Genghis, you probably meant DA20, which is certified according CS-VLA - DA40 is a CS-23 aircraft...
On the VLA subject: I find CS-VLA in present form pretty useless standard, especially if one is trying to build and certify aircraft that would be able to sell. For example, an average Lycontinental in the CS-VLA weight range has a fuel flow of about 20l/h in cruise. If you want to go to places, you need range of about 4 hours + reserves - this means 100 liters of fuel, which makes about 80 kg. Put up 2 people with 90 kg each (after all, it's not 1950 anymore) and you get 180 kg, and adding fuel this gets you to 260kg of load. The CS-VLA limits the maximum takeoff mass to 750kg, which basically gives you 490kg of basic empty mass and I think it's damn hard to make a useful and safe aircraft for "going places" operation that light. This is what made DA20 (until 800kg exemption from CS-VLA, which Diamond got this year) virtually one-seater for most cross-country flights, unless you like to stop every hour or hour and half to refuel. Not to mention that I don't see any practical point in limiting CS-VLA aircraft to night flying. I agree, aicraft must be equipped with similar equipment for night flying (lights, turn coordinator, artificial horizon, etc.) that CS-23 (or common sense for that matter) requires, but to forbid night flights in a brand new full-equipped aircraft just because some EASA bureaucrats failed to adjust the old JAR-VLA standard to the new world - and at the same time, permit night flights in 40 year old spam can, which probably doesn't have half the equipment of a new VLA aircraft, and there's a large posibility that more than half of installed equipment isn't working - just because it's Part 23 certified. That's crap.
Back to the topic: In my opinion, DIY approaches aren't the real solution, ATC in many places around Europe would file a report if you got in under very marginal weather. To add, it would be very suspicious if a single-engine GA aircraft made it to the runway (by flying a DIY GPS approach), when an airliner/business jet flying the same approach you tell ATC you'll be flying couldn't. The main disadvantages of DIY GPS approaches (when there is adequate obstacle clearance) are:
- it increases your workload (especially if you have to put in a lot of waypoints for the approach)
- it's far, far from legal
- you don't have the luxury of published GPS approaches, such as LPV, etc.
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