We took advantage of the fine wx today to fly from Barton to Pembrey, however when we started the engine, the DI started to rotate clockwise. It increased in speed as the engine speed was increased and slowed down as the engine speed was reduced. After about 2 minutes it eventually stopped and behaved normally, so we decided to continue with our trip. The fault hasn't recurred and it worked fine all the time we were out.
The aircraft is a PA28 Archer III. Can someone (a) offer an explanation, and (b) reassure us that it isn't an indication of imminent failure. The AI showed no signs of anything untoward.
