Treehugger - Latest Comments in Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

Mekhong Kurt — Tue, 23 Feb 2010 18:58:38 -0000

This is one slick looking little airplane. This isn't the first time I've seen pictures of it -- it sort of reminds me of a prop version of the BD-5 "microjet" (which is mighty impressive; saw one at an air show where the lady daredevil pilot showed up out of nowhere -- popping up over the end of the runway, which was higher than the land beyond, and popping up *inverted* at that!). I'd LOVE to ride in one of these! Bet they cost a dollar or two. . . .

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

Luke Scharf — Mon, 28 Dec 2009 14:14:19 -0000

That is the rational given for me never having flown an aircraft that is younger than I am. Most of the aircraft I've flown have been 1960s and 1970s builds of designs that were conceived and refined in the 1950s. They are great designs (ever try to stall a Cessna 172 in a descending turn?), but I just don't buy that we can't do better with modern engineering techniques.

Redundancy is an excellent reason that airplanes have dual ignition systems, and why they should have double (or triple?) FADEC controls, and/or multiple engines. However, engineering has come a LONG way since the 1950s. Heck, it's come a long way in my lifetime, and I'm only 30. And, yes, every plane I've flown has been older than I am...

The real reason seems to be the distorted legal, liability, and economic environment that surrounds general aviation. Why design a modern engine for aviation, when you can sell the old design for $30+k/ea -- and not face the absurd level of liability and red-tape that would come with a new design?

Of course, the lead additive for 100LL isn't being manufactured anymore, so those who run high-performance pistons will have to do something in the next couple of decades. But companies that make alternative-fueled engines (like the Thielert aerodiesel) seem to all give it a try, and the pack up their ball and go home. Oh, well, I can't afford an airplane anyway.... :-(

I've heard some rumbles about homebuilt electrics. Maybe using commodity electric motors and batteries and commodity electricity for fuel will change the economics for recreational fliers over the coming decade? I can dream, can't I?

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

dwinkle — Mon, 28 Dec 2009 13:48:32 -0000

It's important to remember that the reason planes are still built as they were 25 years ago is for safety. In a completely analog engine, you can look at every part and determine it's fitness. Determining when a fuel injector or computer will fail is impossible. A dual, completely redundant system would probably make for a safe substitute.

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

cephalopod — Fri, 18 Dec 2009 09:49:39 -0000

>> You must really be american if you consider 30mpg to be better than most cars.... lmao

I'm guessing that if he said "We built a solar car in university," that he's not from the US as that's not really American-English...

But yes, 30mpg is considered good mileage here.

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

Luke Scharf — Wed, 18 Nov 2009 18:19:17 -0000

Fortunately, there are lots of super-cool solutions out there for efficiency! They don't all have to be hybrids -- it's just a matter of analyzing the situation, making the right tradeoffs, and figuring out the right solution.

I've made surprisingly useful improvements to the efficiency of my house with about $50 worth of insulation. Insulation is about the least exciting thing possible at first glance, but if you get thinking about the right places to put it, a few experiments can turn into a geeky hobby fast. :-)

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

Luke Scharf — Wed, 18 Nov 2009 17:54:40 -0000

I'd love a battery-powered emergency reserve, too. That would be great.

You're right that improving the aerodynamics the airplane works wonders -- that's how the Quickie can fly fast on 20hp. Even though the details can choke some of the biggest supercomputers on the planet, aerodynamics in this range is well enough understood that it's a matter of making tradeoffs and small improvements -- rather than a eureka moment. I sure wish it were different -- I'm a geek and I love the eureka moments (even 2nd or 3rd hand).

But, as it stands, a conventional single engine airplane with fuel injection (a newish technology in general aviation) costs as much as a Ferrari. Aviation is not friendly to new technology, because of the legal and economic framework. :-(

I expect we'll see practical fully electric airplanes from EAA members (like the guy in this article with the Vari-EZ) long before any hybrid airplane engine flies.

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

NickGen — Wed, 18 Nov 2009 17:18:07 -0000

The regenerative braking would be used on the planes brakes not in the air.
Also the air used on the flaps to slow the plane down would not be "gotten rid" of but recaptured to charge the batteries.

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

NickGen — Wed, 18 Nov 2009 17:09:08 -0000

Hi, well I in no way would dispute your contentions and expertise in aerodynamics. My point is just that there is wasted kinetic energy, heat and other methods which can improve airplane efficiency. I don't presume to have the answers. The ability to have some quiet time while in a glider by using fuel cells and the emergency capability of that 15-20 minutes of electric power what I was asking for. An ultralight hybrid? This is treehugger and their base ideology is about new and alternative methods -weather they be fully developed-is not the point-getting people to think out of the box and save fuel-increase mileage and make better performance is the goal.

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

Luke Scharf — Wed, 18 Nov 2009 16:13:54 -0000

Unless you fly a slam-dunk approach every time with full-flaps, spoilers, and or dive brakes on, "regenerative braking" in an airplane is going to be a looser.

The first thing you need to know is that when you fly an airplane, you consider the throttle to be your "altitude" control, and you consider the pitch (elevator) to be your speed control. The main reason flying is taught this way because normal airplanes (meaning anything that isn't an F-15) do not have to power to get themselves out of a stall -- but it's also because your rate of climb is Power - Drag. So, if you maintain level flight, and you shove the throttle forward, you'll climb. If you pull the throttle back, you'll descend.

So, how do you approach an airport? Let's skip the formalities, and go to the physics. Suppose you're cruising along at 8000 feet and you're a few miles out (how many miles will depend on how draggy your airplane is), you pull back the power and gradually descend down to the pattern altitude (usually 1000'). Then you put down your gear and flaps and fly around until you're lined up on the runway, and pull back the rest of the power. (The procedure is a little different if you're flying an instrument approach.)

At no time during this procedure do you have energy that you really want get rid of -- except for the gear and the flaps, the airplane does not have and does not use brakes. Up until the time you put the gear down, there is absolutely no advantage to descending at a steeper angle.

People do fly slam-dunk approaches from time to time -- but the reasons usually involve weather or trying to make a schedule. Those don't seem to justify adding weight and complexity to the aircraft -- if you want to fly efficiently, just wait until the last reasonable moment to put the gear and flaps out.

The best place to get performance in a light aircraft is through drag reduction aerodynamic design. That's why the Mooney M20C that I used to fly went 200mph on 180hp, and the Cessna 172 I flew went 120mph on 175hp. Drag increases at the cube of velocity, so you'd need something like 1400hp to get it to 240mph. The Cessna was a forgiving and charming aircraft -- and the Mooney was like a sports car. :-)

The other think you can do to save fuel in an airplane is to cruise at it's best-glide speed. If you fly slower, you get more drag because the wing is at a high angle of attack, and if you fly faster you're going faster than you have to. This is around 70mph in a Cessna 172. Most people I know fly faster than this if they're going somewhere, but if you've got the time it'll save money. Just remember to turn the carburetor heat on, 'cause carb ice sucks.

It's possible that you could put a smaller engine on an airplane that is sized to run at WOT in cruise and use a plugin electric + the engine to climb out, but I'd like to see someone try it before I claim it works. Using standard techniques for descent and approach are about as efficient as you can get.

P.S. I drive a Prius. But since I don't race to stoplights (physically analogous to flying a slam-dunk approach), I get less benefit out of the hybrid system than someone who insists on driving aggressively -- but I get better efficiency than the aggressive driver. The difference between the car and the airplane is that there are stoplights and the brakes work at all times on a car -- and airplanes fall out of the sky when they stop, so the airplanes just don't have the same erratic power requirements as the Prius on a public road.

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

nickgen — Wed, 18 Nov 2009 14:22:31 -0000

Well, I think we can create energy in effect but by reducing things such as drag and recovering wasted heat from engines and wasted kinetic energy.
What do you thing regenerative brakes do? Not creating something from nothing, just using what is there. Hybrids will give you the torque needed for quicker shorter takeoffs, backup when engines fail, and I have already seen a device which deploys on electric failure that uses the wind to create enough electricity to power the plane long enough to get back your mind you probably lost when the lights went out!

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

Luke Scharf — Fri, 13 Nov 2009 16:06:51 -0000

You had me going for a second, but "regenerative braking" is kind-of the opposite of gliding. In an engine-out situation, the last thing you want to do is turn your altitude or airspeed into battery power. Airspeed+altitude is gives you options, and recharging the battery will take them away -- you can neither create nor destroy energy, but you can turn it into waste-heat, which is exactly what charging the battery will do exactly that, while providing no real benefit.

Also, aerodynamically speaking, a windmilling propeller generates just about as much drag as a sheet of plywood with the same radius. You really don't want a windmilling propeller when gliding, unless you're hoping that you can use that effect start the engine again (like, for instance, you change to a fuel-tank that actually contains fuel).

If you're a glider pilot, you can already fly electric:
http://www.lange-aviation.c...

A hybrid airplane seems like a really bad idea at first, but it might have some merit. Airplane engines run at WOT an awful lot of the time, and not much energy is wasted in descents (very few small aircraft have dive-brakes, except for gliders). But, if you're willing to cruise a little slower, you could just use a plugin electric motor for the initial climbout and then run the piston engine at WOT for the whole flight. I'm still not convinced that this is a good idea -- but I'd love to see someone try it. But since we don't even have EFI in most airplanes, I'll be surprised if a hybrid system would get anywhere. I expect to see fully electric GA airplanes first.

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

nickgen — Fri, 13 Nov 2009 15:08:08 -0000

When will we see hybrid planes-at least for some quiet time and possibly for a backup when the gas knocks out-put in a fuel cell that gives 25 minutes of time to land safely? Hybrid ultralights-more torque for takeoff-quiet running time again. Maybe some kind of regeneration that uses air pressure and or a wind driven generator when gliding for more juice.

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

JC — Thu, 12 Nov 2009 10:55:32 -0000

Keep laughing and ignoring reality, but unfortunately there are a lot of low mpg vehicles on the road, and the CAFE average is pretty low in the US.

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

SimsenDK — Wed, 11 Nov 2009 20:12:03 -0000

You must really be american if you consider 30mpg to be better than most cars.... lmao

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

Luke Scharf — Wed, 11 Nov 2009 16:22:18 -0000

Is he really running 100LL in that thing?

In any case, 100 octane "low-lead" fuel is the standard fuel for piston-driven aircraft. The fact that most small airplanes are still running on leaded fuel just shows that, except for panel-mounted GPSs and the occasional $40k glass-cockpit, citizen-aviation is still stuck in the 1960s.

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

James.Michael — Wed, 11 Nov 2009 16:17:24 -0000

Another thing is that this plane runs on "leaded" fuel (not very friendly).

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

james — Wed, 11 Nov 2009 05:48:49 -0000

It's true that amortizing development costs is a huge problem for GA products, but it's also true that that had little to do with Porsche's failure.

There have been very few successful automotive to aircraft engine conversions, partly because the engineering requirements are so different. Airplane engines need to produce near-full power for hours on end, while auto engines only need to do so for a few seconds before producing a small fraction of rated power for long periods. Auto engines are just designed to do something different from airplane engines. Going the other way would probably be just as disastrous, but nobody tries to do it because the economic incentives aren't there. The successful conversions have mostly been small engines that were designed to run at rated power most of the time (because that was the only way they could propel the vehicle at highway speeds).

None of this is to say that auto engine technologies (especially ignition, induction, management, and fuel delivery) couldn't be successfully employed in an airplane engine (as the article aptly demonstrates).

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

james — Wed, 11 Nov 2009 05:35:08 -0000

Actually, if you look at the fixed->retractable conversions that virtually every manufacturer performed in the 60's and 70's, retractable gear starts to be a lot less attractive. Typically, there was less than a 10 knot increase in cruise speed (for planes cruising in the mid-100's) once you increased the gross takeoff weight to compensate for all the extra hardware, and compared the retract version to a fixed gear version with good wheel fairings. Remember, weight=slow in an airplane.

Using two in-production aircraft as another point of comparison: Look at the published cruise speed of the Columbia cum Cessna 400 vs. that of the Mooney Acclaim. To within the airframe-to-airframe variation in cruise speed, these two airplanes fly just as fast, using the same TSIO-550 engine, but the Cessna has fixed gear.

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

John — Sun, 08 Nov 2009 03:39:02 -0000

It's so sad that he's doing that with 80's era technology, which the FAA won't certify, out of a "cover my ass" bearaucratic mindset. Even if the FAA were to certify designs like this (and they're making microscopic process) the liability insurance cost is out of this world. Yes, I'm a pilot and intimately involved with the aviation industry.

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

Luke — Thu, 05 Nov 2009 10:38:48 -0000

I think every GA aircraft I've flown has been older than I am!

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

macrumpton — Thu, 05 Nov 2009 01:13:29 -0000

The interesting thing to me is that the Vari-EZ was designed in 1974. Where is the progress since then? Rutan's sleek 1977 design was the single seater Quickie which got 104mpg at its 120mph cruising speed with an 18hp engine. Here it is:
http://en.wikipedia.org/wik...

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

JC — Wed, 04 Nov 2009 10:24:38 -0000

Yes, I can do basic math.

My point was that even a typical plane gets better mileage relative to most cars. A slight take off from the article title.

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

Paul Turner — Wed, 04 Nov 2009 04:14:35 -0000

Agreed Sivam, but if the market was bigger unit cost woud have come down; the point I was trying to make was that the certification process is very expensive per unit.How big is the piston engined GA market? A few hundred per annum?
Compared to car engines in the millions. Many car derived power plants would make a good basis for a good GA engine; if the market was so big someone would do it.
It's the combination of a comparitively small market and the long expensive certification process that means we are still trolling round the skies in engines with magnetos on them. Know anybody else still using them?

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

Sivam — Wed, 04 Nov 2009 03:16:45 -0000

The Porsche aircraft engine failed because it was extremely expensive and complex, not really because the market is small.

Re: Hypermiling Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG

Paul Turner — Tue, 03 Nov 2009 23:55:32 -0000

General aviation has long relied on engine systems obsolete in automotive applications, not because the manufactureres do not know how to improve their engines, but because the process of certification of new products by the various world wide aviation bodies is long and expensive, and the general aviation market for engines is comparitively small. Porsche tried to introduce it's own engines incorporating many efficiency and operational improvements some years ago, but ultimately terminated the project due in part to this situation.