MD80 flight crew experiences a dual compass system failure during approach. An emergency is declared with the runway in sight and a normal landing ensues. During the approach both transponders also fail.
Synopsis
MD80 flight crew experiences a dual compass system failure during approach. An emergency is declared with the runway in sight and a normal landing ensues. During the approach both transponders also fail.
Narrative
While in descent from 11;000 to 8;000 FT we received a heading annunciation on the FMA Comparator Panel; both Captains and First Officers heading looked alike but checking them with the STBY compass we were 45 degrees off magnetic heading. At this time the Controller was vectoring us to the ILS final. Attempted to slew headings closer to STBY heading and advised the ATC Controller of diminished navigation capability since our heading system was reading erroneously. The Controller continued to issue us numerous heading assignments and traffic information on traffic ahead of us on the approach. We advised the Controller that the field was in sight but he continued with heading and traffic advisories. While approximately 18 DME on final I declared an emergency with the Controller again advising him of the heading system malfunction; really to gain traffic priority and to stop issuing heading assignments which we were unable to follow. Fortunately for us it was severe VFR and traffic and identifying the airport were never a problem. At about 14 DME the #1 and #2 Transponder Data Bus annunciated on the TCAS screen telling us the transponder was not working properly; we advised the Controller who acknowledged it and finally cleared us for the visual approach. Remainder of approach and landing were uneventful and wrote up discrepancies at the gate.
Second reporter narrative
About 25 miles out; I noticed the compass rose display on my ND slewing/moving faster than the airplane was actually turning and heading. This caused a heading disparity between the two compass systems; turned on the 'Heading' annunciator on the FMA; and turned off the Autopilot. Captain; as pilot not flying; was in contact with ATC Final Controller. [I] received several vectors from ATC; which were difficult to comply with while contending with a 65 KTS crosswind at altitude and at the same time; trouble-shooting compass systems. To take advantage of the Day/VMC conditions and to simplify procedures in an otherwise very busy terminal control area; we declared an emergency and called the runway in sight. At this time; both Transponders failed; causing ATC to ask if we had a total electrical failure! We were cleared for the visual approach; and landed safely.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.