Single lever FADECs certainly exist in piston aviation- Austro, Conti aero diesels both have them. The Lycoming IE2 is also a true FADEC.
You'll note that most modern aero engine designs have electronic engine controls, the above mentioned plus Rotax iS, UL power, D-Motor etc.
Few manufacturers would think of releasing a new engine design without this tech today.
I would compare this to the glass panel revolution on a slightly lower scale due to Lyconental not offering such tech on their legacy aero engines. Few folks are building panels with steam gauges today nor are most aircraft OEMs.
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Modern" like 4 stroke, push rod, over head valves, air cooled (or water) horizontal opposed 4 or 6 cylinder engine are "modern". Ha ha. I would call the Rotax/UL tiny new unproven low HP (80-100HP) niche boutique engines with some dubious history (UL Power) new to the market but not modern. Modern in this case does not mean better than tried, true and frankly superior design and power. Besides Carb, Mechanical FI and Mags work beautifully. However you can replace them. You can replace Carb/Mechanical FI with EFI (hummm who sells that?). Ha ha. You can replace the Mags with Electronic Ignition (EI) and choices abound. I think the Rotax and UL power are fine for LSA's but not full hair and teeth sport cross country aerobatic planes. They are different, apples and orange, not a matter of "modern" or new technology. There is nothing new with these small LSA engines and don't have better efficiency on a HP to FF basis, and in some cases are slower. UL520iS (always use lower case "i" in product ID to be cool) has been put in an RV4 and RV7. The numbers are not impressive, slower and similar fuel burn. Some have installed the smaller UL Power in RV12 vs. the recommended Rotax. Again kind of yawn. So the "modern" thing is meaningless since all these engines are 4 stroke, push rods, overhead valves, Horz opposed. Rotax is water cooled (also not new tech) with PSRU. Spinning engine faster to make more power on smaller displacement is not new, it's a choice. It has some pros and cons.
Lyconental are dinosaurs and Rotax and UL Power are "modern" will be winning at this year coming Reno Air Races. Ha ha. These two "modern" brands could not compete, They could not compete even in the Reno O200 Continental Formula class and win. The Rotax/UL are maxed out and need to turn in excess of 3200 to 5500 rpm to make power, thus requiring lower Prop efficiency or geared PSRU. Don't confuse "modern" with superior
Lyconental in both performance and efficiency. These modern engines have nothing but being small. Lower fuel burn? Yes much lower HP. Neither Lyc or TCM compete in this lower HP LSA market, except for the Continental O200 light, one of only three engines (I know of) suitable for and approved for SLSA with Rotax and Jabiru being the other two. However I concede the Rotax has eaten everyone's lunch in the SLSA and LSA market. Modern? No just targeted for that market very well. You can always slap on EFI and EI to any Lycoming or TCM engine and make it "modern".
Airplanes with single lever power control are like cars with EFI and automatic transmission. Drive your Honda Civic from New Orleans (sea level) to 14,160 fr Mount Evans Colorado and never adjust mixture, while adjusting speed with one SINGLE LEVER (skinny pedal on floor) and a single start/start button. We can say the cars have FADEC? OK.
Rotax and UL Power are not single lever are they? They can not accept hydraulic controlled constant speed props, so fixed or an electric prop is needed. Both these engines are electrically dependent and prohibited from aerobatics. "Modern"? Electric props have been around for 80+ years but everything went hydraulic as they are superior. An Airmaster or MT electric prop is about $12K to $18K. My used Hartzell C/S prop was $2500. Ha ha. Add the rebuilt Gov for $1000 I am good to go. Modern? Yep I want oil in my prop that will work with zero maintenance, not a slip disk and brushes and another battery dependent system.
The Continental IO550 in the Cirrus has one lever (kind of) with EFI and mechanical linkage in throttle to control the PROP (I think correction requested). Not Full or Digital. I rather separate Prop control of RPM I select, like I prefer a manual shift car and motorcycle. Modern? My preference and often nothing wrong with existing technology, making modern less desirable for cost reasons and other drawbacks (electrically dependent).
Take any plane with fixed pitch prop, say a Cessna 152, add EFI that automatically adjusts mixture for altitude (as most EFI do). You have one lever. Is it FADEC or just EFI? Some planes have alternate air and cowl flaps "levers", i.e., more levers. Are you going to add that to the FADEC for single lever control to alternate air and cowl flaps? Sometimes pilots have to do pilot stuff.
Diesels doing "FADEC" or single lever is easier because they and run O2 sensors that leaded gas aircraft engines can not due to O2 sensor fouling with lead. However Diamond D62 twin "FADEC" diesels has had some unfortunate accidents do to loss of electrical power. The whole thing is very electrically dependent. Modern? Sure OK. It is also a $1.5M airplane, not very big or fast. The diesels are fairly low power (180HP per side). Most high performance piston twins have 250 to 350 HP per side. I
'd buy a single lever turboprop like a used TBM700, Piper Meridian, or PC12 which can be had for $1M before a D62. WAIT. Hold on. My Accountant called me just now. She said I was delusional. Apparently I can't afford those planes. Never mind. Ha ha. P
oint being old Tech that works well and cost less may be better than new stuff that has new downsides and costs a lot more.
Lyc iE2 is single lever, but
not advertised as FADEC. They call it "iE2 Integrated Electronic Engine".
My point a single lever on a piston plane is a different animal than a Jet FADEC with single lever. It is like comparing apples and oranges.