Corporate aircraft inbound to mtn experienced difficulty capturing the localizer; later discovering ...

Narrative:

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.

Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1080994
Time
Date	201304
Local Time Of Day	0601-1200
Place
Locale Reference	PCT.TRACON
State Reference	VA
Environment
Flight Conditions	IMC
Aircraft 1
Make Model Name	Citation V/Ultra/Encore (C560)
Operating Under FAR Part	Part 91
Flight Phase	Initial Approach
Route In Use	Vectors STAR RVNN3
Flight Plan	IFR
Person 1
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor Flight Crew Multiengine Flight Crew Instrument
Experience	Flight Crew Last 90 Days 108 Flight Crew Total 3391 Flight Crew Type 151
Events
Anomaly	ATC Issue All Types

Corporate aircraft inbound to mtn experienced difficulty capturing the localizer; later discovering ATC had failed to properly align the ILS equipment to the correct runway during a shift change.