188TAS, 16,2 USG/hr
That’s a lot of juice for 188kt TAS (at “some” altitude).
DA62 (twin diesel, probably 160KTAS): 13L/100
I’d say more likely 16L/100 km at this speed.
Peter wrote:
hat’s a lot of juice for 188kt TAS
NA SR22 will not burn less
Sure; and you make my point for me 
Silvaire wrote:
It’s not as much different as you think for small engines when compared with a gasoline piston engine, and the airframe design dominates anyway, but its a lot better than a turbine in many applications.
Agree airframe dominates, but the difference between gasoline and diesel is still huge.
Modern diesel cars run at 4L/100 at 140km/h on the highway. With the same design and speed a gasoline car will burn 6.5-7.5L/100. Although it makes little sense financially, diesel aircrafts cost up to 100k more than their gasoline conterparts, in Europe where there is more 100LL availability than Jet-A1 on GA fields.
172driver wrote:
Wait, what? DA40 140-150kts TAS? We have one in our club and it doesn’t get near these numbers.
As wbardorf said: the DA40 XL easily does 140-148 KTAS around FL090. The XLs in my experience was a tad faster (easily 150) but for 0.4 GPH more fuel flow so I guess it had a more powerful engine. I always wondered whether the ugly “bloated” canopy of the XLS / XLT models was a net aerodynamic gain?
But back to the topic: the DA40 with the Lycoming engine will really do 140+ on 9 GPH and I remember seeing 155 at very low altitude at the (then) horrifying fuel flow of 13 GPH. I wish my Extra could fly at all on 13 GPH these days….
Most DA40 pilots don’t dare / have the knowledge to extract the power from the Lycoming.
Maybe they are instructed to run it over-rich at too low RPM? Probably aeroclub rules?
The result is excessive fuel burn, fouled spark plugs and low speed.
It took me some time to dare “break the rules”. 2400 RPM in cruise and 2500 in the climb and always WOT and both of the engines had a long and very healthy life.
I have posted many times on the DAN forum about Diamond deliberately downplaying the Lycoming powered DA40 for fear of the comparison with their Austro-Engined flying tank. Honestly, the DA40-180 was a genius design with lovely handling and it is still an unfinished development IMO:
Clip the wings, switch construction to carbon (as in DA42), add TKS, fix the gear’s aerodynamics and here comes 160 KTAS and 1000 lb useful load for half the price of an SR22.
That’s what I had in mind, which is a big difference IMO. Airliners these days are chasing 5% efficiency improvements… There is no free lunch, but a 1/4 to 1/3 free lunch is nothing to sneeze at.
Flyingfish wrote:
Clip the wings, switch construction to carbon (as in DA42), add TKS, fix the gear’s aerodynamics and here comes 160 KTAS and 1000 lb useful load for half the price of an SR22.
Although clipping the wings / switching materials may require a new TC. And currently it still ends up thirstier than the TDI / NG (13 vs 8-9L/100).
But thank you for this interesting take, this version is easy to overlook and a nice midway between the (expensive, slow) diesel and older, cheaper but much less efficient airframes (from other manufacturers).
maxbc wrote:
That’s what I had in mind, which is a big difference IMO.
It’s about $8/hr in the US market for a 150 or 180 HP engine running at 65%.
Flyingfish wrote:
Clip the wings, switch construction to carbon (as in DA42), add TKS, fix the gear’s aerodynamics and here comes 160 KTAS and 1000 lb useful load for half the price of an SR22.
I agree that something like that would make a better plane for those that don’t want the powered sailplane design concept. Also do something serious to fix the seats.
The SFC scales with the square root of the CR, so an engine with a CR 10% higher will deliver ~5% (calculus of small changes) more power for the same fuel flow. This is the main advantage of diesel engines – aviation or vehicle.
At low subsonic speeds, cockpit volume is the main thing.
At high subsonic speeds (airliners) there are still tweaks they can do.
