Agree with BPF. Flying a FADEC equipped engine is extremely easy, until things go wrong. Then you'd better know what to do, and the emergency drills are completely different from what you'd do with a non-FADEC piston. Best source of this is obviously the POH and the associated checklists. I have a PDF copy here if you want to.
The other thing that's the result of FADEC is that there's no aural clue about engine performance. Up till my first flight in the DA40 I had only flown behind fixed pitch propellors, and you get used to associating certain engine noises with certain stages of flight. So you don't look at the RPM indicator all that often to get the required performance. With a FADEC, just as with a C/S prop, engine noise doesn't mean anything. You really need to get used to looking at the engine displays to determine the % power the engine is generating.
And some minor things:
- Diesel fuel doesn't evaporate. Not from your hands, nor from your fuel tester. Wear gloves when testing the fuel for water, don't dispose of the fuel on the concrete - it will get very slick very fast.
- The DA40 suffers from a slight roll-yaw oscillation in the cruise. Keep your feet lightly on the rudder pedals and you'll be fine.
- I don't know the exact aerodynamic reason for this but at the cruise setting (70%) it looks as if you need to fly "on the step". If you're doing 70% and less than 115 knots, although you are properly trimmed, move the trimwheel about 1.5 cm forwards anyway. Nose will drop slightly, speed will increase, lift will increase and the altitude will stay the same. But you just gained about 7 knots for free. It sounds very odd and I have no proper explanation for this, but it seems as if there are two correct trim positions around the 70% load mark.
- Castoring nosewheel steering takes some getting used to when taxiing. Only when the engine is doing about 1400 rpm do you have any aerodynamic steering effect from the rudder. Below that, and particularly with no forward speed or even a tailwind, you've got to work hard and use the brakes to get the aircraft where you'll want it to go. My tactic of dealing with this is to set the power at 1300-1400 rpm (1400 rpm is incidentally the warm-up limit rpm), put my feet on top of the rudder pedals and use full deflection of the rudder to see if I can steer the aircraft. If I can't steer it using aerodynamics alone (full deflection) I only have to add a little more pressure for the differential braking to kick in.
- Compared to a PA28 there's significantly more pitch down required when deploying the flaps. If you don't catch this in time you've easily gained 100 feet. Same when retracting the flaps in the take-off. And of course since they're electric it takes a few seconds before the effect kicks in.
- The system with left=main and right=aux tank takes getting used to. It's very easy to forget to turn off the fuel pump, leaving you with a full tank left and an empty tank right, and that leads to a significant sideload on the stick. And there's no way to pump the fuel back from left to right.
- Due to the stick being in your crotch and the significant center console, there's no way you can fit a standard tri-fold kneeboard around your leg and still have full movement of the controls. Best I can manage is just the single A5 metal clipboard which I tuck in between my hips and the center console.
- We have an aircraft with a full IFR kit and the W&B is so that with two adults up front we need a 17kg counterweight (bucket of sand) in the far aft baggage compartment, otherwise we're ahead of the forward limit. Also, three adults and full fuel is not possible, legally.
- It's normal for the stall warner to sound in the initial stages of the climb. As long as your airspeed is OK (around 70 kts) there's no problem whatsoever. Just remember that she climbs a lot shallower than a PA28 or similar.