Does a magnetic compass ever get old and inaccurate?
I had 2 students get "lost" on their first dual X-C flights. Reviewing their headings in flight I couldn't find any errors, so I checked compass headings vs. very straight roads that show up on the charts and can be measured exactly.
I found errors of around 20 degrees (i.e. road on the chart runs directly East / West true, correcting this for the local variation should give a magnetic heading for a windless day. The compass deviation card has only a 2 degree correction for Easterly headings). Overall, the tiny WCA and deviation corrections could never explain a 20 degree difference between the chart and the compass.
The compass deviation card is dated 1999.
What else could cause this large error?
I had 2 students get "lost" on their first dual X-C flights. Reviewing their headings in flight I couldn't find any errors, so I checked compass headings vs. very straight roads that show up on the charts and can be measured exactly.
I found errors of around 20 degrees (i.e. road on the chart runs directly East / West true, correcting this for the local variation should give a magnetic heading for a windless day. The compass deviation card has only a 2 degree correction for Easterly headings). Overall, the tiny WCA and deviation corrections could never explain a 20 degree difference between the chart and the compass.
The compass deviation card is dated 1999.
What else could cause this large error?