Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG (Better Than Most Cars) | Hacker News Reader

Plane Gets 45 MPG at 207 MPH, Capable of 100 MPG (Better Than Most Cars)

aopa.org

46 pointsMikeCapone38 comments

He's flying a modified VariEze, one of a series of planes designed by Burt Rutan (who, among other many other things, designed SpaceShipOne).

The VariEze was sold as a set of plans; buying a set gave you the right to spend an enormous amount of time in your garage with fiberglass and foam, emerging a couple of years later with a fully functional two-seater airplane. The original design was targeted as efficient, long distance flying, at the expense of capabilities like aerobatics; according to the article, this guy has stepped up his with a re-designed engine an ignition system. Very cool, especially when you remember that this is very likely a plane he built himself in the first place.

I find home-built experimental aircraft are fascinating; I'm plotting one of my own for next year. (There are a number of composite fiberglass designs in the VariEze family that are just beautiful, but they take much more effort to build than the more traditional aluminum, so I'm looking right now at the Van's RV Aircraft family.)

I built a RV-8 from Van's. The kits are very well done and you will love the way it flies. Sorry for being some what off topic.

What about the noise in certain circles regarding safety? I've heard the wings tend to snap off if you pull higher G's... your thoughts?

I've always thought the Falco's were pretty nifty.

As long as you stay within the design limits you will be fine. I built mine light as Van intended. My empty weight was 1029 lbs. More and more builders are putting a ton of "goodies" in the panel that I believe distract from the true sport nature of the Van's design. I never felt unsafe in mine doing sport aerobatics.

Falco's are very nice but will take forever to build. There is a reason Van's has a huge number of completions.

I've heard that the completion rate for kit planes is less than 20%. May the force be with you.

"Why don’t you put magnetos in your cars?"

Because we are not likely to die because the car engine stopped.

I sympathize with him, but airworthy and street-legal are very, very different concepts. If he wants advanced electronic controls for airplane systems on non-experimental aircraft, then he should engineer them around the components that have been exhaustively certified and field-proven in a way they can provide adequate fall-back in case of a problem. Given time, they will end-up in commercial aviation.

It's a shame but I don't think I'll ever see digital systems in widespread use in my lifetime. Full Authority Digital Engine Control (FADEC) systems are out there but they're generally not trusted. People understand mags and vacuum pumps and the peace of mind it brings to know you can lose your entire electrical system and still be flying.

Most of the FADEC systems have dual alternators, dual controllers and dual sensors, but people still don't run them very often. Probably the most popular one I know of is in the Rotorway Exec series helis.

SDS also sells a (non-redundant) EFI system that's used in a couple of aviation applications. My dad is using a SDS system in his Jenny.

You also can't run a modern closed loop EFI system because of 100LL (avgas). The lead in it will destroy an oxygen sensor. So you're still stuck with a mixture lever in most cases.

And that's just the experimental crowd. The cost of certifying an EFI engine into an existing airframe would make a retrofit cost prohibitive. Most people won't spend an additional $20k at overhaul time to add fuel injection and digital ignition. It would take a bunch of hours at +20% efficiency to make that back.

A couple years ago I heard about a company selling a modern ignition system packaged into a mag. The idea was to replace one mag with the digital ignition and leave one mag as a safe backup. I don't know what happened to them. Last I heard they were selling units and working on certification for the Lycoming O-320/O-360 and Continental O-300 engines.

Also, I just looked up the guy in the article. He sells his digital ignition systems for around $2k. He's managed to get a STC for a heli, so that's some progress in the right direction.

Dry vacuum pumps fail regularly (<500 hours). Not exactly peace of mind, that. I'll take a battery backed electric gyro or AHRS any day.

I think he's making the point that car engines of today are very reliable, as well as efficient (compared to aircraft engines, that is).

How so? How often do you see cars pulled over at the side of the road, hood flipped up and driver screaming into a cell phone? Sure, it doesn't happen to everyone everyday, but it happens.

Now imagine that happening 8,000 feet in the air.

That is a false analogy because a) the vast numbers of vehicles on the road means that you will see many of them pulled over even if the individual chance of failure is small, and b) they can be pulled over for any number of failures that are not engine related (tires, transmission, axles, etc.) or caused by neglected maintenance.

Moreover, as far as I remember, the majority of GA fatalities fall into two categories: stall/spin and weather. A simple engine out should really not result in a fatality unless it's over very bad terrain.

Let's play with numbers: According to the AOPA there were about 600 general aviation fatalities over 26e6 hours in 2004, which gives a fatality rate is about 1.3e-5/flight hour.

The total number of vehicle miles in the US traveled is 3e12mi/yr (!). If we assume an average speed of 50mph, this means 6e10 hours of driving per year. At the aviation fatality rate, this translates to almost 800,000 fatalities/year! You'd see dead people in cars all over...

But wopuldn't the higher fatality per flown mile rate of aircraft demonstrate the need to be conservative?

You don't die when you aircraft engine stops. You glide.

Every pilot has shot hundreds of landings w/o power.

And, compared to a brake-seizure on a car, you've got lots of time to figure out what to do.

I think the odds of survival are better with a brake seizure than with the loss of an engine on a plane.

You may get lucky and be in a safe speed/altitude and flying over favorable terrain, but one shouldn't count on that.

Magnetos are less reliable than most other parts of an aircraft engine. I'm a relatively low-time private pilot and I've seen mag failures more than once in aircraft I've been in. That's one reason aircraft engines have two of them. You can continue flying with only one but you won't quite as much get as much power and if the other goes you'll have to land promptly using gravity instead of engine power. I like the idea of electronic ignition. Slightly unrelated, but here's a video I made of a simulated engine-out (autorotation) landing in a helicopter: http://www.youtube.com/watch?v=pzWw5U3eCok

Very interesting. I understand the conservatism of aviation engineering, but this is a clear example of how stagnation in an industry can cause even conservative adoption of innovations proven in other realms to lag by decades.

My impression that this is not the conservatism of aviation engineering but rather the conservatism of aviation manufacturers. Whether this is due to product liability concerns (I just eyed through http://www.avweb.com/news/avlaw/181885-1.html) or something else, who knows. It definitely seems that all "technologically advanced" aircraft are in the experimental category.

I wonder if Burt Rutan can be subject to a product liability lawsuit for problems with a Vari-Ez et al?

James Fallows wrote an interesting book a decade ago called Free Flight. Part of the book covered the dismal state of general aviation, resulting from a death spiral in which product liability suits played a prominent role. The rest of the book is about attempts to revive the industry.

So, yes, this is about a stagnant industry that has invested little in engineering over the last 50 years or so. Most general aviation aircraft have a lot in common with cars in Cuba. With that context, I took some of the comments in the article as being directed not at the conservatism not of manufacturers, but of owners doing retrofits and experimental plane builders.

Experimental aircraft (all amateur-built planes are registered with the FAA as "experimental") fall under an entirely different set of laws and regulations specifically designed to avoid that sort of of problem.

That's not to say that experimental designers are completely immune lawsuits, but I've never heard of it happening, and doubt such a thing would survive long in court.

The net result is that home-built aircraft tend to have dramatically better performance numbers than comparable certified aircraft.

Quickie aircraft corporation - the guys who made the quickie Q2 (based on a Rutan design) were sued out of existence back in the 80's.

They had a fantastic plane, fast, fuel efficient and affordable. Then someone died and their widow sued. They won the suit but the debt from defending crushed them.

Do you have a link to that?

I looked around and found http://www.check-six.com/Crash_Sites/N82X-Jewett.htm

Thanks for the reference -- I hadn't heard that story. Definitely the nightmare of the small company selling kit planes or plans.

(Edit: Aside from the nightmare of someone getting hurt and it actually being your fault. (I've written too many defects recently.))

A friend of mine had a Long-EZ. It is a very cool looking plane, fast, and very efficient. The only problem is that it only seats two and has no room for baggage. He had small baggage pods suspended below the wings, but they could only hold something the size of a small duffel bag. I don't think it would be very comfortable to take a long trip in it.

And at the rates given in the article, you could theoretically stay airborne for over 8 hours. Keep in mind that most pilots would like to keep about an extra hour's worth of fuel in reserves should your intended destination be unavailable. Still, figure a 'road' trip of about 6 hours in your seat, with no bathroom breaks, and no rest stops.

It's not like, it's a legal requirement to have 45 minutes of reserve fuel, plus some for maneuvering . So call it a one hour legal requirement.

Although intriguing, this comparison is apples to oranges. Planes can achieve substantially better fuel economy than land-based vehicles because of 2 factors:

1) More flexibility in body design. Cars must have 2/3/4 wheels with reasonable clearance to maintain safe balance on the road surface, which usually adds to drag. Planes can vary from tri-wing to tailless flying wing.

2) Low air resistance at high altitude. Planes, passenger jets especially, capitalize on the reduced drag at high altitude for substantial fuel economy. Cars are generally stuck at sea level most of the time.

I'd also like to add in 3) no stop and go traffic. That, by far, is one of the worst contributors to poor fuel economy in cars. If we could all go directly to our destinations in our cars without stopping for traffic/stop signs/stop lights, our fuel economy would look a whole lot better.

More interesting to me is that he was able to realize significant improvements in fuel consumption with the same airframe and same basic engine by upgrading the ignition and fuel injection systems to something that probably wouldn't look out of place on a 20 year old civic.

True, though it seems flexibility in body design is mostly limited by fashion. Things like the Aptera (www.aptera.com) are road legal.

But I disagree it's apples to oranges. If the comparison is how to get from A to B with the highest fuel efficiency, why should cars be protected from their disadvantages? (Disregarding for a moment the chaos that would ensue if everyone driving had their own plane...)

The 100mpg figure seems to apply to cruise flight at 17500ft. Given that you have to climb up there before you enjoy that advantage, it would be interesting to know what the total trip mpg is for trips of different lengths. How far do you have to go before you beat the cars in fuel efficiency?

And then there is the problem of getting to an airfield first, unless you just happen to have one in your back yard.

Also, an engine in a car cannot run all the time at the same load, because there are hills, crossroads, faster and slower roads, etc., while a plane operates in much more constant conditions, so the engine can work at roughly the same load most of the time. Combustion engines doesn't scale, so the engine cannot have the same efficiency for every possible load. (And it's not practical to put an electric generator and engines, which are much, much better, in a plane or car.)

it's not practical to put an electric generator and engines, which are much, much better, in a plane or car Actually, that's exactly how the Chevrolet Volt works.

Awesome. I like seeing news about the private air industry here. I normally wouldn't think this is hacker related, but knowing a few private pilots they're definitely of the hacker mentality. And seeing this article here just feels rights.

Also, the private pilot culture is definitely of the geeky variety, sans computers (though some cockpit gadgets are pretty impressive now-days).

You just have to built it yourself...

That's pretty common to help keep costs down and employ more experimental designs.

time for flying cars?

http://web.mit.edu/newsoffice/2009/flying-car-0319.html

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