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Terraformer,
Sonex Aircraft Xenos Motor Glider
The airframe is $40K USD, plus whatever shipping is to the UK. To that, you must add shop tools and supplies to drill and rivet Aluminum, an engine of some kind (they do have an electric option available), avionics, and paint / corrosion protection. The wings are designed to detach for easy transport and storage. I can't tell you what the rest of that stuff will cost because I don't know what you want / need and are comfortable with. You can get relatively inexpensive modern avionics for Day VFR and ADS-B Out, though. A full IFR setup will cost considerably more.
If you have welding skills, you could look into a plans-built Steve Wittmann designed steel tube-and-fabric motor glider. It is possible to use substitute materials for 4130 chrome-moly tubing, such as 1018, which is easier to weld without worrying about embrittlement issues near the HAZ. The downside is that 1018 or similar low-Carbon / lower-strength tubing is heavier than 4130 for a given strength. The upside is that you have greater rigidity from stiffer thicker-walled tubing, and little to no issue with reducing the strength of 1018 or having cracking occur near the welded joint. There are some other steels that would work, are also easier to come by, and easier to weld than 4130. That said, 4130 tubing doesn't cost that much more in the required quantities, so if you already work with it, stick with what you already know. You'll need a TIG welder if you don't already have one. Regardless, you need to have your welds inspected by a qualified professional, practice if you don't weld on a regular basis, and follow appropriate welding guidelines for your selected material. You could end up with a more generally usable plane that is more durable than Aluminum construction, provides better protection in a crash, and is more economical to build than Aluminum. In the end, you will probably still spend as much time and money either way. Field repairability is the primary difference between steel tube-and-fabric vs Aluminum, which may or may not be important for you.
I believe your CAA allows experimental amateur-built tube-and-fabric aircraft, just as America does, without having to be a certified aerospace welder. This is not universally the case, though, so check applicable local regulations. You can write our authorities for more info.
If you crash an Aluminum or composite airframe, it's probably toast if any major structural damage is inflicted. If you crash a tube-and-fabric plane, many of those have been rebuilt, sometimes several times. Avoiding crashes is always the best option, but the best option is rarely the same as the most pragmatic option. Any kind of "adventure flying" is inherently more dangerous than flying prescribed routes and altitudes.
If you just want an aircraft and you want it to come from a reputable kit manufacturer, Sonex is a pretty good option. There is also Zenith STOL aircraft, which come to us from a Canadian designer, Chris Heintz, operating out of the US. Those birds are also primarily Aluminum, known to be pretty tough, and have remarkably good rough field short-takeoff and landing performance for out-of-the-box kits. Their wings are also foldable for storage. You can use a wide variety of engines in those. A Zenith CH-701 with an electric motor would make a pretty decent pattern flying trainer for practicing takeoffs and landings at an airport or field that's not too busy.
Lithium-ion batteries are the functional "floor" for acceptable power-to-weight ratios for aircraft propulsion systems, for flights of 30 minutes to 1 hour in duration, perhaps up to 2 hours for motor gliders. I would think 1 hour flights using a combination of electric propulsion and gliding are reasonably practical. If you have days with lots of wind and thermals, then you may be able to stay aloft for longer periods of time, but I would count on having a suitable landing spot within 15 minutes flying time of your position at all times. Flywheels don't store enough energy for a given weight.
Self-launching from a real runway is probably your best option for remaining amongst the living. Towing another aircraft is a sketchy proposition in ideal weather conditions. It can be done and has been done successfully many times, but there are also a significant number of fatal accidents associated with this activity. All "true wilderness" aircraft are powered by gasoline engines because they provide the most power for the least amount of weight.
A VW engine provides enough power to launch a light airframe, it's proven reliable and durable over more than half a century of use, and they have the most aftermarket support of any automotive engine used in an aircraft. If you need up to 110hp, Corvair engines are also much cheaper than Continental O-200s with all-brand-new components except for crankcases and cylinder heads, and smoother because they have 6 vs 4 cylinders. If you must have a "real" aircraft engine, the O-200 is the go-to engine for light aircraft. There are electronic ignition kits that can improve substantially over magnetos, improving fuel economy and ignition consistency. Those can also be run on unleaded 87 Octane MOGAS, as can most Continental O-200s, Lycoming O-320s and O-360s. Magnetos are very old tech, but gear-driven electronic equivalents exist that can deliver a more powerful spark.
For high quality gear-driven alternators, you have B-and-C or Monkworkz. These are far lighter than their automotive equivalents or the price-enhanced versions of Nippon-Denso alternators sold by Continental, Lycoming, and others as "aircraft alternators". Lighting options abound now, but most of them are absurdly over-priced. Avionics can be provided by "black boxes" to collect air data and commercial electronics such as iPads. This has brought the cost down to far lower levels than what it used to be, and you can have data equivalent to what only the largest airliners had available to the pilots only 20 years ago. Experimental avionics are now cutting edge and all the screens and features make the cockpits of these tiny planes look like fighter jet cockpits. Panel mount radios and antennas are still pricey, but there are much cheaper handheld options available.
As neat as the electric aircraft idea seems on paper, I would simply minimize the amount of fuel you burn by using a small / light gasoline engine. Go out and enjoy the fact that you built your own practical personal flying machine for little weekend adventures. You're not going to use it enough for it to have any appreciable impact on Earth's future weather. Most of the time you plan to fly with the engine off, so you're about as "clean and green" as you can manage without an independent source of funding.
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I have run VW engines, Lycoming IO-360's, and a Lycoming O-54 and an IO-54 on E-95 denatured ethanol, neat. I got the STC to do that in a Piper Pawnee with the 540, along with the airframe STC, long ago while working at Baylor U. All these engines test as 5-15% more power with the same or lower cylinderhead temperatures, running on ethanol. That's a measurable increase in the energy conversion efficiency, which I measured directly on a dynamometer with the IO-360.
The specific fuel consumption is higher ion ethanol, but not as high as you might think from heating value ratio or stoichiometric air/fuel ratio, by around a factor of 2 less increase. That is the result of the higher energy conversion efficiency, verified on the dyno, ground static tests, and in flight. My dissertation verified all this, and suggested the sootless ethanol flame as the reason. With no soot to radiate the hardware from the flame, less energy goes into the hardware as waste heat. It has to go into higher gas pressure on the pistons instead. There is nowhere else for it to go.
After that, I experimented in cars with road tests of ethanol and ethanol blends. I got exactly the same results in one VW beetle that I got in the airplanes, on neat ethanol. The conversion was easy in the old technology (carbureted, with simple battery ignition): adjust the jets for the higher fuel/air, add intake heat to get the ethanol to vaporize, and advance the spark timing by about 30 degrees.
With stiff blends, there were no mods, it was a simple drop-in fuel. But I found an upper limit, where power dropped and fuel consumption skyrocketed. This was like a light switch at about E-42. It happens when the ethanol with the longer ignition delay suddenly "takes over control" of the ignition in the cylinders. I had winter cold start troubles become significant at about E-35, which is really the maximum I would recommend. You won't be able to statistically distinguish an ethanol blend in your performance and fuel mileage all the way up past E-35. It's trading higher conversion efficiency for lower heating value, just about 1 for 1.
GW
Last edited by GW Johnson (2025-01-23 15:54:15)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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GW,
The biggest problem I have with Ethanol blended into gasoline is the utter lack of defined specifications for acceptable fuel products and quality control to assure that the fuels meet the specs. The Ethanol content could be 10% or it could be 50%. There's almost no rhyme or reason about what you get. It's like they just blended whatever they had in the tanks and delivered it. The other major issue is the change in vapor pressure of the fuel with varying Ethanol content, which is still a problem even if you never go above 10,000ft, because density altitude can be much higher when it's hot. Ethanol is a fine substitute for TEL to get the Octane boost, and we consume so much of it so fast that only people who don't fly regularly will ever have a problem with it sitting in the tanks and collecting water. However, something must be done about the blending process, because you cannot engineer a well-running propulsion system to run off of "whatever". A gas turbine may be able to run on Chanel No 5, but it will not run very well, and that's the problem.
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There is an ASTM specification for the denatured ethanol product known as E-95. It specifies very dry ethanol at under 0.5% water, and 5% denaturant, specified to be unleaded gasoline or an alkylate precursor.
What you blend depends upon the application. The E-85 product sold for motor vehicles can vary quite a bit, driven by the vapor pressure / cold start issue you cited. It can be as low as E-70 in the winter, usually pretty close to E-75. It's usually very close to E-85 per the name in warm months.
Most of the ASTM-spec unleaded gasolines sold for motor vehicles range from E-0 to E-10. There at least were some moves to let E-15 be sold, maybe done in some locations, but most not. Experimentally, I have run production vehicles on E-20 to E-35 as drop-in fuels for about 20 years now. If there were a problem with that, I would know about it by now. There is not. EPA feared damage to catalytic converters, but I have found extended life, by the solvent action cleaning the soot buildup off the catalyst beads. I also found extended engine life, traceable to reduced carbon deposits.
As for the airplanes, the STC's specify E-95 or gasoline, not blends. There is no water-induced phase separation problem that way, because you drain and replace to switch fuels. Although, I came up with a simple and reliable field test for detecting phase separation risks for blends, too! With E-95, you solve the cold start problem with a start fuel canister, mounted on the engine side of the firewall. Connect the primer to it instead of the main tank, and put gasoline (any grade) in the start canister. That solution is reliable, and it is in the STC's (Piper Pawnee and Cessna 152).
The only difference you ever see in an E95-or-avgas STC'd airplane is the mixture control. Lean-out is the same. Full rich is to the panel on E-95, but only about halfway to the panel on avgas. If you are used to setting mixture by the sound and behavior of the running engine, there is no problem with that. Amateur pilots need a mixture control stop when operating on gasoline (it's just a clip you put on the rod). I talked to the FAA about that, and it went into the STC for the C-152 trainers STC'd for E-95 or avgas.
With blends, you have to avoid phase separation risks and you would have intermediate full rich mixture control positions between E-95 and avgas, reflecting blend strength. That has never been STC'd, but it worked fine experimentally, with experienced pilots who are used to managing mixture by ear and feel. Key: you don't just unthinkingly always slam it all the way forward. You instead move it slowly, and perceive the effects as you move it. Requires a change of habit handling the mixture control.
The biggest problem with ethanol in airplanes is not really water separation (given my field test), but materials compatibility. The aviation manufacturers never transitioned to ethanol-tolerant materials the way the automotive manufacturers did decades ago (for unleaded gasoline, which has always had one or another alcohol in it). Most fuel bladders are urethane, and cannot handle ethanol. The few neoprene bladders can (as was in the Pawnee). If there are plastic parts in the metering devices or fuel pumps, those are usually not compatible with ethanol, unlike automotive equipment.
We did not use ethanol in gas turbines. We did biodiesel-Jet-A blends in those, up to 30% biodiesel. This was an experimental program directly overseen by the FAA. I came up with a 7-month plan to put a Beech King Air A-90 into "experimental" for the testing, and return it to "standard" category afterwards, which had never before been done by the FAA. The exposed engine required a hot section overhaul to verify no damage, so we exposed the weakest engine that needed to be overhauled soon, anyway.
I got the whole program done in 5 months, including flight tests to around 20,000 feet. Freezepoint was the limiting factor. But biodiesel rejuvenates old, stiff fuel bladders, which pleasantly surprised us and the FAA. No change to emissions, but the sooting on surfaces downstream of the exhausts was far easier to clean off. I did find one blend that had no freezepoint trouble. It had military potential. All this took place 1996-1998, at Baylor U.
Oops, sorry, wrote the years down wrong. Baylor U was 1997-1999. Was still in Minnesota 1996 and first part of 1997.
GW
Last edited by GW Johnson (2025-01-24 13:29:07)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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