In a sit-down at AirVenture with members of the Continental Aerospace team, I asked what they think the current market wants in new engine tech. I’m talking about new powerplants for run-of-the-mill models—Bonanzas, Barons, Centurions, and even Cirruses and Mooneys. Frankly, I’m not sure. For Continental, the answer is in the Diamond DA50 RG poster child pictured above. That airplane packs the Continental 3.0 liter CD-300 liquid-cooled, 300-hp V-6, twin-turbo Jet A engine. More on that in a minute.
Talk is cheap until it’s time to slap the money on the table, but for a while there has been some demand for higher-powered Rotax engines that can work in the 200-hp airframe class. Part of the demand is that the lower horsepower 912 through 916 models have earned respect for good performance and decent dispatch reliability, but I wonder if Rotax simply sees a healthier business model in the higher-volume light sport market. Recall that after extensive testing on an engine near close to certification, it never did bring the 936 V6 to market.
With DeltaHawk increasing its marketing footprint in the certified and experimental markets (and penetrating an OEM, with Piper testing the 4-cylinder 180-hp Jet A-burning DHK180s on the Seminole DX twin trainer), interest in DeltaHawk engines is growing, and not without demands for a lower price. The DHK engine is packaged for some experimental kits, including Van’s, but there aren’t aftermarket STCs yet for certified applications. The company is working on other variants, including a 2-cylinder for the light sport market, and a 6-cylinder.
Still, Rotax and DeltaHawk are the ones to watch, and Continental has taken notice even though its CD-300 is hardly a fresh design. Recall that Continental bought Thielert Aircraft Engines in 2013 and has plenty of experience supporting its current line of CD-series Jet A engines.
The flagship CD-300 V-6 was type-certified in 2017 in the plain-vanilla Diamond DA50 and eventually for the DA50RG retrac. Continental currently offers several FAA/EASA certified variants of the CD-series engine (from 135 to 300 hp), including the CD-155 firewall-forward retrofit kit. There are roughly 2,000 Continental Jet A engines in the field. The 155 hp four-cylinder turbocharged CD-155 kit is specific to select Cessna 172, Piper PA-28, and Diamond DA40 models.
Stone Simple
Continental’s Vadim Cateli has worked the engine support side long enough to believe pilots need engines that are stone simple to operate, which means single-lever FADEC, and it’s easy to agree. I fly behind a Rotax and I can tell you with certainty that I don’t miss the mixture and propeller controls. In the Diamond DA50 RG with Continental CD-300, engine start and test is reduced to turning on the engine master switch, waiting for the glow plug annunciator to extinguish, pressing the start button, and then the FADEC test button where the computer fails each redundant ECU (engine control unit) for crosscheck, and cycles the propeller. Turn on the aux fuel pump before takeoff and firewall the throttle. Hot starts, cold starts, forget about these and hit the Start button. The engine is liquid-cooled so for descent, pull it back to idle and hustle down.
Cateli sees value in the CD-series engine on the shop floor, while acknowledging the challenges of training. I’ll throw in the challenge of getting grey-beard mechanics to accept the new tech—there’s more resistance than one might realize. Still, with a CD engine, they’ll have to forget most of what they know about troubleshooting the typical IO-550.
Instead, start with an engine data download, rather than old-school teardown disassembly. The ECUs record everything from the second you switch on the master switch. As for TBR (that’s time before total engine replacement), it’s 2,000 flight hours or 12 calendar years for the CD-300. The engine once had a 600-hour mandatory gearbox replacement, but that’s been changed to on-condition monitoring. No magnetos, no spark plugs. (They’re called diesels because of compression ignition).
All Problems Not Solved
Parts shortages, no matter the engine tech, might not ever go away. Dr. David Dorner, Continental’s VP of global research and development, pointed to the automotive market as the problem for getting some raw materials, including forgings. We hear of lengthy engine replacement lead times because of crankshaft shortages. Dorner said competing for bandwidth in the automotive component supply chain is a continuing problem. “Aviation is a scattering of crumbs on the floor compared to the high-volume automotive component manufacturing market,” he said. Aviation diesels are lower volume yet.
There’s also the challenge of earning aftermarket STCs—a huge investment. A few years ago at AirVenture, Continental announced plans for the first aftermarket STC for the CD-300, which would be for select later-model Cessna 206 Stationairs. Third-party FTI Engineering Network GmbH has been flight testing the engine, with plans now for certification in 2027. Initial pricing for the complete kit looked to be in the $300,000 range. Given the modifications that tag along with transplanting any Jet A engine in an airframe designed for familiar Continental and Lycoming engines, it’s easy to see why the price point is eye-watering. Is it even worth it?
When Continental’s Vadim Cateli pointed out that the requirements for liquid cooling and other supporting systems point to building the aircraft around the engine rather than the other way around, I couldn’t help but remember my time spent with Phil Lockwood at Lockwood’s headquarters in Florida last year. Lockwood gave me a tour of the Van’s RV-9A/Rotax firewall-forward project he was working on, and it sure looked like a lot of rework to the RV-9A airframe—a lot of engineering and challenges even for the talented Lockwood.
From a performance standpoint (around 178 knots true at 12,500 feet and burning around 8 gph of Swift 94 unleaded), Lockwood’s project (working along with Van’s) is a convincing transformation that includes a Rotax 916iS and all of the required cowling modifications to accommodate the right blend of engine cooling, CG weight distribution, and structural tweaks. The payoff goes beyond speed and efficiency.
The single-lever 916 iS engine, with Eco mode, is easy to operate at best efficiency partly because it automatically runs lean of peak EGT. On the second try, Lockwood did a terrific job with the complex cooling system made somewhat simpler with one single-inlet scoop that ultimately sends inlet air where it needs to go once inside the cowling to efficiently cool the engine. But eyeballing the RV-9A mod, Cateli’s point about retrofit complexity—no matter the engine—is well taken. Any Jet A transplant in a legacy airframe will be a ton of work, which means a ton of investment on the front end that buyers will have to pay for.
In the end, we can have all the modern engine choices we want, but if we don’t have third parties that will invest big in the engineering for mass retrofit that’s reasonably easy, my fear is that our legacy airplanes will be forever stuck with the same old powerplants. Diesels may someday be the new OEM standard, but the harsh reality is that the rest of us may never be able to afford diesel-powered new planes no matter how much we want the new tech.
A 12 year throw away diesel coupled with $300,000.00 to start with is a mountain to high to climb for the market. Definitely to high for me to climb. I’m assuming $600,000.00 to start with for a twin.
Here’s the other problem with Continental’s CD 300: Dry weight with the gearbox is approximately 548 lbs to 584 lbs, which is nearly 100 lbs heavier than an IO-550N.
IO-550 TBO:
TIME BETWEEN
OVERHAUL (TBO):
1800 to 2200 hrs or 12 yrs
I realize that this is overhaul vs replacement, but the 12 year part is not unique to the new diesels. Lycoming’s TBO is similar.
Deltahawk has lots of announced projects, but no production certified engine yet. The first will likely be on the Seminole since there are apparently 5-10 aircraft ordered with engine for delivery ??? (quoting Q12027 but we’ll see).
One interesting idea that they have mentioned at Air Venture in conjunction with the 6-cyl Bushliner is something called Perpetual Power. This was mentioned as a replacement for the upfront capital expense, being rather a multi-year contract with an all-inclusive yearly fee including maintenance and engine overhaul at TBO. I suspect this will be limited to fleets but the idea could certainly generate a lot of interest by individual owners.
More like perpetual payments…
Pick your poison. Either put money away each month to replace the engine in 12 years, plus ongoing operating costs, maintenance, parts, ect. Or write a check each month that covers it all and let someone else worry about it. One way or the other the bill comes due.
Agreed. Sounds just like “Power by the Hour” programs that have been around in the turbine world for decades.
I think if you just replace all those single-engine models with just Cirrus, this article makes a lot more sense. If you are willing to put down over a mil for a single-engine piston, what is 300k more for a Jet-A version? A tax round off error. You’re gonna wound up on Jet-A anyway eventually, right?
The real reason diesel aircraft engines are not more popular is overall cost due to complexity. Other downsides include the requirement for power on descents and certification difficulties.
Of course I’d love a turbodiesel to replace my 200HP IO360 Lycoming. But the reality is that old Lycoming is a workhorse, lasts for decades and is in fact very efficient.
the other big problem with diesels is the fuel system needs major modifications, heaters, return lines etc because even Jet A has major problem when cold our stock 100 LL fuel system will not work for heavy fuels.
I think there is a middle ground that should be explored. Some aircraft, low in production numbers (eg Grumman AA-5 series) will never have a market that will support the non-recurring engineering costs. However, these airframes are far from the scrap heap at the same time. As it stands today, if some enterprising owner wants to build a one-off DHK powered AA-5 they would have to put the aircraft into Exhibition Experimental category. The resultant restrictions probably would put him off.
Want to do the same to an RV, no problem. Would propose a middle ground amateur experimental category permitting new technologies to be trialed on certified airframes, with the same restrictions as amateur built experimental. It would be a win win. Small scale adoption and demonstration of new power plant installations would show the way forward, and the aircraft owner would be able to use the aircraft just like their amateur experimental brethren.
People want to fly behind a non-100LL engine but the vast majority of owners will balk at an +$100K diesel engine and the high cost of conversion.
Nope. Just nope. Makes all kinds of sense but the initial cost is a deal killer except, as noted, for the Cirrus crowd. Looks like I’ll never get to fly a Diesel.
Even the RV-9 Rotax 916IS conversion is $130k all-in. Oof.
Someone did an STC to put a TIO-540 (basically a malibu or Navajo engine) and a four-blade prop on a Comanche several years ago. (Early 2000s)? It was going to cost about $70K at that time. You could buy a decent flying 250 for about $50K, then. The FAA kept wanting more and more flight testing and it finally got shelved.
My point is just that, this is a big project, to re-engine existing airframes (Even with proven engines) and may not be worth it.
It sure looked and sounded cool, and was reportedly a HOOT to fly… 🙂
…”Continental’s Vadim Cateli has worked the engine support side long enough to believe pilots need engines that are stone simple to operate, which means single-lever FADEC”…Stone simple for pilot operation means extremely complex systems to achieve stone simple.
…”with Continental CD-300, engine start and test is reduced to turning on the engine master switch, waiting for the glow plug annunciator to extinguish, pressing the start button, and then the FADEC test button where the computer fails each redundant ECU (engine control unit) for crosscheck, and cycles the propeller. Turn on the aux fuel pump before takeoff and firewall the throttle. Hot starts, cold starts, forget about these and hit the Start button. The engine is liquid-cooled so for descent, pull it back to idle and hustle down”.
Add PSRU (the weak link in most if not all automotive derived aircraft powerplants), mix with liquid cooling complexities, aka radiators, fans, sensors, hoses, wiring, engine monitoring, spice with ECU redundancy requirements, backup electric power source(s), integration of auto/FADEC prop control, and blend with engine compartment heat,/cold cycles for a great recipe of excellent performance while new, but very troublesome with chronological age. All we have to do is look at the electronic challenges of diagnosing and repair of 10-25 year old cars and trucks. Plastic gets brittle, wiring harnesses corrode, plastic clips/connectors/pins loosen, and trouble codes with CEL lights abound. And many trouble codes have nothing to do with what is actually wrong.
…The ECUs record everything from the second you switch on the master switch. Absolutely true. And this data can and is used to determine who screwed up in operation, diagnosis, and repair. That means, it can become a warranty nightmare if any recorded data is used as a way of avoiding warranty repairs, or becomes a tool of the legal system. One of the biggest issues in modern engine tech is who owns the vehicle and the right to repair. Does the manufacturer own the software? When and who gets access to the proprietary software needed to accurately diagnose and repair when something goes wrong? Who will maintain the required software updates requirements…the aircraft owner, the A&P, the FBO, the FAA, or combo thereof? Today, because of the lack of applying needed software updates by owners voluntarily, software updates are pushed from manufacturer to the car itself while it sits in your garage. You don’t have a a choice. And if the manufacturer wants to disable your vehicle, it can be done at the click of a mouse. OBD-1 vehicles have virtually no or very limited repair facilities available that have the old software and scanners to diagnose trouble codes. OBD-2 has been the industry standard since 1996. However, since 2015 the added complexities have made formerly reliable powertrains into a multitude of major recalls involving literally millions of now unreliable vehicles from virtually every manufacturer. Class action lawsuits are becoming the norm owning a modern, stone simple to operate vehicle. Will Continental allow anyone outside of Continental fix a Continental manufactured diesel engine? Sound like a crazy question? That is a very serious issue developing between vehicle owners, original manufacturers, dealers, and independent repair shops.
“I’ll throw in the challenge of getting grey-beard mechanics to accept the new tech—there’s more resistance than one might realize.” Yup! “Still, with a CD engine, they’ll have to forget most of what they know about troubleshooting the typical IO-550″ Review previous paragraphs.
.”..We hear of lengthy engine replacement lead times because of crankshaft shortages. Dorner said competing for bandwidth in the automotive component supply chain is a continuing problem. “Aviation is a scattering of crumbs on the floor compared to the high-volume automotive component manufacturing market,” he said. Aviation diesels are lower volume yet.” In our never ending quest for maximising profits for quarterly returns, meeting analysts expectations of profitability has resulted in outsourcing basic manufacturing. Today, we might assemble the parts needed to produce an engine in the USA, we make very little of the components needed for assembly. Look at the Monroney sticker (window sticker) of a new Corvette. Approximately 40% made in Mexico, 30% in Canada, and GM does not legally have to disclose the remaining 30%…but all assembled in Bowling Green, KY. Kinda makes one wonder who is manufacturing a new Continental or Lycoming crank, and where? Dorner has no problem identifying the problem, assigning blame, but offers no solution. The solution, so far, is suck it up, wait for months or longer, and when enough parts arrive at Continental, you get an engine. A very expensive engine. That seems to be the status quo for so many accumulating problems in our country. Lots of blame to justifiably comment and rant about. But very difficult to have a rational discussion about solutions because it is clear we have to completely change our economic system and way of approaching business, especially manufacturing and finance. Easy to say let’s return manufacturing to America. Doing it is an entirely different matter. Yeah, we did it in WWII…which happened in the 20th century, We need 21st century solutions, not 20th century memories.
So, I don’t agree with Continental that US aviation consumers want diesels. WE want reliable affordable aircraft powerplants with equally affordable and well distributed fuel that both can be supported, readily available, and repairable through out where we fly. Those requirements are going in the wrong direction, and have been for a long time. Lots-o-blame but no solutions so far. $300,000 FWF engines are not a viable solution in my estimation. Diesel or otherwise.
Right on the money. If this thinking persists it would be another nail in the coffin for G.A. Regarding electrics, electronics and connectors–you are right– they will and usually do fail at bad times. The best solution will be to detune engines if 100LL becomes scarce or unavailable. Increase cylinder volumes of current cylinders with modern manufacturing techniques ( bigger bores = bigger displacements) to increase output power whilst reducing cylinder and head temps with lower compression ratios as well as fractionally reducing cooling fin outside dimensions and maintaining adequate cooling margins as retrofit cylinders for today’s fleet engines. These modern refits would maintain the same power with less stress on all components and could probably increase T.B.O. times.
There are more than 5,500 diesel Austro Engine units currently in service worldwide.
https://www.businessairnews.com/mag_story.html?ident=36096
The cost has been well covered and is staggering, but something that is worth more than the footnote it got is the weight.
I looked up the dry weight of an IO550B for comparison, it’s 467lbs according to Air Power inc (I went with this because it’s heavier than the 422lbs in the EASA TCDS). I don’t know if “dry weight” has a specific definition including state of engine dress in this case, it’s a nearly meaningless figure unless the state of assembly is specified or someone posts a picture of the engine hanging from the scale so you can see exactly what was included. If the state of dress is the same, 117lbs of extra nose weight is not insignificant on your formerly IO550 powered Bonanza, considering that there’s no takeoff power gain, just high altitude cruise power. I’m curious who in GA wants diesels, the OEs? Because in the consumer aftermarket they make basically zero sense between the conversion cost and weight gain. Commercial operations that fly lots of hours may be able to make the numbers work in their favor.