Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Confusion
ATC Issue All Types; Aircraft Equipment Problem Less Severe
Aircraft Equipment Problem Dissipated; Flight Crew Requested ATC Assistance / Clarification
ATC Equipment / Nav Facility / Buildings; Aircraft
This is a safety report to inform of erratic nav signals being received at GRR.  On approach into GRR 26L; from about 10 DME to 3 DME; we received an erratic localizer signal.   The CDI needle swung erratically from side to side; with the autopilot/flight director chasing the needle.  We were in  VMC conditions and disconnected the autopilot and hand flew the airplane to the airport.  From  3 NM in; the signal was strong and normal.  We reported the bad signal to GRR Tower.  The aircraft was not written up as we had flown 2 coupled ILS approaches earlier in the day with no problems.  From previous experience and [and many Runway 26L approaches]; the 26L Loc seems to give a signal that  does not agree with our avionics.  I have executed a missed approach before on this runway in the  past for the same reasons only to shoot an approach to Runway 35 with no problems.  Similar erratic LOC signals can be found at LEX 22; BUF 05 and LGA 04.
The reporter believes that the erratic localizer operation he experienced is the result of some incompatibility between the localizer transmitter and his aircraft's Honeywell avionics. It occurs on a regular basis on the ILS 26L at GRR and the three other approaches reported.
Air Carrier Captain experiences an erratic localizer signal during the ILS 26L approach to GRR in VMC. The signal becomes stable inside three DME. The instability is a common occurrence on this approach and three others mentioned.