On 6 Sep 2005 19:29:14 -0700, "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?

That's how I was taught. You time the ILS approach, even though it's
not necessary, in case the GS fails and you can climb to the MDA and
continue as a LOC approach. I've read several articles advising that.
I was even told that not timing the ILS approach was a failure item on
the checkride, so I did as I was taught and timed the approach. I
guess it's good practice against the possibility of forgetting to time
the approach when it really does matter.

My GS is included in one radio, the Narco NAV122. The LOC and GS share
some components so if a common component fails, the whole thing is
suspect. In fact, the one time the radio did fail it was the
multiplexer that quit, though the failure was discovered on the ground
and not on approach.

I suspect that other installations may also share components in
unexpected ways, particularly antennas. If something fails, you don't
need to be puzzling about whether you can trust what's left while
you're 300' and barrelling down the glideslope. A miss allows you to
evaluate your condition from a safe altitude.

Unless your tanks are empty and you have seconds to get it on the
ground before the power fails. But then that's a whole different
scenario.

RK Henry