GA pilot discovers magnet in headset will affect magnetic compass.

Attributes
ACN	155181
Time
Date	199008
Day	Wed
Place
Locale Reference	atc facility : bos airport : 1b9
State Reference	MA
Altitude	msl bound lower : 1000 msl bound upper : 3500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Fixed Gear
Flight Phase	climbout : intermediate altitude
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private
ASRS Report	155181
Events
Anomaly	aircraft equipment problem : less severe other anomaly other other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

When I started my turn to the north, I noticed that my dg, which I had set to runway heading on my takeoff roll had apparently precessed. I reset it to the compass and continued my turn. Because of the broken layer below me, ground reference was spotty. As I continued my turn, I noticed more apparent precession. At that point, things didn't 'feel right' so I cross checked my compass with my LORAN. The compass was off by almost 90 degrees! I then noticed that I had left the passenger's headset on top of the instrument panel. When I removed the headset from the panel, the compass immediately swung 90 degrees to the correct heading. It then occurred to me that a magnet in the earpiece had interfered with proper compass operation. I have told this story to about 20 other pilots, and each one of them expressed surprise that an aircraft headset could cause such a severe problem.

Original NASA ASRS Text

Title: GA PLT DISCOVERS MAGNET IN HEADSET WILL AFFECT MAGNETIC COMPASS.

Narrative: WHEN I STARTED MY TURN TO THE N, I NOTICED THAT MY DG, WHICH I HAD SET TO RWY HDG ON MY TKOF ROLL HAD APPARENTLY PRECESSED. I RESET IT TO THE COMPASS AND CONTINUED MY TURN. BECAUSE OF THE BROKEN LAYER BELOW ME, GND REFERENCE WAS SPOTTY. AS I CONTINUED MY TURN, I NOTICED MORE APPARENT PRECESSION. AT THAT POINT, THINGS DIDN'T 'FEEL RIGHT' SO I CROSS CHKED MY COMPASS WITH MY LORAN. THE COMPASS WAS OFF BY ALMOST 90 DEGS! I THEN NOTICED THAT I HAD LEFT THE PAX'S HEADSET ON TOP OF THE INSTRUMENT PANEL. WHEN I REMOVED THE HEADSET FROM THE PANEL, THE COMPASS IMMEDIATELY SWUNG 90 DEGS TO THE CORRECT HDG. IT THEN OCCURRED TO ME THAT A MAGNET IN THE EARPIECE HAD INTERFERED WITH PROPER COMPASS OPERATION. I HAVE TOLD THIS STORY TO ABOUT 20 OTHER PLTS, AND EACH ONE OF THEM EXPRESSED SURPRISE THAT AN ACFT HEADSET COULD CAUSE SUCH A SEVERE PROB.

Data retrieved from NASA's ASRS site as of July 2007 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.