"Yossarian" wrote:
You are on an ILS approach, DH 200'. The localizer-only MDA is 500'.
You are at 300' in IMC when the GS fails. Assuming you are timing the
approach, is it legal to climb to 500 and continue the approach?

I don't know of any rule which explicitly says it is illegal, but my
personal opinion is that it's a stupid idea.

It's a stupid idea in the general sense because the middle of an approach
is no time to be changing plans and diagnosing instrument failures. Go
around, sort things out at a safe altitude, and figure out a new plan when
you have time to consider all your options.

It's a particularly stupid idea in the specific scenario you described. If
you're still IMC at 300 feet, what makes you think climbing to 500 will put
you in a position where you can see the runway?

Consider also how inaccurate timing is. In a typical GA airplane, 100 feet
above DH on the GS is about 10 seconds away from the ILS MAP; what makes
you think your FAF-MAP timing is accurate to within 10 seconds?

Plus, another thing. Transition from descent to climb profile involves
power changes, pitch changes, and trim changes. And all those again as you
level off at 500. Are you going to be doing all those things, and peering
out of the window at the same time trying to see the runway (all the while
paying attention to your timer counting down the last few seconds)? And
then more power/pitch/trim changes (plus get the gear up this time) a few
seconds later as you finally decide to go missed? Low, slow, and IMC is
the wrong place to be doing all these things.