I was able to find that Diamond has a service bulletin, that states that the engine can use “normal diesel” ie non Jet A1.
Anyone has additional information about this? Does this change affect something else, like power or other engine characteristics? If this service buleting is applied, are there any big tradeoffs?
There are some additional fuel temperature limitations. You also need to add about 5% to take off calculations if the OAT is less than 10 deg Celcius. Climb performance is also reduced by about 50ft/min.
Not hindered by any factual knowledge, I feel inclined to think there is no or little issue.
Road diesel, which becomes heating oil when the tax people have added the nice red colouring, is slightly thicker than kerosene, making it a more effective lubricant. Indeed people converting car diesels for aviation use have had lots of trouble to get the injection pump sufficiently lubricated with the thinner kerosene. So that one should be extremely careful, at least, when running a cardiesel on kerosene.
But the inverse can – again, to my little informed mind – only mean the fuel has perhaps a bit less energy content so that a bit less power may be available, or fuel burn might go up.
Another potential issue is the fuel filter: thicker fuel might be quicker to clog it, especially in cold climates. But since you are in Finland, you must be used to the tricks to deal with that even in road vehicles, such as adding a shot of petrol or so to diesel fuel.
I noticed the takeoff 5% from the document. Also you can use blend of jet A1 and normal diesel. We do have winter diesel here in Finland, so the limits should be ok.
The plane at our club flies a lot in Summer and JetA1 is not available usually at the uncontrolled aerodomes. So making the engine to be able to use also normal diesel (for example on summer time only, just to be on the safe side) would add a lot of versatility on planning the routes. Adding 25 liters of diesel from a gas station can make a big difference to the route, so that you don’t have to hop in to large airports for refueling. It also makes it easier to fly smaller hops when more people are onboard (=less fuel).
The question that popped into my mind also is that are these limitations lifted, if one starts using jet A1 again. But again, that power “loss” seems to be quite small and it ads a lot of options for refueling.
IF (and it is a big “if”) your local regulations allow, you can even fly on “red” heating fuel. It is the same stuff as road diesel, only with a tinge of red added. It could be done in my country – local regulations of course forbid using “red” fuel in road vehicles, but say nothing about aircraft.
From spring to autumn I run my DA42NG preferably on Diesel without any issue. I have a heated hangar, so engine starting fuel temperature is no issue. I guess, I could run the engines also in winter on diesel fuel. After start up the main tanks are being heated, whereas you have no heating in the auxiliaries.
Nevertheless basic requirements for Diesel fuel to be sold in Germany are published (it is in German, but I think you can figure out what it means):
Mindestanforderungen an Dieselkraftstoff in Deutschland
Bezeichnung CFPP-Value Zeitraum “Limits Class”
Sommerdiesel 0 °C 15.04. – 30.09. B
Übergangszeit −10 °C 01.10. – 15.11. D
Winterdiesel −20 °C 16.11. – 28.02. F
Übergangszeit −10 °C 01.03. – 14.04. D
(CFPP = Cold Filter Plugging Point)
The Diesel Supplement is refering to these classes.
Peter wrote:
Not sure I would put red diesel in an aircraft engine – having read e.g. this and this…
I agree. I have had diesel bug in my car. It suffered fuel starvation and I had to empty the tank, purge all the fuel lines, change the filters and run fresh diesel through the system to clear it.
A DA42 is capable of flying at FL180 where the temperature is 36°C lower than sea-level. Although warm fuel is being fed back to the tanks, I would watch the fuel temperature carefully at altitude to make sure it remains well above the CFPP.
