Narrative:

A C421 was IFR over-flight through the ZZZ airspace. The pilot had several problems during the flight. I received an amended flight strip showing the aircraft was filed at 120 and now should be at 100. However; the pilot checked on at 120; level at 120. The aircraft started descending and I had the aircraft verify altitude. They said they blew-through and were correcting. The C421 climbed back to 120. A few minutes later the pilot said they had an auto-pilot problem and needed to 'make a one-eighty'. I had no aircraft in the area and approved the maneuver. I notified the flm of the situation. The pilot made the turn and said they problem was resolved and could return on-course to their destination. I called their destination and gave them a 'heads-up' of the problem. The C421 flew about 50-60 miles north into their destinations airspace when the destination's ATC called me and said the C421 was having vacuum problems and wanted to land at ZZZ. At the time their destination had worse weather than ZZZ however there was a cloud layer that would prevent VFR descent into ZZZ. I notified the flm; now a different person that was not aware of the previous problem. ZZZ was advertising runway xxl. The pilot came to me requesting runway yy which would be a 'straight-in'. I asked the pilot to verify they were requesting the GPS yy approach. They replied that they would check the charts. I clarified that they could have any approach they wanted. They pilot then replied that they would take the GPS yy approach. I descended and vectored the aircraft for the approach. The C421 descended very slowly and would have a problem being too high for a safe approach for the GPS yy. I advised the pilot that was trying to avoid vectors because of the aircraft equipment problems and asked if I could turn them to get lower. They replied that turns would be fine. Now; the pilot had difficulty 'dialing-in' the IAF. I spelled the fix to the pilot and they still were unable to fly the approach that they were requesting. The flm asked me if they could see the airport. I asked if they were IMC and the pilot replied no. I called the field and they answered that they were indeed IMC. I called the tower to advise them of the situation and request the approach to the runway that was not advertised. They approved. There is a high' MVA around an antenna on the GPS yy approach that prevented me from descending the aircraft now that the pilot was unable to fly the GPS approach. I zoomed in on my scope to ensure that the C421 did not get into the MVA and left the aircraft on a 140 heading to avoid that MVA and still had to turn the aircraft 10 degrees away from the airport to miss the MVA. I called the tower and let them know the situation and they said I could descend into their airspace to try and get them visual approach. They said that was fine and I could descend to 6;600; my lowest MVA. I descended aircraft to 6;600. The pilot descended to 6;100. A low altitude alert went off; I advised the pilot and the tower call acknowledging the alert. The pilot did not answer several calls and finally called the field in sight. I cleared them for a visual approach to runway yy and told them to call the tower. They again did not answer; the pilot then set-up to land on runway xxl. I called the tower and approved an approach to any runway. During this event the pilot blew through several altitudes and ignored many instructions. We treated the situation as an emergency early on during the event.

Related reports:

Google
 

Original NASA ASRS Text

Title: Approach Controller described a confused event when an IFR light twin was experiencing equipment difficulties and non responsive to ATC directions and less than familiar with approach procedures.

Narrative: A C421 was IFR over-flight through the ZZZ airspace. The pilot had several problems during the flight. I received an amended flight strip showing the aircraft was filed at 120 and now should be at 100. However; the pilot checked on at 120; level at 120. The aircraft started descending and I had the aircraft verify altitude. They said they blew-through and were correcting. The C421 climbed back to 120. A few minutes later the pilot said they had an auto-pilot problem and needed to 'make a one-eighty'. I had no aircraft in the area and approved the maneuver. I notified the FLM of the situation. The pilot made the turn and said they problem was resolved and could return on-course to their destination. I called their destination and gave them a 'heads-up' of the problem. The C421 flew about 50-60 miles north into their destinations airspace when the destination's ATC called me and said the C421 was having vacuum problems and wanted to land at ZZZ. At the time their destination had worse weather than ZZZ however there was a cloud layer that would prevent VFR descent into ZZZ. I notified the FLM; now a different person that was not aware of the previous problem. ZZZ was advertising Runway XXL. The pilot came to me requesting Runway YY which would be a 'straight-in'. I asked the pilot to verify they were requesting the GPS YY approach. They replied that they would check the charts. I clarified that they could have any approach they wanted. They pilot then replied that they would take the GPS YY approach. I descended and vectored the aircraft for the approach. The C421 descended very slowly and would have a problem being too high for a safe approach for the GPS YY. I advised the pilot that was trying to avoid vectors because of the aircraft equipment problems and asked if I could turn them to get lower. They replied that turns would be fine. Now; the pilot had difficulty 'dialing-in' the IAF. I spelled the fix to the pilot and they still were unable to fly the approach that they were requesting. The FLM asked me if they could see the airport. I asked if they were IMC and the pilot replied no. I called the field and they answered that they were indeed IMC. I called the Tower to advise them of the situation and request the approach to the runway that was not advertised. They approved. There is a high' MVA around an antenna on the GPS YY approach that prevented me from descending the aircraft now that the pilot was unable to fly the GPS approach. I zoomed in on my scope to ensure that the C421 did not get into the MVA and left the aircraft on a 140 heading to avoid that MVA and still had to turn the aircraft 10 degrees away from the airport to miss the MVA. I called the Tower and let them know the situation and they said I could descend into their airspace to try and get them visual approach. They said that was fine and I could descend to 6;600; my lowest MVA. I descended aircraft to 6;600. The pilot descended to 6;100. A low altitude alert went off; I advised the pilot and the Tower call acknowledging the alert. The pilot did not answer several calls and finally called the field in sight. I cleared them for a visual approach TO RUNWAY YY and told them to call the Tower. They again did not answer; the pilot then set-up to land on runway XXL. I called the Tower and approved an approach to any runway. During this event the pilot blew through several altitudes and ignored many instructions. We treated the situation as an emergency early on during the event.

Data retrieved from NASA's ASRS site as of April 2012 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.