Diesel powered 337

[ngb1066]

I have been interested for some time in the possibilty of installing diesel engines in a 337. For a time it appeared that the SMA four stroke 230-235HP engine was the only candidate and it appears to have been successful in the Cessna 182. The "improved" version of the SMA engine has just received EASA certification and this amongst other things raises the service ceiling, which was a problem with the original engine. There are apparently plans for SMA to bring out a 280HP model in due course. Tule River raised the suggestion of developing an STC for fitting SMA engines to the 337 a while back, but I do not believe they have taken the idea any further.

Thielert/Centurion have put on hold their plans for their 300+HP version of their engine and in any event the experience of users in the UK of the Thielert product has not been good.

The Deltahawk engine as a two stroke has always looked interesting, offering a better power to weight ratio than the competition. It can also burn motor diesel, unlike the SMA engine which is limited to Jet A or Jet A1. I have looked at the TF Hawk website setting out their plans for the 337 Goldenhawk with Deltahawk engines, but it is not clear how far they have got with that project. My main reservation about this is that the four cylinder Deltahawk engine will when certified, probably later this year, have a maximum power output of 200HP. I wonder if this is really sufficient to power a 337, particularly the heavier pressurised models. I would be interested to hear views on that. Deltahawk plan in due course to bring out 6 and 8 cylinder versions of their engine, offering power up to 400HP, but that is likely to be some time away.

[Morne]

Originally Posted by ngb1066

My main reservation about this is that the four cylinder Deltahawk engine will when certified, probably later this year, have a maximum power output of 200HP. I wonder if this is really sufficient to power a 337, particularly the heavier pressurised models. I would be interested to hear views on that.

Horsepower is not everything.

Check out the diesels on the Diamond Twin Star DA42 (yes, they are Thielerts, but follow along for a moment). They are 135HP each, not even the original Piper Apache had engines that wimpy!

But talk about fuel economy - that puppy cruises on roughly 10gph (5 per side) of Jet A and does it quickly. While the 337 retrofits will never be as aerodynamic or as light as the DA42s they still could be reasonably fast and fairly fuel efficient.

[hharney]

The Golden Hawk also is amazingly quiet -- another result of its original military design goals. The new Hartzell props provide lower noise signature and the engines are so quiet that it is said that it makes less noise on a take off roll than a Cessna 150 taxiing by on the ramp. Skymasters are usually noisy inside, so this will be welcome -- I don't know if the plane's ability to land nearly silently at midnight on a desert strip in the middle of nowhere half a world away is of interest to anyone, though....

TF Hawk said that the costs of operating the Golden Hawk Skymaster are extraordinarily low -- first, the engine maintenance is less than half of an IO-360 powered aircraft; second, the fuel is much cheaper than 100LL; third it burns less than half the fuel per hour and, when at altitude maybe even 1/4 the fuel; and fourth, it flies higher and faster TAS as a result, so you get there quicker. Based on that, the Golden Hawk is likely that your flying costs will go down by as much as $200 to $300 per hour or even more, depending on where you live and the price of fuel at your airport (I imagine that this conversion will be very interesting for European customers, where fuel prices are four to five times higher than they are in the USA).

Thinking about it, this means that if you fly 300 hours a year, the conversion will pay for itself in less than four hours as a result of the cost savings you will enjoy.

More to come.... I am arranging a phone call in the next week or so with one of the top team at TF Hawk, where I intend to confirm this and learn more yet, which I will pass on. When I discussed this with them, the company did state to me that the above is fairly accurate, though they're not confirming anything yet pending the launch of a new civilian conversion announcement on their website. They did confirm that they will deliver an aircraft in as little as six months from date of order and that they can handle up to six aircraft at a time in the shop. This is their first venture into the civilian market, despite nearly four years of development work underway for exclusive military uses, so they are excited about it.

[ngb1066]

Morne and Herb

Thank you for your comments. I can certainly see enormous benefits of diesel aero engines in terms of both performance and economy. I suspect that they are likely to be increasingly seen in GA. This applies even more in Europe than in the USA, in view of the stratospheric cost of 100LL avgas here.

The Golden Hawk project certainly looks very interesting and I will look out for updates on the TF Hawk website about their proposed civilian version of the aircraft. Herb - have you had your phone call yet with TF Hawk? I will certainly consider this option for the 337 I am looking for. My only reservation at this stage is engine power, which will be lower than currently available for any of the 337 varients. I imagine that this will not be a problem at altitude as diesel engines retain maximum power at greater altitude than the avgas fuelled equivalent, but in terms of take off performance do you consider the Deltahawk limit of 200 HP will be a significant factor? My concern is based upon operating from a relatively short grass strip.

Many thanks for your advice and information.

Neil

[CycloneSteve]

Has anything new happened since August?