OK to fly IFR - with CAUTION
My RV4 was technically equipped for IFR but I never did it. I'd only advocate operating an airplane with little to nil systems redundancy in weather that's still manageable if primary systems fail. Systems I'm talking about are:
1) Propulsion
2) Electric
3) Primary Flight indications (anything in your primary flight group)
To illustrate: Lets say you're climbing in IMC with low ceilings below. Your attitude indicator fails. Yes, I know you can use needle-ball. But this actually happened to a good friend of mine - a 16000 hour professional pilot - in his 4, wife in back seat. He had to fly into VMC which took over an hour. Nobody's gonna fly an ILS on the T/B. He barely had the energy to climb out of the airplane and walk to the FBO after he landed.
How about a simple engine failure? Maybe you're even VFR on top. What's the ceiling below? If it only affords maybe 30 seconds of VMC after you break out in your glider, you may not be able to find a good place to park your bird. This scenario also got a buddy of mine. He was in a wheel chair for over a year, and took nearly 3 years to get back in the saddle.
Is it worth it? You decide.
In my humble opinion, I would operate an RV in IFR conditions, but with extreme caution. I'd have an autopilot, electrical system redundancy, attitude indication redundancy, an engine in TOP shape, and NO ice at all. I'd operate on top of no worse than 1000-3 for extended periods. Also, no IFR at night.
If the engine sucks a valve at night, for example, you better be able to select a safe landing area and that means a lit runway, interstate highway, or some obviously open area you can see. Reduced vis makes that job impossible. Don't think you're going to find a runway on your GPS either. Gliding at night, engine out, IMC, and making some sort of "approach" is just impossible. I'd bet against doing that 50:1.
Even the redundancy of twins is questionable. I had the left engine disassemble itself on a B55 Baron in VMC. Prop came apart in cruise. It was pure luck the separated blade didn't come through the fuselage, the nacelle didn't separate from the aircraft, or (worse) the nacelle didn't fail upward and over the wing. We had near full fuel, 4 pax, and about 150# of cargo that day. The flight prior the airplane did a 3 hour night flight with the owner and his family aboard. That plane was an insurance total after I landed it (wing spar damage). Think about that - some twins are essentially single engine airplanes with twice the chance of an engine failure.
Maybe I'm getting too old, or am just too used to flying hardware that's highly redundant. But believe me, I've used the redundancy more than a few times in my career and its been a God send (B707, B737, B757, B767, B777, A320, about 40 GA types and an active CFI since 1987) The FAR's will not keep you safe, they'll only allow you to crash legally.
This is one of the all-time best threads to show up on VAF, and I hope these thoughts make some of you think about the "what if" of IFR operation.
Fly Safe...