Talked to the DA-42 Diamond twin star test pilot...

[BonanzaDriver]

Interesting conversation. I love the look of the airplane, but come on, 150 knots on a twin? Seems a bit slow, especially given that slick airframe.

He told me that diamond is waiting on approval for an ECU modification that increasing the turbo boost in the engine, giving each engine roughly 200 hp which should result in near 200knot cruise speeds.


interesting, just thought I'd share it.

 

[Areeda]

Hmmm sounds a little optimistic to me.

I believe power required goes up by the cube of the velocity. So a 33% increase in speed (200/150) would require 2.3 times the power (1.33^3)

Joe

 

[tonycondon]

150 knots on what? 12gph? is pretty good. its not so much about speed as it is about efficiency

 

[JohnR]

Do the engines still quit if the alternators fail?

 

[jason]

Do the engines still quit if the alternators fail?

The alternators didn't fail, the battery died and the pilot failed to follow the POH. I agree that it's a scary proposition to have a double engine failure (and subsequent auto feather), but if the manufacturer says don't do it...and you do...it's not their fault.

 

[KennyFlys]

By itself, the speed increase seems a stretch just from changing the turbocharging. But, the turbocharge affects performance at altitude. So, how much would higher altitude affect speed increase?

 

[gismo]

By itself, the speed increase seems a stretch just from changing the turbocharging. But, the turbocharge affects performance at altitude. So, how much would higher altitude affect speed increase?

The ratio (speed/power) does change with indicated airspeed, coming closer to speed= power^2 at the most efficient speed (around Vy) so you could say that less power is needed to cause a specific increase in TAS at high altitudes where the IAS is closer to Vy. Another issue on the engines involved is that the power available at high altitude may have increased more than the max power percentage wise. Also, I thought the max cruise speed of the DA-42 was more like 160 KTAS to start with.

 

[wsuffa]

If it increases the maximum authorized altitude, plus the HP increase, you might well get an additional 40-50 knots. Sounds optimistic, but plausible.

 

[TMetzinger]

The -42 cruises at 160 KTAS at 10000 (plane and pilot reported on it this issue), so more boost would allow you to create more power at the same altitude, or more significantly, take the same power to a higher altitude where you will get more knots for the same fuel burn.

Still, adding 40 knots doesn't seem possible, at least intuitively.