"Yossarian" wrote in message
oups.com...
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?

Legality-wise, the only offence someone could really try to prosecute you
for would be that of breaking the approach constraints of the equipment
available to you. Your defence (which I'm 100% sure the court would accept)
would be that the approach was legal until the equipment broke and
immediately switched you to a situation which was (strictly speaking)
illegal, but which you expeditiously got yourself out of by climbing to the
new MDA. Theory notwithstanding, though, the sensible way to go is execute a
missed approach, go back to the start, get the other approach plate out,
remind yourself of the minima, and have another go.

As others have said, I suspect this example is hypothetical - if you're at
300' on the glideslope of an ILS, you're a mile from touchdown and you'll
probably be over the runway by the time you've realised what's going on and
have climbed. It's not inconceivable, however, for something similar to
happen when (say) an airfield has published ILS (precision) and NDB
(non-precision) approaches, where the difference in DH is only a hundred
feet - you could in theory embark on the ILS approach, the glideslope could
fail at 350 feet, and you're still within the legal limits of an NDB
approach. Again, though, this doesn't necessarily mean it's a sensible way
to go.

D.