Citation V/Ultra/Encore (C560)
Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 108; Flight Crew Total 3391; Flight Crew Type 151
ATC Issue All Types
Air Traffic Control Issued New Clearance
Human Factors; Procedure
Aircraft X was filed IFR from ZZZ to MTN via the RAVNN3 arrival. Approaching the DC metro area we were told to expect the Localizer 15 approach into MTN. Avionics set up and the approach brief was conducted for the approach. Subsequently; we were re-advised that Runway 33 was now in use and to expect the LDA33 Approach. A second approach was set up and a briefing conducted as per procedure. Following a short vector for weather avoidance; we were vectored to intercept the LDA33. Though the frequencies were confirmed both visually and audibly for both pilot positions; and the inbound course confirmed and set; there was no stable indication of course guidance and zero vertical guidance. Near or about the time the non flying pilot was to call ATC to confirm our position. We now were shown to be right or North of the inbound course on our moving map. ATC called and confirmed this. We were then issued a vector of 290 to re-intercept the inbound course. Without any stability in the CDI indication; and rather than attempt to troubleshoot this approach any further; we asked for a vector to the RNAV 33 Approach. This was approved and we were vectored to the RNAV 33 Approach which was set up; briefed and conducted without further incident. The most likely error was that we incorrectly set up for the approach. We reviewed the approach procedure as well as our set up and found no errors. Still baffled as to the reason for our difficulty the Captain called MTN Tower to discuss the incident. The Controller on duty readily admitted that a shift change had just occurred and that the approach in use had not been changed from 15 to 33. The approaches use the same frequency. It's clear now that we were seeing an unstable back course indication with reverse sensing from a still in use localizer 15 while executing the LDA33 approach. This possibility had not occurred to the flight crew.
Corporate aircraft inbound to MTN experienced difficulty capturing the LOC; later discovering ATC had failed to properly align the ILS equipment to the correct runway during a shift change.