Diesel powered 337

[Rick Gardner]

I was told today that someone has converted the front engine of a 337 to diesel somewhere in the northeast USA and is flying it under a restricted category. Has anyone heard of this who could elaborate and does anyone know of any plans to retrofit diesels on a 337?

Rick Gardner
www.caribbeanskytours.com

[EB338]

I too would be very interested to hear more on this subject. I have been doing some research on the topic and would assume they used the Centurion 4.0 by Thielert in Germany. That is the 350hp V8 water cooled engine with the gear reduction unit that runs on Jet A. I know it is not safe to assume anything but this is the only diesel I could find that was close to big enough. They already have kits to convert 206's, 340's, 414's, and 421's, as well as Beech Duke B60's, so the front end of a 337 should not be much of a stretch.

They claim more static thrust for the HP than conventional because of the higher torque and to be burning about 12gph (per engine) which could get 350hp 337s running for less than $100/hour in fuel up in the 300mph neighborhood. They are however almost 200lb heavier each than the TSIO550's, not to mention 4" wider, 6" taller, and 3" shorter but I don't know if any of those numbers include the gear reduction unit, and I am not entirely sure how their water cooling system fits in the cowl or how much more weight that adds to the package. I also found it interesting they offer no TBO as they are supposed to be replaced not rebuilt every 2400hours. They also take mixture and prop control and hand them over to the computer which like most new technology sounds great when it works.

Anyone know anything more?

[Skymaster337B]

I would rather have a small turbine running then a diesel.

[AussieO2]

Delta Hawk Diesel Engines, http://www.deltahawkengines.com/archives.shtml
N1700M is the 337E.

[hharney]

Delta Hawk has been testing for several years now. There should be more info on the board about this. Also, at the SOAPA meeting in Kalamazoo 2008 there was a presentation about this work that DH is doing. It pays to attend.

[Skymaster337B]

From what I can see on their web site it looks like a Diesel engine will be more expensive than a regular engine. But will the overhaul time be about the same?

[CO_Skymaster]

Does anyone know, when Thule-River talked about installing SMA diesels in a Skymasters, did they have to perform major modifications to the cowling like SMA had to do with the 182? Is there enough cooling in the Skymaster to dissipate the heat?

Karl

[robw]

We run a pair of 337s for aerial survey work and because of the huge problems getting avgas out here in Africa, we have been tracking both the alternative engine and alternative airframe possibilities for years.

First off, if HAWK are quoting $340k for their Skymaster conversion, I can’t see that they are going to get many takers. Adding in something between $100k and $200k for the basic aircraft means you are throwing around an investment figure above the half million mark and at the end of the day you still have a forty year old airplane no matter how well it has been checked out. For that sort of price you can buy a brand new out of the box Diamond DA42 twin diesel that offers comparable range and operating cost. It makes no sense.

Diesel does seem to be the inevitable way forward but (unfortunately) it is still early days. So far there have been only two certified engine manufacturers, Thielert and SMA, and they have both experienced massive technical difficulties in making their engines reliable. They do now seem to be getting on top of it but it would be naïve to expect any new manufacturer entering the market to instantly have a product that is problem free.

Of the two existing engines we much prefer the SMA. It was designed from the start as an aero engine as opposed to a converted car engine, it has been around for thirteen years, has a lower reliance on electronic wizardry and the major aerospace company behind it (Snecma) has stood solidly behind their warranties. One of the owners of a diesel 182 out here has had his engine replaced twice without quibble.

The SMA is also the closest potential fit to a 337. Compared to the IO360C it is 8” taller, 6” wider and 2” shorter without any sacrifice of horsepower. It weighs 100lbs more but this is largely offset by the lower sg of JetA and the reduced fuel burn. Some years ago we were informed by SMA that the tractor/pusher issue was not a design limitation but merely a matter of testing and certification but of course this carries a cost implication as well.

Cheap it is not. About $65k a pop the last time I looked. Throw in new props, mounts, instrumentation and multiply by two and you can’t be much shy of $180k before STC costs. A few years ago a firm in the USA quoted me $100k to do the STC work so there you are, back in the ball park of the HAWK price with all the same arguments against it.

It was a very smart move by TCM, or maybe it was the new Chinese owners, to buy the SMA technology. It could be they will be able to leapfrog over all the teething problems and they have the muscle and know-how to get a lot of engines onto the market quickly. Originally they were promising a certified, retrofittable 4 cylinder this year and a 6 cylinder in 2013. For which airframes they did not say and whether their plans will include the relatively small fleet of 337s remains to be seen but to my mind this is the only practical hope on the horizon.

[WebMaster]

I note in my iPad App for Oshkosh, that Delta Hawk has a booth. No idea what they will be showing. They are in booth 257, in the main aircraft display area.

Thanks Herb for pointing out the App.

[ngb1066]

Is there any further news from T F Hawk or Deltahawk? Both websites do not appear to have been updated for a while.

[Walter Atkinson]

Two things I don't see discussed about the diesels:

1) the HUGE hit they take in additional cooling drag which makes the fuel efficiency not nearly as good as the claims which do not take that drag into account.

2) the significant peak pressures which are transmitted to the prop in stress vibrations.

[ngb1066]

Originally Posted by Walter Atkinson

Two things I don't see discussed about the diesels:

1) the HUGE hit they take in additional cooling drag which makes the fuel efficiency not nearly as good as the claims which do not take that drag into account.

2) the significant peak pressures which are transmitted to the prop in stress vibrations.

Walter - The 235HP SMA diesel engine seems to have been operated successfully in the Cessna 182, so presumably the two problems you mention must have been addressed in some way. Do you have any further information on this?