Deltahawk is taking a survey on what planes models to make engines for.

Scott Sherer

If you'd like your Piper aircraft model to have a Deltahawk diesel engine you'll need to take a survey. It's free, no obligation. Here's the link: https://www.deltahawk.com/survey/

jacobsja

I know that this is for those who want to participate with a survey for going diesel.

At the same time, am rather curious about the end result.

Will admit that I love diesel, although am less in love with the new generation OTR which is arguably more complex and higher TCO than gas. Fortunately, DeltaHawk is following a less complex design path with manual injection, along with no reference to the other EPA items currently in place for on (and off) road applications. Not really helping the total picture though is that diesel (in this case, Jet-A) is stuck with notable amounts of NOx unless willing to start playing with chemistry, where def trades NOx for amonia, and where hydrogen (ignoring the supply issue) reduces NOx while potentially sacreficing metal integrity in the engine.

In reviewing DeltaHawk's offerings, am curious as to whether there is something in the pipeline other than what looks like the same 3.3L engine merely adjusted for different outputs. If the mod for a Piper is another variant of the 3.3L, am not seeing a real benefit as the engine appears about as heavy as a Lycoming 540. Am open to correction on this one. But if the 3.3L diesel is similar in weight to a 6 cylinder gas, simply tough to predict whether the 4 cylinder crowd will like the additional bulk.

Toward the fuel burn of a diesel, can see where the carburorater crowd will get a nice benefit. For the injected crowd, by installing GAMI injectors and pulling back to ~50% power raises the question of whether converting to diesel is worth the cost. Add in the potential for lead free avgas turning into reality, and Jet-A's fuel burn advantage shrinks a bit.

Last thought is one that might get me in trouble by way of reliance on mental recall, but am good with at least putting it out there for either validation or debunking. Once the gas Lycoming or Continental engine reaches its "end of life", the designation is TBO where the owner may push past this limit if metrics remain good. Owner of a gas engine also has the option of overhaul (if the internals meet specs) or new. Last I checked, the aviation diesel has about the same life span as gas counterparts, but carries a TBR designation. Per an article I found which was dated last year, there are no published TBO or TBR numbers for the 3.3L diesel yet.

If we want to go down the path of a wish list for Jet-A consumption, retrofitting a turboprop makes me salivate 😁

empannin

I first started looking at the deltahawk engines in ~ 2003 for an RV-10 I was building. I figured by the time I finished they would have high power versions... 21 years later I guess they are getting closer.

I think the market is huge for military drones but I am skeptical for general aviation or experimental. The estimated deltahawk 180HP package price (on their website) is $100 - $110k. There is likely some OEM discounts and for a new plane like an SR20 that is already hovering around $1M it might make some sense.

I think the retrofit market is going to be crickets and experimental will require passion and $ over sense.

If they have a military market (and I think they do/will) I don't think they can really undercut their government prices and despite how disappointing it is in terms of my ability to buy I do understand they have 20+ years of NRE to address and recover.

Pricing may improve with economies of scale - but aviation is not really a scale business...

Eric

jacobsja

The least powerful of the series shows 363 ft/lb and the most is 474. I'd suspect that range is a bit more punch than what the RV-10 uses, correct? 🙂

griff390

Scott set up a tour of the Deltahawk facility for his EAA chapter about 6 mos. ago, and I attended.

I'm a long time gearhead (petrolhead to our friends across the pond) and an engineer, so I don't simply accept glossy marketing. Add that to the fact that I have seen dozens of engine companies (who all promised to change aviation engines forever) fail decade after decade, and you'll understand my skepticism.

Deltahawk's engine is the first clean sheet engine design to be certified by the FAA since the 1960's. Obtaining an FAA certification for anything is not an easy feat. I worked for a company that designed heads-up displays and was on the team that ultimately earned the FAA certification, so I understand how grueling and difficult it is.

During the Deltahawk tour, I asked a lot of in-depth engineering based questions. Their answers were intelligent and as detailed as my questions. The engine design is very impressive and well thought out. Everything is designed with the redundancies required in an aviation engine and ease of maintenance.

The $100K price is breathtaking, but includes everything firewall forward (engine, cowling and mount). I think it includes the prop also, but don't quote me.

Airframe manufacturers have taken a big interest. Deltahawk is open to the retrofit and experimental market, and currently have a twin Velocity flying around as a demonstrator.

Out of my price-range, but still very impressive. It remains to be seen how it's accepted by the market. I wish them the best of luck. They earned it.

empannin

https://www.piperowner.org/talk/discussion/comment/1445241#Comment_1445241

The RV-10 typically uses a Lycoming IO-540D4A5 putting out 260HP at 2700rpm. On a HP to HP basis the 230 HP diesel would have less climb at sea level but still might perform better at altitude since turbo/super charged.

The torque on the IO-540 is 505 ft/lbs if I did my math correct.

I believe HP = Torque*RPM/5252

Resq5hvy

@griff390

How does the power output of the Diesel compare to a gas engine? Can the 180HP Diesel really do what a 200HP gas engine can do?

jacobsja

In case any of my comments were taken as a slight against DeltaHawk, that was not the intent. Merely thoughts on how the application might work given aftermarket alternatives. As already noted, I am a big fan of diesel and noticed the lack of unnessisary complxity in DeltaHawk's engine. If a plane was also built clean sheet around the DeltaHawk engine, this might help with decision points. But, in this case, we are looking at retrofitting into existing airframes which have aftermarket options that raise the question of whether it makes economic or practical sense (if it even physically works). Speaking of aftermarket options, we now have electronic ignition which IIRC is available to all of the Piper line; this also stands to shrink the 3.3L's fuel burn advantage.

One lingering thought on Jet-A's future is how this is playing out on our roads. Due to particulates and NOx, diesels are in the cross-hairs and am curious as to whether this will translate into GA. Am suspecting that it already has effected GA as I am not seeing any traction into turbo prop retrofits as this engine is arguably more attractive from a practicality standpoint than a piston engine of any fuel type.

Resq5hvy, whether the 3.3L 180hp diesel can do what a 200hp gas can do might miss the mark for something like an Arrow. Will argue that the better first question is whether the plane will remain within CG once adding notable additional weight to the forward arm. At the moment, DeltaHawk only has the 3.3L engine which weighs about the same as a 6 cylinder GA gas engine. And even if the additional weight is still within an Arrow's CG envelope, this turns into a prortionate reduction in useful load. While on the topic of useful load, Jet-A is a bit heavier than 100LL, but might weigh closer to G100UL (if it ever comes to market).

Eric, to the torque, really have no idea here as the O-540 / IO-540 toque spec is not readily available. Found one article which indicated the 540 might have upwards of 800 ft/lbs. It was a challenge just to find the 540's weight (I had to approximate it by way of compairison to another engine's weight). I do know enough that the GA flat gas engine is one of the rare breeds of gasoline engines that develops more torque than HP without compressed intake air. Disproportionate displacement for low HP output probably has a lot to do with this.

And back to the economics, if this engine is truly TBR at X hours, it raises the quetion of whether there is any payback from the conversion. Maybe the owner of the second engine after TBR will see some payback if the initial conversion cost does need a new cowling and other rigging.

So, while I love diesels, this one has me sitting on the fense given the application and alternatives. And in reading into an interview with DieselHawk, am suspecting that the company realizes that this type of conversion has some headwinds and is more niche.

By the way, am truly loving the conversaiton!

empannin

Jacob,

Good summary of the challenges. I think the airframe would have to be worth 100 to 200k+ to justify that much on a diesel engine conversion. I think they will find the most success in military as well as OEM/new build.

They have also spent some time over the years working with Velocity and the Velocity twin is an interesting application. I think we will see more there than elsewhere as it fits a high and fast mission and the overall kit cost is on the high side regardless.

Eric

griff390

https://piperowner.org/talk/discussion/comment/1445248#Comment_1445248

Resq;

Jacob and Eric did a great job summarizing (the equation Eric posted is correct).

In general, the answer to your question is yes. The background to the answer is more complex, but I'll try to simplify so everyone's eyes don't glaze over. You're a hot-rodder, so you'll get it.

For starters, horsepower is a calculated value. Given the torque an engine develops at a given RPM, HP can be calculated using the formula that Eric posted.

In simple terms, torque is the "twisting" force the engine develops at the crankshaft, and HP represents the rate that the engine can produce that torque. The other important factor is the RPM band where the torque is produced. Example: A gasoline car engine and a diesel semi truck engine are both rated at 400 hp. The automotive engine develops 384 lb-ft of torque at 5,800 RPM, while the semi engine produces 1,900 lb-ft of torque at only 1,700 RPM. They're both rated at 400 hp, but the RPM range where the power is produced is drastically different.

A lot of low RPM torque is required to get a 40 ton semi moving, and also to swing a propeller through the air.

Regardless of the engine type, the same amount of power is required to turn a propeller at a given RPM. Gasoline engines typically make peak power at a higher RPM. Therefore a slightly higher horsepower gasoline engine is required to make the same torque as the diesel at the lower RPM range (where the propeller operates). I hope that makes sense. I know it's an oversimplification, but I see people's eyes beginning to glass over.

If anyone want to follow me down a rabbit hole regarding engine and propeller design, keep reading.

Longer propellers are more efficient, so why aren't our airplanes equipped with them?

As with everything in engineering, there are trade-offs, and limits to propeller length are one. Long propellers have a higher likelihood of a ground strike due to less ground clearance. Additionally, for a given RPM, a longer blade will have a higher tip speed. When the tip of the blade nears the speed of sound (upper transonic range), 2 things happen. First, a shock wave begins to form, making the blade very inefficient. Second, the shock waves puts tremendous stress on the blades, and can lead to total destruction. A typical 74 inch diameter propeller turning at 2,700 RPM will have a tip speed over .77 mach.

Compared to auto engines, our aircraft engines have large cylinder bores, which promote developing torque in the lower RPM range. Not coincidentally, that matches the propeller design limitations (above).

empannin

The geared GTSIO-520's on the 421C I had were the smoothest and most satisfying aviation engines I have ever flown. The gearing allowed for a slow prop speed a big props at very reasonable engine speeds. No headsets needed in the pressurized cabin.

Of course the reality was the gearing was placed in the nose right by a huge hole for the alternator and the whole thing spent it's life trying to twist itself apart. (and often cracked the case over time even if you babied it)

The harmonics were serious and a special damped starter adapter was needed to keep it from self destructing in seconds. The large heavy prop likes to maintain a constant speed. The engine is accelerating and decelerating with combustion and exhaust cycles. You can reach a power setting where you "chatter" the gear too.

If I had a fortune - and a company to write it off against - I would consider getting another 421C and exiting with a small fortune. ;)

Scott Sherer

Wow, I didn't expect this kind of enthusiasm on this discussion. Thanks everyone.

Regarding the engine, my Arrow hangar is about 75 feet from the Deltahawk hangar and I get to watch them testing the engine every week. Dennis Webb, chief engineer for Deltahawk has invited me to fly their SR20 with the new engine sometime in the next two week. Deltahawk founder Doug Doers, CEO Al Ruud and Chief Engineer, along with about 30 of their employees are all members of my EAA Chapter 838. They are all amazing people.

Also, the rumor mill around Racine Batten airport where all of this magic happens is that Deltahawk and Piper inked a deal sometime last week. Nothing official but I do know that Piper and Deltahawk have met privately several times in the last few months.

empannin

Keep us updated Scott! The SR20 is a perfect plane for the deltahawk. It is 215HP now but non turbocharged and close to $600k. A deltahawk powered one would potentially offer extended range and performance. They would likely sell it at a premium to the 100LL SR20 (50-60k?) and it would fit well in the gap to the SR22. (> $800k in many configs).

Would make a great technical advanced aircraft trainer with performance to attract private pilots that an SR22T would be too far of a leap but they wanted turbo too. Also, the international market where 100LL is much more expensive vs the US.

For Piper it would be a better fit than the Archer DLX 155 HP continental diesel and could be good for the Seminole market too as a counter to the Diamond diesel series and also good for the international training market.

I think these new plane platform markets are good opportunities. My skepticism is on the retrofit market that is likely non-existent and the experimental market that is too scattered (although the twin velocity is a good choice as it is an expensive airframe and they have a track record of working with Velocity).

In the experimental space I am considering a Zenair 750 SD or potentially a 750 Cruzer. I would likely put a Viking engine in it (Honda platform) and would have autogas or 100LL flexibility.

Generally the airframe, engine, and avionics should each cost about 1/3 of the total. Only an expensive experimental could justify a $100K engine.