Deltahawk on the Bearhawk

[kestrel]

I sometimes feel that some people just hate change, no matter how badly it is needed. The DeltaHawk is rated at 180 hp, so the immediate jump to an O-360 and look for all the ways it falls short. ...and from that crew, not a single mention of how the O-360 falls short compared to the DeltaHawk. Most of what I'm going to say has been said, but I'm hoping to put some of it in perspective.

For the nay sayers:
- Yes, it is new and unproven
- Yes, it is 100 lbs (or what ever) heavier than an O-360
- Yes, there is a history of failed new engines
- Yes, there is a history of failed new diesel engines
- Yes, it will be expensive

....but do you really want this to fail? I'm not asking if you're ready to pony up your own money. I'm only asking if you want it to fail? Are you trying to ensure that there is no advancement in aircraft engines? There were many failures before the Wright bothers succeeded. It takes time and effort. Before success, there is always failure.

Now the rebuttal (points almost all already stated):
- Every engineered object is unproven before it is proven
- There are MANY Bearhawks that are carrying around an extra 100 lbs and are still fantastic airplanes!
- This engine will have a fuel burn of 10-20%(?) less than an Lycoming
- For a given range, you will depart with less fuel. That is weight savings (even accounting for the higher density of Jet-A)
- Over the life of the engine, you will save money on fuel
- As soon as you are at a density altitude of 1 foot, the DeltaHawk is making more power than an O-360
- Keep climbing, and it will be making more power than an O-540!
- Limited performance isn't a problem at sea level, it is a concern at higher density altitudes. ...unless your Bearhawk is powered by a DeltaHawk

As for the thought that the DeltaHawk is not acceptable for a Bearhawk Five: I disagree. A Five _CAN_ be built lighter than many (most?) 4's are actually built. They operate just fine on a O-360. A 540 powered Bearhawk 4 takes off with load at a density altitude of 5-8 thousand feet with a ground roll of 600-1000 feet just fine. Tell me why a DeltaHawk powered Bearhawk Five won't fly and won't outperform the O-540 powered Five when the thousands of feet get into the double digits?

...and the best part? If they are successful and come out with a 300+ HP DeltaHawk, its going to be awesome!

My current project will be an IO-540. ...but I'm cheering for the DeltaHawk.

[kestrel]

Oh? C-170's do backcountry work with 140 hp. A lot of backcountry airstrips are over 2,000 ft long. My experience is that a loaded 4 place with a carburetted O-540 (260 ish hp) can get off in under 1000 ft with a density altitude in the 8,000 ft range. Seems to me that at those altitudes, a DeltaHawk 4 or Five would be about the same. ...and wouldn't need to carry as much fuel.

Are you sure a DeltaHawk 4 or 5 would be too underpowered for "any kind of backcountry work"?

As I said, the present DeltaHawk isn't my choice, but I still claim it is a very logical choice.

[zkelley2]

A 2000ft strip is akin to an international airport. It's massive.

C170s do backcountry work with the o-360s and constant speed props on them. You never see the o-300 powered ones anywhere we normally fly. They can't do it.

It would be about the same power around 9000ft or so, but 1000ft strip is still really long. 1000+ ft putting greens aren't back country strips.

It'd work better if the bearhawk could fly slower, but it's a rather fast takeoff and approach speed airplane and the only thing you can do to get to rotation is horsepower. The bearhawk needs lots of it to get there as quickly as possible.

The deltahawk is logical if your normal operating DA is above where a 540 puts out 260hp, probably a bit lower than that because you still need to climb to. If I lived in the mountain west, I'd prefer a TIO-360 to a 540, but what I'd actually have is a turbo normalized 540. Anything under about a 11:1 weight to hp ratio doesn't have the acceleration to get to the bearhawk's flying speed quick enough to operate out of anything I'd remotely consider back country.

I've flown a o360 powered bearhawk 4pl. I couldn't believe how anemic it was and we were mostly empty.

[kestrel]

Does length define a backcountry strip? If so, how short does it have to be to qualify as "backcountry"?

I have a very different idea of what a backcountry strip is, but the label doesn't matter. There are a LOT of 1,500+ and 2,000+ ft strips in very remote locations that are not putting greens and very worth the time to visit. I would much prefer a DeltaHawk powered Bearhawk to go in and out of them than any Cessna except maybe a well built C-180.

Even at Johnson Creek, the very definition of a long putting green, I'd prefer a Deltahawk powered Bearhawk to the C-172 that one poor guy was wondering how to get back out of there the one time I visited.

I still say that a Beahawk can fly well with an extra 100 lbs. ...just don't add yet another 100 lbs. Comparing directly to the O-360 is only accurate at sea level. Once you start adding turbo's (normalizing or boosting) you have to reduce or eliminate the weight difference against the DeltaHawk.

...and this is still their first product. I'm really, really, really hoping that they will be successful with their first offering and have the resources to develop a more powerful offering. While the first offering is good for some people, improved offerings will be suitable for a wider audience.

This isn't one size fits all.

[kestrel]

No O-300 powered C-170's?

https://backcountrypilot.org/community/forum/latest/stock-c170-pirep-performance-in-the-idaho-backcountry-26728

[BH4BDennis]

I appreciate the comments both positive and the skeptics. I'm originally from Missouri, the "Show Me' state, so I get it. If I didn't work for DeltaHawk, help engineer and test it, and personally certify it (I'm a DER) I'd be a skeptic as well!

There are a lot of benefits this engine brings that will be rolled out over the next few months. Again, I understand, those are just words until you see it. As for power, the currently announced 180 HP is the bottom end, and you will see higher HP variants soon at the same weight.

[Russellmn]

First thing I thought when I saw you guys at Osh this year was "when do they turn up the boost?"

[Redneckmech]

"Snip" As for power, the currently announced 180 HP is the bottom end, and you will see higher HP variants soon at the same weight.

You have my attention! While I am still leaning towards an O-540 for my BH5, developments such as this are why I am waiting until late in the build to choose/purchase an engine.

[TJ_Slice]

I hate to bring up an old post, but I thought I would link Deltahawks announcement about the higher power variants: https://www.deltahawk.com/2024/02/01...ngine-options/

Does anyone know what the actual difference is? Other than $$$.

[fairchild1934]

why not use the allison 250 . 140 lbs--- 250 -400 hp depending on version. about 25 gPH at full power--- used price under 20K$

[fairchild1934]

if we are comparing these engines to their gas brothers--- looks like to me it comes down to which engine can you turbo-- get more boost without blowing the engine up ? The diesel may be 100 lbs heavier because the crank and rods and case are thicker and stronger to tolerate the 20:1 (or more) compression . if they start blowing jugs off - we will know they went too far. so just like the gas engines-- how much hP can you make before pieces start coming off violently :-)
Of coarse it may go exactly nowhere with a price tag of 100k+ dollars. I see used allison 250's for under 20K.
and a 260 hp O-540 burns 25 GPH. 250 hp allison burns 25 gph. (and weighs 140 lbs)

[Bcone1381]

The Allison ff seemed low to me. Turbine engine fuel consumption is typicallly higher than a spark Ignition engine. A data point I found on the Allison 250 is it burns .7 lb/shp/hr. I see a 250hp engine with that specific fuel consuption consuming 53 gallons per hour. Its weight seems about right to me.

[Rollie]

Bcone, check your math. 250 times .7 is 175 lbs/hr. Jet A is about 6.8 lbs/gal, which makes 100% power fuel flow around 25-26 gph and about 18-19 gph at 75%. This grabbed my attention because I used to fly Jet Rangers and remember them burning about 18gph with around 325 HP flying at 60-70%. I flew an A-Star for a few years with a 985 shp TurboMecca that burned 54 gph at the normal cruise setting of 93%

[Bcone1381]

Rollie is right. My math is wrong

[SpruceForest]

Are we talking actual throttle/power lever position for normal takeoff, or use of maximum power setting for the conditions? Seems like airplanes will require max power for takeoff unless there is a procedure for reduced power approved in the POH/AFM/commonly used or some operational necessity which takes the operation out of the 'normal takeoff' profile. Whether that is throttle full forward/to the stop or some position short of that depends on engine and power management system, right? For turbo- or supercharged engines, you might see a max boost number to be observed for TO/GA whether or not that boost is managed/limited by something besides the pilot, and that may see throttle/power lever in some intermediate setting short of full forward/firewalled.

[Utah-Jay]

I would LOVE a 200hp delta hawk on my companion!

[TJ_Slice]

I would LOVE a 200hp delta hawk on my companion!

At 335 lbs., do you think it would work, or be too heavy for a companion?

[Utah-Jay]

At 335 lbs., do you think it would work, or be too heavy for a companion?

My angle valve O-360 weighed in at 284 without the alternator, oil cooler, hoses etc… Not much difference in the final product I suspect

[SpruceForest]

The Companion numbers don't look too terrible with an extra 100 lbs of engine (OK...less than that, but let's make the math easy). A 1300 lb empty weight still gives 550 in peeps and baggage with full tanks... two 215 pounders and 120 lbs of bags.

[nborer]

I love the idea of the Deltahawk diesel... it's the dream engine for my build (and if I heard right at Osh24, at $110k for firewall forward, will remain just a dream engine). I've been following them since the mid-2000s and always have had good conversations at their booth (in the earlier days, it was the engineers... now it's the salespeople). It's a really smart design. As others have stated, it's a 2-stroke so the torque issue with the prop is mitigated a bit (and this was an early design decision, I believe for just that reason). It's piston ported, so there is no valve train, and it is mechanically fuel injected. It's direct drive, so there is no gearbox (you may recall the downfall of Thielert due to their gearbox TBO, and Austro E4 currently used by Diamond is geared). It uses both a supercharger and a turbocharger, and can "limp home" if the turbo fails or you lose coolant.

As I understand it, the biggest difference between the 180hp and 200/235hp variants is both intercooling and boost. They are also working on their TBO numbers, but you could expect that TBOs will be lower for the higher power versions. In theory, overhauls should be less expensive for the block itself (helped by the lack of valvetrain and gearbox), though the need for intercooling and boost will eat up that difference. It burns jet fuel and diesel, and they claim SAF should it ever come about... so if Avgas availability is your concern, it starts to look very good. (Be wary of SAF - I suspect they'll be approved for at best blends in the future, because the aeromatics in jet/diesel get into the seals and can end up drying out the seals if you use fully synthetic fuels without those aeromatics.)

When doing your performance comparisons, the altitude importance of boost can't be overstated - a decent rule of thumb is that you'll get about 75% power at 8,000 ft density altitude at full throttle for a normally aspirated engine. So, if power at takeoff is your concern, consider your typical and 90th percentile DA in your performance comparisons to normally aspirated engines. Where I live, I don't see DAs above 2000 ft, but they are much higher where I want to fly in retirement.

If you take the plunge, go look up Deltahawk's old site in the way-back machine. Their old site had a lot of great technical information for homebuilders. In particular, fuel venting is different for diesels than it is for avgas, and messing it up can lead to flow or safety issues. I haven't looked to see if their old site is on way-back, but I did ask the salesperson at the Deltahawk booth this year to put some of that info back up. I don't think they will since they are catering to the certified crowd now that they have their type certificate.

I'll end up with an O360 on wheels, but I'll dream of a DHK235 on amphib floats.