It depends on the situation and who is with me...
I regularly used to take "Cloud Climbs" in my glider, which only had one gyro instrument - an electric T&S. However:
- I was entering the base of a cloud - so I knew cloud base was well clear of the ground
- The glider had truly speed limiting airbrakes (i.e. speed limiting in vertical dive)
- I always had the option to spin it (thus avoiding Vne) and recover once clear of cloud (see first point)
In a single engine powered aircraft it depends...
First question is whether the aircraft can be handled in such a way that it won't exceed Vne in the event of loss of all the gyros. For example a Cessna 182 can be configured to fly hands off in a stable descending turn.
Second question is "Who is with me?". If I have passengers my envelope shrinks.
Third question is "How high is cloud base?".
Basically, taking the above into account, I will go IMC with only one operating gyro provided there is high probability of walking away if it fails (not saying the aircraft will be in a fit state for the next punter however).
This thread does, however, remind me of a time (when much less experienced) that I flew back from Cumbernauld to Denham - the first couple of hours (after climbing through a hole) were "VFR on top". When I got back someone indicated they thought this somewhat foolhardy - as there were definitely examples of "embedded towering cumulo granitus", which I would surely have found had the engine stopped. That thought had never occurred to me - lesson learned.
OC619