jetcareers - View Single Post

cre8flyer · September 9th, 2007, 22:33

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?

September 9th, 2007, 22:33	#1
cre8flyer Junior Member Join Date: Oct 2006 Posts: 167	Unexpected compass errors. . . 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?