EMB ERJ 145 ER/LR
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
ATC Issue All Types; Deviation - Track / Heading All Types
Flight Crew Returned To Clearance
ATC Equipment / Nav Facility / Buildings
We were operating to BUF. ATIS advised us that Runway 5 ILS was in operation but coupled approaches were not authorized. As we intercepted the inbound course the autopilot was turned off but the flight director was left engaged. The flight director wandered a significant amount so it was disengaged. The ILS signal intermittently was lost several times outside the final approach fix and when the signal returned; the localizer needle wandered.  [Another air carrier] landed in front of us and when we reported our situation they informed the Controller that he had the same problem. When we broke out to visual conditions at about 500 feet we were left of course but within a perimeter to make a safe landing. We continued to land with no further incident.The weak signal was a known problem and aircraft were using this approach all day. Normally the approach would; in my opinion; be considered unstable and require a go-around but we had anticipated the deviation and would have been faced with the same problem in another attempt.
EMB-145 Captain reported the BUF Runway 5 ILS signal is weak and unreliable.