DA40 (diesel) and DA42 - real performance ?

[Hugh_Jarse]

Does anyone on here have real-world experience of the (Jet A1 burning) DA40 and the DA42 ? I'm really interested in "top of the greens" achievable cruise speed, and associated fuel burn ... ?

Thanks!

[Nigul]

Hi my friend.... i flow the DA42 centurion 2.0 engine for 300 hours...
If you have any question send me an email. [email protected]

[The Grim EPR]

In the DA40D roughly:

6 USG p/h / 120 IAS ish / 85% power
5 USG p/h / 110 IAS ish / 70% power

Standard tanks 28 USG JET A1

Engine rated for continuous use at 100% (although I never have) at around 8USG p/h. That would bring you to around 130 IAS (Vno 129 IAS)

Both the 1.7 and 2.0 Thielert seem to perform about the same as each other. I believe that the 2.0 is derated (but by the 2.0 engine they had fixed some of their 'issues'). Most of my flying has been with the 2.0 engine.

[A and C]

As said above Thielert have had some issues and they have gone a long way to fixing them on the 2.0L engine (one of the bigest problems with the engine was due to the heat exchangers that Diamond fitted in the airframes).

On the whole The Thielert engine has had a lot of improvment due feedback from it's instalation in military drones, the hours flown by the military are far greater than any civilian use, this feedback can only be good for the civilan users in the long run.

Diamond are now fitting the Austro engine, this has a steel crank case and so weighs more than the Thielert, I suspect that the extra power of the Austro is countered by the extra weight and so users will see no more performance it the aircraft.

[IO540]

The DA42 I have flown in was burning 11USG/hr total for 140kt IAS at low level - same as my TB20 but of course the 42 has 2 motors :)

[soay]

In a 1.7 litre DA40, at the recommended 75% cruise power I get 116 kts IAS at 5.6 gph at 2000 ft. I wouldn't run it for long periods at higher power, even though it's rated at 100%.

[A and C]

You are probably quoting the performance at the worst altitude for the aircraft, the Diesel engine performance advantage only kicks in as you go higher.

[soay]

A & C: true, but the figures still look good compared to anything running AVGAS - if you ignore the extra engine costs resulting from Thielert going bankrupt.

[BackPacker]

the Diesel engine performance advantage only kicks in as you go higher.

Why?

Obviously the higher you go the greater the difference between TAS and IAS. That's independent of engine type or fuel. But other than that, why would a diesel be more efficient at high altitude? (Compared to an avgas machine, say?)

It's true that the Thielert has a turbo so it means that it can maintain its rated power up to well into the oxygen levels but at FL100 the 70% fuel burn will still be ~5 USG/hr, and the IAS will still be about 110-115 knots.

(Looking at the performance tables of the DA40 with the 1.7/135 HP Thielert, the engine is capable of producing 100% to FL60, 90% to FL80 and 80% to FL100. then the curve changes, and 70% can be maintained to FL160, which is the end of the graph.

At 70% load, sea level and in ISA conditions, you get a TAS=IAS of 115, at FL100 you get 127kt TAS, which is IAS 108 according to my E6B.)

[BackPacker]

The cruise climb performance chart of the DA40-1.7TDI is a complicated one.

At 7000 feet, ISA conditions and MTOW, the climb rate is ~450 ft/min if I read the chart correctly. A 500 ft/min climb rate is achievable up to about 6000 feet, assuming MTOW and ISA conditions. At 8000 feet the ROC has already dropped to ~380 ft/min, and 10.000 feet gives you ~250 ft/min. According to the chart at least.

Subjectively speaking, the DA40 is not a very good climber. In order to get any meaningful climb rates you've got to fly the correct airspeed exactly (and there's actually three Vx's and Vy's listed in the handbook, each for a different TOW). In fact, we would typically climb to 1000 feet with flaps in T/O instead of UP. It might not give the best compromise between rate of climb and forward speed, but at least that way we got believable rate of climb numbers.

[S-Works]

From the manufacturers point of view, I'm amazed any of them selling to Europe haven't gone after an auto fuel STC, perhaps in collaboration with Lycoming. Must be a story there, there's no technical issue.

In Europe:

6,000ft ceiling for mogas. 20c TANK temp for mogas. Finding Mogas that does not have bioenthanol or some other alcohol in it becoming as hard to find.

[smarthawke]

The Mogas restrictions were UK generated.

[IO540]

10% alcohol is quite a lot, considering e.g. my TB20 manual states that IPA (for fuel icing protection) should not be added at more than (IIRC) 2%, presumably for the sake of the fuel system seals.

[smarthawke]

The Tecnam P2006T is certified for use with EN228 spec Mogas with up to 10% ethanol (or 100LL Avgas).

[letpmar]

As I understand it all Rotax engines are ok for up to 10% Ethenol but the CAA in its wisdom does not allow any in aircraft.

Pete