Euro ultralight that is, in fact, ultralight. The empty weight is around 655 pounds (298 kg) with a useful load of between 390 (177 kg) and more than 600 pounds (272 kg), depending the country. The version I flew had a Rotax 912 at 100 HP and standard fuel of 100 liters or 26 gallons. I'll cut right to the performance numbers. At a high-elevation field in the Slovenian mountains on a near standard day, the Virus SW had no problem bolting off the runway into a 1200 FPM climb. At 7500 feet, it was boring along at a true airspeed of more than 140 knots on about 3.2 to 3.5 GPH. Give up 10 knots and you can whittle the fuel burn down to 2.5 GPH. That works out to 45 to 52 MPG--about what we're getting tooling around in our little FIAT 500, but at three times the speed.

Nothing is for free, of course, and for that reason, people who don't care about mileage or efficiency may resonate with the Virus. It's smallish in the cabin and a bit tight. Headroom is adequate but not generous. Same with the baggage compartment. The seats are functional and spare. At every turn, components are small and lightened, albeit superbly crafted. The systems are simple and well designed. For instance, most Rotax installations have carb heat, but Pipistrel simply routed the induction air through the water radiator and eliminated the need for carb heat. True, it loses some power due to higher induction temperature but Ivo Boscarol says the airplane has more power than it needs anyway so it can afford the compromise.

The Virus makes its numbers because aerodynamically, it's slicker than snot on a door knob. In the pattern, viewed from the ground, it looks like some sort of alien rocket. On final, it doesn't want to slow down, so it has both full-span flaperons and the sort of top-wing spoilers you see in gliders. And you need to work them both to get a satisfyingly short landing without a bunch of float. (In cruise, the SW gets some drag credit by setting the flaperons to -5 degrees.) It takes a little skill to fly it well, but it's an inviting challenge.

In short, this is not just another LSA. It's an example of extreme engineering dominated by one goal: efficiency. But practicality hasn't been thrown out the door. It shows both what's possible and what you have to give up in luxury, weight and size to achieve it. One problem with new LSAs is that they carry a high price tag but are often short on utility. In other words, are you willing to spend $140,000 for a hangar toy you fly locally once a week? Or do you want to fly somewhere in the thing? A 100-knot LSA makes trips doable—just. A 140-knot airplane burning 3 GPH makes them more attractive, just don't plan on taking the family dog and a steamer trunk.

Here in Slovenia, where car gas is $8 a gallon, the club members can scoot off to Venice or Florence and back and have gas to spare. In other words, despite the high cost of fuel and the regulatory burden, airplanes like this, especially in group ownership, make flying affordable. We never seem to hear people complain about high fuel costs here because efficiency is baked into the culture. Energy conservation isn't seen as punitive, as is sometimes the case in the U.S., but just a fact of daily life. In the hotel room where I'm writing, for example, the door key goes into a slot to energize the room's electrics. You can't leave without turning out the lights. This sort of thing is common here. The Pipistrel factory is self-sufficient with solar and passive energy design.

As Pipistrel gets more attention—which it will—and as gas gets more expensive—which it already has—look for this sort of design thinking to percolate into other aircraft. You'll see a lot of it in Pipistrel's soon-to-be four-place certified airplane, the Panthera. Keep on eye on that airplane. It could be a paradigm shift.

Comments (30)

Pipistrel is the future of aviation. They will be dragging the rest into it kicking and screaming. They're they only ones who understand that the prime mover in the future is going to be electric. It might still need a gas, diesel or jet APU to support it until batteries get better, but it WILL be electrically propelled. And it's closer than people think. In fact, with their upcoming Panthera - which is a real stunner in the looks department - it will already start. Electric is the answer to all problems. No leaning, no penalty at altitude, no carb ice, no non-linear power output, no over boost, no need for turbo, no redline, endless TBO, reliability, lightweight (higher power-to-weight ratio than any turbine), etc, etc.

Posted by: Adam Frisch | March 11, 2012 7:46 AM    Report this comment

"Electric is the answer to all problems."

I'm an engineer. Anytime I hear "X is the answer to all problems!!eleventy!!11!" I immediately become very skeptical.

Electric has A LOT of drawbacks, and battery technology does not follow Moore's Law, so I don't foresee the kind of advancement that would make battery powered electric motors feasible any time soon.

A guy I know who's a whole lot smarter than I am provided a pretty compelling argument that rather than going to electric we'd be better off to switch to synthetic hydrocarbons for our fuel (methanol for gas, and dimethylether for diesel). Now, for aviation it would present some problems that are a much bigger hurdle than for surface transportation, but it still should be feasible to overcome those problems.

Posted by: Andrew Upson | March 12, 2012 1:19 AM    Report this comment

Doing so would require ~2TW of new electric generation capacity (preferably nuclear). However according that my source, the breakeven point, even with the current horrific costs of building nuclear power stations, would be at an oil price of around $100/bbl. It would likely take 20-30 years (at least) to make the transition if we as a country decided to go that route. That would give plenty of time for the aviation community to find a solution to leaded avgas, and might actually give them the kick in the butt they seem to need to actually develop that solution.

Advantages of synthetic hydrocarbons over alternative liquid fuels:
1. The infrastructure stays virtually the same (pipelines, trucks, gas stations)
2. Minimal to no vehicle modifications are required (aviation excepted)
3. Carbon-neutral
4. Oil independent!
5. Allows for off-peak use of base-load capacity (makes the power plants more efficient)
6. Allows for economies of scale
7. Much of the current $750bil we spend on fuel per year would go to jobs here rather than paying for imported fuel.

Posted by: Andrew Upson | March 12, 2012 1:23 AM    Report this comment

Darn it. Most of the character returns in my second part got messed up. It was far more readible in Word from whence I pasted it.

Any chance of getting a "Preview" option for comments?

Posted by: Andrew Upson | March 12, 2012 1:30 AM    Report this comment

I've been in Ajdovscina last September and was guided for a plant tour by Taja Boscarol. Being an european (used to 8 USD / Gal gas prices) I came away with a feeling that what M. Ivo Boscarol is doing with Pipistrel is straightforward and so obviously the direction that GA should be taking. What I don't understand now is why all the other manufacturers are so obstinately clinging to an inefficient past. I clearly had the feeling that the US based manufacturers "don't get it". The whole rest of the world is already moving to Jet A or very efficient Mogas engines. There is no surprise that Pipistrel was the launching partner for the new very efficient Rotax engine.

Posted by: Radu Damianov | March 12, 2012 7:02 AM    Report this comment

In your report you didn't mention that on January the 8th, a great pilot and photographer Matevz Lenarcic started at Ljubljana a long journey alone around the world in a little Pipistrel Virus 914, for instance he reached Antarctic, crossed the Pacific Ocean, from Chile to Australia, in the tiny LSA, at 140 knot average, 95 oct gas, amazing Pipistrel technology, the C150 or PA-28 I fly cannot do that, that fast, fuel saver and efficiently.

Posted by: Mario Quiroz | March 12, 2012 7:25 AM    Report this comment

No need to go to Slovenia to get this kind of miles-per-gallon performance: back in the US the LSA kitmaker Sonex Aircraft prominently mentions mileage in its marketing materials: 42 mpg, along with their motto: "Best performance per dollar". Unfortunately, such mindset has not reached US hotels yet - Slovenia definitely has an edge there.

Posted by: Andrei Volkov | March 12, 2012 8:07 AM    Report this comment

"In short, this is not just another LSA"

Correct, it's not an LSA. It does, however, point out that LSA needs to be expanded on both speed and weight to be practical.

Posted by: Mark Fraser | March 12, 2012 9:40 AM    Report this comment

What Pipistrel and the Rotax 912iS are doing is very exciting for American aviation, specifically forcing American engine makers and 3rd-party companies to strong-arm the FAA into approving fuel-efficient STCs for Type-certified engines and airplanes.

The future is high-priced gas because of China or inflation (you choose). There is no going back to $25/barrel oil no matter how many countries you invade.

Posted by: Peter Kuhns | March 12, 2012 11:42 AM    Report this comment

One reason I put up with a gas-guzzling 182 is that's the smallest cabin I've found that will haul my stuff on the most important trips. While I could easily use a Virus to for half the trips, who can afford two airplanes? At the point where I can't afford the 182, a Virus club membership would be appealing.

Posted by: DAVID CHULJIAN | March 12, 2012 12:35 PM    Report this comment

I'm an engineer, too, Andrew. Everytime I hear someone telling me 'electric' is the answer, I go ballistic. MAYBE in time ... but not now. At my local airport restaurant a few weeks ago, some tree hugging moron actually told me that laser powered cars were the answer. Honest!! Where do these people think all the electric comes from??? And how does that person think a laser will turn my cars wheels?

Pipistrel is "on" to something with aerodynamic and weight efficiency gains. Rotax is "on" to something with better engine specifics. Now if we could just get the FAA off their big fat butts and allow slightly heavier and faster ASTM certified LSA's, we'd HAVE our answer. Marry it all together into a right priced ulitarian 2-place airplane.

In the parallel Rotax 912iS article today, Paul B. alluded to Part 23 "light" airplanes. THAT"s the answer. ASTM certified light airplanes which allow all the above. The $100 hamburger could once again cost ... well ... $100.

Posted by: Larry Stencel | March 12, 2012 12:35 PM    Report this comment

I had almost forgotten.. thank you Larry for reminding me to give my long-suffering, drought afflicted eucalyptus some water and a hug today...

And thank you Paul for showing the energy conservation attitude of Slovenia and Pipistrel. Obviously they ignored any derogatory labels from others when pursuing their goals. Kudos to them and a very nice aircraft.

Posted by: David Miller | March 12, 2012 2:01 PM    Report this comment

"...utilitarian 2-place airplane..."

When I look around the ramps at the various airports I frequent, I see very few 2-place airplanes. Without doing a detailed survey, I estimate 80% 4-place or more, all legacy.

Where is the customer base that will buy these small, 2-place wonders for in excess of $140,000?

I know a 2-place would have no utility for my wife and myself. Together, we need to go someplace and do something. That doesn't mean getting a burger.

Posted by: Edd Weninger | March 12, 2012 2:09 PM    Report this comment

I think the Pipestral and other similar airplanes are coming in about where Piper was with the E-2 Cub versus the Wacos and Travelaires available at the time. A small economical plane versus the big legacy airplanes. A repeat of history. It may be a slower process this time however, because there are so many legacy airplanes out there and the payback in fuel cost of the new plane versus fuel cost of an occasionally used old airplane is long. But for flight schools and clubs, the new Pipestral would be the only way to go. Hopefully, the U.S. manufacturer's will catch on too.

Posted by: Stephen Phoenix | March 12, 2012 2:39 PM    Report this comment

When Cessna introduced the Skycatcher with carbs and carb heat, I lost all hope for Continental and Lycoming. These people have not innovated in 70 years, yet they charge you like their s**t is the latest in development. They will never innovate. They haven't been able to geta diesel certified ion 30 years and they probably never will. Darn, they can't even provide is with Fadec or injection TODAY! Best to leave these dinosaurs to die from their own hand and move on to electric. Batteries still have problems, but electric has none. I can buy a 20hp brushless of the shelf today that weighs 4lbs. Try to beat that power-to-weight ratio any turbine or any turboprop. They're not even close. Electric IS the future.

Posted by: Adam Frisch | March 12, 2012 5:52 PM    Report this comment

Adam - Here's the problem with electric (battery powered anyway) propulsion for aircraft.

The absolute BEST batteries you can buy today have energy densities of around 150Watt-hours/kg. Do some easy math to convert that to lbs/hp-hr (which, conveniently is the units for BSFC) and that works out to 10.96. Note that this Rotax burning gasoline is around 0.4.

To even match the BSFC of the worst (in terms of fuel efficiency) turbine currently on the market they'd need an order of magnitude improvement in energy density. They'd need the better part of ANOTHER order of magnitude to match the Rotax 912.

Given that in the 1880's batteries were able to achieve 25W-hr/kg (so a 6x improvement in 130 years) I wouldn't hold my breath waiting on a 600x improvement in batteries.

To give this a little more relevance to the real world, how many lbs of batteries would you need to power the Pipistrel Virus just for a 2 hour cruise endurance (assume you'd need 75% of it's designed 100 horsepower)? 1,644lbs of batteries. For the same mission with a Rotax 912? About 60lbs of gasoline.

Remind me again where you see a weight savings with electric power?

Posted by: Andrew Upson | March 12, 2012 6:37 PM    Report this comment

While not an engineer, I have maintained an interest in the "efficiency" side of flying for many years. As a result of this, I do not share the generic view that all USA-produced aircraft are inefficient "spam cans".

Back in the seventies and eighties, I flew Mooneys........a great series of aircraft that defined efficiency (especially after Roy Lopresti got his hands on it).

And then of course there was Jim Griswold, first with his remarkably efficient Malibu (while he was still with Piper), and then, his celebrated Questair Venture.

You want efficiency? How about a top speed of over 300 mph or a 75% cruise speed of 275 mph @ 12.8 US gallons per hour? Want more "efficiency"? Climb on up to 20,000 plus feet (in less than 10 minutes) and routinely cross Mother earth at better than 4 miles per minute while burning 10 gph or less.... all courtesy of a loafing IO-550 G.

Canadian winters can be both long and severe. I can jump in my Venture after breakfast and meet pals for lunch in Florida (4 1/2 hours....non-stop if I run 60 percent power), and enjoy plenty of elbow room enroute to boot.

Yes, Pipistel builds superbly efficient aircraft....... but that excellent company does not own a monopoly on airborne efficiency.

Larry Woods

Posted by: Larry Woods | March 12, 2012 6:55 PM    Report this comment

Andrew - yes, the batteries is what's holding electric back for now. But just recently the new Li-Ion ones have come closer to 400W/kg. Capacity is increasing fast and will only accelerate now that the auto industry is demanding more and more. You have to remember that a gas engine only turns 20% of the power into work, whereas an electric motor turns 90% into work. Therefore, battery capacity doesn't have to match gas in Wh/kg. At around 2000Wh/Kg, considerably less than gas can store, the scale will start to tip and it will be all over for the combustion engine. That's not going to happen tomorrow, but it will happen a lot faster than many think.

Posted by: Adam Frisch | March 12, 2012 7:26 PM    Report this comment

Here's a prediction: it will be electric, but it won't be batteries. Solid oxide fuel cells can convert Jet-A into electricity using only 1 moving part (a fuel pump). Existing SOFC run at very high temperatures and require exotic (expensive) materials, but there are teams making progress on getting those temperatures and costs down. An airplane power system that uses Jet-A (high energy density), plus a fuel cell/electric motor combination with just 2 moving parts (the fuel pump and the rotor of the electric motor itself) will be much more efficient, reliable and quiet than the current internal combustion systems. Also, because battery energy density is improving fairly slowly, roughly doubling every 10 years, even taking the cutting-edge number of 400Wh/kg as a starting point we're more than 20 years from that 2kWh/kg equivalence point - so batteries could be viable in the mid-2030s. Meanwhile, SOFCs - albeit rather expensive ones - are commercially available now. My bet is on the SOFCs.
The green lobby won't be all that pleased, since these systems will still burn hydrocarbons. On the other hand, they'll burn a lot less hydrocarbon, and from the perspectives of noise, reliability and maintenance costs they should be leaps and bounds better than internal combustion. In addition, remember that there's a lot less waste heat from a fuel cell/electric motor, and cooling drag is a major contributor to airframe drag, so fuel cell/electric should enable further drag reductions too.

Posted by: Thomas Boyle | March 12, 2012 9:43 PM    Report this comment

Paul, I completely agree that most pilots don't care about MPG but will scream and whine about the cost of fuel. But, as usual, I am NOT most and MPG is how I think. I once had a 35+ MPG Mooney Mite which I flew between Canada and Costa Rica and it was a really neat airplane but 65 year old glue is not appealing. A high MPG airplane burning MOGAS (alky included) makes nearly all of our fuel problems disappear. Waiting for miracle batteries is hardly a practical solution for my lifetime. I do NOT fly to impress my friends nor as a hobby but to actually travel, typically 200 to 800 mile trips (how bizarre!).

Posted by: ARTHUR THOMPSON | March 12, 2012 11:56 PM    Report this comment

The batteries in a Toyota Prius hybrid weigh about 100 pounds. The batteries in a Chevy Volt all electric weigh 700 pounds. The Prius is a decent selling right priced car that gets great gas mileage and owners don't have to worry about energy if they need to drive 500 miles. The owners of a Volt can do that but the car is running on gas after

Posted by: Larry Stencel | March 13, 2012 5:11 AM    Report this comment

As I re-read Paul's article and the subsequent blogs, we went from highlighting a super efficient little Slovenian airplane with a new high efficiency Rotax GAS engine to immediately deciding that electric airplanes are the 'answer.' Pipistrel IS onto something. They recognize that making the airframe more efficient and light in weight is the only way that they can do more with less. I commend them. At the present time, thats the only direction we can go. With the new Rotax 912iS installed the Virus SW may well be a winner. Same HP with lower fuel consumption specifics. I'd like to see them build a one place super efficient low drag airplane ... that'd go one step further. There will always be a need for heavy haulers as well as high efficiency light airplanes for cutting holes in the sky. When the price of fuel in the US gets to that of Europe (and we're getting there fast), efficiency will be on the minds of anyone who still wishes to enjoy the freedome of flight. Pipistrel will have prepositioned themselves for that market. We don't need G1000 IFR equipped $150K+ LSA's, we need right priced high efficiency machines to enjoy flying. Pipistrel must agree. Great article, Paul ... thanks.

Posted by: Larry Stencel | March 13, 2012 5:48 AM    Report this comment

Yes, Larry, super efficincy is the answer for a traveling. If someone thinks a single place can't be fun try a Pitts or a P-51. For hobby flying a 4 GPH Cub or Aeronca is already out there and very cheap.

Paul, why not a "Consumer" article by an Aero engineer on just what we could expect from such a single place airplane with a Mite type mechanical retractable gear? MPG should be also figured by cruising well into the teens (oxy is cheap if you fill at home). And the engine MUST burn E-10 MOGAS; it will always be the last to go. Slightly pressurizeing the gas tank can eliminate vapor lock concerns.

Posted by: ARTHUR THOMPSON | March 13, 2012 10:15 AM    Report this comment

Funny you should mention the Mooney Mite, Art. I was thinking of one when I brought up a single place design. They ARE fun. One of the problems with the current LSA ASTM standard is that 1320 pounds MGTOW is just too low to allow a decent airplane with sufficient structural reserves (that's why many have )to have either a good useful load, long range and/or speed. There ARE a couple that come close but most don't. Besides that issue, the high cost of a new LSA for the limited capability turns many folks off. That's why so few airplanes (relative) have sold after more than six years of light sport.

Now imagine if someone built a sleek single place design. The missing second person could translate to lower cross-sectional area (drag), more fuel with attendant range and likely lower cost. Using Pipistrel's penchant for aero efficiency, such an airplane could be built with a smaller engine for efficiency or a larger engine for speed. They're already using this idea.

I would love to see the FAA allow ASTM to raise the speed and MGTOW for LSA's to something more rational. Existing private pilots and above are genuinely interested in light sport because of the no medical provision but then find the airplanes are too expensive given their limited performance and don't justify giving up their heavier certificated machines. A light airplane that could do 150mph with a five hour range and priced right would be a big hit. I hope Pipistrel is listening.

Posted by: Larry Stencel | March 13, 2012 11:44 AM    Report this comment

Electric is not the answer, at least to our broad transportation needs. MAYBE for currently piston powered GA, or another similarly small niche market, but even then I'm skeptical. And that is regardless of advances in battery specific energy density (which I still doubt will materialize anywhere even close to as fast as Adam thinks).

The problem is the raw materials needed for the batteries, motors, and control systems. It's unlikely enough can be dug out of the ground. And even if it could the price would be astronomical and would take what might well be viable technology and price out of reach of even moderatly wealthy consumers.

Hopefully the link below makes it through (replace *dot* with .)


Posted by: Andrew Upson | March 13, 2012 11:53 AM    Report this comment

Because I am also a skinflint or cheap bastard the Pipistrel really appeals to me. Now if only I were 20 years younger so I could pick up a good used one in the year 2032!

Posted by: Unknown | March 14, 2012 7:26 AM    Report this comment

Electric and Pipistrel need the same thing to change to be successful, aviation culture in the US. Flying as an avocation in the US tend to get mixed with travel and other interests. We fly to get places. Europe has had ultralight and soaring groups that treat flying more like golf.

At this point, the destruction of the flight schools by the FAA and aircraft manufacturers and insurers and the schools themselves has removed the community part of flying at too many airports.

Posted by: Eric Warren | March 14, 2012 9:52 AM    Report this comment

Andrew ... I took the time to read the article in your link and am absolutely BLOWN AWAY by this alternative "problem" with using batteries as 'everyman's' source of all-electric motive power for transportation. The charts and viewpoint provided in this article once again substantiate MY position that there is no better way to power an autonomous moving vehicle than chemical energy (read oil).

I urge anyone interested in electric propulsion for anything beyond a quirky niche market to read the article.

Paul ... I urge you to read the article in the link and come up with a relevant thread for further discussion.

Now then ... back to that highly efficient Pipistrel with the new Rotax 912iS. GREAT way to turn gasolene into mechanical energy to turn my propeller so I can cut holes in the sky!

Posted by: Larry Stencel | March 17, 2012 4:16 AM    Report this comment

I bought a Virus SW last year, here's my thoughts...

after 340 hours of flight time in one year, I have saved approximately $25,000 in fuel compared to anything that matches the speed and range of the Virus.
Everywhere I go, the aircraft generates an incredible amount of interest.
My longest trip was over 5,500 NM, costing a little over $800 in fuel. I had the wife, and all of her crap in the back for a two week trip (1 1/2 day flight there,10 days at the beach, 1 1/2 day back). She was happy with what she brought. That alone says the cargo area is big enough! (115 lbs baggage limit in my particular plane)
I built it as an Amateur built kit, so the useful load was calculated at what the plane can actually carry, not what the category maximum is. The useful load is more than the aircraft empty weight.
There is much more room than a 150, same width as a 172, but if you are taller than 6'3" you will find the headroom tight.
The biggest guy I have taken up is 6'4" and 311 lbs. He fit.
The performance and handling has left every pilot I have taken for a flight with a giant grin on his face.

Posted by: Jonas Boll | March 18, 2012 11:43 PM    Report this comment

Paul, When you visited Pipistrel was there any discussion of the Panthera?

Posted by: Thomas Reilly | March 22, 2012 4:23 PM    Report this comment

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