Funfly,
I think the guy has asked a valid question based on personal ability rather than flight safety
I don't think that's what Krallu was asking. I think he was specifically asking about flight safety. If it was personal ability he was talking about, then it would make no difference whether the flight was single-engine or multi-engine, but he has specifically asked about single-engine where there is an additional flight safety factor to consider. He also said himself:
You develope your own personal minima for lets say perhaps 800ft where you at least have some VMC below the clouds in case of engine failure.
Englishal has made a good point, though, which is worth emphasising. Personal ability should dictate in-flight minima ("I am out of practice, so I will use a higher DA than that published"), and if weather worse than these minima should occur, then a diversion must be made.
But if we are talking about flight safety in a single, then the minima we are talking about are
planning minima. You should not set off if the forecast weather is below whatever planning minima you set yourself - but that doesn't mean that if you encouter weather worse than this, you need to turn back.
For example, you may set yourself a DA of 600' agl for an ILS (slightly higher than the published DA, because you are out of practice). But you might also set yourself a single-engine minimum cloud-base of 1000' agl for the entire route. That doesn't mean that if you reach your destination and the cloudbase is 800', you need to divert. On the contrary, the safest course of action is to continue the approach until you become visual, which hopefully will be just before your DA, then land. If you were to make the misguided decision to divert when the weather is below your planning minima but above your in-flight minima, all you are doing is subjecting yourself to further flying time with a low cloud base when have an increased risk of a bad outcome if the engine should fail. That is a counter-productive use of these minima. (Before everyone shouts at me, I'll add that a go-around must be carried out if not visual by your self-imposed DA, possibly followed by a diversion, but for the purpose of my argument I'm assuming that's not going to be the case.)
FFF
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