It's rather academic, since if you can't see the runway at 300 feet, you're
unlikely to climb to 500, see it, and then be in a position to descend down
for a normal landing. But to answer your question, no it's not legal
according to 14 CFR 91.175(e)(1)(i) since you'd be operating below the MDA
for the LOC approach.

Section 91.175: Takeoff and landing under IFR.
(e) Missed approach procedures. Each pilot operating an aircraft, except a
military aircraft of the United States, shall immediately execute an
appropriate missed approach procedure when either of the following
conditions exist:

(1) Whenever operating an aircraft pursuant to paragraph (c) or (l) of this
section and the requirements of that paragraph are not met at either of the
following times:

(i) When the aircraft is being operated below MDA; or






"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?